Add sRGB capable default framebuffer support for WGL

Not that it changes much since one tyically gets sRGB capable by default
on AMD and NVIDIA at least, but let's handle the QSurfaceFormat flag
correctly via WGL_EXT_framebuffer_sRGB.

Task-number: QTBUG-50987
Change-Id: I898c3757ab6fea51323d6c041b2511bea780c3fb
Reviewed-by: Andy Nichols <andy.nichols@qt.io>

1 files changed, 54 insertions, 18 deletions

diff --git a/src/plugins/platforms/windows/qwindowsglcontext.cpp b/src/plugins/platforms/windows/qwindowsglcontext.cpp
index 751807e897..78368d87de 100644
--- a/src/plugins/platforms/windows/qwindowsglcontext.cpp
+++ b/src/plugins/platforms/windows/qwindowsglcontext.cpp
@@ -145,6 +145,10 @@
 #define RESET_NOTIFICATION_STRATEGY_ARB 0x8256
 #define LOSE_CONTEXT_ON_RESET_ARB 0x8252
 
+#ifndef WGL_FRAMEBUFFER_SRGB_CAPABLE_EXT
+#define WGL_FRAMEBUFFER_SRGB_CAPABLE_EXT 0x20A9
+#endif
+
 QT_BEGIN_NAMESPACE
 
 QWindowsOpengl32DLL QOpenGLStaticContext::opengl32;
@@ -489,7 +493,7 @@ static int choosePixelFormat(HDC hdc,
                              const QWindowsOpenGLAdditionalFormat &additional,
                              PIXELFORMATDESCRIPTOR *obtainedPfd)
 {
-    enum { attribSize =40 };
+    enum { attribSize = 42 };
     if ((additional.formatFlags & QWindowsGLRenderToPixmap) || !staticContext.hasExtensions())
         return 0;
 
@@ -570,7 +574,15 @@ static int choosePixelFormat(HDC hdc,
         iAttributes[i++] = WGL_SAMPLE_BUFFERS_ARB;
         iAttributes[i++] = FALSE;
     }
-    // If sample buffer request cannot be satisfied, reduce request.
+    // must be the last
+    bool srgbRequested = format.colorSpace() == QSurfaceFormat::sRGBColorSpace;
+    int srgbValuePosition = 0;
+    if (srgbRequested) {
+        srgbValuePosition = i;
+        iAttributes[i++] = WGL_FRAMEBUFFER_SRGB_CAPABLE_EXT;
+        iAttributes[i++] = TRUE;
+    }
+    // If sample or sRGB request cannot be satisfied, reduce request.
     int pixelFormat = 0;
     uint numFormats = 0;
     while (true) {
@@ -578,20 +590,25 @@ static int choosePixelFormat(HDC hdc,
             staticContext.wglChoosePixelFormatARB(hdc, iAttributes, 0, 1,
                                                &pixelFormat, &numFormats)
                 && numFormats >= 1;
-        if (valid || !sampleBuffersRequested)
-            break;
-        if (iAttributes[samplesValuePosition] > 1) {
-            iAttributes[samplesValuePosition] /= 2;
-        } else if (iAttributes[samplesValuePosition] == 1) {
-            // Fallback in case it is unable to initialize with any
-            // samples to avoid falling back to the GDI path
-            // NB: The sample attributes needs to be at the end for this
-            // to work correctly
-            iAttributes[samplesValuePosition - 1] = FALSE;
-            iAttributes[samplesValuePosition] = 0;
-            iAttributes[samplesValuePosition + 1] = 0;
-        } else {
+        if (valid || (!sampleBuffersRequested && !srgbRequested))
             break;
+        if (srgbRequested) {
+            iAttributes[srgbValuePosition] = 0;
+            srgbRequested = false;
+        } else if (sampleBuffersRequested) {
+            if (iAttributes[samplesValuePosition] > 1) {
+                iAttributes[samplesValuePosition] /= 2;
+            } else if (iAttributes[samplesValuePosition] == 1) {
+                // Fallback in case it is unable to initialize with any
+                // samples to avoid falling back to the GDI path
+                // NB: The sample attributes needs to be at the end for this
+                // to work correctly
+                iAttributes[samplesValuePosition - 1] = FALSE;
+                iAttributes[samplesValuePosition] = 0;
+                iAttributes[samplesValuePosition + 1] = 0;
+            } else {
+                break;
+            }
         }
     }
     // Verify if format is acceptable. Note that the returned
@@ -628,7 +645,7 @@ static QSurfaceFormat
                           HDC hdc, int pixelFormat,
                           QWindowsOpenGLAdditionalFormat *additionalIn = 0)
 {
-    enum { attribSize =40 };
+    enum { attribSize = 42 };
 
     QSurfaceFormat result;
     result.setRenderableType(QSurfaceFormat::OpenGL);
@@ -641,6 +658,7 @@ static QSurfaceFormat
 
     int i = 0;
     const bool hasSampleBuffers = testFlag(staticContext.extensions, QOpenGLStaticContext::SampleBuffers);
+    const bool hasSrgbSupport = testFlag(staticContext.extensions, QOpenGLStaticContext::sRGBCapableFramebuffer);
 
     iAttributes[i++] = WGL_DOUBLE_BUFFER_ARB; // 0
     iAttributes[i++] = WGL_DEPTH_BITS_ARB; // 1
@@ -658,6 +676,9 @@ static QSurfaceFormat
         iAttributes[i++] = WGL_SAMPLE_BUFFERS_ARB; // 12
         iAttributes[i++] = WGL_SAMPLES_ARB; // 13
     }
+    if (hasSrgbSupport)
+        iAttributes[i++] = WGL_FRAMEBUFFER_SRGB_CAPABLE_EXT; // 12 or 14
+
     if (!staticContext.wglGetPixelFormatAttribIVARB(hdc, pixelFormat, 0, i,
                                         iAttributes, iValues)) {
         qErrnoWarning("%s: wglGetPixelFormatAttribIVARB() failed for basic parameters.", __FUNCTION__);
@@ -673,8 +694,14 @@ static QSurfaceFormat
     if (iValues[9])
         result.setOption(QSurfaceFormat::StereoBuffers);
 
-    if (hasSampleBuffers)
+    if (hasSampleBuffers) {
         result.setSamples(iValues[13]);
+        if (hasSrgbSupport && iValues[14])
+            result.setColorSpace(QSurfaceFormat::sRGBColorSpace);
+    } else {
+        if (hasSrgbSupport && iValues[12])
+            result.setColorSpace(QSurfaceFormat::sRGBColorSpace);
+    }
     if (additionalIn) {
         if (iValues[7])
             additionalIn->formatFlags |= QWindowsGLAccumBuffer;
@@ -947,7 +974,8 @@ QOpenGLStaticContext::QOpenGLStaticContext() :
     wglChoosePixelFormatARB((WglChoosePixelFormatARB)QOpenGLStaticContext::opengl32.wglGetProcAddress("wglChoosePixelFormatARB")),
     wglCreateContextAttribsARB((WglCreateContextAttribsARB)QOpenGLStaticContext::opengl32.wglGetProcAddress("wglCreateContextAttribsARB")),
     wglSwapInternalExt((WglSwapInternalExt)QOpenGLStaticContext::opengl32.wglGetProcAddress("wglSwapIntervalEXT")),
-    wglGetSwapInternalExt((WglGetSwapInternalExt)QOpenGLStaticContext::opengl32.wglGetProcAddress("wglGetSwapIntervalEXT"))
+    wglGetSwapInternalExt((WglGetSwapInternalExt)QOpenGLStaticContext::opengl32.wglGetProcAddress("wglGetSwapIntervalEXT")),
+    wglGetExtensionsStringARB((WglGetExtensionsStringARB)QOpenGLStaticContext::opengl32.wglGetProcAddress("wglGetExtensionsStringARB"))
 {
     if (extensionNames.startsWith(SAMPLE_BUFFER_EXTENSION " ")
             || extensionNames.indexOf(" " SAMPLE_BUFFER_EXTENSION " ") != -1)
@@ -1091,6 +1119,14 @@ QWindowsGLContext::QWindowsGLContext(QOpenGLStaticContext *staticContext,
                 && !(QWindowsIntegration::instance()->options() & QWindowsIntegration::DisableArb);
         QWindowsOpenGLAdditionalFormat obtainedAdditional;
         if (tryExtensions) {
+            if (m_staticContext->wglGetExtensionsStringARB) {
+                const char *exts = m_staticContext->wglGetExtensionsStringARB(hdc);
+                if (exts) {
+                    qCDebug(lcQpaGl) << __FUNCTION__ << "WGL extensions:" << exts;
+                    if (strstr(exts, "WGL_EXT_framebuffer_sRGB"))
+                        m_staticContext->extensions |= QOpenGLStaticContext::sRGBCapableFramebuffer;
+                }
+            }
             m_pixelFormat =
                 ARB::choosePixelFormat(hdc, *m_staticContext, format,
                                        requestedAdditional, &m_obtainedPixelFormatDescriptor);