Texture display bounds for non-uniform sprite content #235

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opened 2026-02-02 16:22:22 +00:00 by john · 0 comments

john commented

2026-02-02 16:22:22 +00:00

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Summary

Support textures where the actual sprite content doesn't fill the entire cell, allowing centered or offset sprites within larger texture cells.

Parent issue: #233

Use Case

A 32×32 texture atlas where each cell contains a centered 16×24 sprite with transparent padding. The texture stores sprites in a uniform grid, but the actual content is smaller and offset.

Current Behavior

// src/PyTexture.cpp:59-61
auto ir = sf::IntRect(tx * sprite_width, ty * sprite_height, sprite_width, sprite_height);
auto sprite = sf::Sprite(texture, ir);

The entire cell is used; no concept of "display bounds" vs "cell bounds".

Proposed Changes

Extend PyTexture constructor:

# Current
tex = mcrfpy.Texture("sprites.png", 32, 32)

# Proposed (optional parameters)
tex = mcrfpy.Texture("sprites.png", 32, 32, 
                     display_size=(16, 24),
                     display_origin=(8, 4))  # Offset within cell

Add to PyTexture class:

int display_width = -1;   // -1 = same as sprite_width
int display_height = -1;
int display_origin_x = 0; // Offset from cell top-left
int display_origin_y = 0;

Modify sprite creation:

sf::Sprite PyTexture::sprite(int index, ...) {
    // Create sprite as before...
    if (display_origin_x != 0 || display_origin_y != 0) {
        sprite.setOrigin(-display_origin_x, -display_origin_y);
    }
    return sprite;
}

Performance Impact

None - conditional origin set in existing code path.

Files Affected

src/PyTexture.h - Add display bounds properties
src/PyTexture.cpp - Modify constructor and sprite() method

## Summary Support textures where the actual sprite content doesn't fill the entire cell, allowing centered or offset sprites within larger texture cells. **Parent issue**: #233 ## Use Case A 32×32 texture atlas where each cell contains a centered 16×24 sprite with transparent padding. The texture stores sprites in a uniform grid, but the actual content is smaller and offset. ## Current Behavior ```cpp // src/PyTexture.cpp:59-61 auto ir = sf::IntRect(tx * sprite_width, ty * sprite_height, sprite_width, sprite_height); auto sprite = sf::Sprite(texture, ir); ``` The entire cell is used; no concept of "display bounds" vs "cell bounds". ## Proposed Changes 1. **Extend PyTexture constructor**: ```python # Current tex = mcrfpy.Texture("sprites.png", 32, 32) # Proposed (optional parameters) tex = mcrfpy.Texture("sprites.png", 32, 32, display_size=(16, 24), display_origin=(8, 4)) # Offset within cell ``` 2. **Add to PyTexture class**: ```cpp int display_width = -1; // -1 = same as sprite_width int display_height = -1; int display_origin_x = 0; // Offset from cell top-left int display_origin_y = 0; ``` 3. **Modify sprite creation**: ```cpp sf::Sprite PyTexture::sprite(int index, ...) { // Create sprite as before... if (display_origin_x != 0 || display_origin_y != 0) { sprite.setOrigin(-display_origin_x, -display_origin_y); } return sprite; } ``` ## Performance Impact None - conditional origin set in existing code path. ## Files Affected - `src/PyTexture.h` - Add display bounds properties - `src/PyTexture.cpp` - Modify constructor and sprite() method