Windows QPA: Also wrap DescribePixelFormat()

GDI and the software rendering opengl32sw.dll may have very different
pixel formats so use wglDescribePixelFormat() in that case. This mirrors
the existing behavior for SetPixelFormat().

Change-Id: I55e658ab69bad84bb10cc5a042d62e84c005c0e6
Reviewed-by: Oliver Wolff <oliver.wolff@qt.io>

2 files changed, 11 insertions, 3 deletions

diff --git a/src/plugins/platforms/windows/qwindowsglcontext.cpp b/src/plugins/platforms/windows/qwindowsglcontext.cpp
index 101db75d0b..64b83e2bc4 100644
--- a/src/plugins/platforms/windows/qwindowsglcontext.cpp
+++ b/src/plugins/platforms/windows/qwindowsglcontext.cpp
@@ -196,6 +196,7 @@ bool QWindowsOpengl32DLL::init(bool softwareRendering)
     wglShareLists = reinterpret_cast<BOOL (WINAPI *)(HGLRC, HGLRC)>(resolve("wglShareLists"));
     wglSwapBuffers = reinterpret_cast<BOOL (WINAPI *)(HDC)>(resolve("wglSwapBuffers"));
     wglSetPixelFormat = reinterpret_cast<BOOL (WINAPI *)(HDC, int, const PIXELFORMATDESCRIPTOR *)>(resolve("wglSetPixelFormat"));
+    wglDescribePixelFormat = reinterpret_cast<int (WINAPI *)(HDC, int, UINT, PIXELFORMATDESCRIPTOR *)>(resolve("wglDescribePixelFormat"));
 
     glGetError = reinterpret_cast<GLenum (APIENTRY *)()>(resolve("glGetError"));
     glGetIntegerv = reinterpret_cast<void (APIENTRY *)(GLenum , GLint *)>(resolve("glGetIntegerv"));
@@ -214,6 +215,11 @@ BOOL QWindowsOpengl32DLL::setPixelFormat(HDC dc, int pf, const PIXELFORMATDESCRI
     return moduleIsNotOpengl32() ? wglSetPixelFormat(dc, pf, pfd) : SetPixelFormat(dc, pf, pfd);
 }
 
+int QWindowsOpengl32DLL::describePixelFormat(HDC dc, int pf, UINT size, PIXELFORMATDESCRIPTOR *pfd)
+{
+    return moduleIsNotOpengl32() ? wglDescribePixelFormat(dc, pf, size, pfd) : DescribePixelFormat(dc, pf, size, pfd);
+}
+
 QWindowsOpenGLContext *QOpenGLStaticContext::createContext(QOpenGLContext *context)
 {
     return new QWindowsGLContext(this, context);
@@ -322,11 +328,11 @@ static inline bool
 
 static void describeFormats(HDC hdc)
 {
-    const int pfiMax = DescribePixelFormat(hdc, 0, 0, nullptr);
+    const int pfiMax = QOpenGLStaticContext::opengl32.describePixelFormat(hdc, 0, 0, nullptr);
     for (int i = 0; i < pfiMax; i++) {
         PIXELFORMATDESCRIPTOR pfd;
         initPixelFormatDescriptor(&pfd);
-        DescribePixelFormat(hdc, i, sizeof(PIXELFORMATDESCRIPTOR), &pfd);
+        QOpenGLStaticContext::opengl32.describePixelFormat(hdc, i, sizeof(PIXELFORMATDESCRIPTOR), &pfd);
         qCDebug(lcQpaGl) << '#' << i << '/' << pfiMax << ':' << pfd;
     }
 }
@@ -617,7 +623,7 @@ static int choosePixelFormat(HDC hdc,
     // Verify if format is acceptable. Note that the returned
     // formats have been observed to not contain PFD_SUPPORT_OPENGL, ignore.
     initPixelFormatDescriptor(obtainedPfd);
-    DescribePixelFormat(hdc, pixelFormat, sizeof(PIXELFORMATDESCRIPTOR), obtainedPfd);
+    QOpenGLStaticContext::opengl32.describePixelFormat(hdc, pixelFormat, sizeof(PIXELFORMATDESCRIPTOR), obtainedPfd);
     if (!isAcceptableFormat(additional, *obtainedPfd, true)) {
         qCDebug(lcQpaGl) << __FUNCTION__ << " obtained px #" << pixelFormat
             << " not acceptable=" << *obtainedPfd;
diff --git a/src/plugins/platforms/windows/qwindowsglcontext.h b/src/plugins/platforms/windows/qwindowsglcontext.h
index 1abe2eb390..e962af39c2 100644
--- a/src/plugins/platforms/windows/qwindowsglcontext.h
+++ b/src/plugins/platforms/windows/qwindowsglcontext.h
@@ -107,6 +107,7 @@ struct QWindowsOpengl32DLL
     // Wrappers. Always use these instead of SwapBuffers/wglSwapBuffers/etc.
     BOOL swapBuffers(HDC dc);
     BOOL setPixelFormat(HDC dc, int pf, const PIXELFORMATDESCRIPTOR *pfd);
+    int describePixelFormat(HDC dc, int pf, UINT size, PIXELFORMATDESCRIPTOR *pfd);
 
     // WGL
     HGLRC (WINAPI * wglCreateContext)(HDC dc);
@@ -130,6 +131,7 @@ private:
     // For Mesa llvmpipe shipped with a name other than opengl32.dll
     BOOL (WINAPI * wglSwapBuffers)(HDC dc);
     BOOL (WINAPI * wglSetPixelFormat)(HDC dc, int pf, const PIXELFORMATDESCRIPTOR *pfd);
+    int (WINAPI * wglDescribePixelFormat)(HDC dc, int pf, UINT size, PIXELFORMATDESCRIPTOR *pfd);
 };
 
 class QOpenGLStaticContext : public QWindowsStaticOpenGLContext