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MultiSelect: Demo: Assets Browser: track scrolling target so we can roughly land on hovered item.

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It's impossible to do this perfectly without some form of locking on item because as the hovered item X position changes it's easy to drift.
This commit is contained in:
ocornut 2023-12-12 17:26:02 +01:00
parent 750e23998f
commit 7546a2d345
1 changed files with 76 additions and 38 deletions
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96
imgui_demo.cpp
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@ -9634,6 +9634,15 @@ struct ExampleAssetsBrowser
bool RequestSort = false; // Deferred sort request
float ZoomWheelAccum = 0.0f; // Mouse wheel accumulator to handle smooth wheels better
// Calculated sizes for layout, output of UpdateLayoutSizes(). Could be locals but our code is simpler this way.
ImVec2 LayoutItemSize;
ImVec2 LayoutItemStep; // == LayoutItemSize + LayoutItemSpacing
float LayoutItemSpacing = 0.0f;
float LayoutSelectableSpacing = 0.0f;
float LayoutOuterPadding = 0.0f;
int LayoutColumnCount = 0;
int LayoutLineCount = 0;
// Functions
ExampleAssetsBrowser()
{
@ -9654,6 +9663,29 @@ struct ExampleAssetsBrowser
Selection.Clear();
}
// Logic would be written in the main code BeginChild() and outputing to local variables.
// We extracted it into a function so we can call it easily from multiple places.
void UpdateLayoutSizes(float avail_width)
{
// Layout: when not stretching: allow extending into right-most spacing.
LayoutItemSpacing = (float)IconSpacing;
if (StretchSpacing == false)
avail_width += floorf(LayoutItemSpacing * 0.5f);
// Layout: calculate number of icon per line and number of lines
LayoutItemSize = ImVec2(floorf(IconSize), floorf(IconSize));
LayoutColumnCount = IM_MAX((int)(avail_width / (LayoutItemSize.x + LayoutItemSpacing)), 1);
LayoutLineCount = (Items.Size + LayoutColumnCount - 1) / LayoutColumnCount;
// Layout: when stretching: allocate remaining space to more spacing. Round before division, so item_spacing may be non-integer.
if (StretchSpacing && LayoutColumnCount > 1)
LayoutItemSpacing = floorf(avail_width - LayoutItemSize.x * LayoutColumnCount) / LayoutColumnCount;
LayoutItemStep = ImVec2(LayoutItemSize.x + LayoutItemSpacing, LayoutItemSize.y + LayoutItemSpacing);
LayoutSelectableSpacing = IM_MAX(floorf(LayoutItemSpacing) - IconHitSpacing, 0.0f);
LayoutOuterPadding = floorf(LayoutItemSpacing * 0.5f);
}
void Draw(const char* title, bool* p_open)
{
ImGui::SetNextWindowSize(ImVec2(IconSize * 25, IconSize * 15), ImGuiCond_FirstUseEver);
@ -9722,27 +9754,18 @@ struct ExampleAssetsBrowser
}
ImGui::PopStyleVar();
if (ImGui::BeginChild("Assets", ImVec2(0, -ImGui::GetTextLineHeightWithSpacing()), true, ImGuiWindowFlags_NoMove))
ImGuiIO& io = ImGui::GetIO();
ImGui::SetNextWindowContentSize(ImVec2(0.0f, LayoutOuterPadding + LayoutLineCount * (LayoutItemSize.x + LayoutItemSpacing)));
if (ImGui::BeginChild("Assets", ImVec2(0.0f, -ImGui::GetTextLineHeightWithSpacing()), ImGuiChildFlags_Border, ImGuiWindowFlags_NoMove))
{
ImDrawList* draw_list = ImGui::GetWindowDrawList();
const ImVec2 item_size(floorf(IconSize), floorf(IconSize));
// Layout: when not stretching: allow extending into right-most spacing.
float item_spacing = (float)IconSpacing;
const float avail_width = ImGui::GetContentRegionAvail().x + (StretchSpacing ? 0.0f : floorf(item_spacing * 0.5f));
// Layout: calculate number of icon per line and number of lines
const int column_count = IM_MAX((int)(avail_width / (item_size.x + IconSpacing)), 1);
const int line_count = (Items.Size + column_count - 1) / column_count;
// Layout: when stretching: allocate remaining space to more spacing. Round before division, so item_spacing may be non-integer.
if (StretchSpacing && column_count > 1)
item_spacing = floorf(avail_width - item_size.x * column_count) / column_count;
const float avail_width = ImGui::GetContentRegionAvail().x;
UpdateLayoutSizes(avail_width);
// Calculate and store start position.
const float outer_padding = floorf(item_spacing * 0.5f);
ImVec2 start_pos = ImGui::GetCursorScreenPos();
start_pos = ImVec2(start_pos.x + outer_padding, start_pos.y + outer_padding);
start_pos = ImVec2(start_pos.x + LayoutOuterPadding, start_pos.y + LayoutOuterPadding);
ImGui::SetCursorScreenPos(start_pos);
// Multi-select
@ -9760,22 +9783,22 @@ struct ExampleAssetsBrowser
const int item_curr_idx_to_focus = want_delete ? Selection.ApplyDeletionPreLoop(ms_io, Items.Size) : -1;
RequestDelete = false;
// Altering ItemSpacing may seem unnecessary as we position every items using SetCursorScreenPos()...
// Push LayoutSelectableSpacing (which is LayoutItemSpacing minus hit-spacing, if we decide to have hit gaps between items)
// Altering style ItemSpacing may seem unnecessary as we position every items using SetCursorScreenPos()...
// But it is necessary for two reasons:
// - Selectables uses it by default to visually fill the space between two items.
// - The vertical spacing would be measured by Clipper to calculate line height if we didn't provide it explicitly (here we do).
const float selectable_spacing = IM_MAX(floorf(item_spacing) - IconHitSpacing, 0.0f);
ImGui::PushStyleVar(ImGuiStyleVar_ItemSpacing, ImVec2(selectable_spacing, selectable_spacing));
ImGui::PushStyleVar(ImGuiStyleVar_ItemSpacing, ImVec2(LayoutSelectableSpacing, LayoutSelectableSpacing));
// Rendering parameters
const ImU32 icon_bg_color = IM_COL32(48, 48, 48, 128);
const ImU32 icon_type_overlay_colors[3] = { 0, IM_COL32(200, 70, 70, 255), IM_COL32(70, 170, 70, 255) };
const ImVec2 icon_type_overlay_size = ImVec2(4.0f, 4.0f);
const bool display_label = (item_size.x >= ImGui::CalcTextSize("999").x);
const bool display_label = (LayoutItemSize.x >= ImGui::CalcTextSize("999").x);
const float line_height = item_size.y + item_spacing;
const int column_count = LayoutColumnCount;
ImGuiListClipper clipper;
clipper.Begin(line_count, line_height);
clipper.Begin(LayoutLineCount, LayoutItemStep.y);
if (item_curr_idx_to_focus != -1)
clipper.IncludeItemByIndex(item_curr_idx_to_focus / column_count); // Ensure focused item line is not clipped.
if (ms_io->RangeSrcItem != -1)
@ -9792,17 +9815,17 @@ struct ExampleAssetsBrowser
ImGui::PushID((int)item_data->ID);
// Position item
ImVec2 pos = ImVec2(start_pos.x + (item_idx % column_count) * (item_size.x + item_spacing), start_pos.y + (line_idx * line_height));
ImVec2 pos = ImVec2(start_pos.x + (item_idx % column_count) * LayoutItemStep.x, start_pos.y + line_idx * LayoutItemStep.y);
ImGui::SetCursorScreenPos(pos);
// Draw box
ImVec2 box_min(pos.x - 1, pos.y - 1);
ImVec2 box_max(box_min.x + item_size.x + 2, box_min.y + item_size.y + 2);
ImVec2 box_max(box_min.x + LayoutItemSize.x + 2, box_min.y + LayoutItemSize.y + 2);
draw_list->AddRect(box_min, box_max, IM_COL32(90, 90, 90, 255));
ImGui::SetNextItemSelectionUserData(item_idx);
bool item_is_selected = Selection.Contains((ImGuiID)item_data->ID);
ImGui::Selectable("", item_is_selected, ImGuiSelectableFlags_None, item_size);
ImGui::Selectable("", item_is_selected, ImGuiSelectableFlags_None, LayoutItemSize);
// Update our selection state immediately (without waiting for EndMultiSelect() requests)
// because we use this to alter the color of our text/icon.
@ -9865,11 +9888,8 @@ struct ExampleAssetsBrowser
// FIXME-MULTISELECT: Find a way to expose this in public API. This currently requires "imgui_internal.h"
//ImGui::NavMoveRequestTryWrapping(ImGui::GetCurrentWindow(), ImGuiNavMoveFlags_WrapX);
}
// Zooming with CTRL+Wheel
// FIXME-MULTISELECT: Try to maintain scroll.
ImGuiIO& io = ImGui::GetIO();
if (ImGui::IsWindowAppearing())
ZoomWheelAccum = 0.0f;
if (ImGui::IsWindowHovered() && io.MouseWheel != 0.0f && ImGui::IsKeyDown(ImGuiMod_Ctrl) && ImGui::IsAnyItemActive() == false)
@ -9877,13 +9897,31 @@ struct ExampleAssetsBrowser
ZoomWheelAccum += io.MouseWheel;
if (fabsf(ZoomWheelAccum) >= 1.0f)
{
// Calculate hovered item index from mouse location
// FIXME: Locking aiming on 'hovered_item_idx' (with a cool-down timer) would ensure zoom keeps on it.
const float hovered_item_nx = (io.MousePos.x - start_pos.x + LayoutItemSpacing * 0.5f) / LayoutItemStep.x;
const float hovered_item_ny = (io.MousePos.y - start_pos.y + LayoutItemSpacing * 0.5f) / LayoutItemStep.y;
const int hovered_item_idx = ((int)hovered_item_ny * LayoutColumnCount) + (int)hovered_item_nx;
//ImGui::SetTooltip("%f,%f -> item %d", hovered_item_nx, hovered_item_ny, hovered_item_idx); // Move those 4 lines in block above for easy debugging
// Zoom
IconSize *= powf(1.1f, (float)(int)ZoomWheelAccum);
IconSize = IM_CLAMP(IconSize, 16.0f, 128.0f);
ZoomWheelAccum -= (int)ZoomWheelAccum;
}
}
UpdateLayoutSizes(avail_width);
// Manipulate scroll to that we will land at the same Y location of currently hovered item.
// - Calculate next frame position of item under mouse
// - Set new scroll position to be used in next ImGui::BeginChild() call.
float hovered_item_rel_pos_y = ((float)(hovered_item_idx / LayoutColumnCount) + fmodf(hovered_item_ny, 1.0f)) * LayoutItemStep.y;
hovered_item_rel_pos_y += ImGui::GetStyle().WindowPadding.y;
float mouse_local_y = io.MousePos.y - ImGui::GetWindowPos().y;
ImGui::SetScrollY(hovered_item_rel_pos_y - mouse_local_y);
}
}
}
ImGui::EndChild();
ImGui::Text("Selected: %d/%d items", Selection.Size, Items.Size);
ImGui::End();
}