Added showing slow scroll rectangles in Layers panel.

Source/devtools/front_end/Layers3DView.js

Index: Source/devtools/front_end/Layers3DView.js
diff --git a/Source/devtools/front_end/Layers3DView.js b/Source/devtools/front_end/Layers3DView.js
index 411036b855fe2f0b2d4a4711d916642a3a44daa6..37555c55d1a2052a7496d7b39ee0729bc3857bb0 100644
--- a/Source/devtools/front_end/Layers3DView.js
+++ b/Source/devtools/front_end/Layers3DView.js
@@ -50,6 +50,7 @@ WebInspector.Layers3DView = function(model)
     this.element.addEventListener("mousemove", this._onMouseMove.bind(this), false);
     this.element.addEventListener("contextmenu", this._onContextMenu.bind(this), false);
     this._elementsByLayerId = {};
+    this._scrollRectElementsByLayerId = {}

[caseq, 2014/03/11 11:14:38]

unused?

[malch, 2014/03/11 11:49:08]

Done.

     this._scaleAdjustmentStylesheet = this.element.ownerDocument.head.createChild("style");
     this._scaleAdjustmentStylesheet.disabled = true;
     this._lastOutlinedElement = {};
@@ -82,6 +83,15 @@ WebInspector.Layers3DView.PaintRectColors = [
     WebInspector.Color.fromRGBA([0, 0xFF, 0, 0x3F])
 ]
 
+/**
+ * @enum {string}
+ */
+WebInspector.Layers3DView.ScrollRectTitles = {
+    RepaintsOnScroll: WebInspector.UIString("repaints on scroll"),
+    TouchEventHandler: WebInspector.UIString("touch event listener"),
+    WheelEventHandler: WebInspector.UIString("mousewheel event listener")
+}
+
 WebInspector.Layers3DView.prototype = {
     onResize: function()
     {
@@ -153,18 +163,20 @@ WebInspector.Layers3DView.prototype = {
 
     _scaleToFit: function()
     {
-        var root = this._model.contentRoot();
-        if (!root)
+        // var root = this._model.root();
+        // TODO: RENAME
+        var contentRoot = this._model.contentRoot();

[caseq, 2014/03/11 11:14:38]

Do we really have to rename it here?

[malch, 2014/03/11 11:49:08]

Done.

+        if (!contentRoot)
             return;
 
         const padding = 40;
-        var scaleX = this._clientWidth / (root.width() + 2 * padding);
-        var scaleY = this._clientHeight / (root.height() + 2 * padding);
+        var scaleX = this._clientWidth / (contentRoot.width() + 2 * padding);
+        var scaleY = this._clientHeight / (contentRoot.height() + 2 * padding);
         var autoScale = Math.min(scaleX, scaleY);
 
         this._scale = autoScale * this._transformController.scale();
-        this._paddingX = ((this._clientWidth / autoScale - root.width()) >> 1) * this._scale;
-        this._paddingY = ((this._clientHeight / autoScale - root.height()) >> 1) * this._scale;
+        this._paddingX = ((this._clientWidth / autoScale - contentRoot.width()) >> 1) * this._scale;
+        this._paddingY = ((this._clientHeight / autoScale - contentRoot.height()) >> 1) * this._scale;
         const screenLayerSpacing = 20;
         this._layerSpacing = screenLayerSpacing + "px";
         const screenLayerThickness = 4;
@@ -180,7 +192,7 @@ WebInspector.Layers3DView.prototype = {
         else
             stylesheetTextNode.nodeValue = stylesheetContent;
 
-        var style = this._elementForLayer(root).style;
+        var style = this._elementForLayer(contentRoot).style;
         style.left = Math.round(this._paddingX) + "px";
         style.top = Math.round(this._paddingY) + "px";
         style.webkitTransformOrigin = "";
@@ -215,6 +227,61 @@ WebInspector.Layers3DView.prototype = {
         style.webkitTransformOrigin = Math.round(this._paddingX + offsetX + root.width() * this._scale / 2) + "px " + Math.round(this._paddingY + offsetY + root.height() * this._scale / 2) + "px";
     },
 
+    /**
+     * @param {!Element} element
+     */
+    _removeElement: function(element)

[caseq, 2014/03/11 11:14:38]

looks like you can define it within the only remaining function that uses it
now.

[malch, 2014/03/11 11:49:08]

Done.

+    {
+        element.remove()
+    },
+
+    /**
+     * @param {!WebInspector.Layer} layer
+     * @param {!LayerTreeAgent.ScrollRect} scrollRect
+     * @return {!Element}
+     */
+    _createScrollRectElement: function(layer, scrollRect)
+    {
+        var element = document.createElement("div");
+        var style = element.style;

[caseq, 2014/03/11 11:14:38]

unused?

[malch, 2014/03/11 11:49:08]

Done.

+        var parentLayerId = layer.id();

[caseq, 2014/03/11 11:14:38]

inline

[malch, 2014/03/11 11:49:08]

Done.

+        var parentLayerElement = this._elementsByLayerId[parentLayerId];
+        element.className = "scroll-rect";
+        element.title = WebInspector.Layers3DView.ScrollRectTitles[scrollRect.type];
+        parentLayerElement.appendChild(element);
+        return element;
+    },
+
+    /**
+     * @param {!Array.<!Element>} elements
+     * @param {!LayerTreeAgent.ScrollRect} scrollRect
+     * @param {!number} index
+     */
+    _updateScrollRectElement: function(elements, scrollRect, index)
+    {
+        var element = elements[index];
+        var style = element.style;
+        style.width = Math.round(scrollRect.rect.width * this._scale) + "px";
+        style.height = Math.round(scrollRect.rect.height * this._scale) + "px";
+        style.left = Math.round(scrollRect.rect.x * this._scale) + "px";
+        style.top = Math.round(scrollRect.rect.y * this._scale) + "px";
+    },
+
+    /**
+     * @param {!WebInspector.Layer} layer
+     */
+     _updateScrollRectsForLayer: function(layer)
+     {
+        var newScrollRects = layer.scrollRects(),
+            layerDetails = this._elementsByLayerId[layer.id()].__layerDetails;
+        if (newScrollRects != layerDetails.scrollRects) {

[caseq, 2014/03/11 11:14:38]

We use !==

[malch, 2014/03/11 11:49:08]

Done.

+            layerDetails.scrollRectElements.forEach(this._removeElement);
+            layerDetails.scrollRects = newScrollRects;
+            layerDetails.scrollRectElements = layerDetails.scrollRects.map(this._createScrollRectElement.bind(this, layer));
+        }
+        layerDetails.scrollRects.forEach(this._updateScrollRectElement.bind(this, layerDetails.scrollRectElements));
+    },
+
     _update: function()
     {
         if (!this.isShowing()) {
@@ -245,7 +312,8 @@ WebInspector.Layers3DView.prototype = {
         }
         this._scaleToFit();
         this._updateTransform();
-        this._model.forEachLayer(updateLayer.bind(this), this._model.contentRoot());
+        this._model.forEachLayer(updateLayer.bind(this));
+        this._model.forEachLayer(this._updateScrollRectsForLayer.bind(this));
         this._needsUpdate = false;
     },
 
@@ -255,7 +323,8 @@ WebInspector.Layers3DView.prototype = {
     _onLayerPainted: function(event)
     {
         var layer = /** @type {!WebInspector.Layer} */ (event.data);
-        this._updatePaintRect(this._elementForLayer(layer));
+        if (layer.nodeId())
+            this._updatePaintRect(this._elementForLayer(layer));
     },
 
     /**
@@ -272,9 +341,14 @@ WebInspector.Layers3DView.prototype = {
             return element;
         }
         element = document.createElement("div");
-        element.className = "layer-container";
-        ["fill back-wall", "side-wall top", "side-wall right", "side-wall bottom", "side-wall left"].forEach(element.createChild.bind(element, "div"));
-        element.__layerDetails = new WebInspector.LayerDetails(layer, element.createChild("div", "paint-rect"));
+        if (layer.nodeId()) {
+            element.className = "layer-container";
+            ["fill back-wall", "side-wall top", "side-wall right", "side-wall bottom", "side-wall left"].forEach(element.createChild.bind(element, "div"));
+            element.__layerDetails = new WebInspector.LayerDetails(layer, element.createChild("div", "paint-rect"));
+        } else {
+            element.className = "layer-transparent";
+            element.__layerDetails = new WebInspector.LayerDetails(layer);
+        }
         this._elementsByLayerId[layer.id()] = element;
         return element;
     },
@@ -286,18 +360,23 @@ WebInspector.Layers3DView.prototype = {
     {
         var layer = element.__layerDetails.layer;
         var style = element.style;
-        var isContentRoot = layer === this._model.contentRoot();
-        var parentElement = isContentRoot ? this._rotatingContainerElement : this._elementForLayer(layer.parent());
+
+        var contentRoot = /** @type {!WebInspector.Layer} */ (this._model.contentRoot());
+        var isContentRoot = layer === contentRoot;
+        var isRoot = layer === this._model.root();
+        var parentElement = isContentRoot ? this._rotatingContainerElement : (isRoot ? this._elementForLayer(contentRoot) : this._elementForLayer(layer.parent()));
         element.__layerDetails.depth = parentElement.__layerDetails ? parentElement.__layerDetails.depth + 1 : 0;
         element.classList.toggle("invisible", layer.invisible());
-        this._updateElementColor(element);
+        if (layer.nodeId())
+            this._updateElementColor(element);
         if (parentElement !== element.parentElement)
             parentElement.appendChild(element);
 
         style.width = Math.round(layer.width() * this._scale) + "px";
         style.height = Math.round(layer.height() * this._scale) + "px";
-        this._updatePaintRect(element);
-        if (isContentRoot)
+        if (layer.nodeId())
+            this._updatePaintRect(element);
+        if (isContentRoot || isRoot)
             return;
         style.left = Math.round(layer.offsetX() * this._scale) + "px";
         style.top = Math.round(layer.offsetY() * this._scale) + "px";
@@ -322,6 +401,9 @@ WebInspector.Layers3DView.prototype = {
         }
     },
 
+    /**
+     * @param {!Element} element
+     */
     _updatePaintRect: function(element)
     {
         var details = element.__layerDetails;
@@ -426,12 +508,15 @@ WebInspector.Layers3DView.prototype = {
 /**
  * @constructor
  * @param {!WebInspector.Layer} layer
- * @param {!Element} paintRectElement
+ * @param {!Element=} paintRectElement
  */
 WebInspector.LayerDetails = function(layer, paintRectElement)
 {
     this.layer = layer;
     this.depth = 0;
-    this.paintRectElement = paintRectElement;
+    if (paintRectElement)

[caseq, 2014/03/11 11:14:38]

I think you can omit this check.

[malch, 2014/03/11 11:49:08]

Done.

+        this.paintRectElement = paintRectElement;
     this.paintCount = 0;
+    this.scrollRects = [];
+    this.scrollRectElements = [];
 }