macOS: Expand and tighten plumbing of QWindow's requested color space

A QWindow can have a requested target color space via its QSurfaceFormat.
This allows users who know what color space their source material is in,
or who do their own color matching, to ensure a consistent target color
space.

In the past we plumbed this to NSWindow's colorSpace property. This meant
that you could only have one color space per top level, even if child
windows were in play, and we could only set the color space if we were
the ones creating the NSWindow, failing the color space request in cases
where the window was embedded in a non-Qt window hierarchy.

We now store the requested color space in our QNSView, and propagate it
to both the IOSurfaces we use in QCALayerBackingStore, and to the view's
layer, in case it's a CAMetalLayer. We also pick up any changes to the
backing properties of the view, and ensure we update the color space
accordingly.

We still propagate the color space to NSWindow, as for OpenGL we don't
use CAOpenGLLayer (which has a colorSpace property), but instead use
NSOpenGLContext. This is not something we're going to change, so as
a workaround we set the NSWindow color space, which does affect GL
drawing via NSOpenGLContext. The granular color spaces we set on
the IOSurfaces and CAMetalLayer will override the NSWindow state.

Pick-to: 6.7
Change-Id: I5d9765d95140b8523ee09f70ff09a8c9400ffdc7
Reviewed-by: Pavel Dubsky <pavel.dubsky@qt.io>
Reviewed-by: Allan Sandfeld Jensen <allan.jensen@qt.io>
Reviewed-by: Artem Dyomin <artem.dyomin@qt.io>
Reviewed-by: Jøger Hansegård <joger.hansegard@qt.io>

5 files changed, 53 insertions, 20 deletions

diff --git a/src/plugins/platforms/cocoa/qcocoabackingstore.mm b/src/plugins/platforms/cocoa/qcocoabackingstore.mm
index 6970c44a12..b211b5d02d 100644
--- a/src/plugins/platforms/cocoa/qcocoabackingstore.mm
+++ b/src/plugins/platforms/cocoa/qcocoabackingstore.mm
@@ -23,8 +23,9 @@ QCocoaBackingStore::QCocoaBackingStore(QWindow *window)
 
 QCFType<CGColorSpaceRef> QCocoaBackingStore::colorSpace() const
 {
-    NSView *view = static_cast<QCocoaWindow *>(window()->handle())->view();
-    return QCFType<CGColorSpaceRef>::constructFromGet(view.window.colorSpace.CGColorSpace);
+    const auto *platformWindow = static_cast<QCocoaWindow *>(window()->handle());
+    const QNSView *view = qnsview_cast(platformWindow->view());
+    return QCFType<CGColorSpaceRef>::constructFromGet(view.colorSpace.CGColorSpace);
 }
 
 // ----------------------------------------------------------------------------
@@ -188,8 +189,9 @@ bool QCALayerBackingStore::recreateBackBufferIfNeeded()
         }
 #endif
 
-        qCInfo(lcQpaBackingStore) << "Creating surface of" << requestedBufferSize
-            << "based on requested" << m_requestedSize << "and dpr =" << devicePixelRatio;
+        qCInfo(lcQpaBackingStore)<< "Creating surface of" << requestedBufferSize
+            << "for" << window() << "based on requested" << m_requestedSize
+            << "dpr =" << devicePixelRatio << "and color space" << colorSpace();
 
         static auto pixelFormat = QImage::toPixelFormat(QImage::Format_ARGB32_Premultiplied);
         auto *newBackBuffer = new GraphicsBuffer(requestedBufferSize, devicePixelRatio, pixelFormat, colorSpace());
@@ -477,10 +479,11 @@ void QCALayerBackingStore::backingPropertiesChanged()
 
     qCDebug(lcQpaBackingStore) << "Backing properties for" << window() << "did change";
 
-    qCDebug(lcQpaBackingStore) << "Updating color space of existing buffers";
+    const auto newColorSpace = colorSpace();
+    qCDebug(lcQpaBackingStore) << "Updating color space of existing buffers to" << newColorSpace;
     for (auto &buffer : m_buffers) {
         if (buffer)
-            buffer->setColorSpace(colorSpace());
+            buffer->setColorSpace(newColorSpace);
     }
 }
 
diff --git a/src/plugins/platforms/cocoa/qcocoawindow.mm b/src/plugins/platforms/cocoa/qcocoawindow.mm
index 14c72fd91a..4a245a0f8a 100644
--- a/src/plugins/platforms/cocoa/qcocoawindow.mm
+++ b/src/plugins/platforms/cocoa/qcocoawindow.mm
@@ -1812,11 +1812,15 @@ QCocoaNSWindow *QCocoaWindow::createNSWindow(bool shouldBePanel)
 
     applyContentBorderThickness(nsWindow);
 
-    if (QColorSpace colorSpace = format().colorSpace(); colorSpace.isValid()) {
-        NSData *iccData = colorSpace.iccProfile().toNSData();
-        nsWindow.colorSpace = [[[NSColorSpace alloc] initWithICCProfileData:iccData] autorelease];
-        qCDebug(lcQpaDrawing) << "Set" << this << "color space to" << nsWindow.colorSpace;
-    }
+    // We propagate the view's color space granulary to both the IOSurfaces
+    // used for QSurface::RasterSurface, as well as the CAMetalLayer used for
+    // QSurface::MetalSurface, but for QSurface::OpenGLSurface we don't have
+    // that option as we use NSOpenGLContext instead of CAOpenGLLayer. As a
+    // workaround we set the NSWindow's color space, which affects GL drawing
+    // with NSOpenGLContext as well. This does not conflict with the granular
+    // modifications we do to each surface for raster or Metal.
+    if (auto *qtView = qnsview_cast(m_view))
+        nsWindow.colorSpace = qtView.colorSpace;
 
     return nsWindow;
 }
diff --git a/src/plugins/platforms/cocoa/qnsview.h b/src/plugins/platforms/cocoa/qnsview.h
index e41f5a7296..7f845a5c3b 100644
--- a/src/plugins/platforms/cocoa/qnsview.h
+++ b/src/plugins/platforms/cocoa/qnsview.h
@@ -32,6 +32,12 @@ QT_DECLARE_NAMESPACED_OBJC_INTERFACE(QNSView, NSView
 - (void)cancelComposingText;
 @end
 
+Q_FORWARD_DECLARE_OBJC_CLASS(NSColorSpace);
+
+@interface QNSView (DrawingAPI)
+@property (nonatomic, readonly) NSColorSpace *colorSpace;
+@end
+
 @interface QNSView (QtExtras)
 @property (nonatomic, readonly) QCocoaWindow *platformWindow;
 @end
diff --git a/src/plugins/platforms/cocoa/qnsview.mm b/src/plugins/platforms/cocoa/qnsview.mm
index 6cb10efa7f..1286e8e382 100644
--- a/src/plugins/platforms/cocoa/qnsview.mm
+++ b/src/plugins/platforms/cocoa/qnsview.mm
@@ -90,6 +90,7 @@ QT_NAMESPACE_ALIAS_OBJC_CLASS(QNSViewMenuHelper);
 @property (assign) NSView* previousSuperview;
 @property (assign) NSWindow* previousWindow;
 @property (retain) QNSViewMenuHelper* menuHelper;
+@property (nonatomic, retain) NSColorSpace *colorSpace;
 @end
 
 @implementation QNSView {
@@ -119,6 +120,8 @@ QT_NAMESPACE_ALIAS_OBJC_CLASS(QNSViewMenuHelper);
     NSDraggingContext m_lastSeenContext;
 }
 
+@synthesize colorSpace = m_colorSpace;
+
 - (instancetype)initWithCocoaWindow:(QCocoaWindow *)platformWindow
 {
     if ((self = [super initWithFrame:NSZeroRect])) {
diff --git a/src/plugins/platforms/cocoa/qnsview_drawing.mm b/src/plugins/platforms/cocoa/qnsview_drawing.mm
index 77fa8259ac..bf102e43f8 100644
--- a/src/plugins/platforms/cocoa/qnsview_drawing.mm
+++ b/src/plugins/platforms/cocoa/qnsview_drawing.mm
@@ -13,6 +13,14 @@
             << " QT_MAC_WANTS_LAYER/_q_mac_wantsLayer has no effect.";
     }
 
+    // Pick up and persist requested color space from surface format
+    const QSurfaceFormat surfaceFormat = m_platformWindow->format();
+    if (QColorSpace colorSpace = surfaceFormat.colorSpace(); colorSpace.isValid()) {
+        NSData *iccData = colorSpace.iccProfile().toNSData();
+        self.colorSpace = [[[NSColorSpace alloc] initWithICCProfileData:iccData] autorelease];
+    }
+
+    // Trigger creation of the layer
     self.wantsLayer = YES;
 }
 
@@ -28,6 +36,12 @@
     return YES;
 }
 
+- (NSColorSpace*)colorSpace
+{
+    // If no explicit color space was set, use the NSWindow's color space
+    return m_colorSpace ? m_colorSpace : self.window.colorSpace;
+}
+
 // ----------------------- Layer setup -----------------------
 
 - (BOOL)shouldUseMetalLayer
@@ -93,12 +107,7 @@
 
     [super setLayer:layer];
 
-    // When adding a view to a view hierarchy the backing properties will change
-    // which results in updating the contents scale, but in case of switching the
-    // layer on a view that's already in a view hierarchy we need to manually ensure
-    // the scale is up to date.
-    if (self.superview)
-        [self updateLayerContentsScale];
+    [self propagateBackingProperties];
 
     if (self.opaque && lcQpaDrawing().isDebugEnabled()) {
         // If the view claims to be opaque we expect it to fill the entire
@@ -131,8 +140,7 @@
 {
     qCDebug(lcQpaDrawing) << "Backing properties changed for" << self;
 
-    if (self.layer)
-        [self updateLayerContentsScale];
+    [self propagateBackingProperties];
 
     // Ideally we would plumb this situation through QPA in a way that lets
     // clients invalidate their own caches, recreate QBackingStore, etc.
@@ -141,8 +149,11 @@
     [self setNeedsDisplay:YES];
 }
 
-- (void)updateLayerContentsScale
+- (void)propagateBackingProperties
 {
+    if (!self.layer)
+        return;
+
     // We expect clients to fill the layer with retina aware content,
     // based on the devicePixelRatio of the QWindow, so we set the
     // layer's content scale to match that. By going via devicePixelRatio
@@ -153,6 +164,12 @@
     auto devicePixelRatio = m_platformWindow->devicePixelRatio();
     qCDebug(lcQpaDrawing) << "Updating" << self.layer << "content scale to" << devicePixelRatio;
     self.layer.contentsScale = devicePixelRatio;
+
+    if ([self.layer isKindOfClass:CAMetalLayer.class]) {
+        CAMetalLayer *metalLayer = static_cast<CAMetalLayer *>(self.layer);
+        metalLayer.colorspace = self.colorSpace.CGColorSpace;
+        qCDebug(lcQpaDrawing) << "Set" << metalLayer << "color space to" << metalLayer.colorspace;
+    }
 }
 
 /*