QOpenGLContext: Use color depth information from QSurfaceFormat

When a new QOpenGLContext is requested, the color depth
information is now also taken into account on OS X and WGL.

Task-number: QTBUG-37411
Change-Id: I69d04989a20de3ace041b009fbbdc03fa02cfdf8
Reviewed-by: Laszlo Agocs <laszlo.agocs@digia.com>
Reviewed-by: Morten Johan Sørvig <morten.sorvig@digia.com>
Reviewed-by: Friedemann Kleint <Friedemann.Kleint@digia.com>

src/gui/kernel/qsurfaceformat.cpp

@@ -522,6 +522,10 @@ int QSurfaceFormat::alphaBufferSize() const
 
 /*!
     Set the desired \a size in bits of the red channel of the color buffer.
+
+    \note On Mac OSX, be sure to set the buffer size of all color channels,
+    otherwise this setting will have no effect. If one of the buffer sizes is not set,
+    the current bit-depth of the screen is used.
 */
 void QSurfaceFormat::setRedBufferSize(int size)
 {
@@ -533,6 +537,10 @@ void QSurfaceFormat::setRedBufferSize(int size)
 
 /*!
     Set the desired \a size in bits of the green channel of the color buffer.
+
+    \note On Mac OSX, be sure to set the buffer size of all color channels,
+    otherwise this setting will have no effect. If one of the buffer sizes is not set,
+    the current bit-depth of the screen is used.
 */
 void QSurfaceFormat::setGreenBufferSize(int size)
 {
@@ -544,6 +552,10 @@ void QSurfaceFormat::setGreenBufferSize(int size)
 
 /*!
     Set the desired \a size in bits of the blue channel of the color buffer.
+
+    \note On Mac OSX, be sure to set the buffer size of all color channels,
+    otherwise this setting will have no effect. If one of the buffer sizes is not set,
+    the current bit-depth of the screen is used.
 */
 void QSurfaceFormat::setBlueBufferSize(int size)
 {

src/platformsupport/cglconvenience/cglconvenience.mm

@@ -114,6 +114,14 @@ void *qcgl_createNSOpenGLPixelFormat(const QSurfaceFormat &format)
         attrs << NSOpenGLPFAStencilSize << format.stencilBufferSize();
     if (format.alphaBufferSize() > 0)
         attrs << NSOpenGLPFAAlphaSize << format.alphaBufferSize();
+    if ((format.redBufferSize() > 0) &&
+        (format.greenBufferSize() > 0) &&
+        (format.blueBufferSize() > 0)) {
+        const int colorSize = format.redBufferSize() +
+                              format.greenBufferSize() +
+                              format.blueBufferSize();
+        attrs << NSOpenGLPFAColorSize << colorSize << NSOpenGLPFAMinimumPolicy;
+    }
 
     if (format.samples() > 0) {
         attrs << NSOpenGLPFAMultisample

src/plugins/platforms/windows/qwindowsglcontext.cpp

@@ -387,7 +387,12 @@ static int choosePixelFormat(HDC hdc,
     iAttributes[i++] = WGL_DRAW_TO_WINDOW_ARB;
     iAttributes[i++] = TRUE;
     iAttributes[i++] = WGL_COLOR_BITS_ARB;
-    iAttributes[i++] = 24;
+
+    iAttributes[i++] = (format.redBufferSize() > 0)
+                       && (format.greenBufferSize() > 0)
+                       && (format.blueBufferSize() > 0) ?
+                       format.redBufferSize() + format.greenBufferSize() + format.blueBufferSize() :
+                       24;
     switch (format.swapBehavior()) {
     case QSurfaceFormat::SingleBuffer:
         iAttributes[i++] = WGL_DOUBLE_BUFFER_ARB;