macOS: Modernize and clean up QCocoaGLContext::updateSurfaceFormat()

The updateFormatFromContext function that read GL state has been
merged into updateSurfaceFormat(), we're using AppKit classes
and functions instead of Core GL, and the logic has been simplified
by using attribute/parameter helpers.

Change-Id: Iec6717f457a0b4dbc8e34c3e15fcbcc42895b23e
Reviewed-by: Gabriel de Dietrich <gabriel.dedietrich@qt.io>

1 files changed, 76 insertions, 97 deletions

diff --git a/src/plugins/platforms/cocoa/qcocoaglcontext.mm b/src/plugins/platforms/cocoa/qcocoaglcontext.mm
index b4cd8149c0..47ad930cf6 100644
--- a/src/plugins/platforms/cocoa/qcocoaglcontext.mm
+++ b/src/plugins/platforms/cocoa/qcocoaglcontext.mm
@@ -54,6 +54,24 @@ static inline QByteArray getGlString(GLenum param)
     return QByteArray();
 }
 
+@implementation NSOpenGLPixelFormat (QtHelpers)
+- (GLint)qt_getAttribute:(NSOpenGLPixelFormatAttribute)attribute
+{
+    int value = 0;
+    [self getValues:&value forAttribute:attribute forVirtualScreen:0];
+    return value;
+}
+@end
+
+@implementation NSOpenGLContext (QtHelpers)
+- (GLint)qt_getParameter:(NSOpenGLContextParameter)parameter
+{
+    int value = 0;
+    [self getValues:&value forParameter:parameter];
+    return value;
+}
+@end
+
 QT_BEGIN_NAMESPACE
 
 Q_LOGGING_CATEGORY(lcQpaOpenGLContext, "qt.qpa.openglcontext", QtWarningMsg);
@@ -217,126 +235,87 @@ NSOpenGLPixelFormat *QCocoaGLContext::pixelFormatForSurfaceFormat(const QSurface
     return [[NSOpenGLPixelFormat alloc] initWithAttributes:attrs.constData()];
 }
 
-static void updateFormatFromContext(QSurfaceFormat *format)
+/*!
+    Updates the surface format of this context based on properties of
+    the native context and GL state, so that the result of creating
+    the context is reflected back in QOpenGLContext.
+*/
+void QCocoaGLContext::updateSurfaceFormat()
 {
-    Q_ASSERT(format);
+    NSOpenGLContext *oldContext = [NSOpenGLContext currentContext];
+    [m_context makeCurrentContext];
+
+    // --------------------- Query GL state ---------------------
 
-    // Update the version, profile, and context bit of the format
     int major = 0, minor = 0;
     QByteArray versionString(getGlString(GL_VERSION));
     if (QPlatformOpenGLContext::parseOpenGLVersion(versionString, major, minor)) {
-        format->setMajorVersion(major);
-        format->setMinorVersion(minor);
+        m_format.setMajorVersion(major);
+        m_format.setMinorVersion(minor);
     }
 
-    format->setProfile(QSurfaceFormat::NoProfile);
-
-    Q_ASSERT(format->renderableType() == QSurfaceFormat::OpenGL);
-    if (format->version() < qMakePair(3, 0)) {
-        format->setOption(QSurfaceFormat::DeprecatedFunctions);
-        return;
+    m_format.setProfile(QSurfaceFormat::NoProfile);
+    if (m_format.version() >= qMakePair(3, 2)) {
+        GLint value = 0;
+        glGetIntegerv(GL_CONTEXT_PROFILE_MASK, &value);
+        if (value & GL_CONTEXT_CORE_PROFILE_BIT)
+            m_format.setProfile(QSurfaceFormat::CoreProfile);
+        else if (value & GL_CONTEXT_COMPATIBILITY_PROFILE_BIT)
+            m_format.setProfile(QSurfaceFormat::CompatibilityProfile);
     }
 
-    // Version 3.0 onwards - check if it includes deprecated functionality
-    GLint value = 0;
-    glGetIntegerv(GL_CONTEXT_FLAGS, &value);
-    if (!(value & GL_CONTEXT_FLAG_FORWARD_COMPATIBLE_BIT))
-        format->setOption(QSurfaceFormat::DeprecatedFunctions);
+    m_format.setOption(QSurfaceFormat::DeprecatedFunctions, [&]() {
+        if (m_format.version() < qMakePair(3, 0)) {
+            return true;
+        } else {
+            GLint value = 0;
+            glGetIntegerv(GL_CONTEXT_FLAGS, &value);
+            return !(value & GL_CONTEXT_FLAG_FORWARD_COMPATIBLE_BIT);
+        }
+    }());
 
-    // Debug context option not supported on OS X
+    // Debug contexts not supported on macOS
+    m_format.setOption(QSurfaceFormat::DebugContext, false);
 
-    if (format->version() < qMakePair(3, 2))
-        return;
+    // ------------------ Query the pixel format ------------------
 
-    // Version 3.2 and newer have a profile
-    value = 0;
-    glGetIntegerv(GL_CONTEXT_PROFILE_MASK, &value);
+    NSOpenGLPixelFormat *pixelFormat = m_context.pixelFormat;
 
-    if (value & GL_CONTEXT_CORE_PROFILE_BIT)
-        format->setProfile(QSurfaceFormat::CoreProfile);
-    else if (value & GL_CONTEXT_COMPATIBILITY_PROFILE_BIT)
-        format->setProfile(QSurfaceFormat::CompatibilityProfile);
-}
+    int colorSize = [pixelFormat qt_getAttribute:NSOpenGLPFAColorSize];
+    colorSize /= 4; // The attribute includes the alpha component
+    m_format.setRedBufferSize(colorSize);
+    m_format.setGreenBufferSize(colorSize);
+    m_format.setBlueBufferSize(colorSize);
 
-void QCocoaGLContext::updateSurfaceFormat()
-{
-    // At present it is impossible to turn an option off on a QSurfaceFormat (see
-    // https://codereview.qt-project.org/#change,70599). So we have to populate
-    // the actual surface format from scratch
-    QSurfaceFormat requestedFormat = m_format;
-    m_format = QSurfaceFormat();
-    m_format.setRenderableType(QSurfaceFormat::OpenGL);
-
-    // CoreGL doesn't require a drawable to make the context current
-    CGLContextObj oldContext = CGLGetCurrentContext();
-    CGLContextObj ctx = static_cast<CGLContextObj>([m_context CGLContextObj]);
-    CGLSetCurrentContext(ctx);
-
-    // Get the data that OpenGL provides
-    updateFormatFromContext(&m_format);
-
-    // Get the data contained within the pixel format
-    CGLPixelFormatObj cglPixelFormat = static_cast<CGLPixelFormatObj>(CGLGetPixelFormat(ctx));
-    NSOpenGLPixelFormat *pixelFormat = [[NSOpenGLPixelFormat alloc] initWithCGLPixelFormatObj:cglPixelFormat];
-
-    int colorSize = -1;
-    [pixelFormat getValues:&colorSize forAttribute:NSOpenGLPFAColorSize forVirtualScreen:0];
-    if (colorSize > 0) {
-        // This seems to return the total color buffer depth, including alpha
-        m_format.setRedBufferSize(colorSize / 4);
-        m_format.setGreenBufferSize(colorSize / 4);
-        m_format.setBlueBufferSize(colorSize / 4);
-    }
+    // Surfaces on macOS always have an alpha channel, but unless the user requested
+    // one via setAlphaBufferSize(), which triggered setting NSOpenGLCPSurfaceOpacity
+    // to make the surface non-opaque, we don't want to report back the actual alpha
+    // size, as that will make the user believe the alpha channel can be used for
+    // something useful, when in reality it can't, due to the surface being opaque.
+    if (m_format.alphaBufferSize() > 0)
+        m_format.setAlphaBufferSize([pixelFormat qt_getAttribute:NSOpenGLPFAAlphaSize]);
 
-    // The pixel format always seems to return 8 for alpha. However, the framebuffer only
-    // seems to have alpha enabled if we requested it explicitly. I can't find any other
-    // attribute to check explicitly for this so we use our best guess for alpha.
-    int alphaSize = -1;
-    [pixelFormat getValues:&alphaSize forAttribute:NSOpenGLPFAAlphaSize forVirtualScreen:0];
-    if (alphaSize > 0 && requestedFormat.alphaBufferSize() > 0)
-        m_format.setAlphaBufferSize(alphaSize);
-
-    int depthSize = -1;
-    [pixelFormat getValues:&depthSize forAttribute:NSOpenGLPFADepthSize forVirtualScreen:0];
-    if (depthSize > 0)
-        m_format.setDepthBufferSize(depthSize);
-
-    int stencilSize = -1;
-    [pixelFormat getValues:&stencilSize forAttribute:NSOpenGLPFAStencilSize forVirtualScreen:0];
-    if (stencilSize > 0)
-        m_format.setStencilBufferSize(stencilSize);
-
-    int samples = -1;
-    [pixelFormat getValues:&samples forAttribute:NSOpenGLPFASamples forVirtualScreen:0];
-    if (samples > 0)
-        m_format.setSamples(samples);
-
-    int doubleBuffered = -1;
-    int tripleBuffered = -1;
-    [pixelFormat getValues:&doubleBuffered forAttribute:NSOpenGLPFADoubleBuffer forVirtualScreen:0];
-    [pixelFormat getValues:&tripleBuffered forAttribute:NSOpenGLPFATripleBuffer forVirtualScreen:0];
-
-    if (tripleBuffered == 1)
+    m_format.setDepthBufferSize([pixelFormat qt_getAttribute:NSOpenGLPFADepthSize]);
+    m_format.setStencilBufferSize([pixelFormat qt_getAttribute:NSOpenGLPFAStencilSize]);
+    m_format.setSamples([pixelFormat qt_getAttribute:NSOpenGLPFASamples]);
+
+    if ([pixelFormat qt_getAttribute:NSOpenGLPFATripleBuffer])
         m_format.setSwapBehavior(QSurfaceFormat::TripleBuffer);
-    else if (doubleBuffered == 1)
+    else if ([pixelFormat qt_getAttribute:NSOpenGLPFADoubleBuffer])
         m_format.setSwapBehavior(QSurfaceFormat::DoubleBuffer);
     else
         m_format.setSwapBehavior(QSurfaceFormat::SingleBuffer);
 
-    int steroBuffers = -1;
-    [pixelFormat getValues:&steroBuffers forAttribute:NSOpenGLPFAStereo forVirtualScreen:0];
-    if (steroBuffers == 1)
-        m_format.setOption(QSurfaceFormat::StereoBuffers);
+    m_format.setOption(QSurfaceFormat::StereoBuffers, [pixelFormat qt_getAttribute:NSOpenGLPFAStereo]);
 
-    [pixelFormat release];
+    // ------------------- Query the context -------------------
 
-    GLint swapInterval = -1;
-    [m_context getValues:&swapInterval forParameter:NSOpenGLCPSwapInterval];
-    if (swapInterval >= 0)
-        m_format.setSwapInterval(swapInterval);
+    m_format.setSwapInterval([m_context qt_getParameter:NSOpenGLCPSwapInterval]);
 
-    // Restore the original context
-    CGLSetCurrentContext(oldContext);
+    if (oldContext)
+        [oldContext makeCurrentContext];
+    else
+        [NSOpenGLContext clearCurrentContext];
 }
 
 QCocoaGLContext::~QCocoaGLContext()