DevTools: [Console] Separate height caching from willHide event

Source/devtools/front_end/ui/ViewportControl.js

Index: Source/devtools/front_end/ui/ViewportControl.js
diff --git a/Source/devtools/front_end/ui/ViewportControl.js b/Source/devtools/front_end/ui/ViewportControl.js
index 80fc0820200c41a3a01b411bab206c377cfd44df..8565ec81068b8d4300009f78fdb76c8461b0d498 100644
--- a/Source/devtools/front_end/ui/ViewportControl.js
+++ b/Source/devtools/front_end/ui/ViewportControl.js
@@ -88,6 +88,8 @@ WebInspector.ViewportControl.Provider.prototype = {
  */
 WebInspector.ViewportElement = function() { }
 WebInspector.ViewportElement.prototype = {
+    cacheHeight: function() { },

[aandrey, 2014/06/17 19:21:34]

maybe willReLayout()?
one may want to cache something else than height, e.g. clientWidth or scrollTop.

or is it only the height that needs to be cached?

is there any contract between this method and
ViewportControl.Provider.fastHeight?
if so, maybe call it cacheFastHeight?
moreover, maybe it should be moved to ViewportControl.Provider interface next to
fastHeight, or move the fastHeight into this interface?

+
     willHide: function() { },
 
     wasShown: function() { },
@@ -109,6 +111,8 @@ WebInspector.StaticViewportElement = function(element)
 }
 
 WebInspector.StaticViewportElement.prototype = {
+    cacheHeight: function() { },
+
     willHide: function() { },
 
     wasShown: function() { },
@@ -330,6 +334,8 @@ WebInspector.ViewportControl.prototype = {
         var itemCount = this._provider.itemCount();
         if (!itemCount) {
             for (var i = 0; i < this._renderedItems.length; ++i)
+                this._renderedItems[i].cacheHeight();
+            for (var i = 0; i < this._renderedItems.length; ++i)
                 this._renderedItems[i].willHide();
             this._renderedItems = [];
             this._contentElement.removeChildren();
@@ -350,7 +356,7 @@ WebInspector.ViewportControl.prototype = {
         if (this._cumulativeHeights && itemCount !== this._cumulativeHeights.length)
             delete this._cumulativeHeights;
         for (var i = 0; i < this._renderedItems.length; ++i) {
-            this._renderedItems[i].willHide();
+            this._renderedItems[i].cacheHeight();
             // Tolerate 1-pixel error due to double-to-integer rounding errors.
             if (this._cumulativeHeights && Math.abs(this._cachedItemHeight(this._firstVisibleIndex + i) - this._provider.fastHeight(i + this._firstVisibleIndex)) > 1)
                 delete this._cumulativeHeights;
@@ -372,6 +378,8 @@ WebInspector.ViewportControl.prototype = {
         this._bottomGapElement._active = !!bottomGapHeight;
 
         this._contentElement.style.setProperty("height", "10000000px");
+        for (var i = 0; i < this._renderedItems.length; ++i)
+            this._renderedItems[i].willHide();
         this._renderedItems = [];
         this._contentElement.removeChildren();
         for (var i = this._firstVisibleIndex; i <= this._lastVisibleIndex; ++i) {