Add enabled/disable support for Slider plasma component

- The current disabled slider have less opacity when disabled
   instead of custom graphics. Needs to be defined if this is
   the expected behaviour.

- The gallery example was also updated.

Signed-off-by: Daker Fernandes Pinheiro <dakerfp@gmail.com>

declarativeimports/plasmacomponents/Slider.qml

@@ -45,9 +45,12 @@ Item {
 
     width: _isVertical ? 22 : 200
     height: _isVertical ? 200 : 22
+    // TODO: needs to define if there will be specific graphics for
+    //     disabled sliders
+    opacity: enabled ? 1.0 : 0.5
 
     Keys.onUpPressed: {
-        if (!_isVertical)
+        if (!enabled || !_isVertical)
             return;
 
         if (inverted)
@@ -57,6 +60,9 @@ Item {
     }
 
     Keys.onDownPressed: {
+        if (!enabled || !enabled)
+            return;
+
         if (!_isVertical)
             return;
 
@@ -67,7 +73,7 @@ Item {
     }
 
     Keys.onLeftPressed: {
-        if (_isVertical)
+        if (!enabled || _isVertical)
             return;
 
         if (inverted)
@@ -77,7 +83,7 @@ Item {
     }
 
     Keys.onRightPressed: {
-        if (_isVertical)
+        if (!enabled || _isVertical)
             return;
 
         if (inverted)
@@ -189,6 +195,7 @@ Item {
             id: mouseArea
 
             anchors.fill: parent
+            enabled: slider.enabled
             drag {
                 target: fakeHandle
                 axis: Drag.XAxis

declarativeimports/test/gallery/Gallery.qml

@@ -30,8 +30,7 @@ Rectangle {
 
         anchors.fill: parent
         contentWidth: 2200
-        contentHeight: 600
-//        contentX: 500
+        contentHeight: 1000
 
         Row {
             x: 30

declarativeimports/test/gallery/Sliders.qml

@@ -90,33 +90,32 @@ Column {
         }
     }
 
+    Text { text: "Disabled Horizontal Slider" }
+
     PlasmaComponents.Slider {
-        id: slider1
+        id: horizontalSlider
         width: 140
         height: 20
         animated: true
-        Component.onCompleted: {
-            forceActiveFocus();
+        enabled: false
+    }
+
+    Text { text: "Vertical Slider" }
+
+    Row {
+        spacing: 30
+        PlasmaComponents.Slider {
+            id: verticalSlider
+            width: 20
+            height: 140
+            orientation: Qt.Vertical
+            minimumValue: 10
+            maximumValue: 1000
+            stepSize: 50
+            inverted: true
+            animated: true
         }
+        Text { text: verticalSlider.value }
     }
 
-    Text {
-        text: slider1.value
-    }
-
-    PlasmaComponents.Slider {
-        id: slider2
-        width: 20
-        height: 140
-        orientation: Qt.Vertical
-        minimumValue: 10
-        maximumValue: 1000
-        stepSize: 50
-        inverted: true
-        animated: true
-    }
-
-    Text {
-        text: slider2.value
-    }
 }