altos/draw: Add transforms to polygon code

[fw/altos] / src / draw / ao_draw_int.h

diff --git a/src/draw/ao_draw_int.h b/src/draw/ao_draw_int.h
index 433aa409b6e934bfdf7a1715d1262a7f8e26b444..f353526d338be7558909cce1f2ec416eba7283f3 100644 (file)
--- a/src/draw/ao_draw_int.h
+++ b/src/draw/ao_draw_int.h
@@ -76,7 +76,7 @@ ao_bits_mask(int16_t x, int16_t w) {
     r = ao_right_mask((x)+n); \
     l = ao_left_mask(x); \
     if (l) { \
-       n -= AO_UNIT - ((x) & AO_MASK); \
+       n -= (int16_t) (AO_UNIT - ((x) & AO_MASK));     \
        if (n < 0) { \
            n = 0; \
            l &= r; \