Remove unnecessary placeholder

Text.implicitWidth holds the size the text would be if it wasn't
truncated

src/declarativeimports/core/private/DefaultToolTip.qml

@@ -71,18 +71,10 @@ Row {
         x: _s
         y: _s
 
-        //This instance is purely for metrics
-        PlasmaExtras.Heading {
-            id: tooltipMaintextPlaceholder
-            visible: false
-            level: 3
-            text: toolTip ? toolTip.mainText : ""
-        }
         PlasmaExtras.Heading {
             id: tooltipMaintext
             level: 3
-            width: Math.min(tooltipMaintextPlaceholder.width, preferredTextWidth)
-            //width: 400
+            width: Math.min(tooltipMaintext.implicitWidth, preferredTextWidth)
             elide: Text.ElideRight
             text: toolTip ? toolTip.mainText : ""
         }

tests/tooltip.qml

@@ -0,0 +1,71 @@
+import QtQuick 2.2
+
+import org.kde.plasma.core 2.0 as PlasmaCore
+
+Rectangle {
+    color: "white"
+    width: 600
+    height: 800
+
+    Column {
+        anchors.centerIn: parent
+        spacing: 4
+
+        PlasmaCore.ToolTipArea {
+            width: 300
+            height: 50
+
+            mainText: "This is some really really really really long text that should be truncated"
+            subText: "subtext"
+
+            Rectangle {
+                color: "red"
+                anchors.fill: parent
+            }
+
+            Text {
+                anchors.fill: parent
+                text: "long tooltip"
+            }
+
+        }
+
+        PlasmaCore.ToolTipArea {
+            width: 300
+            height: 50
+
+            mainText: "A"
+            subText: "B"
+
+            Rectangle {
+                color: "red"
+                anchors.fill: parent
+            }
+
+            Text {
+                anchors.fill: parent
+                text: "short tooltip"
+            }
+        }
+
+        PlasmaCore.ToolTipArea {
+            width: 300
+            height: 50
+
+            mainText: "A"
+            subText: "Lorem ipsum dolor sit amet, consectetur adipiscing spaghetti italiano random cheesecake blah blah"
+
+            Rectangle {
+                color: "red"
+                anchors.fill: parent
+            }
+
+            Text {
+                anchors.fill: parent
+                text: "long subtext"
+            }
+        }
+
+    }
+}
+