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.
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