SwitchStyle: Make it work with pre-Holo Android

The Switch control was introduced in Android 4.0 together with
the Holo UI. Therefore, there's no way we can extract assets
on devices running earlier versions. In that case, we fall back
to the Base style Switch visuals.

Change-Id: I48d8a5cd94999cd5687fab62c8d16beb4fc53b5c
Reviewed-by: J-P Nurmi <jpnurmi@digia.com>

src/controls/Styles/Android/SwitchStyle.qml

@@ -41,88 +41,95 @@ import QtQuick 2.4
 import QtQuick.Window 2.2
 import QtQuick.Controls 1.2
 import QtQuick.Controls.Private 1.0
+import QtQuick.Controls.Styles 1.2
 import QtQuick.Controls.Styles.Android 1.0
 import "drawables"
 
-Style {
+SwitchStyle {
     property Switch control: __control
+    readonly property bool hasHoloSwitch: !!AndroidStyle.styleDef.switchStyle
 
-    property Component panel: Item {
-        id: panel
+    Component.onCompleted: if (hasHoloSwitch) panel = holoPanel
 
-        // TODO: API level < 14
-        readonly property var styleDef: AndroidStyle.styleDef.switchStyle
-
-        implicitWidth: Math.max(styleDef.Switch_switchMinWidth, Math.max(track.implicitWidth, 2 * thumb.implicitWidth))
-        implicitHeight: Math.max(track.implicitHeight, thumb.implicitHeight)
-
-        property real min: track.padding.left
-        property real max: track.width - thumb.width - track.padding.left
-        property var __handle: thumb
-
-        DrawableLoader {
-            id: track
-            anchors.fill: parent
-            pressed: control.pressed
-            checked: control.checked
-            focused: control.activeFocus
-            window_focused: control.window && control.window.active
-            styleDef: panel.styleDef.Switch_track
-        }
+    Component {
+        id: holoPanel
 
         Item {
-            id: thumb
-
-            x: control.checked ? max : min
-
-            FontMetrics {
-                id: metrics
-                font: label.font
-            }
+            id: panel
 
-            readonly property real maxTextWidth: Math.max(metrics.boundingRect(panel.styleDef.Switch_textOn).width,
-                                                          metrics.boundingRect(panel.styleDef.Switch_textOff).width)
+            readonly property var styleDef: AndroidStyle.styleDef.switchStyle
 
-            implicitWidth: Math.max(loader.implicitWidth, maxTextWidth + 2 * panel.styleDef.Switch_thumbTextPadding)
-            implicitHeight: Math.max(loader.implicitHeight, metrics.height)
+            implicitWidth: Math.max(styleDef.Switch_switchMinWidth, Math.max(track.implicitWidth, 2 * thumb.implicitWidth))
+            implicitHeight: Math.max(track.implicitHeight, thumb.implicitHeight)
 
-            anchors.top: parent.top
-            anchors.bottom: parent.bottom
-
-            Behavior on x {
-                id: behavior
-                enabled: thumb.status === Loader.Ready
-                NumberAnimation {
-                    duration: 150
-                    easing.type: Easing.OutCubic
-                }
-            }
+            property real min: track.padding.left
+            property real max: track.width - thumb.width - track.padding.left
+            property var __handle: thumb
 
             DrawableLoader {
-                id: loader
-                anchors.left: parent.left
-                anchors.right: parent.right
-                anchors.leftMargin: -padding.left
-                anchors.rightMargin: -padding.right
-                anchors.verticalCenter: parent.verticalCenter
+                id: track
+                anchors.fill: parent
                 pressed: control.pressed
                 checked: control.checked
                 focused: control.activeFocus
                 window_focused: control.window && control.window.active
-                styleDef: panel.styleDef.Switch_thumb
+                styleDef: panel.styleDef.Switch_track
             }
 
-            LabelStyle {
-                id: label
-                text: control.checked ? panel.styleDef.Switch_textOn : panel.styleDef.Switch_textOff
+            Item {
+                id: thumb
 
-                pressed: control.pressed
-                focused: control.activeFocus
-                selected: control.checked
-                window_focused: control.window && control.window.active
-                styleDef: panel.styleDef.Switch_switchTextAppearance
+                x: control.checked ? max : min
 
-                anchors.fill: parent
+                FontMetrics {
+                    id: metrics
+                    font: label.font
+                }
+
+                readonly property real maxTextWidth: Math.max(metrics.boundingRect(panel.styleDef.Switch_textOn).width,
+                                                              metrics.boundingRect(panel.styleDef.Switch_textOff).width)
+
+                implicitWidth: Math.max(loader.implicitWidth, maxTextWidth + 2 * panel.styleDef.Switch_thumbTextPadding)
+                implicitHeight: Math.max(loader.implicitHeight, metrics.height)
+
+                anchors.top: parent.top
+                anchors.bottom: parent.bottom
+
+                Behavior on x {
+                    id: behavior
+                    enabled: thumb.status === Loader.Ready
+                    NumberAnimation {
+                        duration: 150
+                        easing.type: Easing.OutCubic
+                    }
+                }
+
+                DrawableLoader {
+                    id: loader
+                    anchors.left: parent.left
+                    anchors.right: parent.right
+                    anchors.leftMargin: -padding.left
+                    anchors.rightMargin: -padding.right
+                    anchors.verticalCenter: parent.verticalCenter
+                    pressed: control.pressed
+                    checked: control.checked
+                    focused: control.activeFocus
+                    window_focused: control.window && control.window.active
+                    styleDef: panel.styleDef.Switch_thumb
+                }
+
+                LabelStyle {
+                    id: label
+                    text: control.checked ? panel.styleDef.Switch_textOn : panel.styleDef.Switch_textOff
+
+                    pressed: control.pressed
+                    focused: control.activeFocus
+                    selected: control.checked
+                    window_focused: control.window && control.window.active
+                    styleDef: panel.styleDef.Switch_switchTextAppearance
+
+                    anchors.fill: parent
+                }
             }
         }
     }