Timeline: Don't add and remove batch roots

Every time a batch root is added or removed the whole scene is rebuilt.
Instead of using the "visible" property we can collapse items to a
height of 0 in order to make them invisible while keeping them in the
scene. This avoids the rebuilds.

Change-Id: Icc6dddb8c8f892a37ef4ed5bced501e5f1658d80
Reviewed-by: Joerg Bornemann <joerg.bornemann@theqtcompany.com>

src/libs/timeline/qml/MainView.qml

@@ -284,12 +284,12 @@ Rectangle {
     Flickable {
         flickableDirection: Flickable.HorizontalFlick
         clip: true
-        visible: selectionRangeMode &&
-                 selectionRange.creationState !== selectionRange.creationInactive
         interactive: false
         x: content.x + content.flickableItem.x
         y: content.y + content.flickableItem.y
-        height: content.flickableItem.height
+        height: (selectionRangeMode &&
+                 selectionRange.creationState !== selectionRange.creationInactive) ?
+                    content.flickableItem.height : 0
         width: content.flickableItem.width
         contentX: content.contentX
         contentWidth: content.contentWidth
@@ -297,7 +297,6 @@ Rectangle {
         SelectionRange {
             id: selectionRange
             zoomer: zoomControl
-            visible: parent.visible
 
             onRangeDoubleClicked: {
                 var diff = 500 - zoomer.selectionDuration;
@@ -319,11 +318,12 @@ Rectangle {
 
         clip: true
         id: selectionRangeDetails
-        visible: selectionRange.visible
         startTime: zoomControl.selectionStart
         duration: zoomControl.selectionDuration
         endTime: zoomControl.selectionEnd
         showDuration: selectionRange.rangeWidth > 1
+        hasContents: selectionRangeMode &&
+                     selectionRange.creationState !== selectionRange.creationInactive
 
         onRecenter: {
             if ((zoomControl.selectionStart < zoomControl.rangeStart) ^
@@ -342,7 +342,6 @@ Rectangle {
         id: rangeDetails
 
         z: 3
-        visible: false
         x: 200
         y: 25
 
@@ -350,6 +349,7 @@ Rectangle {
         locked: content.selectionLocked
         models: timelineModelAggregator.models
         notes: timelineModelAggregator.notes
+        hasContents: false
         onRecenterOnItem: {
             content.gotoSourceLocation(file, line, column);
             content.select(selectedModel, selectedItem)

src/libs/timeline/qml/RangeDetails.qml

@@ -40,6 +40,7 @@ Item {
     property int line
     property int column
     property bool isBindingLoop
+    property bool hasContents
 
     property int selectedModel: -1
     property int selectedItem: -1
@@ -54,11 +55,11 @@ Item {
     signal clearSelection
 
     width: col.width + 25
-    height: contentArea.height + titleBar.height
+    height: hasContents ? contentArea.height + titleBar.height : 0
 
     function hide() {
         noteEdit.focus = false;
-        visible = false;
+        hasContents = false;
         selectedModel = selectedItem = -1;
         noteEdit.text = "";
         duration = "";
@@ -97,7 +98,7 @@ Item {
                 eventInfo.append({content : eventData[k]});
             }
         }
-        rangeDetails.visible = true;
+        hasContents = true;
 
         var location = timelineModel.location(selectedItem)
         if (location.hasOwnProperty("file")) { // not empty

src/libs/timeline/qml/SelectionRangeDetails.qml

@@ -40,9 +40,10 @@ Item {
     property string endTime
     property string duration
     property bool showDuration
+    property bool hasContents
 
     width: Math.max(150, col.width + 25)
-    height: col.height + 30
+    height: hasContents ? col.height + 30 : 0
 
     // keep inside view
     Connections {