From 8648486400949ab088da642a6a7ee6523ca76157 Mon Sep 17 00:00:00 2001
From: Chun-wei Fan <fanchunwei@src.gnome.org>
Date: Mon, 19 Jul 2021 10:32:28 +0800
Subject: [PATCH] GDK-Win32: Fixup, and cleanup WGL HDC handling

It turns out that the problem of the WGL window not drawing was due to
the fact that I messed up where I placed SwapBuffers() during the
conversion... doh:|

At the same time, stop storing the HDC in the GdkWin32GLContextWGL, but
instead always create it along the surface we created, so that it is ready
for use for operating with WGL when we are not dealing with "surfaceless"
contexts.  If we are dealing with "surfaceless" contexts, just use the
HDC of the dummy window that we created when we created the
Gdk(Win32)Display.

WGL contexts should now be in working order at this point.
---
 gdk/win32/gdkglcontext-win32-wgl.c | 44 ++++++++++++------------------
 gdk/win32/gdksurface-win32.c       |  1 +
 2 files changed, 18 insertions(+), 27 deletions(-)

diff --git a/gdk/win32/gdkglcontext-win32-wgl.c b/gdk/win32/gdkglcontext-win32-wgl.c
index 16b904d9c6..4b000f4792 100644
--- a/gdk/win32/gdkglcontext-win32-wgl.c
+++ b/gdk/win32/gdkglcontext-win32-wgl.c
@@ -46,8 +46,6 @@ struct _GdkWin32GLContextWGL
 {
   GdkWin32GLContext parent_instance;
 
-  HWND wgl_hwnd;
-  HDC wgl_hdc;
   HGLRC wgl_context;
   guint do_frame_sync : 1;
 };
@@ -70,8 +68,6 @@ gdk_win32_gl_context_wgl_dispose (GObject *gobject)
 
       wglDeleteContext (context_wgl->wgl_context);
       context_wgl->wgl_context = NULL;
-
-      ReleaseDC (context_wgl->wgl_hwnd, context_wgl->wgl_hdc);
     }
 
   G_OBJECT_CLASS (gdk_win32_gl_context_wgl_parent_class)->dispose (gobject);
@@ -84,8 +80,10 @@ gdk_win32_gl_context_wgl_end_frame (GdkDrawContext *draw_context,
   GdkGLContext *context = GDK_GL_CONTEXT (draw_context);
   GdkWin32GLContextWGL *context_wgl = GDK_WIN32_GL_CONTEXT_WGL (context);
   GdkSurface *surface = gdk_gl_context_get_surface (context);
-  GdkWin32Display *display = (GDK_WIN32_DISPLAY (gdk_gl_context_get_display (context)));
+  GdkWin32Display *display_win32 = (GDK_WIN32_DISPLAY (gdk_gl_context_get_display (context)));
   cairo_rectangle_int_t whole_window;
+  gboolean can_wait = display_win32->hasWglOMLSyncControl;
+  HDC hdc;
 
   GDK_DRAW_CONTEXT_CLASS (gdk_win32_gl_context_wgl_parent_class)->end_frame (draw_context, painted);
 
@@ -94,26 +92,31 @@ gdk_win32_gl_context_wgl_end_frame (GdkDrawContext *draw_context,
 
   gdk_profiler_add_mark (GDK_PROFILER_CURRENT_TIME, 0, "win32", "swap buffers");
 
-  gboolean can_wait = display->hasWglOMLSyncControl;
+  if (surface != NULL)
+    hdc = GDK_WIN32_SURFACE (surface)->hdc;
+  else
+    hdc = display_win32->dummy_context_wgl.hdc;
 
   if (context_wgl->do_frame_sync)
     {
+
       glFinish ();
 
       if (can_wait)
         {
           gint64 ust, msc, sbc;
 
-          wglGetSyncValuesOML (context_wgl->wgl_hdc, &ust, &msc, &sbc);
-          wglWaitForMscOML (context_wgl->wgl_hdc,
+          wglGetSyncValuesOML (hdc, &ust, &msc, &sbc);
+          wglWaitForMscOML (hdc,
                             0,
                             2,
                             (msc + 1) % 2,
                            &ust, &msc, &sbc);
         }
 
-      SwapBuffers (context_wgl->wgl_hdc);
     }
+
+  SwapBuffers (hdc);
 }
 
 static void
@@ -551,15 +554,9 @@ gdk_win32_gl_context_wgl_realize (GdkGLContext *context,
   compat_bit = gdk_gl_context_get_forward_compatible (context);
 
   if (surface != NULL)
-    {
-      hwnd = GDK_SURFACE_HWND (surface);
-      context_wgl->wgl_hdc = hdc = GetDC (hwnd);
-    }
+    hdc = GDK_WIN32_SURFACE (surface)->hdc;
   else
-    {
-      hwnd = display_win32->hwnd;
-      hdc = display_win32->dummy_context_wgl.hdc;
-    }
+    hdc = display_win32->dummy_context_wgl.hdc;
 
   /*
    * A legacy context cannot be shared with core profile ones, so this means we
@@ -642,13 +639,13 @@ gdk_win32_gl_context_wgl_make_current (GdkGLContext *context,
   GdkWin32GLContextWGL *context_wgl = GDK_WIN32_GL_CONTEXT_WGL (context);
   GdkDisplay *display = gdk_gl_context_get_display (context);
   GdkWin32Display *display_win32 = GDK_WIN32_DISPLAY (display);
-  GdkSurface *surface;
+  GdkSurface *surface = gdk_gl_context_get_surface (context);
   HDC hdc;
 
-  if (surfaceless)
+  if (surfaceless || surface == NULL)
     hdc = display_win32->dummy_context_wgl.hdc;
   else
-    hdc = context_wgl->wgl_hdc;
+    hdc = GDK_WIN32_SURFACE (surface)->hdc;
 
   if (!wglMakeCurrent (hdc, context_wgl->wgl_context))
     return FALSE;
@@ -656,7 +653,6 @@ gdk_win32_gl_context_wgl_make_current (GdkGLContext *context,
   if (!surfaceless && display_win32->hasWglEXTSwapControl)
     {
       gboolean do_frame_sync = FALSE;
-      GdkSurface *surface = gdk_gl_context_get_surface (context);
 
       /* If there is compositing there is no particular need to delay
        * the swap when drawing on the offscreen, rendering to the screen
@@ -696,12 +692,6 @@ gdk_win32_gl_context_wgl_init (GdkWin32GLContextWGL *wgl_context)
 {
 }
 
-void gdk_win32_gl_context_wgl_bind_surface (GdkWin32GLContextWGL *wgl_context,
-                                            GdkWin32Surface      *impl)
-{
-  wgl_context->wgl_hwnd = impl->handle;
-  wgl_context->wgl_hdc = GetDC (impl->handle);
-}
 
 /**
  * gdk_win32_display_get_wgl_version:
diff --git a/gdk/win32/gdksurface-win32.c b/gdk/win32/gdksurface-win32.c
index 2623ba7f95..4c1f7c1a3f 100644
--- a/gdk/win32/gdksurface-win32.c
+++ b/gdk/win32/gdksurface-win32.c
@@ -655,6 +655,7 @@ _gdk_win32_display_create_surface (GdkDisplay     *display,
                     impl);
 
   g_object_unref (frame_clock);
+  impl->hdc = GetDC (impl->handle);
 
   return surface;
 }