Fixed alpha inheritance for GUI

dist/preview release/canvas2D/babylon.canvas2d.d.ts

@@ -3066,6 +3066,7 @@ declare module BABYLON {
         addNewTransparentPrimitiveInfo(prim: RenderablePrim2D, gii: GroupInstanceInfo): TransparentPrimitiveInfo;
         removeTransparentPrimitiveInfo(tpi: TransparentPrimitiveInfo): void;
         transparentPrimitiveZChanged(tpi: TransparentPrimitiveInfo): void;
+        resetPrimDirtyList(): void;
         _primDirtyList: Array<Prim2DBase>;
         _primNewDirtyList: Array<Prim2DBase>;
         _childrenRenderableGroups: Array<Group2D>;

dist/preview release/canvas2D/babylon.canvas2d.js

@@ -12095,7 +12095,7 @@ var BABYLON;
                         engine.setViewport(curVP);
                     }
                 }
-                this._renderableData._primDirtyList.length = 0;
+                this._renderableData.resetPrimDirtyList();
                 // Restore saved states
                 engine.setAlphaTesting(curAlphaTest);
                 engine.setDepthWrite(curDepthWrite);
@@ -12618,6 +12618,16 @@ var BABYLON;
             this._transparentListChanged = true;
             //this.updateSmallestZChangedPrim(tpi);
         };
+        RenderableGroupData.prototype.resetPrimDirtyList = function () {
+            var dirtyList = this._primDirtyList;
+            var numDirty = dirtyList.length;
+            for (var i = 0; i < numDirty; i++) {
+                if (dirtyList[i]._isFlagSet(BABYLON.SmartPropertyPrim.flagPrimInDirtyList)) {
+                    dirtyList[i]._resetPropertiesDirty();
+                }
+            }
+            dirtyList.length = 0;
+        };
         return RenderableGroupData;
     }());
     BABYLON.RenderableGroupData = RenderableGroupData;

dist/preview release/gui/babylon.gui.d.ts

@@ -105,6 +105,7 @@ declare module BABYLON.GUI {
     class Control {
         name: string;
         private _alpha;
+        private _alphaSet;
         private _zIndex;
         _root: Container;
         _host: AdvancedDynamicTexture;

dist/preview release/gui/babylon.gui.js

@@ -558,6 +558,7 @@ var BABYLON;
             function Control(name) {
                 this.name = name;
                 this._alpha = 1;
+                this._alphaSet = false;
                 this._zIndex = 0;
                 this._currentMeasure = GUI.Measure.Empty();
                 this._fontFamily = "Arial";
@@ -631,6 +632,7 @@ var BABYLON;
                     if (this._alpha === value) {
                         return;
                     }
+                    this._alphaSet = true;
                     this._alpha = value;
                     this._markAsDirty();
                 },
@@ -1035,7 +1037,9 @@ var BABYLON;
                 if (this._color) {
                     context.fillStyle = this._color;
                 }
-                context.globalAlpha = this._alpha;
+                if (this._alphaSet) {
+                    context.globalAlpha = this._alpha;
+                }
             };
             Control.prototype._processMeasures = function (parentMeasure, context) {
                 if (this._isDirty || !this._cachedParentMeasure.isEqualsTo(parentMeasure)) {

gui/src/controls/control.ts

@@ -3,6 +3,7 @@
 module BABYLON.GUI {
     export class Control {       
         private _alpha = 1; 
+        private _alphaSet = false; 
         private _zIndex = 0;
         public _root: Container;
         public _host: AdvancedDynamicTexture;
@@ -93,7 +94,7 @@ module BABYLON.GUI {
             if (this._alpha === value) {
                 return;
             }
-
+            this._alphaSet = true;
             this._alpha = value;
             this._markAsDirty();
         }                 
@@ -485,7 +486,9 @@ module BABYLON.GUI {
                 context.fillStyle = this._color;
             }
 
-            context.globalAlpha = this._alpha;
+            if (this._alphaSet) {
+                context.globalAlpha = this._alpha;
+            }
         }
 
         protected _processMeasures(parentMeasure: Measure, context: CanvasRenderingContext2D): boolean {