on_hover receives absolute mouse coordinates; every other mouse callback receives relative ones
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Description
Summary
on_hover is the only mouse callback that receives window-absolute coordinates. on_click, on_any_click, on_mouse_move and on_mouse_up all receive coordinates relative to the widget's own shape.
Because both hand you an Event with mouse_x / mouse_y, nothing signals the difference. Hit-testing code written against one and reused for the other silently reads the wrong position.
Where it comes from
The relative path goes through execute_mouse_callback in event_traversal.v:61, which converts before dispatch:
// Make mouse coordinates relative to layout.shape
mut ev := event_relative_to(layout.shape, e)
callback(layout, mut ev, mut w)
on_hover is dispatched from layout_hover in layout.v:145 instead, which builds a synthetic event straight from the context and never converts:
mut ev := Event{
...
mouse_x: ctx.mouse_pos_x
mouse_y: ctx.mouse_pos_y
...
}
on_hover := layout.shape.events.on_hover
Effect
Inside a canvas that hit-tests its own content, the two handlers need different arithmetic for the same pointer position:
on_any_click: fn (l &gui.Layout, mut e gui.Event, mut w gui.Window) {
hit(e.mouse_x, e.mouse_y) // already relative
}
on_hover: fn (mut l gui.Layout, mut e gui.Event, mut w gui.Window) {
hit(e.mouse_x - l.shape.x, e.mouse_y - l.shape.y) // must subtract
}
Using the same expression in both compiles, runs, and quietly misses every target in one of them.
Suggestion
Either convert in layout_hover the way execute_mouse_callback does, or document the difference on on_hover. Converting looks like the smaller surprise, though it would change behaviour for anyone already compensating.
Version: gui at e699bcf, V 0.5.2, macOS arm64.
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First steps
- Read the whole issue, then the project's contributing guide.
- Comment on the issue to say you are picking it up — it saves two people doing the same work.
- Fork the repository and make your change on a branch.
- Open a pull request that references the issue number.
Research direction
Start in layout.v:145 at layout_hover and compare its synthetic Event with execute_mouse_callback in event_traversal.v:61, including event_relative_to. Decide how on_hover should align with the other mouse callbacks, then verify that hit-testing receives consistent widget-relative mouse_x and mouse_y values without breaking the documented behavior.
Written by the indexing model from the issue text.
Assessment
- Domain
- desktop
- Issue type
- Bug
- Difficulty
- 2/5
- Estimated time
- 1-3 hours
- Activity status
- Active
- Clarity
- Mostly clear
- Newbie friendliness
- 74/100