Nuklear/demo/gdi_native_nuklear/window.h

#ifndef NK_GDI_WINDOW
#define NK_GDI_WINDOW

#define NK_GDI_WINDOW_CLS L"WNDCLS_NkGdi"

#include <windows.h>

/* Functin pointer types for window callbacks */
typedef int(*nkgdi_window_func_close)(void);
typedef int(*nkgdi_window_func_draw)(struct nk_context*);

/* Window container / context */
struct nkgdi_window
{
    /* The window can be sized */
    int allow_sizing;
    /* The window can be maximized by double clicking the titlebar */
    int allow_maximize;
    /* The window is allowed to be moved by the user */
    int allow_move;
    /* The window will render it's title bar */
    int has_titlebar;

    /* Callbacks */
    /* Called when the user or os requests a window close (return 1 to accept the reqest)*/
    nkgdi_window_func_close cb_on_close;
    /* Called each time the window content should be drawn. Here you will do your nuklear drawing code
     * but WITHOUT nk_begin and nk_end. Return 1 to keep the window open.
     */
    nkgdi_window_func_draw cb_on_draw;

    /* Internal Data */
    struct
    {
        /* Window handle */
        HWND window_handle;

        /* Nuklear & GDI context */
        nk_gdi_ctx nk_gdi_ctx;
        struct nk_context* nk_ctx;

        /* GDI required objects */
        GdiFont* gdi_font;
        HDC window_dc;

        /* Internally used state variables */
        int is_open; 
        int is_draggin;
        int ws_override;
        int is_maximized;
        POINT drag_offset;
        int width;
        int height;
    }_internal;
};

/* API */
/* This function will init all resources used by the implementation */
void nkgdi_window_init(void);
/* This function will free all globally used resources */
void nkgdi_window_shutdown(void);
/* Creates a new window (for the wnd context) */
void nkgdi_window_create(struct nkgdi_window* wnd, unsigned int width, unsigned int height, const char* name, int posX, int posY);
/* Updates the window (Windows message loop, nuklear loop and drawing). Returns one as long as the window is valid and open */
int nkgdi_window_update(struct nkgdi_window* wnd);
/* Destroys the window context wnd */
void nkgdi_window_destroy(struct nkgdi_window* wnd);

#ifdef NKGDI_IMPLEMENT_WINDOW

/* Predeclare the windows window message procs */
/* This proc will setup the pointer to the window context */
LRESULT nkgdi_window_proc_setup(HWND wnd, UINT msg, WPARAM wParam, LPARAM lParam);
/* This proc will take the window context pointer and performs operations on it*/ 
LRESULT nkgdi_window_proc_run(HWND wnd, UINT msg, WPARAM wParam, LPARAM lParam);

void nkgdi_window_init(void)
{
    /* Describe the window class */
    WNDCLASSEXW cls;
    cls.cbSize = sizeof(WNDCLASSEXW);
    cls.style = CS_OWNDC | CS_DBLCLKS;
    cls.lpfnWndProc = &nkgdi_window_proc_setup;
    cls.cbClsExtra = 0;
    cls.cbWndExtra = 0;
    cls.hInstance = GetModuleHandle(NULL);
    cls.hIcon = LoadIcon(NULL, IDI_APPLICATION);
    cls.hCursor = LoadCursor(NULL, IDC_ARROW);
    cls.hbrBackground = NULL;
    cls.lpszMenuName = NULL;
    cls.lpszClassName = NK_GDI_WINDOW_CLS;
    cls.hIconSm = NULL;

    /* Register the window class */
    RegisterClassExW(&cls);
}

void nkgdi_window_shutdown(void)
{
    /* Windows class no longer required, unregister it */
    UnregisterClassW(NK_GDI_WINDOW_CLS, GetModuleHandle(NULL));
}

void nkgdi_window_create(struct nkgdi_window* wnd, unsigned int width, unsigned int height, const char* name, int posX, int posY)
{
    DWORD styleEx = WS_EX_WINDOWEDGE;
    DWORD style = WS_POPUP;

    /* Adjust window size to fit selected window styles */
    RECT cr;
    cr.left = 0;
    cr.top = 0;
    cr.right = width;
    cr.bottom = height;
    AdjustWindowRectEx(&cr, style, FALSE, styleEx);

    /* Create the new window */
    wnd->_internal.window_handle = CreateWindowExW(
        styleEx,
        NK_GDI_WINDOW_CLS,
        L"NkGdi",
        style | WS_VISIBLE,
        posX, posY,
        cr.right - cr.left, cr.bottom - cr.top,
        NULL, NULL,
        GetModuleHandleW(NULL),
        wnd
    );
 
    /* Give the window the ascii char name */
    SetWindowTextA(wnd->_internal.window_handle, name);

    /* Extract the window dc for gdi drawing */
    wnd->_internal.window_dc = GetWindowDC(wnd->_internal.window_handle);

    /* Create the gdi font required to draw text */
    wnd->_internal.gdi_font = nk_gdifont_create("Arial", 16);

    /* Init the gdi backend */
    wnd->_internal.nk_ctx = nk_gdi_init(&wnd->_internal.nk_gdi_ctx, wnd->_internal.gdi_font, wnd->_internal.window_dc, width, height);

    /* Bring all internal variables to a defined and valid initial state */
    wnd->_internal.is_open = 1;
    wnd->_internal.is_draggin = 0;
    wnd->_internal.ws_override = 0;
    wnd->_internal.is_maximized = 0;
    wnd->_internal.drag_offset.x = 0;
    wnd->_internal.drag_offset.y = 0;
    wnd->_internal.width = width;
    wnd->_internal.height = height;
}

void nkgdi_window_destroy(struct nkgdi_window* wnd)
{
    /* Destroy all objects in reverse order */
    if (wnd->_internal.nk_gdi_ctx)
    {
        nk_gdi_shutdown(wnd->_internal.nk_gdi_ctx);
    }
    if (wnd->_internal.gdi_font)
    {
        nk_gdifont_del(wnd->_internal.gdi_font);
    }
    if (wnd->_internal.window_dc)
    {
        ReleaseDC(wnd->_internal.window_handle, wnd->_internal.window_dc);
    }
    if (wnd->_internal.window_handle)
    {
        CloseWindow(wnd->_internal.window_handle);
        DestroyWindow(wnd->_internal.window_handle);
    }
}

int nkgdi_window_update(struct nkgdi_window* wnd)
{
    /* The window will only be updated when it is open / valid */
    if (wnd->_internal.is_open)
    {
        /* First all pending window events will be processed */
        MSG msg;
        nk_input_begin(wnd->_internal.nk_ctx);
        while (PeekMessage(&msg, wnd->_internal.window_handle, 0, 0, PM_REMOVE))
        {
            TranslateMessage(&msg);
            DispatchMessageW(&msg);
        }
        nk_input_end(wnd->_internal.nk_ctx);

        /* To setup the nuklear window we need the windows title */
        char title[1024];
        GetWindowTextA(wnd->_internal.window_handle, title, 1024);

        /* The nk window flags are beeing create based on the context setup */
        nk_flags window_flags = NK_WINDOW_BORDER;
        if(wnd->has_titlebar)
            window_flags |= NK_WINDOW_CLOSABLE | NK_WINDOW_TITLE;
        if(!wnd->_internal.is_maximized && wnd->allow_sizing)
            window_flags |= NK_WINDOW_SCALABLE;

        /* Override the nuklear windows size when required */
        if (wnd->_internal.ws_override)
            nk_window_set_bounds(wnd->_internal.nk_ctx, title, nk_rect(0, 0, wnd->_internal.width, wnd->_internal.height));

        /* Start the nuklear window */
        if (nk_begin(wnd->_internal.nk_ctx, title, nk_rect(0, 0, wnd->_internal.width, wnd->_internal.height), window_flags))
        {
            /* Call user drawing callback */
            if(wnd->cb_on_draw && !wnd->cb_on_draw(wnd->_internal.nk_ctx))
                wnd->_internal.is_open = 0;

            /* Update the windows window to reflect the nuklear windows size */
            struct nk_rect bounds = nk_window_get_bounds(wnd->_internal.nk_ctx);
            if(bounds.w != wnd->_internal.width || bounds.h != wnd->_internal.height)
                SetWindowPos(wnd->_internal.window_handle, NULL, 0, 0, bounds.w, bounds.h, SWP_NOMOVE | SWP_NOOWNERZORDER);
        }
        else
        {
            /* Nuklear window was closed. Handle close internally */
            if(!wnd->cb_on_close || wnd->cb_on_close())
                wnd->_internal.is_open = 0;
        }
        nk_end(wnd->_internal.nk_ctx);

        /* We no longer need the window size override flag to be set */
        wnd->_internal.ws_override = 0;

        /* Pass context to the nuklear gdi renderer */
        nk_gdi_render(wnd->_internal.nk_gdi_ctx, nk_rgb(0, 0, 0));
    }

    return wnd->_internal.is_open;
}

LRESULT nkgdi_window_proc_setup(HWND wnd, UINT msg, WPARAM wParam, LPARAM lParam)
{
    /* Waiting to receive the NCCREATE message with the custom window data */
    if (msg == WM_NCCREATE)
    {
        /* Extracting the window context from message parameters */
        CREATESTRUCT* ptrCr = (CREATESTRUCT*)lParam;
        struct nkgdi_window* nkgdi_wnd = (struct nkgdi_window*)ptrCr->lpCreateParams;

        /* Store the context in the window and redirect any further message to the run window proc*/
        SetWindowLongPtr(wnd, GWLP_USERDATA, (LONG_PTR)nkgdi_wnd);
        SetWindowLongPtr(wnd, GWLP_WNDPROC, (LONG_PTR)&nkgdi_window_proc_run);

        /* Already call the run proc so that it gets the chance to handle NCCREATE as well */
        return nkgdi_window_proc_run(wnd, msg, wParam, lParam);
    }

    /* Until we get WM_NCCREATE windows is going to handle the messages */
    return DefWindowProc(wnd, msg, wParam, lParam);
}

LRESULT nkgdi_window_proc_run(HWND wnd, UINT msg, WPARAM wParam, LPARAM lParam)
{
    /* The window context is extracted from the window data */
    struct nkgdi_window* nkwnd = (struct nkgdi_window*)GetWindowLongPtrW(wnd, GWLP_USERDATA);
    
    /* Switch on the message code to handle all required messages */
    switch (msg)
    {
        /* Window close event */
        case WM_CLOSE:
            /* Call custom close callback */
            if(!nkwnd->cb_on_close || nkwnd->cb_on_close())
                nkwnd->_internal.is_open = 0;
            return 0; /* No default behaviour. We do it our own way */
        
        /* Window sizing event (is currently beeing sized) */
        case WM_SIZING:
            {
            /* Size of the client / active are is extracted and stored */
            RECT cr;
            GetClientRect(wnd, &cr);
            nkwnd->_internal.width = cr.right - cr.left;
            nkwnd->_internal.height = cr.bottom - cr.top;
            }
            break;

        /* Window size event (done sizing, maximize, minimize, ...) */
        case WM_SIZE:
            {
            /* Window was maximized */
            if (wParam == SIZE_MAXIMIZED)
            {
                /* Get the nearest monitor and retrive its details */
                HMONITOR monitor = MonitorFromWindow(wnd, MONITOR_DEFAULTTOPRIMARY);
                MONITORINFO monitorInfo;
                monitorInfo.cbSize = sizeof(MONITORINFO);
                if (GetMonitorInfoW(monitor, &monitorInfo))
                {
                    /* Adjust the window size and position by the monitor working area (without taskbar) */
                    nkwnd->_internal.height = monitorInfo.rcWork.bottom - monitorInfo.rcWork.top;
                    nkwnd->_internal.width = monitorInfo.rcWork.right - monitorInfo.rcWork.left;
                    nkwnd->_internal.ws_override = 1; /* Sizing was done without nuklear beeing aware. So we need to override it */
                    nkwnd->_internal.is_maximized = 1;
                    SetWindowPos(wnd, NULL, 0, 0, nkwnd->_internal.width, nkwnd->_internal.height, SWP_NOMOVE | SWP_NOZORDER);
                }
            }
            /* Window was restored (no longer maximized) */
            else if (wParam == SIZE_RESTORED)
            {
                nkwnd->_internal.is_maximized = 0;
            }

            /* Always get the new bounds of the window */
            RECT cr;
            GetClientRect(wnd, &cr);
            nkwnd->_internal.width = cr.right - cr.left;
            nkwnd->_internal.height = cr.bottom - cr.top;
            }
            break;

        /* Mouse started left click */
        case WM_LBUTTONDOWN:
            {
            /* Handle dragging when allowed, has titlebar and mouse is in titlebar (Y <= 30) */
            if (HIWORD(lParam) <= 30 && nkwnd->allow_move && nkwnd->has_titlebar)
            {
                /* Mark dragging internally and store mouse click offset */
                nkwnd->_internal.is_draggin = 1;
                nkwnd->_internal.drag_offset.x = LOWORD(lParam);
                nkwnd->_internal.drag_offset.y = HIWORD(lParam);
            }
            }
            break;

        /* Mouse stoped left click */
        case WM_LBUTTONUP:
            /* No longer dragging the window */
            nkwnd->_internal.is_draggin = 0;
            break;

        /* Mouse is moving on the window */
        case WM_MOUSEMOVE:
            {
            /* When we are dragging and are not maximized process dragging */
            if (nkwnd->_internal.is_draggin && !nkwnd->_internal.is_maximized)
            {
                /* Get the current global position of the mouse */
                POINT cursorPos;
                GetCursorPos(&cursorPos);
                /* Substract the internal offset */
                cursorPos.x -= nkwnd->_internal.drag_offset.x;
                cursorPos.y -= nkwnd->_internal.drag_offset.y;
                /* Update position of out window and make sure window is in a movable state (= Restored) */
                ShowWindow(wnd, SW_RESTORE);
                SetWindowPos(wnd, NULL, cursorPos.x, cursorPos.y, 0, 0, SWP_NOSIZE | SWP_NOZORDER);
            }
            }
            break;

        /* Mouse double clicked */
        case WM_LBUTTONDBLCLK:
            {
            /* Will only affect window when on the titlebar */
            if (HIWORD(lParam) <= 30 && nkwnd->allow_maximize && nkwnd->has_titlebar)
            {
                /* When the window is already maximized restore it */
                if (nkwnd->_internal.is_maximized)
                {
                    ShowWindow(wnd, SW_RESTORE);
                }
                /* Else we gonna do maximize it*/
                else
                {
                    ShowWindow(wnd, SW_MAXIMIZE);
                }
                /* We overrideed the window size, make sure to affect the nk window as well */
                nkwnd->_internal.ws_override = 1;
            }
            }
            break;
    }

    /* Allow nuklear to handle the message as well */
    if (nkwnd->_internal.nk_gdi_ctx && nk_gdi_handle_event(nkwnd->_internal.nk_gdi_ctx, wnd, msg, wParam, lParam))
        return 0;

    /* In case we reach this line our code and nuklear did not respond to the message. Allow windows to handle it s*/
    return DefWindowProc(wnd, msg, wParam, lParam);
}

#endif
#endif