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High-DPI not working

See original GitHub issue

I’m trying to use the high-dpi mode of Squeak 6.0 but whenever I open or move SqueakJS on a high-DPI screen, the VM seems to scale up the entire canvas instead of informing the image about the new scale factor via primitiveScreenScaleFactor (which always fails right now).

Shouldn’t pixelation already work? I tried something like

https://9090-codefrau-squeakjs-39cuvd00s49.ws-eu53.gitpod.io/run/#pixelated=true&image=/FreshTrunk.image
https://9090-codefrau-squeakjs-39cuvd00s49.ws-eu53.gitpod.io/run/#pixelated=false&image=/FreshTrunk.image

But there was no visible difference.

Issue Analytics

State:
Created a year ago
Comments:9 (6 by maintainers)

Top GitHub Comments

3reactions

codefraucommented, Jul 13, 2022

Okay, so commit c6288043b59db529901c9aa8e0b0bf89ac1298d7 adds a highdpi mode via url option and 54a8539549f58afbdec326093f4f6f3c550db577 adds primitiveScreenScaleFactor. And I am somewhat pleased with how trivial these two are 😊

Appears to work, see e.g. https://squeak.js.org/run/#url=https://freudenbergs.de/vanessa/squeakjs&zip=[Squeak5.3-19452-64bit.zip,SqueakV50.sources.zip]&wizard=false&highdpi=true (note highdpi option in url)

I’m somewhat hesitant now to make this the default, even for 6.0 images, because with 4x the number of pixels to draw everything does become slower. What do we think?

2reactions

codefraucommented, Jul 11, 2022

I just tried out-of-the-box Squeak 6.0 on a Mac screen that has PlatformScaleFactor = 2.0 and when I use the menu to change the scale from the default 200% to 100% the host window’s size shrinks by half, making every pixel smaller. Is that the intended behavior?

I find that confusing. Can you describe how a VM should behave that cannot change the visual size of the host window, but could support “small” or “big” pixels on a high-dpi screen?

Here’s what I think SqueakJS could do:

add a “small pixel / high-dpi mode” flag meaning the display bitmap the VM creates would use devicePixelRatio times as many pixels for the given window size, disabled by default
add primitiveScreenScaleFactor to answer either 1.0 (if in big-pixel-mode) or devicePixelRatio (in small-pixel-mode)
if the image is a 6.0 image (as indicated by the Sista format bit), enable small-pixel-mode by default
optionally, we could add a VM option to “force” small-pixel-mode for older images, e.g. by adding highdpi=true to the URL

How does that sound?

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