gpui: Make inactive frame throttling configurable

[nolight132]

Objective

I am building an app with GPUI, and the current animation throttling implementation does not quite meet its requirements. I needed the window to stay at a smooth framerate when unfocused to display lyrics, which was not possible at the time without modifying GPUI’s frame scheduling behavior. I understand that this is not a problem for Zed, but I believe making this behavior a field in WindowOptions could be beneficial for other programs going forward.

Solution

Added a field to WindowOptions struct which controls the minimum interval between animation frames while the window is inactive (documented). Kept the default value GPUI currently uses.

Testing

• Ran gpui/src/examples/animation.rs with different presets - works as expected. Zed compiles. One thing worth noting: this setting does not guarantee the window refreshes at this exact interval, as frames are still paced by the compositor. For granular FPS control, a helper function is needed. I have decided to keep it simple and use the existing logic.
• Tested on NixOS x86_64, Niri.

Self-Review Checklist:

• I've reviewed my own diff for quality, security, and reliability
• Unsafe blocks (if any) have justifying comments
• The content adheres to Zed's UI standards (UX/UI and icon guidelines)
• Tests cover the new/changed behavior (the default didn't change, tests still pass)
• Performance impact has been considered and is acceptable (no performance impact unless explicitly set)

Showcase

Before (unfocused):

After (unfocused with inactive_frame_interval set to 16ms):

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Release Notes:

• Added WindowOptions::inactive_frame_interval for configuring animation frame throttling on inactive GPUI windows.