Correctly recognize when wglChoosePixelFormatARB() fails.

This function returns TRUE even if it failed to find any matching formats, so
test not only its return value but also the number of formats it found.

Closes #12474.

git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/trunk@65575 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775

diff --git a/src/msw/glcanvas.cpp b/src/msw/glcanvas.cpp
index 15ad41545b27d4e9a951f88e164add4f4bcced31..e446fe096bddb60cb20efb0a57c19534eca9be3c 100644 (file)
--- a/src/msw/glcanvas.cpp
+++ b/src/msw/glcanvas.cpp
@@ -493,12 +493,21 @@ static int ChoosePixelFormatARB(HDC hdc, const int *attribList)
 
     int pf;
     UINT numFormats = 0;
+
     if ( !wglChoosePixelFormatARB(hdc, iAttributes, NULL, 1, &pf, &numFormats) )
     {
         wxLogLastError(wxT("wglChoosePixelFormatARB"));
         return 0;
     }
 
+    // Although TRUE is returned if no matching formats are found (see
+    // http://www.opengl.org/registry/specs/ARB/wgl_pixel_format.txt), pf is
+    // not initialized in this case so we need to check for numFormats being
+    // not 0 explicitly (however this is not an error so don't call
+    // wxLogLastError() here).
+    if ( !numFormats )
+        pf = 0;
+
     return pf;
 }