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[Public WebGL] How to unambiguously set canvas pixel size to be pixel-perfect?



Hi there,

I raised a discussion about the need for explicit API or spec-guaranteed mechanism for resizing a WebGL canvas size to be pixel-perfect in the WebGL issue tracker. In the interest of not retyping everything, here's a link to the details: 

https://github.com/KhronosGroup/WebGL/issues/587

The quick summary: When trying to come up the proper device pixel size for a WebGL canvas so that it properly matches the actual size displayed by the browser, fractional window.devicePixelRatio values in the wild (1.5 and 2.25 have been seen) pose problems, and to get the right result, one has to either floor, round or ceil the result depending on the devicePixelRatio and device resolution in question.

We need to spec down a method that is guaranteed to work so that off-by-one-pixel errors cannot possibly occur. What should such a mechanism look like that can take into account arbitrarily fractional devicePixelRatios out there?

Jukka