AABB / Hit Testing System #138

New Issue

john · 2025-11-27T18:34:41Z

john commented

2025-11-27 18:34:41 +00:00

Universal axis-aligned bounding box computation for all UIDrawables, enabling mouse event handling and composite bounds calculation.

Context

Mouse events (click, enter, exit) require knowing whether a point is inside an element. Currently hit testing is ad-hoc. This issue creates a consistent AABB system across all drawable types.

Definition of Done

All UIDrawable subclasses implement getBounds() returning sf::FloatRect
UIFrame, UISprite, UIGrid: straightforward AABB from position + size
UICaption: compute bounds after render, cache until text/font changes
UIEntity: bounds relative to containing grid's transform
Composite AABB: parent's bounds union with all children's bounds
overflow property on UIFrame: when true, clip children to parent bounds during render
Python-accessible bounds property returning (x, y, w, h) tuple
Hit testing utility: point_in_bounds(drawable, x, y) considering global position

Technical Notes

Caption Challenge

SFML doesn't provide text bounds until after rendering. Solution:

Call sf::Text::getLocalBounds() after setting string/font
Cache result, invalidate when text or font changes
Dirty flag integration: text change marks AABB dirty

Composite Bounds

For parent-child hierarchies (post #122):

composite_bounds = parent.bounds
for child in parent.children:
    composite_bounds = union(composite_bounds, child.global_bounds)

Overflow Clipping

When frame.overflow = False (default), children render beyond parent bounds.
When frame.overflow = True, use scissor test or render-to-texture to clip.

Dependencies

Blocked by: #122 (Parent-Child UI System) - need hierarchy for composite bounds
Blocked by: #102 (Global Position) - need global coords for hit testing nested elements

Enables: #111 (Click Events)
Enables: Mouse Enter/Exit Events (NEW)
Enables: Grid Cell Events (NEW)

Universal axis-aligned bounding box computation for all UIDrawables, enabling mouse event handling and composite bounds calculation. ## Context Mouse events (click, enter, exit) require knowing whether a point is inside an element. Currently hit testing is ad-hoc. This issue creates a consistent AABB system across all drawable types. ## Definition of Done - [ ] All UIDrawable subclasses implement `getBounds()` returning `sf::FloatRect` - [ ] UIFrame, UISprite, UIGrid: straightforward AABB from position + size - [ ] UICaption: compute bounds after render, cache until text/font changes - [ ] UIEntity: bounds relative to containing grid's transform - [ ] Composite AABB: parent's bounds union with all children's bounds - [ ] `overflow` property on UIFrame: when true, clip children to parent bounds during render - [ ] Python-accessible `bounds` property returning (x, y, w, h) tuple - [ ] Hit testing utility: `point_in_bounds(drawable, x, y)` considering global position ## Technical Notes ### Caption Challenge SFML doesn't provide text bounds until after rendering. Solution: - Call `sf::Text::getLocalBounds()` after setting string/font - Cache result, invalidate when text or font changes - Dirty flag integration: text change marks AABB dirty ### Composite Bounds For parent-child hierarchies (post #122): ``` composite_bounds = parent.bounds for child in parent.children: composite_bounds = union(composite_bounds, child.global_bounds) ``` ### Overflow Clipping When `frame.overflow = False` (default), children render beyond parent bounds. When `frame.overflow = True`, use scissor test or render-to-texture to clip. ## Dependencies - **Blocked by**: #122 (Parent-Child UI System) - need hierarchy for composite bounds - **Blocked by**: #102 (Global Position) - need global coords for hit testing nested elements ## Related Issues - Enables: #111 (Click Events) - Enables: Mouse Enter/Exit Events (NEW) - Enables: Grid Cell Events (NEW)

john added the

Major Feature

system:ui-hierarchy

system:input

priority:tier1-active

workflow:blocked

labels 2025-11-27 19:28:37 +00:00

john added this to the Cursor, Grid, and Callback project 2025-11-27 19:28:52 +00:00

john referenced this issue from a commit

2025-11-28 03:36:15 +00:00

feat: Add AABB/hit testing foundation (#138)

john commented