Re: nsIDOMCanvasRenderingContext2d embedding in 1.9.2 ?

On 08/11/2010 13:45, Benjamin Smedberg wrote:
> This really doesn't make any sense. The way to get a canvas rendering 
> context is to create a <canvas> element and then call 
> .getContext('2d') on it. Otherwise your rendering context isn't 
> actually backed by a drawing buffer.
>
> --BDS

I may well be mistaken :).  The full sequence I've actually coded is 
below. Still not quite sure how to get bitmap data from the context but 
this should associate a canvas with the context?

// create context
nsCOMPtr<nsICanvasRenderingContextInternal> context;
     context = 
do_CreateInstance("@mozilla.org/content/canvas-rendering-context;1?id=2d", 
&rv);
     if (!(NS_SUCCEEDED(rv) && context))
     {
         return 0;
     }

     context->SetDimensions(widthIn,heightIn);
     context->SetCanvasElement(nsnull);

// create canvas
     nsCOMPtr<nsIDOMCanvasRenderingContext2D> canvas;
     canvas = do_QueryInterface(context, &rv);
     if (!(NS_SUCCEEDED(rv) && canvas))
     {
         return 0;
     }

// get canvas to draw
     PRUint32 flags = 0;
     nsString bg(L"rgb(0,0,0)");
     rv = canvas->DrawWindow(domWindow,xIn,yIn,widthIn,heightIn,bg,flags);
     if (!(NS_SUCCEEDED(rv)))
     {
         return 0;
     }
// recover bitmap ...

Thx.