macOS: Make retina OpenGL work on VMware

Qt requests full resolution OpenGL surfaces by default.
However, when running as a VMware guest it looks like
the OS silently creates low-resolution surfaces.

This is not possible to detect using the standard NSWindow
APIs for converting to backing coordinates or for
reading the backing scale factor. The result of this
is that Qt will incorrectly display one quarter of
the window content only.

Fall back to detecting if the OpenGL renderer is the
Apple software renderer, which it will be on VMware.
Cancel the high-resolution surface request if this
is the case. This needs to be done while we have a
valid OpenGL context.

Task-number: QTBUG-62357
Change-Id: I33bf12b3bb0408249e6d66e0a8ca86b044bea781
Reviewed-by: Tor Arne Vestbø <tor.arne.vestbo@qt.io>

1 files changed, 18 insertions, 1 deletions

diff --git a/src/plugins/platforms/cocoa/qcocoaglcontext.mm b/src/plugins/platforms/cocoa/qcocoaglcontext.mm
index be5029b7e0..b656025ec7 100644
--- a/src/plugins/platforms/cocoa/qcocoaglcontext.mm
+++ b/src/plugins/platforms/cocoa/qcocoaglcontext.mm
@@ -121,7 +121,8 @@ QCocoaGLContext::QCocoaGLContext(const QSurfaceFormat &format, QPlatformOpenGLCo
                                  const QVariant &nativeHandle)
     : m_context(nil),
       m_shareContext(nil),
-      m_format(format)
+      m_format(format),
+      m_didCheckForSoftwareContext(false)
 {
     if (!nativeHandle.isNull()) {
         if (!nativeHandle.canConvert<QCocoaNativeContext>()) {
@@ -262,6 +263,22 @@ bool QCocoaGLContext::makeCurrent(QPlatformSurface *surface)
 
     QWindow *window = static_cast<QCocoaWindow *>(surface)->window();
     setActiveWindow(window);
+
+    // Disable high-resolution surfaces when using the software renderer, which has the
+    // problem that the system silently falls back to a to using a low-resolution buffer
+    // when a high-resolution buffer is requested. This is not detectable using the NSWindow
+    // convertSizeToBacking and backingScaleFactor APIs. A typical result of this is that Qt
+    // will display a quarter of the window content when running in a virtual machine.
+    if (!m_didCheckForSoftwareContext) {
+        m_didCheckForSoftwareContext = true;
+
+        const GLubyte* renderer = glGetString(GL_RENDERER);
+        if (qstrcmp((const char *)renderer, "Apple Software Renderer") == 0) {
+            NSView *view = static_cast<QCocoaWindow *>(surface)->m_view;
+            [view setWantsBestResolutionOpenGLSurface:NO];
+        }
+    }
+
     update();
     return true;
 }