Check for a valid rendering context before we actually start drawing. Use a new stack-based class for saving rendering context state. Hopefully, it won't live here forever, but will be ok for everyone to use.

layout/xul/base/src/nsToolboxFrame.cpp

@@ -35,6 +35,28 @@
 #include "nsXULAtoms.h"
 
 
+//
+// class StRenderingContext
+//
+// A stack-based helper class that guarantees taht the state will be restored to it's 
+// previous state when the current scope finishes. It is exception safe.
+//
+class StRenderingContextSaver
+{
+public:
+  StRenderingContextSaver ( nsIRenderingContext & inContext ) : mContext(&inContext) { mContext->PushState(); };
+  ~StRenderingContextSaver ( )
+  {
+    PRBool ignored;
+    mContext->PopState(ignored);
+  }
+
+private:
+  nsCOMPtr<nsIRenderingContext> mContext;
+
+}; // class StRenderingContextSaver
+
+
 //
 // NS_NewToolboxFrame
 //
@@ -180,10 +202,16 @@ void
 nsToolboxFrame :: DrawGrippy (  nsIPresContext& aPresContext, nsIRenderingContext & aRenderingContext,
                                   const nsRect & aBoundingRect, PRBool aDrawHilighted ) const
 {
-  aRenderingContext.PushState();
+  StRenderingContextSaver saved(aRenderingContext);
   
   nsCOMPtr<nsIStyleContext> style ( aDrawHilighted ? mGrippyRolloverStyle : mGrippyNormalStyle ) ;
-  
+  if ( !mGrippyRolloverStyle ) {
+    #ifdef NS_DEBUG
+    printf("nsToolboxFrame::DrawGrippy() -- style context null, css file not loaded correctly??\n");
+    #endif
+    return;   // something must be seriously wrong
+  }
+
   const nsStyleColor*   grippyColor   = (const nsStyleColor*)style->GetStyleData(eStyleStruct_Color);
   const nsStyleSpacing* grippySpacing = (const nsStyleSpacing*)style->GetStyleData(eStyleStruct_Spacing);
   const nsStyleFont*    grippyFont    = (const nsStyleFont*)style->GetStyleData(eStyleStruct_Font);
@@ -194,9 +222,6 @@ nsToolboxFrame :: DrawGrippy (  nsIPresContext& aPresContext, nsIRenderingContex
   nsCSSRendering::PaintBorder(aPresContext, aRenderingContext, nonConstSelf,
                                 aBoundingRect, aBoundingRect, *grippySpacing, style, 0);
 
-  PRBool clipState;
-  aRenderingContext.PopState(clipState);
-
 } // DrawGrippy
 
 
@@ -477,4 +502,4 @@ nsToolboxFrame :: ExpandToolbar ( TabInfo & inTab )
     
   mContent->UnsetAttribute ( nsXULAtoms::nameSpaceID, kSelectedAtom, PR_TRUE );
 
-} // ExpandToolbar
+} // ExpandToolbar