Begin fading the OSD immediately

REVIEW: 124409

lookandfeel/contents/osd/Osd.qml

@@ -38,6 +38,20 @@ PlasmaCore.Dialog {
     // false for displaying the value as normal text
     property bool showingProgress: false
 
+    property bool animateOpacity: false
+
+    Behavior on opacity {
+        SequentialAnimation {
+            // prevent press and hold from flickering
+            PauseAnimation { duration: 100 }
+            NumberAnimation {
+                duration: root.timeout
+                easing.type: Easing.InQuad
+            }
+        }
+        enabled: root.animateOpacity
+    }
+
     mainItem: OsdItem {
         rootItem: root
     }

shell/osd.cpp

@@ -125,7 +125,21 @@ void Osd::showText(const QString &icon, const QString &text)
 
 void Osd::showOsd()
 {
-    m_osdObject->rootObject()->setProperty("visible", true);
+    m_osdTimer->stop();
+    auto *rootObject = m_osdObject->rootObject();
+
+    // if our OSD understands animating the opacity, do it;
+    // otherwise just show it to not break existing lnf packages
+    if (rootObject->property("animateOpacity").isValid()) {
+        rootObject->setProperty("animateOpacity", false);
+        rootObject->setProperty("opacity", 1);
+        rootObject->setProperty("visible", true);
+        rootObject->setProperty("animateOpacity", true);
+        rootObject->setProperty("opacity", 0);
+    } else {
+        rootObject->setProperty("visible", true);
+    }
+
     m_osdTimer->start(m_timeout);
 }