[webkit-dev] Canvas backing resolution

[Kenneth Rohde Christiansen]

Hi again,

> I'm trying to keep the canvas bitmap at the same pixel resolution as the
> device,
> otherwise it is blurry.

OK, I see.

> This, for example, works if the pixel ratio is 2.
> <canvas style="width: 100px; height: 100px;" width="200"
> height="200"></canvas>
>

> Yes, when the user has a zoom level set, I'd like to paint to match the
> pixel ratio,
> so that, a zoomed in user still receives crisp output, instead of blurry
> output.

-webkit-device-pixel-ratio does not change when the user scaled the
content; it is a device value.

On old iPhone it is 1.0, on Android it can be 0.5, 1.0 and 1.5
depending on it being a low, medium (160) or high dpi (240) device. On
the iPhone 4 and the new iPod Touch it is 2.0.

On Android devices, with for instance, a device-pixel-ratio of 1.5,
you can disable the upscaling by adding target-densitydpi=device-dpi
to the viewport meta tag.

What you can do is to disable user scaling (add user-scaling=no to the
viewport meta tag) and then handle zooming in your app using the touch
events. This only works on mobile devices though.

Cheers,

-- 
Kenneth Rohde Christiansen
Senior Engineer
Application and Service Frameworks, Nokia Danmark A/S
Phone  +45 4093 0598 / E-mail kenneth.christiansen at gmail.com

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