gpui: Fix rounded corners on images with object-fit cover

[J0R6IT0]

Objective

rounded did not work properly on images using ObjectFit::Cover. The image is scaled to be larger than the element so it can cover the bounds, and the overflow was clipped to a plain rectangle, so the rounded corners were applied to the oversized image quad, outside the visible element box. FIxes #44339.

Solution

PolychromeSprite now carries a clip_bounds field in addition to bounds, that shaders use to round and clip.
Done in all three renderers.

Testing

• Tested in both Windows and MacOS. I have not been able to test in LInux but it should work too since the changes are minimal.
• Added the object_fit example to showcase the different ObjectFit options and aspect ratios.

Self-Review Checklist:

• I've reviewed my own diff for quality, security, and reliability
• Performance impact has been considered and is acceptable

Showcase

BEFORE:

AFTER:

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Release Notes:

• N/A

[pingpong74]

Hi, I have been looking into this issue and from what I can understand, a much simpler way of doing this is to just crop the image CPU side before passing it to the renderer. This seems to be a simpler fix it only affects one function ( paint_image in window.rs). Here are my tests using this method:

[J0R6IT0]

Hi, looks good to me too. Each implementation has its advantages, so the Zed team will have to choose the one they prefer.

[J0R6IT0]

#61383