gdkglcontext-win32.c: Fix running with Mesa driversmesa.win32-4.0

Some GL drivers such as Mesa-D3D12 do not allow one to call SetPixelFormat() on
a given HDC if one pixel format has been already set for it, so first check the
HDC with GetPixelFormat() to see whether a pixel format has already been set
with the HDC, and only attempt to acquire the pixel format if one has not been
set.

This will fix running with GL on Windows using the Mesa drivers.

1 files changed, 18 insertions, 8 deletions

diff --git a/gdk/win32/gdkglcontext-win32.c b/gdk/win32/gdkglcontext-win32.c
index c7e7fa3345..610711d3b8 100644
--- a/gdk/win32/gdkglcontext-win32.c
+++ b/gdk/win32/gdkglcontext-win32.c
@@ -712,20 +712,30 @@ _set_pixformat_for_hdc (HDC              hdc,
                         int             *best_idx,
                         GdkWin32Display *display)
 {
-  PIXELFORMATDESCRIPTOR pfd;
-  gboolean set_pixel_format_result = FALSE;
+  gboolean already_checked = TRUE;
+  *best_idx = GetPixelFormat (hdc);
 
   /* one is only allowed to call SetPixelFormat(), and so ChoosePixelFormat()
    * one single time per window HDC
    */
-  *best_idx = _get_wgl_pfd (hdc, &pfd, display);
+  if (*best_idx == 0)
+    {
+      PIXELFORMATDESCRIPTOR pfd;
+      gboolean set_pixel_format_result = FALSE;
 
-  if (*best_idx != 0)
-    set_pixel_format_result = SetPixelFormat (hdc, *best_idx, &pfd);
+      GDK_NOTE (OPENGL, g_print ("requesting pixel format...\n"));
+	  already_checked = FALSE;
+      *best_idx = _get_wgl_pfd (hdc, &pfd, display);
 
-  /* ChoosePixelFormat() or SetPixelFormat() failed, bail out */
-  if (*best_idx == 0 || !set_pixel_format_result)
-    return FALSE;
+      if (*best_idx != 0)
+        set_pixel_format_result = SetPixelFormat (hdc, *best_idx, &pfd);
+
+      /* ChoosePixelFormat() or SetPixelFormat() failed, bail out */
+      if (*best_idx == 0 || !set_pixel_format_result)
+        return FALSE;
+    }
+
+  GDK_NOTE (OPENGL, g_print ("%s""requested and set pixel format: %d\n", already_checked ? "already " : "", *best_idx));
 
   return TRUE;
 }