diff options
| -rw-r--r-- | src/til_fb.h | 33 |
1 files changed, 23 insertions, 10 deletions
diff --git a/src/til_fb.h b/src/til_fb.h index 80ffeb4..f6763e1 100644 --- a/src/til_fb.h +++ b/src/til_fb.h @@ -80,18 +80,31 @@ static inline uint32_t til_fb_fragment_get_pixel_unchecked(til_fb_fragment_t *fr } -/* gets a pixel from the fragment, coordinates are clipped to the fragment's frame bounds */ +/* gets a pixel from the fragment, coordinates are clipped to the fragment's bounds */ static inline uint32_t til_fb_fragment_get_pixel_clipped(til_fb_fragment_t *fragment, int x, int y) { - if (x < 0) - x = 0; - else if (x >= fragment->frame_width) - x = fragment->frame_width - 1; - - if (y < 0) - y = 0; - else if (y >= fragment->frame_height) - y = fragment->frame_height - 1; + /* XXX: this originally clipped to the fragment's frame bounds, but checkers introduced + * a practice of shifting edge fragments to center the filled checkers, while preserving the + * whole frame size. So if something like fill_module=drizzle got used, and the edge cells + * were clipped by the fragment while the frame hung off the edge, the snapshot would be of + * strictly the fragment with the logical frame size running off the buffer, resulting in a + * segfault. It's slightly complicated in that drizzle::style=map would actually appreciate + * being able to access pixels outside the fragment, but that's only really remotely safe when + * the snapshot it's operating on is a full page snapshot - not the fragment-sized copy-based + * snapshot you get from something like checkers::fill_module=drizzle. So for now, this is + * simply getting clipped to the fragment bounds, which is the simple and correct thing to do. + * For drizzle to be able to sample outside its given fragment, it's just not viable today as-is, + * let's just stop the crashing for now. + */ + if (x < fragment->x) + x = fragment->x; + else if (x >= fragment->x + fragment->width) + x = fragment->x + fragment->width - 1; + + if (y < fragment->y) + y = fragment->y; + else if (y >= fragment->y + fragment->height) + y = fragment->y + fragment->height - 1; return til_fb_fragment_get_pixel_unchecked(fragment, x, y); } |