[whatwg] Why Canvas?

WeBMartians webmartians at verizon.net
Wed Aug 1 04:25:41 PDT 2007

Sorry, Andrew. I missed seeing your email and did not include it in my latest - I haven't had my orange juice yet, and while I may be standing with my eyes open, my brain hasn't yet caught up.

I completely missed the CSS aspect and the foreground/background image slant as well. Good call.

The introduction of foreground images as well as background images makes things a lot more complicated:

- Which one is selected by
	var cvs = document.getElementById(<elementIdentity>);?
- If you have one foreground image, why not have many in layers?
- If you have layers, what about transparency (or alpha) and what about Z-order changes?
	Wow! World of Warcraft superimposed over the nightly news video!
	...given 3D ... Halo superimposed over WWft over nightly news...

Shudder... I think this will require more than orange juice. It may be best to let this monster snooze until HTML 6.

-----Original Message-----
From: Andrew Fedoniouk [mailto:news at terrainformatica.com] 
Sent: Tuesday, 2007 July 31 20:44
To: WeBMartians; whatwg at whatwg.org
Subject: Re: [whatwg] Why Canvas?

----- Original Message -----
From: "WeBMartians" <webmartians at verizon.net>
To: <whatwg at whatwg.org>
Sent: Tuesday, July 31, 2007 4:34 PM
Subject: [whatwg] Why Canvas?

> 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)?

I think this discussion
is related to the subject.

Image (object) has pixel buffer so it is pretty logical to add
Graphics interface to it. The only feature left is 
style.setBackgroundImage() method:

var el = document.getElement....;
el.style.setBackgroundImage( el );

In this case it would be possible to render graphics on any element.

And if we will add 'foreground-image' CSS attribute & friends (similar to
backround-*** attributes) then you would have an option to choose where
to draw it - on background or on foreground layer (on top of the content)

Andrew Fedoniouk.

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