[Bugfix] UIFrame: box.setPosition(0,0) corrupts position when using clip_children #223

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opened 2026-01-22 15:48:53 +00:00 by john · 0 comments

john commented

2026-01-22 15:48:53 +00:00

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Summary

When clip_children=True, UIFrame::render() sets box.setPosition(0, 0) to render the box at the origin of the RenderTexture, but never restores box to its original position. This corrupts the position state and causes incorrect rendering.

Root Cause

In UIFrame.cpp lines 128-163:

if (use_render_texture && render_dirty) {
    render_texture->clear(sf::Color::Transparent);

    box.setPosition(0, 0);  // ← Sets box to origin for texture
    render_texture->draw(box);
    
    // ... children rendered ...
    render_dirty = false;
}

if (use_render_texture) {
    render_sprite.setPosition(offset + box.getPosition());  // ← box.getPosition() is (0,0)!
    target.draw(render_sprite);
}

Symptoms

Frame appears at wrong position when clip_children=True
Toggling clip_children off causes frame to appear at origin + offset
Modifying frame.x or frame.y "fixes" the position (because onPositionChanged() restores box)

Proposed Fix

Use position (the canonical source of truth) instead of box.getPosition():

render_sprite.setPosition(offset + position);

Or restore box after texture rendering:

box.setPosition(0, 0);
render_texture->draw(box);
box.setPosition(position);  // ← Restore

Option 1 is cleaner since position is the authoritative value.

## Summary When `clip_children=True`, `UIFrame::render()` sets `box.setPosition(0, 0)` to render the box at the origin of the RenderTexture, but **never restores** `box` to its original position. This corrupts the position state and causes incorrect rendering. ## Root Cause In `UIFrame.cpp` lines 128-163: ```cpp if (use_render_texture && render_dirty) { render_texture->clear(sf::Color::Transparent); box.setPosition(0, 0); // ← Sets box to origin for texture render_texture->draw(box); // ... children rendered ... render_dirty = false; } if (use_render_texture) { render_sprite.setPosition(offset + box.getPosition()); // ← box.getPosition() is (0,0)! target.draw(render_sprite); } ``` ## Symptoms 1. Frame appears at wrong position when `clip_children=True` 2. Toggling `clip_children` off causes frame to appear at origin + offset 3. Modifying `frame.x` or `frame.y` "fixes" the position (because `onPositionChanged()` restores `box`) ## Proposed Fix Use `position` (the canonical source of truth) instead of `box.getPosition()`: ```cpp render_sprite.setPosition(offset + position); ``` Or restore box after texture rendering: ```cpp box.setPosition(0, 0); render_texture->draw(box); box.setPosition(position); // ← Restore ``` Option 1 is cleaner since `position` is the authoritative value.