[whatwg] Why Canvas?

[WeBMartians]

With <canvas> a relatively stable (and implemented, actually) tag, this may be a doubtful question. However, I can't think of any answer, so here goes...

Why <canvas>?

Why not allow the graphics primitives to operate on any element (not just <canvas>) that has a height and width that may be expressed in picture elements... ...even window.screen with its .availHeight, .availWidth, .height, and .width (yeah, I know, the Screen object is actually a JavaScript object, not an HTML DOM object)?

The utility is amazing: a tutorial option could then lead a user through a page or series of pages, circling/outlining an input item ("Fill in this, first!"), then circling a set of, say, radio buttons ("Now, select one of these!"), and, finally, circling the Submit button ("Congratulations! You did it!"). You can see how this would give an instant advantage in Total-Ownership-Cost to Web Applications.

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B. de Graaf - WeBMartians at Verizon.net