macOS: Add native interface API to manage visual effect view

NSVisualEffectView is the only supported way to add effects to
views, such as showing a blurred representation of the content
under the window, or within the window.

Now that we render the content of our QNSView into a sublayer
of the view's root layer, we can add NSVisualEffectViews as
child views without obscuring the view's own content, by making
sure that the NSVisualEffectView layer has a lower Z order in
the layer tree of our view's root layer. This works because
adding a layer-backed or -hosted view as a subview will also
add its layer as a sublayer of the view's layer, making the
effect layer and our content layer sibling layers.

Change-Id: Iab822e8462f54025559b3e3f26c7df668c885d75
Reviewed-by: Richard Moe Gustavsen <richard.gustavsen@qt.io>

src/gui/kernel/qplatformwindow_p.h

@@ -30,6 +30,10 @@ struct wl_surface;
 
 #if defined(Q_OS_MACOS)
 Q_FORWARD_DECLARE_OBJC_CLASS(CALayer);
+typedef long NSInteger;
+enum NSVisualEffectMaterial : NSInteger;
+enum NSVisualEffectBlendingMode : NSInteger;
+enum NSVisualEffectState: NSInteger;
 #endif
 
 QT_BEGIN_NAMESPACE
@@ -63,6 +67,9 @@ struct Q_GUI_EXPORT QCocoaWindow
     virtual void setContentBorderEnabled(bool enable) = 0;
     virtual QPoint bottomLeftClippedByNSWindowOffset() const = 0;
     virtual CALayer *contentLayer() const = 0;
+    virtual void manageVisualEffectArea(quintptr identifier, const QRect &rect,
+        NSVisualEffectMaterial material, NSVisualEffectBlendingMode blendMode,
+        NSVisualEffectState activationState) = 0;
 };
 #endif
 

src/plugins/platforms/cocoa/qcocoawindow.h

@@ -19,11 +19,12 @@
 #include <MoltenVK/mvk_vulkan.h>
 #endif
 
-#include <QHash>
+#include <QtCore/private/qflatmap_p.h>
 
 Q_FORWARD_DECLARE_OBJC_CLASS(NSWindow);
 Q_FORWARD_DECLARE_OBJC_CLASS(NSView);
 Q_FORWARD_DECLARE_OBJC_CLASS(NSCursor);
+Q_FORWARD_DECLARE_OBJC_CLASS(NSVisualEffectView);
 
 #if !defined(__OBJC__)
 using NSInteger = long;
@@ -227,6 +228,11 @@ public: // for QNSView
 
     CALayer *contentLayer() const override;
 
+    void manageVisualEffectArea(quintptr identifier, const QRect &rect,
+        NSVisualEffectMaterial material, NSVisualEffectBlendingMode blendMode,
+        NSVisualEffectState activationState) override;
+    QFlatMap<quintptr, NSVisualEffectView*> m_effectViews;
+
     NSView *m_view = nil;
     QCocoaNSWindow *m_nsWindow = nil;
 

src/plugins/platforms/cocoa/qcocoawindow.mm

@@ -2224,6 +2224,47 @@ CALayer *QCocoaWindow::contentLayer() const
     return layer;
 }
 
+void QCocoaWindow::manageVisualEffectArea(quintptr identifier, const QRect &rect,
+    NSVisualEffectMaterial material, NSVisualEffectBlendingMode blendMode,
+    NSVisualEffectState activationState)
+{
+    if (!qt_objc_cast<QContainerLayer*>(m_view.layer)) {
+        qCWarning(lcQpaWindow) << "Can not manage visual effect areas"
+            << "in views without a container layer";
+        return;
+    }
+
+    qCDebug(lcQpaWindow) << "Updating visual effect area" << identifier
+        << "to" << rect << "with material" << material << "blend mode"
+        << blendMode << "and activation state" << activationState;
+
+    NSVisualEffectView *effectView = nullptr;
+    if (m_effectViews.contains(identifier)) {
+        effectView = m_effectViews.value(identifier);
+        if (rect.isEmpty()) {
+            [effectView removeFromSuperview];
+            m_effectViews.remove(identifier);
+            return;
+        }
+    } else if (!rect.isEmpty()) {
+        effectView = [NSVisualEffectView new];
+        // Ensure that the visual effect layer is stacked well
+        // below our content layer (which defaults to a z of 0).
+        effectView.wantsLayer = YES;
+        effectView.layer.zPosition = -FLT_MAX;
+        [m_view addSubview:effectView];
+        m_effectViews.insert(identifier, effectView);
+    }
+
+    if (!effectView)
+        return;
+
+    effectView.frame = rect.toCGRect();
+    effectView.material = material;
+    effectView.blendingMode = blendMode;
+    effectView.state = activationState;
+}
+
 #ifndef QT_NO_DEBUG_STREAM
 QDebug operator<<(QDebug debug, const QCocoaWindow *window)
 {