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See https://zed.dev/channel/gpui-536 Fixes https://github.com/zed-industries/zed/issues/9010 Fixes https://github.com/zed-industries/zed/issues/8883 Fixes https://github.com/zed-industries/zed/issues/8640 Fixes https://github.com/zed-industries/zed/issues/8598 Fixes https://github.com/zed-industries/zed/issues/8579 Fixes https://github.com/zed-industries/zed/issues/8363 Fixes https://github.com/zed-industries/zed/issues/8207 ### Problem After transitioning Zed to GPUI 2, we started noticing that interacting with the mouse on many UI elements would lead to a pretty annoying flicker. The main issue with the old approach was that hover state was calculated based on the previous frame. That is, when computing whether a given element was hovered in the current frame, we would use information about the same element in the previous frame. However, inspecting the previous frame tells us very little about what should be hovered in the current frame, as elements in the current frame may have changed significantly. ### Solution This pull request's main contribution is the introduction of a new `after_layout` phase when redrawing the window. The key idea is that we'll give every element a chance to register a hitbox (see `ElementContext::insert_hitbox`) before painting anything. Then, during the `paint` phase, elements can determine whether they're the topmost and draw their hover state accordingly. We are also removing the ability to give an arbitrary z-index to elements. Instead, we will follow the much simpler painter's algorithm. That is, an element that gets painted after will be drawn on top of an element that got painted earlier. Elements can still escape their current "stacking context" by using the new `ElementContext::defer_draw` method (see `Overlay` for an example). Elements drawn using this method will still be logically considered as being children of their original parent (for keybinding, focus and cache invalidation purposes) but their layout and paint passes will be deferred until the currently-drawn element is done. With these changes we also reworked geometry batching within the `Scene`. The new approach uses an AABB tree to determine geometry occlusion, which allows the GPU to render non-overlapping geometry in parallel. ### Performance Performance is slightly better than on `main` even though this new approach is more correct and we're maintaining an extra data structure (the AABB tree).  Release Notes: - Fixed a bug that was causing popovers to flicker. --------- Co-authored-by: Nathan Sobo <nathan@zed.dev> Co-authored-by: Thorsten <thorsten@zed.dev> |
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Design notes:
This crate is split into two conceptual halves:
- The terminal.rs file and the src/mappings/ folder, these contain the code for interacting with Alacritty and maintaining the pty event loop. Some behavior in this file is constrained by terminal protocols and standards. The Zed init function is also placed here.
- Everything else. These other files integrate the
Terminalstruct created in terminal.rs into the rest of GPUI. The main entry point for GPUI is the terminal_view.rs file and the modal.rs file.
ttys are created externally, and so can fail in unexpected ways. However, GPUI currently does not have an API for models than can fail to instantiate. TerminalBuilder solves this by using Rust's type system to split tty instantiation into a 2 step process: first attempt to create the file handles with TerminalBuilder::new(), check the result, then call TerminalBuilder::subscribe(cx) from within a model context.
The TerminalView struct abstracts over failed and successful terminals, passing focus through to the associated view and allowing clients to build a terminal without worrying about errors.
#Input
There are currently many distinct paths for getting keystrokes to the terminal:
-
Terminal specific characters and bindings. Things like ctrl-a mapping to ASCII control character 1, ANSI escape codes associated with the function keys, etc. These are caught with a raw key-down handler in the element and are processed immediately. This is done with the
try_keystroke()method on Terminal -
GPU Action handlers. GPUI clobbers a few vital keys by adding bindings to them in the global context. These keys are synthesized and then dispatched through the same
try_keystroke()API as the above mappings -
IME text. When the special character mappings fail, we pass the keystroke back to GPUI to hand it to the IME system. This comes back to us in the
View::replace_text_in_range()method, and we then send that to the terminal directly, bypassingtry_keystroke(). -
Pasted text has a separate pathway.
Generally, there's a distinction between 'keystrokes that need to be mapped' and 'strings which need to be written'. I've attempted to unify these under the '.try_keystroke()' API and the .input() API (which try_keystroke uses) so we have consistent input handling across the terminal