Speed up SVG thumbnail rendering

[infacto]

Enhancement

The SVG thumbnail preview is great and useful. It should be built-in Windows by default (as other OS already do).

I just wish the rendering was a lot faster than it is now. Currently it is rendering for about 1 second sequential. Ca. 1 minute per 60 files. I'm wondering if we can parallelize it or improve it in some other way.

[yuyoyuppe]

Hi, the generator is called by the OS, so we cannot parallelize this code.

Does it happen with older PowerToys versions as well, though? Perhaps it's a slowdown that was introduced by the recent changes.

/needinfo

[infacto]

I tested in 0.6x.x and 0.74.0 and can't see any difference. Can you reproduce it on your version? Otherwise, I can test this on another PC... I don't know how to measure what's slow here. Either the OS API or the renderer. You noticed in another issue that MS Edge is used to render the SVG. But in browser the rendering is not that slow. Even though vector graphics are more complex than pixel graphics, it would be great if we can improve the speed...

[yuyoyuppe]

Thank you for the testing @infacto! I can reproduce the issue, but it's very hard for us to fix - the reason it's slow is that the OS calls our thumbnail generator like this:

for(file in directory)
  generate_thumbnail(file);

instead of this:

for(file in directory)
  task.spawn(generate_thumbnail(file)); // doesn't wait until finished

The reason it's faster in the actual browser because the browser doesn't need to go into full initialization process like we do in our generator. The alternative is to always have a background service with a browser initialized, but that approach has a lot of drawbacks as well.