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zed/crates/gpui
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Philipp Schaffrath 664b7ecb40
gpui: Fix hover state not clearing when mouse leaves window (#60275) 
# Objective

Fix two gaps in element hover tracking at window boundaries. Hover was
only re-evaluated on `MouseMove`, so when the pointer left the window no
event fired `on_hover(false)` and the element stayed hovered.
Symmetrically on Wayland, no `Motion` follows `Enter` until the pointer
moves again, so hover was not established at the entry pixel. Both cases
are easy to miss since most hover-styled elements don't sit flush
against the window edge, but they surfaced while implementing
layer_shell popups with input_regions, which should close when stop
hovering.

## Solution

The hover compare-and-fire logic in `div` is refactored into a shared
`update_hover` closure, and a second listener on `MouseExitEvent` clears
hover when the pointer leaves the window. It clears unconditionally
because `MouseExited` doesn't update the tracked mouse position, so a
hit test during that dispatch would still report the element as hovered.

On Wayland, a `MouseMove` is synthesized at the entry position on
`wl_pointer.enter`, mirroring the `MouseExited` already dispatched on
`Leave`.

## Testing

Tested manually on Wayland/Linux: hover on a window-edge element clears
when the pointer leaves the window, and hover is established immediately
when the pointer enters a surface with an element under the entry pixel.

Not tested on other platforms. The `div` change relies on each
platform's existing `MouseExited` dispatch: macOS and X11 emit it, so
they get the exit fix too. Windows never dispatches `MouseExited`
(`WM_MOUSELEAVE` only flips the window-level hover flag), so the
stuck-hover case might remain there, unchanged from before.

Before:


https://github.com/user-attachments/assets/6af83bb3-de9d-40e2-a64c-bdefc98fc96d

After:


https://github.com/user-attachments/assets/721a9b5c-108a-499f-867e-da111836a34a


Here is an example application to test this:

```rs
#![cfg_attr(target_family = "wasm", no_main)]

use gpui::{
    App, Bounds, Context, Window, WindowBounds, WindowOptions, div, prelude::*, px, rgb, size,
};
use gpui_platform::application;

struct HoverExit {
    hovered: bool,
}

impl Render for HoverExit {
    fn render(&mut self, _window: &mut Window, cx: &mut Context<Self>) -> impl IntoElement {
        // Fills the whole window so its edge is the window edge: moving the mouse
        // out of the window is what exercises the MouseExited path.
        div()
            .id("hover-exit")
            .size_full()
            .flex()
            .justify_center()
            .items_center()
            .text_xl()
            .text_color(rgb(0xffffff))
            .bg(if self.hovered {
                rgb(0x585f58)
            } else {
                rgb(0x505050)
            })
            .child(if self.hovered { "HOVERED" } else { "not hovered" })
            .on_hover(cx.listener(|this, hovered, _, cx| {
                this.hovered = *hovered;
                cx.notify();
            }))
    }
}

fn run_example() {
    application().run(|cx: &mut App| {
        let bounds = Bounds::centered(None, size(px(240.), px(160.0)), cx);
        cx.open_window(
            WindowOptions {
                window_bounds: Some(WindowBounds::Windowed(bounds)),
                app_id: Some("gpui-hover-exit".to_string()),
                ..Default::default()
            },
            |_, cx| cx.new(|_| HoverExit { hovered: false }),
        )
        .unwrap();
        cx.activate(true);
    });
}

#[cfg(not(target_family = "wasm"))]
fn main() {
    run_example();
}

#[cfg(target_family = "wasm")]
#[wasm_bindgen::prelude::wasm_bindgen(start)]
pub fn start() {
    gpui_platform::web_init();
    run_example();
}
```


## Self-Review Checklist:

- [x] I've reviewed my own diff for quality, security, and reliability
- [x] Unsafe blocks (if any) have justifying comments
- [x] The content adheres to Zed's UI standards
([UX/UI](https://github.com/zed-industries/zed/blob/main/CONTRIBUTING.md#uiux-checklist)
and
[icon](https://github.com/zed-industries/zed/blob/main/crates/icons/README.md)
guidelines)
- [ ] Tests cover the new/changed behavior
- [x] Performance impact has been considered and is acceptable

---

Release Notes:

- Fixed element hover state not clearing when the mouse leaves the
window
2026-07-08 20:27:47 +00:00
..
docs
examples Unify Render and RenderOnce into View (#58087) 2026-07-08 15:52:48 +00:00
resources/windows Enable segment heap for Zed (#54538) 2026-04-22 16:58:55 -04:00
src gpui: Fix hover state not clearing when mouse leaves window (#60275) 2026-07-08 20:27:47 +00:00
tests Use serde 1.0.221 instead of serde_derive hackery (#38137) 2025-09-14 14:01:04 +02:00
build.rs GPUI on the web (#50228) 2026-02-26 18:36:50 +01:00
Cargo.toml gpui: Add parent-anchored native popup windows (with wayland xdg_popup implementation only so far) (#60232) 2026-07-08 19:22:23 +00:00
LICENSE-APACHE
README.md gpui: Document standalone app setup (#58766) 2026-06-09 20:13:23 +00:00

README.md

Welcome to GPUI!

GPUI is a hybrid immediate and retained mode, GPU accelerated, UI framework for Rust, designed to support a wide variety of applications.

Getting Started

GPUI is still in active development as we work on the Zed code editor, and is still pre-1.0. There will often be breaking changes between versions. You'll also need to use the latest version of stable Rust. Add gpui, and optionally gpui_platform, to your Cargo.toml:

gpui = { version = "*" }
gpui_platform = { version = "*", features = ["font-kit", "wayland", "x11"] }

Everything in a standalone GPUI app starts with an Application. You can create one with gpui_platform::application(), which picks the windowing and text backends for the host OS, and kick off your application by passing a callback to Application::run(). Inside this callback, you can create a new window with App::open_window() and register your first root view.

use gpui::*;

fn main() {
    gpui_platform::application().run(|cx: &mut App| {
        // ..
    });
}

gpui_platform

The features on gpui_platform are platform-specific, so the list above is a safe cross-platform default. If you build for a single platform, you can trim it:

  • macOS — Rendering uses Metal and is always available, but glyph rasterization needs font-kit. Without it, GPUI falls back to a placeholder text system that lays text out but renders no glyphs.

    gpui_platform = { version = "*", features = ["font-kit"] }

  • Linux / FreeBSD — enable at least one windowing backend for desktop windows: wayland, x11, or both. These features also compile the renderer and text system, so no separate text feature is needed.

    gpui_platform = { version = "*", features = ["wayland", "x11"] }

  • Windows — no features are required. Windowing uses Win32 and text uses DirectWrite. font-kit has no effect here.

Additional Topics

Dependencies

GPUI has various system dependencies that it needs in order to work.

macOS

On macOS, GPUI uses Metal for rendering. In order to use Metal, you need to do the following:

  • Install Xcode from the macOS App Store, or from the Apple Developer website. Note this requires a developer account.

Ensure you launch Xcode after installing, and install the macOS components, which is the default option.

  • Install Xcode command line tools

    xcode-select --install

  • Ensure that the Xcode command line tools are using your newly installed copy of Xcode:

    sudo xcode-select --switch /Applications/Xcode.app/Contents/Developer

The Big Picture

GPUI offers three different registers depending on your needs:

  • State management and communication with Entity's. Whenever you need to store application state that communicates between different parts of your application, you'll want to use GPUI's entities. Entities are owned by GPUI and are only accessible through an owned smart pointer similar to an Rc. See the app::context module for more information.

  • High level, declarative UI with views. All UI in GPUI starts with a view. A view is simply an Entity that can be rendered, by implementing the Render trait. At the start of each frame, GPUI will call this render method on the root view of a given window. Views build a tree of elements, lay them out and style them with a tailwind-style API, and then give them to GPUI to turn into pixels. See the div element for an all purpose swiss-army knife of rendering.

  • Low level, imperative UI with Elements. Elements are the building blocks of UI in GPUI, and they provide a nice wrapper around an imperative API that provides as much flexibility and control as you need. Elements have total control over how they and their child elements are rendered and can be used for making efficient views into large lists, implement custom layouting for a code editor, and anything else you can think of. See the element module for more information.

Each of these registers has one or more corresponding contexts that can be accessed from all GPUI services. This context is your main interface to GPUI, and is used extensively throughout the framework.

Other Resources

In addition to the systems above, GPUI provides a range of smaller services that are useful for building complex applications:

  • Actions are user-defined structs that are used for converting keystrokes into logical operations in your UI. Use this for implementing keyboard shortcuts, such as cmd-q. See the action module for more information.

  • Platform services, such as quit the app or open a URL are available as methods on the app::App.

  • An async executor that is integrated with the platform's event loop. See the executor module for more information.,

  • The [gpui::test] macro provides a convenient way to write tests for your GPUI applications. Tests also have their own kind of context, a TestAppContext which provides ways of simulating common platform input. See app::test_context and test modules for more details.

Currently, the best way to learn about these APIs is to read the Zed source code or drop a question in the Zed Discord. We're working on improving the documentation, creating more examples, and will be publishing more guides to GPUI on our blog.