gdk/win32: Fix Win32 GL Context switching

Since on Windows we need to use a good amount of temporary GL contexts,
we need to switch back to the original GL contexts we were using when
we are done with the temporary GL contexts, otherwise multi-GL windows
will cause confusions causing display artifacts and crashes.

Also, use the GdkWin32GLContext::gl_hdc consistently throughout
the code and remove the GdkWin32Display::gl_hdc as Lukas K pointed out
that GdkWin32Display::gl_hdc becomes out-of-date and so the HDC that the
GL context is bound to becomes incorrect in sceanarios using multiple
windows with GtkGLArea/GdkGLArea items (which would cause the artifacts in
programs that use multiple windows with GtkGLArea/GdkGLArea items, and it
turns out that GdkWin32Display::gl_hdc is actually not necessary to help
keep track of the HDCs we use for our GL contexts.

This will also fix on Windows with GDK_GL=always, or when GSK's gl
renderer is used.

Partly based on patch from Lukas K <lu@0x83.eu>

https://bugzilla.gnome.org/show_bug.cgi?id=789213

1 files changed, 0 insertions, 1 deletions

diff --git a/gdk/win32/gdkdisplay-win32.h b/gdk/win32/gdkdisplay-win32.h
index c468a0e8e3..9d7a18dd52 100644
--- a/gdk/win32/gdkdisplay-win32.h
+++ b/gdk/win32/gdkdisplay-win32.h
@@ -72,7 +72,6 @@ struct _GdkWin32Display
   /* WGL/OpenGL Items */
   guint have_wgl : 1;
   guint gl_version;
-  HDC gl_hdc;
   HWND gl_hwnd;
 
   GPtrArray *monitors;