From 4299c3e3b0d87926ccd2919fc08a8d1e171f8c43 Mon Sep 17 00:00:00 2001
From: vurtun <polygone@gmx.net>
Date: Thu, 30 Jul 2015 22:19:06 +0200
Subject: [PATCH] changed tab to layout tree

---
 demo/demo.c   | 420 +++++++++++++++++++++++++-----------------
 demo/nanovg.c |  14 +-
 demo/opengl.c |  13 +-
 demo/xlib.c   |  13 +-
 gui.c         | 496 ++++++++++++++++++++++++++++++++++++--------------
 gui.h         | 324 ++++++++++++++++++++++-----------
 6 files changed, 842 insertions(+), 438 deletions(-)

diff --git a/demo/demo.c b/demo/demo.c
index 198f4ed..3a90fe0 100644
--- a/demo/demo.c
+++ b/demo/demo.c
@@ -3,14 +3,30 @@
 #define WINDOW_WIDTH 800
 #define WINDOW_HEIGHT 600
 
-struct show_window {
-    struct gui_panel hook;
-    gui_flags header_flags;
+struct tree_node {
+    gui_tree_node_state state;
+    const char *name;
+    struct tree_node *parent;
+    struct tree_node *children[8];
+    int count;
+};
+
+struct test_tree {
+    struct tree_node root;
+    struct tree_node *clipboard[16];
+    int count;
+};
+
+struct state {
     /* input buffer */
     gui_char input_buffer[MAX_BUFFER];
     struct gui_edit_box input;
+    gui_char in_buf[MAX_BUFFER];
+    gui_size in_len;
+    gui_bool in_active;
 
     /* widgets state */
+    gui_size menu_item;
     gui_bool scaleable;
     gui_bool checkbox;
     gui_float slider;
@@ -19,31 +35,27 @@ struct show_window {
     gui_bool spinner_active;
     gui_size item_current;
     gui_size shelf_selection;
-    gui_int combo_selection;
     gui_bool toggle;
     gui_int option;
-    gui_size text_box;
+
+    /* tree */
+    struct test_tree tree;
+    struct tree_node nodes[8];
+    gui_float tree_offset;
+
     /* tabs */
-    gui_bool combobox_tab;
-    gui_bool widget_tab;
-    gui_bool table_tab;
+    enum gui_node_state config_tab;
+    enum gui_node_state widget_tab;
+    enum gui_node_state style_tab;
+    enum gui_node_state round_tab;
+    enum gui_node_state color_tab;
+    enum gui_node_state flag_tab;
+
     /* scrollbars */
     gui_float shelf_scrollbar;
     gui_float table_scrollbar;
-    gui_float time_scrollbar;
-    /* menu */
-    gui_size menu_item;
-};
+    gui_float tree_scrollbar;
 
-struct control_window {
-    struct gui_panel hook;
-    gui_flags show_flags;
-    gui_flags header_flags;
-    /* tabs */
-    gui_bool flag_tab;
-    gui_bool style_tab;
-    gui_bool round_tab;
-    gui_bool color_tab;
     /* color picker */
     gui_bool picker_active;
     gui_bool spinner_r_active;
@@ -52,23 +64,102 @@ struct control_window {
     gui_bool spinner_a_active;
     gui_size current_color;
     struct gui_color color;
+
 };
 
 struct demo_gui {
     gui_bool running;
-    unsigned int ms;
     void *memory;
-    struct gui_command_buffer show_buffer;
-    struct gui_command_buffer control_buffer;
+    struct gui_command_buffer buffer;
     struct gui_config config;
     struct gui_font font;
-    struct control_window control;
-    struct show_window show;
-    struct gui_stack stack;
+    struct gui_panel panel;
+    struct state state;
 };
 
 static void
-widget_panel(struct gui_panel_layout *panel, struct show_window *demo)
+tree_remove_node(struct tree_node *parent, struct tree_node *child)
+{
+    int i = 0;
+    child->parent = NULL;
+    if (!parent->count) return;
+    if (parent->count == 1) {
+        parent->count = 0;
+        return;
+    }
+    for (i = 0; i < parent->count; ++i) {
+        if (parent->children[i] == child)
+            break;
+    }
+    if (i == parent->count) return;
+    if (i == parent->count - 1) {
+        parent->count--;
+        return;
+    } else{
+        parent->children[i] = parent->children[parent->count-1];
+        parent->count--;
+    }
+}
+
+static void
+tree_add_node(struct tree_node *parent, struct tree_node *child)
+{
+    assert(parent->count < 8);
+    child->parent = parent;
+    parent->children[parent->count++] = child;
+}
+
+static void
+tree_push_node(struct test_tree *tree, struct tree_node *node)
+{
+    assert(tree->count < 16);
+    tree->clipboard[tree->count++] = node;
+}
+
+static struct tree_node*
+tree_pop_node(struct test_tree *tree)
+{
+    assert(tree->count > 0);
+    return tree->clipboard[--tree->count];
+}
+
+static int
+upload_tree(struct test_tree *base, struct gui_tree *tree, struct tree_node *node)
+{
+    int i = 0, n = 0;
+    enum gui_tree_node_operation op;
+    if (node->count) {
+        i = 0;
+        op = gui_panel_tree_begin_node(tree, node->name, &node->state);
+        while (i < node->count)
+            i += upload_tree(base, tree, node->children[i]);
+        gui_panel_tree_end_node(tree);
+    }
+    else op = gui_panel_tree_leaf(tree, node->name, &node->state);
+
+    switch (op) {
+    case GUI_NODE_NOP: break;
+    case GUI_NODE_CUT:
+        tree_remove_node(node->parent, node);
+        tree_push_node(base, node);
+        return 0;
+    case GUI_NODE_DELETE:
+        tree_remove_node(node->parent, node); break;
+        return 0;
+    case GUI_NODE_PASTE:
+        i = 0; n = base->count;
+        while (i < n) {
+            tree_add_node(node, tree_pop_node(base));
+            i++;
+        }
+    case GUI_NODE_CLONE:
+    default:break;
+    }
+    return 1;
+}
+
+static void
+widget_panel(struct gui_panel_layout *panel, struct state *demo)
 {
     const char *items[] = {"Fist", "Pistol", "Shotgun", "Railgun", "BFG"};
 
@@ -129,6 +220,8 @@ widget_panel(struct gui_panel_layout *panel, struct show_window *demo)
 
     demo->item_current = gui_panel_selector(panel, items, LEN(items), demo->item_current);
     demo->spinner = gui_panel_spinner(panel, 0, demo->spinner, 250, 10, &demo->spinner_active);
+    demo->in_len = gui_panel_edit(panel, demo->in_buf, demo->in_len, MAX_BUFFER,
+                        &demo->in_active, GUI_INPUT_DEFAULT);
 
     if (demo->scaleable) {
         gui_panel_layout_flux_row_begin(panel, 30, 2);
@@ -154,7 +247,6 @@ widget_panel(struct gui_panel_layout *panel, struct show_window *demo)
             }
         }
         gui_panel_layout_static_row_end(panel);
-
     }
 }
 
@@ -189,26 +281,7 @@ table_panel(struct gui_panel_layout *panel)
 }
 
 static void
-init_show(struct show_window *win, struct gui_config *config,
-    struct gui_command_buffer *buffer, struct gui_stack *stack)
-{
-    memset(win, 0, sizeof(*win));
-    gui_panel_init(&win->hook, 20, 20, 310, 550,
-        GUI_PANEL_BORDER|GUI_PANEL_MOVEABLE|
-        GUI_PANEL_SCALEABLE, buffer, config);
-    gui_stack_push(stack, &win->hook);
-    gui_edit_box_init_fixed(&win->input, win->input_buffer, MAX_BUFFER, NULL, NULL);
-
-    win->header_flags = GUI_CLOSEABLE|GUI_MINIMIZABLE;
-    win->widget_tab = GUI_MAXIMIZED;
-    win->combobox_tab = GUI_MINIMIZED;
-    win->slider = 10.0f;
-    win->progressbar = 50;
-    win->spinner = 100;
-}
-
-static void
-update_menu(struct gui_panel_layout *layout, struct show_window *win, struct gui_config *config)
+update_menu(struct gui_panel_layout *layout, struct state *win, struct gui_config *config)
 {
     int i = 0;
     enum level_id {LEVEL_MENU,LEVEL_FILE,LEVEL_OPEN,LEVEL_EDIT};
@@ -268,18 +341,12 @@ update_menu(struct gui_panel_layout *layout, struct show_window *win, struct gui
         {EDIT_DELETE, LEVEL_EDIT, ITEM_EDIT_DELETE}
     };
 
-    const struct level *lvl = &levels[win->menu_item];
-    const struct combi *iter = &combis[lvl->list];
     {
         /* calculate column row count to fit largets menu item  */
-        gui_size cols, max = 0;
-        for (i = 0; i < lvl->items; ++i) {
-            gui_size text_w, w;
-            const struct item *item = &items[iter->item];
-            text_w = config->font.width(config->font.userdata,item->name,strlen(item->name));
-            w = text_w + (gui_size)config->properties[GUI_PROPERTY_ITEM_PADDING].x * 2;
-            if (w > max) max = w;
-            iter++;
+        gui_int max = 0;
+        for (i = 0; i < (int)LEN(levels); ++i) {
+            if (levels[0].items > max)
+                max = levels[0].items;
         }
         gui_panel_layout_flux_fixed(layout, 18, 5);
     }
@@ -287,9 +354,10 @@ update_menu(struct gui_panel_layout *layout, struct show_window *win, struct gui
     /* output current menu level entries */
     gui_panel_menu_begin(layout);
     {
+        const struct level *lvl = &levels[win->menu_item];
+        const struct combi *iter = &combis[lvl->list];
         gui_config_push_color(config, GUI_COLOR_BUTTON_BORDER, 45, 45, 45, 250);
         gui_config_push_property(config, GUI_PROPERTY_ITEM_SPACING, 0, 4.0f);
-        iter = &combis[lvl->list];
         for (i = 0; i < lvl->items; ++i) {
             const struct item *item = &items[iter->item];
             if (gui_panel_button_text(layout, item->name, GUI_BUTTON_DEFAULT)) {
@@ -321,38 +389,7 @@ update_menu(struct gui_panel_layout *layout, struct show_window *win, struct gui
 }
 
 static void
-update_show(struct show_window *show, struct gui_stack *stack, struct gui_input *in, struct gui_config *config)
-{
-    struct gui_panel_layout tab;
-    struct gui_panel_layout layout;
-    static const char *shelfs[] = {"Histogram", "Lines"};
-    gui_panel_begin_stacked(&layout, &show->hook, stack, in);
-    gui_panel_header(&layout, "Show", show->header_flags, 0, GUI_HEADER_RIGHT);
-    update_menu(&layout, show, config);
-    {
-        /* Widgets */
-        show->widget_tab = gui_panel_tab_begin(&layout, &tab, "Widgets",GUI_BORDER, show->widget_tab);
-        widget_panel(&tab, show);
-        gui_panel_tab_end(&layout, &tab);
-
-        /* Graph */
-        gui_panel_layout_flux_fixed(&layout, 180, 1);
-        show->shelf_selection = gui_panel_shelf_begin(&layout, &tab, shelfs,
-            LEN(shelfs), show->shelf_selection, show->shelf_scrollbar);
-        graph_panel(&tab, show->shelf_selection);
-        show->shelf_scrollbar = gui_panel_shelf_end(&layout, &tab);
-
-        /* Table */
-        gui_panel_layout_flux_fixed(&layout, 180, 1);
-        gui_panel_group_begin(&layout, &tab, "Table", show->table_scrollbar);
-        table_panel(&tab);
-        show->table_scrollbar = gui_panel_group_end(&layout, &tab);
-    }
-    gui_panel_end(&layout, &show->hook);
-}
-
-static void
-update_flags(struct gui_panel_layout *panel, struct control_window *control)
+update_flags(struct gui_panel_layout *panel)
 {
     gui_size n = 0;
     gui_flags res = 0;
@@ -360,11 +397,11 @@ update_flags(struct gui_panel_layout *panel, struct control_window *control)
     const char *options[]={"Hidden","Border","Header Border", "Moveable","Scaleable", "Minimized"};
     gui_panel_layout_flux_fixed(panel, 30, 2);
     do {
-        if (gui_panel_check(panel,options[n++],(control->show_flags & i)?gui_true:gui_false))
+        if (gui_panel_check(panel,options[n++],(panel->flags & i)?gui_true:gui_false))
             res |= i;
         i = i << 1;
     } while (i <= GUI_PANEL_MINIMIZED);
-    control->show_flags = res;
+    panel->flags = res;
 }
 
 static void
@@ -402,7 +439,7 @@ round_tab(struct gui_panel_layout *panel, struct gui_config *config)
 }
 
 static struct gui_color
-color_picker(struct gui_panel_layout *panel, struct control_window *control,
+color_picker(struct gui_panel_layout *panel, struct state *control,
     const char *name, struct gui_color color)
 {
     int i;
@@ -430,7 +467,7 @@ color_picker(struct gui_panel_layout *panel, struct control_window *control,
 }
 
 static void
-color_tab(struct gui_panel_layout *panel, struct control_window *control, struct gui_config *config)
+color_tab(struct gui_panel_layout *panel, struct state *control, struct gui_config *config)
 {
     gui_size i = 0;
     static const char *labels[] = {"Text:", "Panel:", "Header:", "Border:", "Button:",
@@ -442,7 +479,8 @@ color_tab(struct gui_panel_layout *panel, struct control_window *control, struct
         "Selector:", "Selector Border:", "Selector Triangle:", "Selector Text:",
         "Histo:", "Histo Bars:", "Histo Negative:", "Histo Hovering:", "Plot:", "Plot Lines:",
         "Plot Hightlight:", "Scrollbar:", "Scrollbar Cursor:", "Scrollbar Border:",
-        "Table lines:", "Shelf:", "Shelf Text:", "Shelf Active:", "Shelf Active Text:", "Scaler:",
+        "Table lines:", "Tab header", "Tab border",
+        "Shelf:", "Shelf Text:", "Shelf Active:", "Shelf Active Text:", "Scaler:",
         "Tiled Scaler"
     };
 
@@ -472,89 +510,143 @@ color_tab(struct gui_panel_layout *panel, struct control_window *control, struct
     }
 }
 
-static void
-init_control(struct control_window *win, struct gui_config *config,
-    struct gui_command_buffer *buffer, struct gui_stack *stack)
-{
-    memset(win, 0, sizeof(*win));
-    gui_panel_init(&win->hook, 380, 20, 350, 500,
-        GUI_PANEL_BORDER|GUI_PANEL_MOVEABLE|GUI_PANEL_SCALEABLE, buffer, config);
-    gui_stack_push(stack, &win->hook);
-    win->show_flags = win->hook.flags;
-    win->color_tab = GUI_MINIMIZED;
-}
-
-static gui_bool
-update_control(struct control_window *control, struct gui_stack *stack,
-    struct gui_input *in, struct gui_config *config)
-{
-    gui_bool running;
-    struct gui_panel_layout layout;
-    struct gui_panel_layout tab;
-
-    gui_panel_begin_stacked(&layout, &control->hook, stack, in);
-    running = !gui_panel_header(&layout, "Control", GUI_CLOSEABLE|GUI_MINIMIZABLE,
-                                GUI_CLOSEABLE, GUI_HEADER_LEFT);
-    {
-        control->flag_tab = gui_panel_tab_begin(&layout, &tab, "Options", GUI_BORDER, control->flag_tab);
-        update_flags(&tab, control);
-        gui_panel_tab_end(&layout, &tab);
-
-        control->style_tab = gui_panel_tab_begin(&layout, &tab, "Properties", GUI_BORDER, control->style_tab);
-        properties_tab(&tab, config);
-        gui_panel_tab_end(&layout, &tab);
-
-        control->round_tab = gui_panel_tab_begin(&layout, &tab, "Rounding", GUI_BORDER, control->round_tab);
-        round_tab(&tab, config);
-        gui_panel_tab_end(&layout, &tab);
-
-        control->color_tab = gui_panel_tab_begin(&layout, &tab, "Color", GUI_BORDER, control->color_tab);
-        color_tab(&tab, control, config);
-        gui_panel_tab_end(&layout, &tab);
-    }
-    gui_panel_end(&layout, &control->hook);
-    return running;
-}
-
 static void
 init_demo(struct demo_gui *gui, struct gui_font *font)
 {
     struct gui_config *config = &gui->config;
+    struct state *win = &gui->state;
     gui->font = *font;
     gui->running = gui_true;
 
-    gui_command_buffer_init_fixed(&gui->show_buffer, gui->memory, MAX_MEMORY/2, GUI_CLIP);
-    gui_command_buffer_init_fixed(&gui->control_buffer,
-        gui_ptr_add(void*, gui->memory, (MAX_MEMORY/2)), MAX_MEMORY/2, GUI_CLIP);
+    gui_command_buffer_init_fixed(&gui->buffer, gui->memory, MAX_MEMORY, GUI_CLIP);
     gui_config_default(config, GUI_DEFAULT_ALL, font);
+    gui_panel_init(&gui->panel, 30, 30, 280, 530,
+        GUI_PANEL_BORDER|GUI_PANEL_MOVEABLE|GUI_PANEL_SCALEABLE, &gui->buffer, config);
 
-    gui_stack_clear(&gui->stack);
-    init_show(&gui->show, config, &gui->show_buffer, &gui->stack);
-    init_control(&gui->control, config, &gui->control_buffer, &gui->stack);
-    gui->control.header_flags = gui->show.header_flags;
+    gui_edit_box_init_fixed(&win->input, win->input_buffer, MAX_BUFFER, NULL, NULL);
+    win->config_tab = GUI_MINIMIZED;
+    win->widget_tab = GUI_MINIMIZED;
+    win->style_tab = GUI_MINIMIZED;
+    win->round_tab = GUI_MINIMIZED;
+    win->color_tab = GUI_MINIMIZED;
+    win->flag_tab = GUI_MINIMIZED;
+    win->scaleable = gui_true;
+
+    win->slider = 2.0f;
+    win->progressbar = 50;
+    win->spinner = 100;
+
+    {
+        struct test_tree *tree = &win->tree;
+        tree->root.state = GUI_NODE_ACTIVE;
+        tree->root.name = "Primitives";
+        tree->root.parent = NULL;
+        tree->root.count = 2;
+        tree->root.children[0] = &win->nodes[0];
+        tree->root.children[1] = &win->nodes[4];
+
+        win->nodes[0].state = 0;
+        win->nodes[0].name = "Boxes";
+        win->nodes[0].parent = &tree->root;
+        win->nodes[0].count = 2;
+        win->nodes[0].children[0] = &win->nodes[1];
+        win->nodes[0].children[1] = &win->nodes[2];
+
+        win->nodes[1].state = 0;
+        win->nodes[1].name = "Box0";
+        win->nodes[1].parent = &win->nodes[0];
+        win->nodes[1].count = 0;
+
+        win->nodes[2].state = 0;
+        win->nodes[2].name = "Box1";
+        win->nodes[2].parent = &win->nodes[0];
+        win->nodes[2].count = 0;
+
+        win->nodes[4].state = GUI_NODE_ACTIVE;
+        win->nodes[4].name = "Cylinders";
+        win->nodes[4].parent = &tree->root;
+        win->nodes[4].count = 2;
+        win->nodes[4].children[0] = &win->nodes[5];
+        win->nodes[4].children[1] = &win->nodes[6];
+
+        win->nodes[5].state = 0;
+        win->nodes[5].name = "Cylinder0";
+        win->nodes[5].parent = &win->nodes[4];
+        win->nodes[5].count = 0;
+
+        win->nodes[6].state = 0;
+        win->nodes[6].name = "Cylinder1";
+        win->nodes[6].parent = &win->nodes[4];
+        win->nodes[6].count = 0;
+    }
 }
 
 static void
 run_demo(struct demo_gui *gui, struct gui_input *input)
 {
-    gui_flags prev;
-    struct control_window *control = &gui->control;
-    struct show_window *show = &gui->show;
+    struct gui_panel_layout layout;
+    struct state *state = &gui->state;
+    struct gui_panel_layout tab;
+    struct gui_config *config = &gui->config;
+    static const char *shelfs[] = {"Histogram", "Lines"};
 
-    gui->running = update_control(control, &gui->stack, input, &gui->config);
+    gui_panel_begin(&layout, &gui->panel, input);
+    {
+        /* Header + Menubar  */
+        gui->running = !gui_panel_header(&layout, "Demo",
+            GUI_CLOSEABLE|GUI_MINIMIZABLE, GUI_CLOSEABLE, GUI_HEADER_RIGHT);
+        update_menu(&layout, state, config);
 
-    if (show->hook.flags & GUI_PANEL_ACTIVE)
-        show->hook.flags = control->show_flags|GUI_PANEL_ACTIVE;
-    else show->hook.flags = control->show_flags;
-    gui->show.header_flags = gui->control.header_flags;
+        /* Panel style configuration  */
+        if (gui_panel_layout_push(&layout, GUI_LAYOUT_TAB, "Style", &state->config_tab))
+        {
+            if (gui_panel_layout_push(&layout, GUI_LAYOUT_NODE, "Options", &state->flag_tab)) {
+                update_flags(&layout);
+                gui_panel_layout_pop(&layout);
+            }
+            if (gui_panel_layout_push(&layout, GUI_LAYOUT_NODE, "Properties", &state->style_tab)) {
+                properties_tab(&layout, config);
+                gui_panel_layout_pop(&layout);
+            }
+            if (gui_panel_layout_push(&layout, GUI_LAYOUT_NODE, "Rounding", &state->round_tab)) {
+                round_tab(&layout, config);
+                gui_panel_layout_pop(&layout);
+            }
+            if (gui_panel_layout_push(&layout, GUI_LAYOUT_NODE, "Color", &state->color_tab)) {
+                color_tab(&layout, state, config);
+                gui_panel_layout_pop(&layout);
+            }
+            gui_panel_layout_pop(&layout);
+        }
 
-    prev = show->hook.flags;
-    update_show(show, &gui->stack, input, &gui->config);
-    if (show->hook.flags & GUI_PANEL_HIDDEN)
-        control->show_flags |= GUI_PANEL_HIDDEN;
-    if (show->hook.flags & GUI_PANEL_MINIMIZED && !(prev & GUI_PANEL_MINIMIZED))
-        control->show_flags |= GUI_PANEL_MINIMIZED;
-    else if (prev & GUI_PANEL_MINIMIZED && !(show->hook.flags & GUI_PANEL_MINIMIZED))
-        control->show_flags &= ~(gui_flags)GUI_PANEL_MINIMIZED;
+        /* Widgets examples */
+        if (gui_panel_layout_push(&layout, GUI_LAYOUT_TAB, "Widgets", &state->widget_tab)) {
+            widget_panel(&layout, state);
+            gui_panel_layout_pop(&layout);
+        }
+
+        /* Shelf + Graphes  */
+        gui_panel_layout_flux_fixed(&layout, 180, 1);
+        state->shelf_selection = gui_panel_shelf_begin(&layout, &tab, shelfs,
+            LEN(shelfs), state->shelf_selection, state->shelf_scrollbar);
+        graph_panel(&tab, state->shelf_selection);
+        state->shelf_scrollbar = gui_panel_shelf_end(&layout, &tab);
+
+        /* Tables */
+        gui_panel_layout_flux_fixed(&layout, 180, 1);
+        gui_panel_group_begin(&layout, &tab, "Table", state->table_scrollbar);
+        table_panel(&tab);
+        state->table_scrollbar = gui_panel_group_end(&layout, &tab);
+
+        {
+            /* Tree */
+            struct gui_tree tree;
+            gui_panel_layout_flux_fixed(&layout, 250, 1);
+            gui_panel_tree_begin(&layout, &tree, "Tree", 20, state->tree_offset);
+            upload_tree(&state->tree, &tree, &state->tree.root);
+            state->tree_offset = gui_panel_tree_end(&layout, &tree);
+        }
+    }
+    gui_panel_end(&layout, &gui->panel);
 }
 
diff --git a/demo/nanovg.c b/demo/nanovg.c
index 1880b40..8a8292d 100644
--- a/demo/nanovg.c
+++ b/demo/nanovg.c
@@ -122,7 +122,7 @@ draw_image(NVGcontext *ctx, gui_handle img, float x, float y, float w, float h,
 }
 
 static void
-execute(NVGcontext *nvg, struct gui_command_buffer *list, int width, int height)
+draw(NVGcontext *nvg, struct gui_command_buffer *list, int width, int height)
 {
     const struct gui_command *cmd;
     glPushAttrib(GL_ENABLE_BIT|GL_COLOR_BUFFER_BIT);
@@ -174,14 +174,6 @@ execute(NVGcontext *nvg, struct gui_command_buffer *list, int width, int height)
     glPopAttrib();
 }
 
-static void
-draw(NVGcontext *nvg,struct gui_stack *stack, int width, int height)
-{
-    struct gui_panel*iter;
-    gui_foreach_panel(iter, stack)
-        execute(nvg, iter->buffer, width, height);
-}
-
 static void
 key(struct gui_input *in, SDL_Event *evt, gui_bool down)
 {
@@ -323,13 +315,11 @@ main(int argc, char *argv[])
         /* Draw */
         glClearColor(0.4f, 0.4f, 0.4f, 1.0f);
         glClear(GL_COLOR_BUFFER_BIT|GL_DEPTH_BUFFER_BIT);
-        draw(vg, &gui.stack, width, height);
-        gui.ms = SDL_GetTicks() - started;
+        draw(vg, &gui.buffer, width, height);
         SDL_GL_SwapWindow(win);
 
         /* Timing */
         dt = SDL_GetTicks() - started;
-        gui.ms = dt;
         if (dt < DTIME)
             SDL_Delay(DTIME - dt);
     }
diff --git a/demo/opengl.c b/demo/opengl.c
index f142ad7..597eb7b 100644
--- a/demo/opengl.c
+++ b/demo/opengl.c
@@ -406,7 +406,7 @@ draw_circle(float x, float y, float r, const gui_byte *c)
 }
 
 static void
-execute(struct gui_command_buffer *list, int width, int height)
+draw(struct gui_command_buffer *list, int width, int height)
 {
     const struct gui_command *cmd;
     glPushAttrib(GL_ENABLE_BIT|GL_COLOR_BUFFER_BIT|GL_TRANSFORM_BIT);
@@ -472,14 +472,6 @@ execute(struct gui_command_buffer *list, int width, int height)
     glPopAttrib();
 }
 
-static void
-draw(struct gui_stack *stack, int width, int height)
-{
-    struct gui_panel*iter;
-    gui_foreach_panel(iter, stack)
-        execute(iter->buffer, width, height);
-}
-
 static void
 key(struct gui_input *in, SDL_Event *evt, gui_bool down)
 {
@@ -608,12 +600,11 @@ main(int argc, char *argv[])
         /* Draw */
         glClearColor(0.4f, 0.4f, 0.4f, 1.0f);
         glClear(GL_COLOR_BUFFER_BIT);
-        draw(&gui.stack, width, height);
+        draw(&gui.buffer, width, height);
         SDL_GL_SwapWindow(win);
 
         /* Timing */
         dt = SDL_GetTicks() - started;
-        gui.ms = dt;
         if (dt < DTIME)
             SDL_Delay(DTIME - dt);
     }
diff --git a/demo/xlib.c b/demo/xlib.c
index f7f3e3c..717f618 100644
--- a/demo/xlib.c
+++ b/demo/xlib.c
@@ -324,7 +324,7 @@ surface_del(XSurface *surf)
 }
 
 static void
-execute(XSurface *surf, struct gui_command_buffer *buffer)
+draw(XSurface *surf, struct gui_command_buffer *buffer)
 {
     const struct gui_command *cmd;
     gui_foreach_command(cmd, buffer) {
@@ -367,14 +367,6 @@ execute(XSurface *surf, struct gui_command_buffer *buffer)
     }
 }
 
-static void
-draw(XSurface *surf, struct gui_stack *stack)
-{
-    struct gui_panel *iter;
-    gui_foreach_panel(iter, stack)
-        execute(surf, iter->buffer);
-}
-
 static void
 key(struct XWindow *xw, struct gui_input *in, XEvent *evt, gui_bool down)
 {
@@ -498,13 +490,12 @@ main(int argc, char *argv[])
         /* Draw */
         XClearWindow(xw.dpy, xw.win);
         surface_clear(xw.surf, 0x00646464);
-        draw(xw.surf, &gui.stack);
+        draw(xw.surf, &gui.buffer);
         surface_blit(xw.win, xw.surf, xw.width, xw.height);
         XFlush(xw.dpy);
 
         /* Timing */
         dt = timestamp() - started;
-        gui.ms = (unsigned int)dt;
         if (dt < DTIME)
             sleep_for(DTIME - dt);
     }
diff --git a/gui.c b/gui.c
index dbec4ea..d1f5c3d 100644
--- a/gui.c
+++ b/gui.c
@@ -1010,7 +1010,7 @@ gui_edit_box_init(struct gui_edit_box *eb, struct gui_allocator *a,
     gui_buffer_init(&eb->buffer, a, initial_size, grow_fac);
     if (clip) eb->clip = *clip;
     if (f) eb->filter = f;
-    else eb->filter = gui_filter_input_default;
+    else eb->filter = gui_filter_default;
     eb->cursor = 0;
     eb->glyphes = 0;
 }
@@ -1025,7 +1025,7 @@ gui_edit_box_init_fixed(struct gui_edit_box *eb, void *memory, gui_size size,
     gui_buffer_init_fixed(&eb->buffer, memory, size);
     if (clip) eb->clip = *clip;
     if (f) eb->filter = f;
-    else eb->filter = gui_filter_input_default;
+    else eb->filter = gui_filter_default;
     eb->cursor = 0;
     eb->glyphes = 0;
 }
@@ -1773,14 +1773,14 @@ gui_editbox(struct gui_command_buffer *out, gui_float x, gui_float y, gui_float
 }
 
 gui_bool
-gui_filter_input_default(gui_long unicode)
+gui_filter_default(gui_long unicode)
 {
     (void)unicode;
     return gui_true;
 }
 
 gui_bool
-gui_filter_input_ascii(gui_long unicode)
+gui_filter_ascii(gui_long unicode)
 {
     if (unicode < 0 || unicode > 128)
         return gui_false;
@@ -1788,7 +1788,7 @@ gui_filter_input_ascii(gui_long unicode)
 }
 
 gui_bool
-gui_filter_input_float(gui_long unicode)
+gui_filter_float(gui_long unicode)
 {
     if ((unicode < '0' || unicode > '9') && unicode != '.' && unicode != '-')
         return gui_false;
@@ -1796,7 +1796,7 @@ gui_filter_input_float(gui_long unicode)
 }
 
 gui_bool
-gui_filter_input_decimal(gui_long unicode)
+gui_filter_decimal(gui_long unicode)
 {
     if (unicode < '0' || unicode > '9')
         return gui_false;
@@ -1804,7 +1804,7 @@ gui_filter_input_decimal(gui_long unicode)
 }
 
 gui_bool
-gui_filter_input_hex(gui_long unicode)
+gui_filter_hex(gui_long unicode)
 {
     if ((unicode < '0' || unicode > '9') &&
         (unicode < 'a' || unicode > 'f') &&
@@ -1814,7 +1814,7 @@ gui_filter_input_hex(gui_long unicode)
 }
 
 gui_bool
-gui_filter_input_oct(gui_long unicode)
+gui_filter_oct(gui_long unicode)
 {
     if (unicode < '0' || unicode > '7')
         return gui_false;
@@ -1822,7 +1822,7 @@ gui_filter_input_oct(gui_long unicode)
 }
 
 gui_bool
-gui_filter_input_binary(gui_long unicode)
+gui_filter_binary(gui_long unicode)
 {
     if (unicode < '0' || unicode > '1')
         return gui_false;
@@ -1853,13 +1853,13 @@ gui_edit(struct gui_command_buffer *out, gui_float x, gui_float y, gui_float w,
     const struct gui_input *in, const struct gui_font *font)
 {
     static const gui_filter filter[] = {
-        gui_filter_input_default,
-        gui_filter_input_ascii,
-        gui_filter_input_float,
-        gui_filter_input_decimal,
-        gui_filter_input_hex,
-        gui_filter_input_oct,
-        gui_filter_input_binary,
+        gui_filter_default,
+        gui_filter_ascii,
+        gui_filter_float,
+        gui_filter_decimal,
+        gui_filter_hex,
+        gui_filter_oct,
+        gui_filter_binary,
     };
     return gui_edit_filtered(out, x, y, w, h, buffer, len, max, active,
                 field, filter[f], in, font);
@@ -2109,6 +2109,7 @@ gui_config_default_properties(struct gui_config *config)
     config->properties[GUI_PROPERTY_ITEM_SPACING] = gui_vec2(4.0f, 4.0f);
     config->properties[GUI_PROPERTY_ITEM_PADDING] = gui_vec2(4.0f, 4.0f);
     config->properties[GUI_PROPERTY_SCALER_SIZE] = gui_vec2(16.0f, 16.0f);
+    config->properties[GUI_PROPERTY_NODE_SPACING] = gui_vec2(4.0f, 4.0f);
 }
 
 static void
@@ -2128,7 +2129,7 @@ gui_config_default_color(struct gui_config *config)
     config->colors[GUI_COLOR_TEXT] = gui_rgba(135, 135, 135, 255);
     config->colors[GUI_COLOR_PANEL] = gui_rgba(45, 45, 45, 255);
     config->colors[GUI_COLOR_HEADER] = gui_rgba(40, 40, 40, 255);
-    config->colors[GUI_COLOR_BORDER] = gui_rgba(100, 100, 100, 255);
+    config->colors[GUI_COLOR_BORDER] = gui_rgba(25, 25, 25, 255);
     config->colors[GUI_COLOR_BUTTON] = gui_rgba(50, 50, 50, 255);
     config->colors[GUI_COLOR_BUTTON_HOVER] = gui_rgba(35, 35, 35, 255);
     config->colors[GUI_COLOR_BUTTON_TOGGLE] = gui_rgba(35, 35, 35, 255);
@@ -2169,6 +2170,8 @@ gui_config_default_color(struct gui_config *config)
     config->colors[GUI_COLOR_SCROLLBAR_CURSOR] = gui_rgba(70, 70, 70, 255);
     config->colors[GUI_COLOR_SCROLLBAR_BORDER] = gui_rgba(45, 45, 45, 255);
     config->colors[GUI_COLOR_TABLE_LINES] = gui_rgba(100, 100, 100, 255);
+    config->colors[GUI_COLOR_TAB_HEADER] = gui_rgba(40, 40, 40, 255);
+    config->colors[GUI_COLOR_TAB_BORDER] = gui_rgba(25, 25, 25, 255);
     config->colors[GUI_COLOR_SHELF] = gui_rgba(45, 45, 45, 255);
     config->colors[GUI_COLOR_SHELF_TEXT] = gui_rgba(150, 150, 150, 255);
     config->colors[GUI_COLOR_SHELF_ACTIVE] = gui_rgba(30, 30, 30, 255);
@@ -2469,7 +2472,6 @@ gui_panel_begin(struct gui_panel_layout *layout, struct gui_panel *panel,
     if (!(panel->flags & GUI_PANEL_TAB)) {
         gui_float clicked_x = (in) ? in->mouse_clicked_pos.x : -1;
         gui_float clicked_y = (in) ? in->mouse_clicked_pos.y : -1;
-        panel->flags |= GUI_PANEL_SCROLLBAR;
         if (in && in->mouse_down) {
             if (GUI_INBOX(clicked_x, clicked_y, panel->x, panel->y, panel->w, panel->h))
                 panel->flags |= GUI_PANEL_ACTIVE;
@@ -2482,7 +2484,6 @@ gui_panel_begin(struct gui_panel_layout *layout, struct gui_panel *panel,
     /* calculate the panel footer bounds */
     layout->footer_h = scaler_size.y + item_padding.y;
     if ((layout->flags & GUI_PANEL_SCALEABLE) &&
-        (layout->flags & GUI_PANEL_SCROLLBAR) &&
         !(layout->flags & GUI_PANEL_MINIMIZED)) {
         gui_float footer_x, footer_y, footer_w;
         footer_x = panel->x;
@@ -2493,7 +2494,7 @@ gui_panel_begin(struct gui_panel_layout *layout, struct gui_panel *panel,
     }
 
     /* draw panel background if fixed panel size */
-    if (layout->flags & GUI_PANEL_SCROLLBAR) {
+    {
         const struct gui_color *color = &c->colors[GUI_COLOR_PANEL];
         layout->width = panel->w - scrollbar_width;
         layout->height = panel->h - (layout->header.h + 2 * item_spacing.y);
@@ -2513,12 +2514,12 @@ gui_panel_begin(struct gui_panel_layout *layout, struct gui_panel *panel,
     layout->clip.x = panel->x;
     layout->clip.y = panel->y;
     layout->clip.w = panel->w;
-    if (layout->flags & GUI_PANEL_SCROLLBAR) {
+    {
         if (layout->flags & GUI_PANEL_SCALEABLE)
             layout->clip.h = panel->h - (layout->footer_h + layout->header.h);
         else layout->clip.h = panel->h - layout->header.h;
         layout->clip.h -= (panel_padding.y + item_padding.y);
-    } else layout->clip.h = gui_null_rect.h;
+    }
     gui_command_buffer_push_scissor(out, layout->clip.x, layout->clip.y,
         layout->clip.w, layout->clip.h);
 }
@@ -2791,7 +2792,7 @@ gui_panel_end(struct gui_panel_layout *layout, struct gui_panel *panel)
     scrollbar_width = gui_config_property(config, GUI_PROPERTY_SCROLLBAR_WIDTH).x;
     scaler_size = gui_config_property(config, GUI_PROPERTY_SCALER_SIZE);
 
-    if (layout->flags & GUI_PANEL_SCROLLBAR && layout->valid) {
+    if (layout->valid) {
         struct gui_scroll scroll;
         gui_float panel_y;
         gui_float scroll_x, scroll_y;
@@ -2837,13 +2838,9 @@ gui_panel_end(struct gui_panel_layout *layout, struct gui_panel *panel)
 
     if (layout->flags & GUI_PANEL_BORDER) {
         /* draw the border around the complete panel */
-        const gui_float width = (layout->flags & GUI_PANEL_SCROLLBAR) ?
-                layout->width + scrollbar_width : layout->width;
+        const gui_float width = layout->width + scrollbar_width;
         const gui_float padding_y = (!layout->valid) ?
-                panel->y + layout->header.h:
-                (panel->flags & GUI_PANEL_SCROLLBAR) ?
-                layout->y + layout->h :
-                panel->y + layout->height + item_padding.y;
+                panel->y + layout->header.h: layout->y + layout->h;
 
         if (panel->flags & GUI_PANEL_BORDER_HEADER)
             gui_command_buffer_push_line(out, panel->x, panel->y + layout->header.h,
@@ -2904,7 +2901,7 @@ gui_panel_header_begin(struct gui_panel_layout *layout)
     layout->header.back = layout->header.x + layout->header.w;
 
     /* setup and draw panel layout footer and header background */
-    if (layout->flags & GUI_PANEL_SCROLLBAR) {
+    {
         const struct gui_color *color = &c->colors[GUI_COLOR_PANEL];
         layout->height = layout->h - (layout->header.h + 2 * item_spacing.y);
         if (layout->flags & GUI_PANEL_SCALEABLE) layout->height -= layout->footer_h;
@@ -3165,7 +3162,7 @@ gui_panel_header_end(struct gui_panel_layout *layout)
     item_padding = gui_config_property(c, GUI_PROPERTY_ITEM_PADDING);
 
     /* draw scrollbar panel footer */
-    if (layout->flags & GUI_PANEL_SCROLLBAR) {
+    {
         const struct gui_color *color = &c->colors[GUI_COLOR_PANEL];
         if (layout->valid)
             gui_command_buffer_push_rect(out, layout->x, layout->y + layout->header.h,
@@ -3175,8 +3172,7 @@ gui_panel_header_end(struct gui_panel_layout *layout)
     /* draw panel header border */
     if (layout->flags & GUI_PANEL_BORDER) {
         gui_float scrollbar_width = gui_config_property(c, GUI_PROPERTY_SCROLLBAR_WIDTH).x;
-        const gui_float width = (layout->flags & GUI_PANEL_SCROLLBAR) ?
-                layout->width + scrollbar_width : layout->width;
+        const gui_float width = layout->width + scrollbar_width;
 
         /* draw the header border lines */
         gui_command_buffer_push_line(out, layout->x, layout->y, layout->x,
@@ -3193,12 +3189,12 @@ gui_panel_header_end(struct gui_panel_layout *layout)
     layout->clip.x = layout->x;
     layout->clip.w = layout->w;
     layout->clip.y = layout->y + layout->header.h;
-    if (layout->flags & GUI_PANEL_SCROLLBAR) {
-        if (layout->flags & GUI_PANEL_SCALEABLE)
-            layout->clip.h = layout->h - (layout->footer_h + layout->header.h);
-        else layout->clip.h = layout->h - layout->header.h;
-        layout->clip.h -= (panel_padding.y + item_padding.y);
-    } else layout->clip.h = gui_null_rect.h;
+
+    if (layout->flags & GUI_PANEL_SCALEABLE)
+        layout->clip.h = layout->h - (layout->footer_h + layout->header.h);
+    else layout->clip.h = layout->h - layout->header.h;
+    layout->clip.h -= (panel_padding.y + item_padding.y);
+
     gui_command_buffer_push_scissor(out, layout->clip.x, layout->clip.y,
         layout->clip.w, layout->clip.h);
 }
@@ -3276,12 +3272,10 @@ gui_panel_menu_end(struct gui_panel_layout *layout)
     layout->height -= layout->menu.h;
     layout->offset = layout->menu.offset;
 
-    if (layout->flags & GUI_PANEL_SCROLLBAR) {
-        if (layout->flags & GUI_PANEL_SCALEABLE)
-            layout->clip.h = layout->h - (layout->footer_h + layout->header.h + layout->menu.h);
-        else layout->clip.h = layout->h - (layout->header.h + layout->menu.h);
-        layout->clip.h -= (panel_padding.y + item_padding.y);
-    } else layout->clip.h = gui_null_rect.h;
+    if (layout->flags & GUI_PANEL_SCALEABLE)
+        layout->clip.h = layout->h - (layout->footer_h + layout->header.h + layout->menu.h);
+    else layout->clip.h = layout->h - (layout->header.h + layout->menu.h);
+    layout->clip.h -= (panel_padding.y + item_padding.y);
     gui_command_buffer_push_scissor(out, layout->clip.x, layout->clip.y,
         layout->clip.w, layout->clip.h);
 }
@@ -3574,6 +3568,8 @@ gui_panel_layout_static_begin(struct gui_panel_layout *layout, gui_float height,
 
     gui_unify(&clip, &layout->clip, space.x, space.y, space.x + space.w, space.y + space.h);
     gui_command_buffer_push_scissor(layout->buffer, clip.x, clip.y, clip.w, clip.h);
+    layout->row.clip = layout->clip;
+    layout->clip = clip;
 }
 
 void
@@ -3598,6 +3594,7 @@ gui_panel_layout_static_end(struct gui_panel_layout *layout)
     layout->row.item_width = 0;
     layout->row.item_height = 0;
     layout->row.item_offset = 0;
+    layout->clip = layout->row.clip;
     gui_command_buffer_push_scissor(layout->buffer, layout->clip.x,
         layout->clip.y, layout->clip.w, layout->clip.h);
 }
@@ -3722,6 +3719,136 @@ gui_panel_alloc_space(struct gui_rect *bounds, struct gui_panel_layout *layout)
     layout->row.index++;
 }
 
+gui_bool
+gui_panel_layout_push(struct gui_panel_layout *layout,
+    enum gui_panel_layout_node_type type,
+    const char *title, enum gui_node_state *state)
+{
+    const struct gui_config *config;
+    struct gui_command_buffer *out;
+    struct gui_vec2 item_spacing;
+    struct gui_vec2 item_padding;
+    struct gui_vec2 panel_padding;
+    struct gui_vec2 node_spacing;
+    struct gui_rect header;
+    struct gui_rect sym;
+
+    GUI_ASSERT(layout);
+    GUI_ASSERT(layout->config);
+    GUI_ASSERT(layout->buffer);
+
+    if (!layout) return gui_false;
+    if (!layout->valid) return gui_false;
+
+    /* cache some data */
+    out = layout->buffer;
+    config = layout->config;
+
+    item_spacing = gui_config_property(config, GUI_PROPERTY_ITEM_SPACING);
+    item_padding = gui_config_property(config, GUI_PROPERTY_ITEM_PADDING);
+    panel_padding = gui_config_property(config, GUI_PROPERTY_PADDING);
+    node_spacing = gui_config_property(config, GUI_PROPERTY_NODE_SPACING);
+
+    /* calculate header bounds and draw background */
+    gui_panel_layout(layout, config->font.height + 4 * item_padding.y, 1);
+    gui_panel_alloc_space(&header, layout);
+    if (type == GUI_LAYOUT_TAB)
+        gui_command_buffer_push_rect(out, header.x, header.y, header.w, header.h,
+            0, config->colors[GUI_COLOR_TAB_HEADER]);
+
+    {
+        /* and draw closing/open icon */
+        enum gui_heading heading;
+        struct gui_vec2 points[3];
+        heading = (*state == GUI_MAXIMIZED) ? GUI_DOWN : GUI_RIGHT;
+
+        sym.w = sym.h = config->font.height;
+        sym.y = header.y + item_padding.y + config->font.height/2;
+        sym.x = header.x + panel_padding.x;
+
+        /* calculate the triangle point positions and draw triangle */
+        gui_triangle_from_direction(points, sym.x, sym.y, sym.w, sym.h, 0, 0, heading);
+        gui_command_buffer_push_triangle(layout->buffer,  points[0].x, points[0].y,
+            points[1].x, points[1].y, points[2].x, points[2].y, config->colors[GUI_COLOR_TEXT]);
+
+        /* calculate the space the icon occupied */
+        sym.w = config->font.height + 2 * item_padding.x;
+    }
+    {
+        /* draw node label */
+        struct gui_color color;
+        struct gui_rect label;
+        gui_size text_len;
+
+        header.w = MAX(header.w, sym.w + item_spacing.y + panel_padding.x);
+        label.x = sym.x + sym.w + item_spacing.x;
+        label.y = sym.y;
+        label.w = header.w - (sym.w + item_spacing.y + panel_padding.x);
+        label.h = config->font.height;
+        text_len = gui_strsiz(title);
+        color = (type == GUI_LAYOUT_TAB) ? config->colors[GUI_COLOR_TAB_HEADER]:
+            config->colors[GUI_COLOR_PANEL];
+
+        gui_command_buffer_push_text(out, label.x, label.y, label.w, label.h,
+            (const gui_char*)title, text_len, &config->font,
+            color, config->colors[GUI_COLOR_TEXT]);
+    }
+
+    /* update node state */
+    if (layout->input) {
+        gui_float clicked_x = layout->input->mouse_clicked_pos.x;
+        gui_float clicked_y = layout->input->mouse_clicked_pos.y;
+        gui_float mouse_x = layout->input->mouse_pos.x;
+        gui_float mouse_y = layout->input->mouse_pos.y;
+        if (GUI_INBOX(mouse_x, mouse_y, sym.x, sym.y, sym.w, sym.h)) {
+            if (GUI_INBOX(clicked_x, clicked_y, sym.x, sym.y, sym.w, sym.h)) {
+                if (layout->input->mouse_down && layout->input->mouse_clicked)
+                    *state = (*state == GUI_MAXIMIZED) ? GUI_MINIMIZED : GUI_MAXIMIZED;
+            }
+        }
+    }
+
+    if (type == GUI_LAYOUT_TAB) {
+        /* special node with border around the header */
+        gui_command_buffer_push_line(out, header.x, header.y,
+            header.x + header.w, header.y, config->colors[GUI_COLOR_TAB_BORDER]);
+        gui_command_buffer_push_line(out, header.x, header.y,
+            header.x, header.y + header.h, config->colors[GUI_COLOR_TAB_BORDER]);
+        gui_command_buffer_push_line(out, header.x + header.w, header.y,
+            header.x + header.w, header.y + header.h, config->colors[GUI_COLOR_TAB_BORDER]);
+        gui_command_buffer_push_line(out, header.x, header.y + header.h,
+            header.x + header.w, header.y + header.h, config->colors[GUI_COLOR_TAB_BORDER]);
+    }
+
+    if (*state == GUI_MAXIMIZED) {
+        layout->at_x = header.x + node_spacing.x;
+        layout->width = MAX(layout->width, 2 * panel_padding.x + node_spacing.x);
+        layout->width -= 2 * panel_padding.x + node_spacing.x;
+        return gui_true;
+    } else return gui_false;
+}
+
+void
+gui_panel_layout_pop(struct gui_panel_layout *layout)
+{
+    const struct gui_config *config;
+    struct gui_vec2 panel_padding;
+    struct gui_vec2 node_spacing;
+
+    GUI_ASSERT(layout);
+    GUI_ASSERT(layout->config);
+    GUI_ASSERT(layout->buffer);
+
+    if (!layout) return;
+    if (!layout->valid) return;
+
+    config = layout->config;
+    panel_padding = gui_config_property(config, GUI_PROPERTY_PADDING);
+    node_spacing = gui_config_property(config, GUI_PROPERTY_NODE_SPACING);
+    layout->at_x -= panel_padding.x + node_spacing.x;
+    layout->width += 2 * panel_padding.x + node_spacing.x;
+}
+
 /*
  * -------------------------------------------------------------
  *
@@ -4586,13 +4713,14 @@ gui_panel_graph_ex(struct gui_panel_layout *layout, enum gui_graph_type type,
 static void
 gui_panel_table_horizontal_line(struct gui_panel_layout *l, gui_size row_height)
 {
+    gui_float x, y, w;
     struct gui_command_buffer *out = l->buffer;
     const struct gui_config *c = l->config;
     const struct gui_vec2 item_padding = gui_config_property(c, GUI_PROPERTY_ITEM_PADDING);
     const struct gui_vec2 item_spacing = gui_config_property(c, GUI_PROPERTY_ITEM_SPACING);
+    if (!l->valid) return;
 
     /* draws a horizontal line under the current item */
-    gui_float x, y, w;
     w = MAX(l->width, (2 * item_spacing.x + 2 * item_padding.x));
     y = (l->at_y + (gui_float)row_height + item_padding.y) - l->offset;
     x = l->at_x + item_spacing.x + item_padding.x;
@@ -4610,6 +4738,7 @@ gui_panel_table_vertical_line(struct gui_panel_layout *layout, gui_size cols)
     GUI_ASSERT(layout);
     GUI_ASSERT(cols);
     if (!layout || !cols) return;
+    if (!layout->valid) return;
 
     out = layout->buffer;
     config = layout->config;
@@ -4650,6 +4779,7 @@ gui_panel_table_row(struct gui_panel_layout *layout)
     struct gui_vec2 item_spacing;
     GUI_ASSERT(layout);
     if (!layout) return;
+    if (!layout->valid) return;
 
     config = layout->config;
     item_spacing = gui_config_property(config, GUI_PROPERTY_ITEM_SPACING);
@@ -4667,6 +4797,190 @@ gui_panel_table_end(struct gui_panel_layout *layout)
     layout->is_table = gui_false;
 }
 
+/*
+ * -------------------------------------------------------------
+ *
+ *                          TREE
+ *
+ * --------------------------------------------------------------
+ */
+void
+gui_panel_tree_begin(struct gui_panel_layout *p, struct gui_tree *tree,
+                        const char *title, gui_float height, gui_float offset)
+{
+    struct gui_vec2 padding;
+    const struct gui_config *config;
+    gui_panel_group_begin(p, &tree->group, title, offset);
+    gui_panel_layout(&tree->group, height, 1);
+
+    config = tree->group.config;
+    padding = gui_config_property(config, GUI_PROPERTY_ITEM_PADDING);
+
+    tree->at_x = 0;
+    tree->skip = -1;
+    tree->depth = 0;
+    tree->x_off = tree->group.config->font.height + 2 * padding.x;
+}
+
+static enum gui_tree_node_operation
+gui_panel_tree_node(struct gui_tree *tree, enum gui_tree_node_symbol symbol,
+    const char *title, struct gui_image *img, gui_tree_node_state *state)
+{
+    struct gui_text text;
+    struct gui_rect bounds = {0,0,0,0};
+    struct gui_rect sym, label, icon;
+
+    const struct gui_input *i;
+    const struct gui_config *config;
+    struct gui_vec2 item_padding;
+    struct gui_color col;
+
+    enum gui_tree_node_operation op = GUI_NODE_NOP;
+    struct gui_panel_layout *layout = &tree->group;
+    if (tree->skip >= 0 || !gui_panel_widget(&bounds, layout)) {
+        if (!tree->depth) tree->at_x = bounds.x;
+        return op;
+    }
+
+    if (tree->depth){
+        bounds.w = (bounds.x + bounds.w) - tree->at_x;
+        bounds.x = tree->at_x;
+    } else tree->at_x = bounds.x;
+
+    /* fetch some configuration constants */
+    i = layout->input;
+    config = layout->config;
+    item_padding = gui_config_property(config, GUI_PROPERTY_ITEM_PADDING);
+    col = gui_config_color(config, GUI_COLOR_TEXT);
+
+    /* calculate symbol bounds */
+    sym.x = bounds.x;
+    sym.y = bounds.y + (bounds.h/2) - (config->font.height/2);
+    sym.w = config->font.height;
+    sym.h = config->font.height;
+
+    if (img) {
+        icon.x = sym.x + sym.w + item_padding.x;
+        icon.y = sym.y;
+        icon.w = bounds.h;
+        icon.h = bounds.h;
+        label.x = icon.x + icon.w + item_padding.x;
+    } else label.x = sym.x + sym.w + item_padding.x;
+
+    /* calculate text bounds */
+    label.y = bounds.y;
+    label.h = bounds.h;
+    label.w = bounds.w - (sym.w + 2 * item_padding.x);
+
+    /* output symbol */
+    if (symbol == GUI_TREE_NODE_TRIANGLE) {
+        /* parent node */
+        struct gui_vec2 points[3];
+        enum gui_heading heading;
+        if (gui_input_clicked(i, &sym)) {
+            if (*state & GUI_NODE_ACTIVE)
+                *state &= ~(gui_flags)GUI_NODE_ACTIVE;
+            else *state |= GUI_NODE_ACTIVE;
+        }
+
+        heading = (*state & GUI_NODE_ACTIVE) ? GUI_DOWN : GUI_RIGHT;
+        gui_triangle_from_direction(points, sym.x, sym.y, sym.w, sym.h, 0, 0, heading);
+        gui_command_buffer_push_triangle(layout->buffer,  points[0].x, points[0].y,
+            points[1].x, points[1].y, points[2].x, points[2].y, col);
+    } else {
+        /* leaf node */
+        gui_command_buffer_push_circle(layout->buffer, sym.x, sym.y, sym.w, sym.h, col);
+    }
+
+    /* node selection */
+    if (gui_input_clicked(i, &label)) {
+        if (*state & GUI_NODE_SELECTED)
+            *state &= ~(gui_flags)GUI_NODE_SELECTED;
+        else *state |= GUI_NODE_SELECTED;
+    }
+
+    {
+        /* tree node opderations */
+        if (gui_input_pressed(i, GUI_KEY_DEL) && (*state & GUI_NODE_SELECTED)) {
+            *state &= ~(gui_flags)GUI_NODE_SELECTED;
+            op = GUI_NODE_DELETE;
+        }
+        if (gui_input_pressed(i, GUI_KEY_COPY) && (*state & GUI_NODE_SELECTED)) {
+            *state &= ~(gui_flags)GUI_NODE_SELECTED;
+            op = GUI_NODE_CLONE;
+        }
+        if (gui_input_pressed(i, GUI_KEY_CUT) && (*state & GUI_NODE_SELECTED)) {
+            *state &= ~(gui_flags)GUI_NODE_SELECTED;
+            op = GUI_NODE_CUT;
+        }
+        if (gui_input_pressed(i, GUI_KEY_PASTE) && (*state & GUI_NODE_SELECTED)) {
+            *state &= ~(gui_flags)GUI_NODE_SELECTED;
+            op = GUI_NODE_PASTE;
+        }
+    }
+
+    /* output label */
+    text.padding.x = item_padding.x;
+    text.padding.y = item_padding.y;
+    text.foreground = config->colors[GUI_COLOR_TEXT];
+    text.background = (*state & GUI_NODE_SELECTED) ?
+        config->colors[GUI_COLOR_BUTTON_HOVER]:
+        config->colors[GUI_COLOR_PANEL];
+    gui_text(layout->buffer,label.x,label.y,label.w,label.h, title, gui_strsiz(title),
+        &text, GUI_TEXT_LEFT, &config->font);
+    return op;
+}
+
+enum gui_tree_node_operation
+gui_panel_tree_begin_node(struct gui_tree *tree, const char *title,
+    gui_tree_node_state *state)
+{
+    enum gui_tree_node_operation op;
+    op = gui_panel_tree_node(tree, GUI_TREE_NODE_TRIANGLE, title, 0, state);
+    tree->at_x += tree->x_off;
+    if (tree->skip < 0 && !(*state & GUI_NODE_ACTIVE))
+        tree->skip = tree->depth;
+    tree->depth++;
+    return op;
+}
+
+enum gui_tree_node_operation
+gui_panel_tree_begin_node_icon(struct gui_tree *tree, const char *title,
+    struct gui_image img, gui_tree_node_state *state)
+{
+    enum gui_tree_node_operation op;
+    op = gui_panel_tree_node(tree, GUI_TREE_NODE_TRIANGLE, title, &img, state);
+    tree->at_x += tree->x_off;
+    if (tree->skip < 0 && !(*state & GUI_NODE_ACTIVE))
+        tree->skip = tree->depth;
+    tree->depth++;
+    return op;
+}
+
+enum gui_tree_node_operation
+gui_panel_tree_leaf(struct gui_tree *tree, const char *title,
+    gui_tree_node_state *state)
+{return gui_panel_tree_node(tree, GUI_TREE_NODE_BULLET, title, 0, state);}
+
+enum gui_tree_node_operation
+gui_panel_tree_leaf_icon(struct gui_tree *tree, const char *title, struct gui_image img,
+    gui_tree_node_state *state)
+{return gui_panel_tree_node(tree, GUI_TREE_NODE_BULLET, title, &img, state);}
+
+void
+gui_panel_tree_end_node(struct gui_tree *tree)
+{
+    GUI_ASSERT(tree->depth);
+    tree->depth--;
+    tree->at_x -= tree->x_off;
+    if (tree->skip == tree->depth)
+        tree->skip = -1;
+}
+
+gui_float
+gui_panel_tree_end(struct gui_panel_layout *p, struct gui_tree* tree)
+{return gui_panel_group_end(p, &tree->group);}
+
 /*
  * -------------------------------------------------------------
  *
@@ -4674,88 +4988,6 @@ gui_panel_table_end(struct gui_panel_layout *layout)
  *
  * --------------------------------------------------------------
  */
-gui_bool
-gui_panel_tab_begin(struct gui_panel_layout *parent, struct gui_panel_layout *tab,
-    const char *title, gui_bool border, gui_bool minimized)
-{
-    struct gui_rect bounds;
-    struct gui_command_buffer *out;
-    struct gui_panel panel;
-    struct gui_rect clip;
-    gui_flags flags = 0;
-
-    GUI_ASSERT(parent);
-    GUI_ASSERT(tab);
-    if (!parent || !tab) return gui_true;
-    out = parent->buffer;
-    gui_zero(tab, sizeof(*tab));
-    tab->valid = !minimized;
-
-    if (!parent->valid) {
-        tab->valid = gui_false;
-        tab->config = parent->config;
-        tab->buffer = parent->buffer;
-        tab->input = parent->input;
-        return minimized;
-    }
-
-    /* NOTE: tabs need to allocate a complete row since the size of the tab is
-     * not known beforehand.  */
-    parent->row.index = 0;
-    gui_panel_layout_flux_fixed(parent, 0, 1);
-    gui_panel_alloc_space(&bounds, parent);
-
-    /* create a fake panel to create a panel layout from */
-    flags = GUI_PANEL_TAB;
-    if (border) flags |= GUI_PANEL_BORDER|GUI_PANEL_BORDER_HEADER;
-    if (minimized) flags |= GUI_PANEL_MINIMIZED;
-    gui_panel_init(&panel, bounds.x, bounds.y, bounds.w,
-        gui_null_rect.h,flags,out,parent->config);
-
-    gui_panel_begin(tab, &panel, parent->input);
-    gui_unify(&clip, &parent->clip, tab->clip.x, tab->clip.y, tab->clip.x + tab->clip.w,
-        tab->clip.y + tab->clip.h);
-    gui_command_buffer_push_scissor(out, clip.x, clip.y, clip.w, clip.h);
-    gui_panel_header(tab, title, GUI_MINIMIZABLE, 0, GUI_HEADER_LEFT);
-
-    /* calculate the tab clipping rect */
-    gui_unify(&clip, &parent->clip, tab->clip.x, tab->clip.y, tab->clip.x + tab->clip.w,
-        tab->clip.y + tab->clip.h);
-    gui_command_buffer_push_scissor(out, clip.x, clip.y, clip.w, clip.h);
-    tab->clip = clip;
-    return (tab->flags & GUI_PANEL_MINIMIZED) ? gui_true : gui_false;
-}
-
-void
-gui_panel_tab_end(struct gui_panel_layout *p, struct gui_panel_layout *t)
-{
-    struct gui_panel panel;
-    struct gui_command_buffer *out;
-    struct gui_vec2 item_spacing;
-    struct gui_vec2 panel_padding;
-    GUI_ASSERT(t);
-    GUI_ASSERT(p);
-    if (!p || !t || !p->valid)
-        return;
-
-    /* setup fake panel to end the tab */
-    panel.x = t->at_x;
-    panel.y = t->y;
-    panel.w = t->width;
-    panel.h = t->height;
-    panel.flags = t->flags|GUI_PANEL_BORDER|GUI_PANEL_BORDER_HEADER;
-    gui_panel_end(t, &panel);
-
-    /*calculate the from the tab occupied space and allocate it in the parent panel */
-    item_spacing = gui_config_property(p->config, GUI_PROPERTY_ITEM_SPACING);
-    panel_padding = gui_config_property(p->config, GUI_PROPERTY_PADDING);
-    if (t->valid)
-        p->at_y += t->height + 2 * item_spacing.y;
-    else p->at_y += t->height - panel_padding.x + 2 * item_spacing.y;
-    out = p->buffer;
-    gui_command_buffer_push_scissor(out, p->clip.x, p->clip.y, p->clip.w, p->clip.h);
-}
-
 void
 gui_panel_group_begin(struct gui_panel_layout *p, struct gui_panel_layout *g,
     const char *title, gui_float offset)
@@ -4782,7 +5014,7 @@ gui_panel_group_begin(struct gui_panel_layout *p, struct gui_panel_layout *g,
 
     /* initialize a fake panel to create the layout from */
     out = p->buffer;
-    flags = GUI_PANEL_BORDER|GUI_PANEL_SCROLLBAR|GUI_PANEL_TAB;
+    flags = GUI_PANEL_BORDER|GUI_PANEL_TAB;
     gui_panel_init(&panel, bounds.x, bounds.y,bounds.w,bounds.h,flags, out, p->config);
     gui_panel_begin(g, &panel, p->input);
     g->offset = offset;
@@ -4827,7 +5059,7 @@ gui_panel_group_end(struct gui_panel_layout *p, struct gui_panel_layout *g)
     pan.y = g->y;
     pan.w = g->width;
     pan.h = g->height;
-    pan.flags = GUI_PANEL_BORDER|GUI_PANEL_TAB|GUI_PANEL_SCROLLBAR;
+    pan.flags = GUI_PANEL_BORDER|GUI_PANEL_TAB;
 
     /* setup clipping rect to finalize group panel drawing*/
     gui_unify(&clip, &p->clip, g->clip.x, g->clip.y, g->x + g->w, g->y + g->h);
@@ -4939,7 +5171,7 @@ gui_panel_shelf_begin(struct gui_panel_layout *parent, struct gui_panel_layout *
     bounds.h -= header_h;
 
     /* setup fake panel to create a panel layout from */
-    flags = GUI_PANEL_BORDER|GUI_PANEL_SCROLLBAR|GUI_PANEL_TAB;
+    flags = GUI_PANEL_BORDER|GUI_PANEL_TAB;
     gui_panel_init(&panel, bounds.x, bounds.y, bounds.w, bounds.h, flags, out, config);
     gui_panel_begin(shelf, &panel, parent->input);
     shelf->offset = offset;
@@ -4975,7 +5207,7 @@ gui_panel_shelf_end(struct gui_panel_layout *p, struct gui_panel_layout *s)
 
     out = p->buffer;
     pan.x = s->at_x; pan.y = s->y;
-    pan.flags = GUI_PANEL_BORDER|GUI_PANEL_TAB|GUI_PANEL_SCROLLBAR;
+    pan.flags = GUI_PANEL_BORDER|GUI_PANEL_TAB;
 
     gui_unify(&clip, &p->clip, s->clip.x, s->clip.y, s->x + s->w, s->y + s->h);
     gui_command_buffer_push_scissor(out, clip.x, clip.y, clip.w, clip.h);
diff --git a/gui.h b/gui.h
index fda12fa..e307b63 100644
--- a/gui.h
+++ b/gui.h
@@ -25,8 +25,6 @@ extern "C" {
 #endif
 
 /* Constants */
-#define GUI_BORDER gui_true
-#define GUI_NO_BORDER gui_false
 #define GUI_UTF_INVALID 0xFFFD
 #define GUI_UTF_SIZE 4
 /* describes the number of bytes a glyph consists of*/
@@ -702,21 +700,27 @@ struct gui_clipboard {
 typedef struct gui_buffer gui_edit_buffer;
 struct gui_edit_box {
     gui_edit_buffer buffer;
+    /* glyph buffer to add text into */
     gui_bool active;
+    /* flag indicating if the buffer is currently being modified  */
     gui_size cursor;
+    /* current glyph (not byte) cursor position */
     gui_size glyphes;
+    /* number of glyphes inside the edit box */
     struct gui_clipboard clip;
+    /* copy paste callbacks */
     gui_filter filter;
+    /* input filter callback */
 };
 
 /* filter function */
-gui_bool gui_filter_input_default(gui_long unicode);
-gui_bool gui_filter_input_ascii(gui_long unicode);
-gui_bool gui_filter_input_float(gui_long unicode);
-gui_bool gui_filter_input_decimal(gui_long unicode);
-gui_bool gui_filter_input_hex(gui_long unicode);
-gui_bool gui_filter_input_oct(gui_long unicode);
-gui_bool gui_filter_input_binary(gui_long unicode);
+gui_bool gui_filter_default(gui_long unicode);
+gui_bool gui_filter_ascii(gui_long unicode);
+gui_bool gui_filter_float(gui_long unicode);
+gui_bool gui_filter_decimal(gui_long unicode);
+gui_bool gui_filter_hex(gui_long unicode);
+gui_bool gui_filter_oct(gui_long unicode);
+gui_bool gui_filter_binary(gui_long unicode);
 
 /* editbox */
 void gui_edit_box_init(struct gui_edit_box*, struct gui_allocator*, gui_size initial,
@@ -1377,6 +1381,8 @@ enum gui_config_colors {
     GUI_COLOR_SCROLLBAR_CURSOR,
     GUI_COLOR_SCROLLBAR_BORDER,
     GUI_COLOR_TABLE_LINES,
+    GUI_COLOR_TAB_HEADER,
+    GUI_COLOR_TAB_BORDER,
     GUI_COLOR_SHELF,
     GUI_COLOR_SHELF_TEXT,
     GUI_COLOR_SHELF_ACTIVE,
@@ -1403,6 +1409,7 @@ enum gui_config_properties {
     GUI_PROPERTY_SCALER_SIZE,
     GUI_PROPERTY_SCROLLBAR_WIDTH,
     GUI_PROPERTY_SIZE,
+    GUI_PROPERTY_NODE_SPACING,
     GUI_PROPERTY_MAX
 };
 
@@ -1584,86 +1591,6 @@ enum gui_widget_state {
     GUI_ROM /* The widget is partially visible and cannot be updated */
 };
 
-enum gui_table_lines {
-    GUI_TABLE_HHEADER = 0x01,
-    /* Horizontal table header lines */
-    GUI_TABLE_VHEADER = 0x02,
-    /* Vertical table header lines */
-    GUI_TABLE_HBODY = 0x04,
-    /* Horizontal table body lines */
-    GUI_TABLE_VBODY = 0x08
-    /* Vertical table body lines */
-};
-
-enum gui_graph_type {
-    GUI_GRAPH_LINES,
-    /* Line graph with each data point being connected with its previous and next node */
-    GUI_GRAPH_COLUMN,
-    /* Column graph/Histogram with value represented as bars */
-    GUI_GRAPH_MAX
-};
-
-struct gui_graph {
-    gui_bool valid;
-    /* graph valid flag to make sure that the graph is visible */
-    enum gui_graph_type type;
-    /* graph type with either line or column graph */
-    gui_float x, y;
-    /* graph canvas space position */
-    gui_float w, h;
-    /* graph canvas space size */
-    gui_float min, max;
-    /* min and max value for correct scaling of values */
-    struct gui_vec2 last;
-    /* last line graph point to connect to. Only used by the line graph */
-    gui_size index;
-    /* current graph value index*/
-    gui_size count;
-    /* number of values inside the graph */
-};
-
-enum gui_panel_tab {
-    GUI_MAXIMIZED = gui_false,
-    /* Flag indicating that the panel tab is open */
-    GUI_MINIMIZED = gui_true
-    /* Flag indicating that the panel tab is closed */
-};
-
-enum gui_panel_header_flags {
-    GUI_CLOSEABLE = 0x01,
-    /* adds a closeable icon into the header */
-    GUI_MINIMIZABLE = 0x02,
-    /* adds a minimize icon into the header */
-    GUI_SCALEABLE = 0x04,
-    /* adds a scaleable flag icon into the header */
-    GUI_MOVEABLE = 0x08
-    /* adds a moveable flag icon into the header */
-};
-
-enum gui_panel_header_symbol {
-    GUI_SYMBOL_X,
-    GUI_SYMBOL_UNDERSCORE,
-    GUI_SYMBOL_CIRCLE,
-    GUI_SYMBOL_CIRCLE_FILLED,
-    GUI_SYMBOL_RECT,
-    GUI_SYMBOL_RECT_FILLED,
-    GUI_SYMBOL_TRIANGLE_UP,
-    GUI_SYMBOL_TRIANGLE_DOWN,
-    GUI_SYMBOL_TRIANGLE_LEFT,
-    GUI_SYMBOL_TRIANGLE_RIGHT,
-    GUI_SYMBOL_PLUS,
-    GUI_SYMBOL_MINUS,
-    GUI_SYMBOL_IMAGE,
-    GUI_SYMBOL_MAX
-};
-
-enum gui_panel_header_align {
-    GUI_HEADER_LEFT,
-    /* header elements are added at the left side of the header */
-    GUI_HEADER_RIGHT
-    /* header elements are added at the right side of the header */
-};
-
 enum gui_panel_flags {
     GUI_PANEL_HIDDEN = 0x01,
     /* Hiddes the panel and stops any panel interaction and drawing can be set
@@ -1683,9 +1610,6 @@ enum gui_panel_flags {
     /* marks the panel as minimized */
     GUI_PANEL_ACTIVE = 0x40,
     /* INTERNAL ONLY!: marks the panel as active, used by the panel stack */
-    GUI_PANEL_SCROLLBAR = 0x80,
-    /* INTERNAL ONLY!: adds a scrollbar to the panel which enables fixed size
-     * panels with unlimited amount of space to fill */
     GUI_PANEL_TAB = 0x100,
     /* INTERNAL ONLY!: Marks the panel as an subpanel of another panel(Groups/Tabs/Shelf)*/
     GUI_PANEL_DO_NOT_RESET = 0x200
@@ -1730,6 +1654,16 @@ enum gui_panel_row_layout_type {
     /* retain mode widget specific widget pixel width layout */
 };
 
+enum gui_node_state {
+    GUI_MINIMIZED = gui_false,
+    GUI_MAXIMIZED = gui_true
+};
+
+enum gui_panel_layout_node_type {
+    GUI_LAYOUT_NODE,
+    GUI_LAYOUT_TAB
+};
+
 #define GUI_UNDEFINED (-1.0f)
 struct gui_panel_row_layout {
     enum gui_panel_row_layout_type type;
@@ -1750,19 +1684,22 @@ struct gui_panel_row_layout {
     /* total fill ratio */
     struct gui_rect item;
     /* item bounds */
+    struct gui_rect clip;
+    /* temporary clipping rect */
 };
 
 struct gui_panel_header {
     gui_float x, y, w, h;
     /* header bounds */
     gui_float front, back;
-    /* header filling stack */
+    /* visual header filling deque */
 };
 
 struct gui_panel_menu {
     gui_float x, y, w, h;
     /* menu bounds */
     gui_float offset;
+    /* saved panel scrollbar offset */
 };
 
 struct gui_panel_layout {
@@ -1942,6 +1879,41 @@ void gui_panel_end(struct gui_panel_layout*, struct gui_panel*);
     gui_panel_menu_begin            -- marks the beginning of the menubar building process
     gui_panel_menu_end              -- marks the end the menubar build up process
 */
+enum gui_panel_header_flags {
+    GUI_CLOSEABLE = 0x01,
+    /* adds a closeable icon into the header */
+    GUI_MINIMIZABLE = 0x02,
+    /* adds a minimize icon into the header */
+    GUI_SCALEABLE = 0x04,
+    /* adds a scaleable flag icon into the header */
+    GUI_MOVEABLE = 0x08
+    /* adds a moveable flag icon into the header */
+};
+
+enum gui_panel_header_symbol {
+    GUI_SYMBOL_X,
+    GUI_SYMBOL_UNDERSCORE,
+    GUI_SYMBOL_CIRCLE,
+    GUI_SYMBOL_CIRCLE_FILLED,
+    GUI_SYMBOL_RECT,
+    GUI_SYMBOL_RECT_FILLED,
+    GUI_SYMBOL_TRIANGLE_UP,
+    GUI_SYMBOL_TRIANGLE_DOWN,
+    GUI_SYMBOL_TRIANGLE_LEFT,
+    GUI_SYMBOL_TRIANGLE_RIGHT,
+    GUI_SYMBOL_PLUS,
+    GUI_SYMBOL_MINUS,
+    GUI_SYMBOL_IMAGE,
+    GUI_SYMBOL_MAX
+};
+
+enum gui_panel_header_align {
+    GUI_HEADER_LEFT,
+    /* header elements are added at the left side of the header */
+    GUI_HEADER_RIGHT
+    /* header elements are added at the right side of the header */
+};
+
 void gui_panel_header_begin(struct gui_panel_layout*);
 /*  this function begins the panel header build up process */
 gui_bool gui_panel_header_button(struct gui_panel_layout *layout,
@@ -2061,7 +2033,27 @@ void gui_panel_menu_end(struct gui_panel_layout*);
     gui_panel_layout_static_begin       -- creates a free drawing space in the panel
     gui_panel_layout_static_widget      -- pushes a widget into the space
     gui_panel_layout_static_end         -- finishes the free drawingp process
+
+    panel tree layout function API
+    gui_panel_layout_push               -- pushes a new node/collapseable header/tab
+    gui_panel_layout_pop                -- pops the the previously added node
+
 */
+gui_bool gui_panel_layout_push(struct gui_panel_layout*,
+                                enum gui_panel_layout_node_type,
+                                const char *title, enum gui_node_state*);
+/*  this functions pushes either a tree node, collapseable header or tab into
+ *  the current panel layout
+    Input:
+    - title of the node to push into the panel
+    - type of then node with either default node, collapseable header or tab
+    - state of the node with either GUI_MINIMIZED or GUI_MAXIMIZED
+    Output:
+    - returns the updated state as either gui_true if open and gui_false otherwise
+    - updates the state of the node pointer to the updated state
+*/
+void gui_panel_layout_pop(struct gui_panel_layout*);
+/*  this functions ends the previously added node */
 void gui_panel_layout_flux_fixed(struct gui_panel_layout*, gui_float row_height, gui_size cols);
 /*  this function sets the current row layout to a scaleable table like layout where each
     widget occupies a fixed ratio of the panel width
@@ -2442,8 +2434,84 @@ gui_size gui_panel_selector(struct gui_panel_layout*, const char *items[],
     gui_panel_table_begin           -- begin table build up process
     gui_panel_table_row             -- seperates tables rows
     gui_panel_table_end             -- ends the table build up process
-
+    gui_panel_tree_begin            -- begins the tree build up processs
+    gui_panel_tree_begin_node       -- adds and opens a normal node to the tree
+    gui_panel_tree_begin_node_icon  -- adds a opens a node with an icon to the tree
+    gui_panel_tree_end_node         -- ends and closes a previously added node
+    gui_panel_tree_leaf             -- adds a leaf node to a prev opened node
+    gui_panel_tree_leaf_icon        -- adds a leaf icon node to a prev opended node
+    gui_panel_tree_end              -- ends the tree build up process
 */
+enum gui_table_lines {
+    GUI_TABLE_HHEADER = 0x01,
+    /* Horizontal table header lines */
+    GUI_TABLE_VHEADER = 0x02,
+    /* Vertical table header lines */
+    GUI_TABLE_HBODY = 0x04,
+    /* Horizontal table body lines */
+    GUI_TABLE_VBODY = 0x08
+    /* Vertical table body lines */
+};
+
+enum gui_graph_type {
+    GUI_GRAPH_LINES,
+    /* Line graph with each data point being connected with its previous and next node */
+    GUI_GRAPH_COLUMN,
+    /* Column graph/Histogram with value represented as bars */
+    GUI_GRAPH_MAX
+};
+
+struct gui_graph {
+    gui_bool valid;
+    /* graph valid flag to make sure that the graph is visible */
+    enum gui_graph_type type;
+    /* graph type with either line or column graph */
+    gui_float x, y;
+    /* graph canvas space position */
+    gui_float w, h;
+    /* graph canvas space size */
+    gui_float min, max;
+    /* min and max value for correct scaling of values */
+    struct gui_vec2 last;
+    /* last line graph point to connect to. Only used by the line graph */
+    gui_size index;
+    /* current graph value index*/
+    gui_size count;
+    /* number of values inside the graph */
+};
+
+typedef gui_flags gui_tree_node_state;
+enum gui_tree_nodes_states {
+    GUI_NODE_ACTIVE = 0x01,
+    /* the node is currently opened */
+    GUI_NODE_SELECTED = 0x02
+    /* the node has been seleted by the user */
+};
+
+enum gui_tree_node_operation {
+    GUI_NODE_NOP,
+    /* node did not receive a command */
+    GUI_NODE_CUT,
+    /* cut the node from the current tree and add into a buffer */
+    GUI_NODE_CLONE,
+    /* copy current node and add copy into the parent node */
+    GUI_NODE_PASTE,
+    /* paste all node in the buffer into the tree */
+    GUI_NODE_DELETE
+    /* remove the node from the parent tree */
+};
+
+struct gui_tree {
+    struct gui_panel_layout group;
+    /* panel to add the tree into  */
+    gui_float x_off, at_x;
+    /* current x position of the next node */
+    gui_int skip;
+    /* flag that indicates that a node will be skipped */
+    gui_int depth;
+    /* current depth of the tree */
+};
+
 void gui_panel_graph_begin(struct gui_panel_layout*, struct gui_graph*,
                             enum gui_graph_type, gui_size count,
                             gui_float min, gui_float max);
@@ -2499,6 +2567,60 @@ void gui_panel_table_end(struct gui_panel_layout*);
 /*  this function finished the table build up process and reverts the panel back
     to its normal state.
 */
+void gui_panel_tree_begin(struct gui_panel_layout*, struct gui_tree*,
+                            const char*, gui_float row_height, gui_float offset);
+/*  this function begins the tree building process
+    Input:
+    - title describing the tree or NULL
+    - height of every node inside the panel
+    - scrollbar offset
+    Output:
+    - tree build up state structure
+*/
+enum gui_tree_node_operation gui_panel_tree_begin_node(struct gui_tree*, const char*,
+                                                    gui_tree_node_state*);
+/*  this function begins a parent node
+    Input:
+    - title of the node
+    - current node state
+    Output:
+    - operation identifier what should be done with this node
+*/
+enum gui_tree_node_operation gui_panel_tree_begin_node_icon(struct gui_tree*,
+                                                    const char*, struct gui_image,
+                                                    gui_tree_node_state*);
+/*  this function begins a text icon parent node
+    Input:
+    - title of the node
+    - icon of the node
+    - current node state
+    Output:
+    - operation identifier what should be done with this node
+*/
+void gui_panel_tree_end_node(struct gui_tree*);
+/*  this function ends a parent node */
+enum gui_tree_node_operation gui_panel_tree_leaf(struct gui_tree*, const char*,
+                                                    gui_tree_node_state*);
+/*  this function pushes a leaf node to the tree
+    Input:
+    - title of the node
+    - current leaf node state
+    Output:
+    - operation identifier what should be done with this node
+*/
+enum gui_tree_node_operation gui_panel_tree_leaf_icon(struct gui_tree*,
+                                                    const char*, struct gui_image,
+                                                    gui_tree_node_state*);
+/*  this function pushes a leaf icon node to the tree
+    Input:
+    - title of the node
+    - icon of the node
+    - current leaf node state
+    Output:
+    - operation identifier what should be done with this node
+*/
+gui_float gui_panel_tree_end(struct gui_panel_layout*, struct gui_tree*);
+/*  this function ends a the tree building process */
 /*
  * -------------------------------------------------------------
  *                          GROUP
@@ -2509,20 +2631,6 @@ void gui_panel_table_end(struct gui_panel_layout*);
     gui_panel_shelf_begin           -- begins a shelf with a number of selectable tabs
     gui_panel_shelf_end             -- ends a previously started shelf build up process
 */
-gui_bool gui_panel_tab_begin(struct gui_panel_layout*, struct gui_panel_layout *tab,
-                            const char*, gui_bool border, gui_bool minimized);
-/*  this function adds a tab subpanel into the parent panel
-    Input:
-    - tab title to write into the header
-    - state of the tab with either collapsed(GUI_MINIMIZED) or open state
-    Output:
-    - tab layout to fill with widgets
-    - wether the tab is currently collapsed(gui_true) or open(gui_false)
-*/
-void gui_panel_tab_end(struct gui_panel_layout*, struct gui_panel_layout *tab);
-/*  this function finishes the previously started tab and allocated the needed
-    tab space in the parent panel
-*/
 void gui_panel_group_begin(struct gui_panel_layout*, struct gui_panel_layout *tab,
                             const char *title, gui_float offset);
 /*  this function adds a grouped subpanel into the parent panel