Native style: add hover effects to ScrollBar on macOS

Change-Id: I61bb0c2b1fd4dce2939bc4fe91a498a280802cb9
Reviewed-by: Mitch Curtis <mitch.curtis@qt.io>

3 files changed, 48 insertions, 0 deletions

diff --git a/src/imports/controls/macos/ScrollBar.qml b/src/imports/controls/macos/ScrollBar.qml
index cfd5735e..8facff8e 100644
--- a/src/imports/controls/macos/ScrollBar.qml
+++ b/src/imports/controls/macos/ScrollBar.qml
@@ -40,4 +40,24 @@ import QtQuick.Controls.impl 2.12
 import QtQuick.NativeStyle 6.0 as NativeStyle
 
 NativeStyle.DefaultScrollBar {
+    id: controlRoot
+
+    contentItem: NativeStyle.ScrollBar {
+        control: controlRoot
+        subControl: NativeStyle.ScrollBar.Handle
+        overrideState: NativeStyle.ScrollBar.NeverHovered
+    }
+
+    NativeStyle.ScrollBar {
+        // Fade a hovered-looking version of the handle
+        // on top of the default handle when hovering it
+        anchors.fill: contentItem
+        control: controlRoot
+        subControl: NativeStyle.ScrollBar.Handle
+        overrideState: NativeStyle.ScrollBar.AlwaysHovered
+        opacity: controlRoot.hovered || control.pressed ? 1 : 0
+        visible: contentItem instanceof NativeStyle.StyleItem
+        Behavior on opacity { NumberAnimation { duration: 150 } }
+    }
+
 }
diff --git a/src/imports/nativestyle/items/qquickstyleitemscrollbar.cpp b/src/imports/nativestyle/items/qquickstyleitemscrollbar.cpp
index 7a462082..72f850a8 100644
--- a/src/imports/nativestyle/items/qquickstyleitemscrollbar.cpp
+++ b/src/imports/nativestyle/items/qquickstyleitemscrollbar.cpp
@@ -83,6 +83,17 @@ void QQuickStyleItemScrollBar::initStyleOption(QStyleOptionSlider &styleOption)
     if (scrollBar->isPressed())
         styleOption.state |= QStyle::State_Sunken;
 
+#ifdef Q_OS_MACOS
+    if (m_overrideState != None) {
+        // In ScrollBar.qml we fade between two versions of
+        // the handle, depending on if it's hovered or not
+        if (m_overrideState & AlwaysHovered)
+            styleOption.state |= QStyle::State_Sunken;
+        else if (m_overrideState & NeverHovered)
+            styleOption.state &= ~QStyle::State_Sunken;
+    }
+#endif
+
     // The following values will let the handle fill 100% of the
     // groove / imageSize. But when the handle is resized by
     // QQuickScrollBar, it will end up with the correct size visually.
diff --git a/src/imports/nativestyle/items/qquickstyleitemscrollbar.h b/src/imports/nativestyle/items/qquickstyleitemscrollbar.h
index e181d4ec..db241ad8 100644
--- a/src/imports/nativestyle/items/qquickstyleitemscrollbar.h
+++ b/src/imports/nativestyle/items/qquickstyleitemscrollbar.h
@@ -46,6 +46,10 @@ class QQuickStyleItemScrollBar : public QQuickStyleItem
 
     Q_PROPERTY(SubControl subControl MEMBER m_subControl)
 
+#ifdef Q_OS_MACOS
+    Q_PROPERTY(OverrideState overrideState MEMBER m_overrideState)
+#endif
+
     QML_NAMED_ELEMENT(ScrollBar)
 
 public:
@@ -55,6 +59,15 @@ public:
     };
     Q_ENUM(SubControl)
 
+#ifdef Q_OS_MACOS
+    enum OverrideState {
+        None = 0,
+        AlwaysHovered,
+        NeverHovered,
+    };
+    Q_ENUM(OverrideState)
+#endif
+
     QFont styleFont(QQuickItem *control) override;
 
 protected:
@@ -67,6 +80,10 @@ private:
 
 private:
    SubControl m_subControl = Groove;
+
+#ifdef Q_OS_MACOS
+    OverrideState m_overrideState = None;
+#endif
 };
 
 #endif // QQUICKSTYLEITEMSCROLLBAR_H