[vlc-devel] [PATCH] wgl: fix failing wglMakeCurrent

[Alexandre Janniaux]

wglMakeCurrent on close() is called from a different thread than other
functions, thus the DC handle was not valid for the closing thread,
leading to spurrious 2004 errors or invalid handle errors, leading then
to OpenGL call failures because no context is current when destroying
the ressources in the display.

Since this was happening on Close(), there was no way to make it fail
gracefully so get a new DC on the closing thread instead to fix the
error.
---
 modules/video_output/win32/wgl.c | 16 +++++++++++++---
 1 file changed, 13 insertions(+), 3 deletions(-)

diff --git a/modules/video_output/win32/wgl.c b/modules/video_output/win32/wgl.c
index 1f87fb073c..2e9d5a839d 100644
--- a/modules/video_output/win32/wgl.c
+++ b/modules/video_output/win32/wgl.c
@@ -272,12 +272,22 @@ static void *OurGetProcAddress(vlc_gl_t *gl, const char *name)
 static int MakeCurrent(vlc_gl_t *gl)
 {
     vout_display_sys_t *sys = gl->sys;
-    bool success = wglMakeCurrent(sys->hGLDC, sys->hGLRC);
-    return success ? VLC_SUCCESS : VLC_EGENERIC;
+
+    /* After painting with a common DC, the ReleaseDC function must be called
+     * to release the DC. Class and private DCs do not have to be released.
+     * ReleaseDC must be called from the same thread that called GetDC. The
+     * number of DCs is limited only by available memory. */
+
+    HDC winDC = GetDC(sys->hvideownd);
+    bool success = wglMakeCurrent(winDC, sys->hGLRC);
+    /* vlc_gl_MakeCurrent should never fail. */
+    assert(success);
+    ReleaseDC(sys->hvideownd, winDC);
+    return VLC_SUCCESS;
 }
 
 static void ReleaseCurrent(vlc_gl_t *gl)
 {
     vout_display_sys_t *sys = gl->sys;
-    wglMakeCurrent (sys->hGLDC, NULL);
+    wglMakeCurrent(NULL, NULL);
 }
-- 
2.30.2