Minor fp math cleanup

2 files changed, 12 insertions, 11 deletions

diff --git a/src/gba/gba.h b/src/gba/gba.h
index d607eee..99eb1f7 100644
--- a/src/gba/gba.h
+++ b/src/gba/gba.h
@@ -661,6 +661,7 @@ wait_vsync(void) {
 #define LEN(ARR) (sizeof(ARR) / sizeof((ARR)[0]))
 
 // Fixed-point arithmetic for (i.P) numbers.
+#define FP_NUM(A,P)        ((A) << (P))
 #define FP_MUL(A,B,P)      (((A) * (B)) >> (P))
 #define FP_DIV(A,B,P)      (((A) << (P)) / (B))
 #define FP_LERP(Y0,Y1,X,P) ((Y0) + FP_MUL((X), ((Y1) - (Y0)), P))
diff --git a/src/renderer_m0.c b/src/renderer_m0.c
index 36ed01b..904c2a1 100644
--- a/src/renderer_m0.c
+++ b/src/renderer_m0.c
@@ -179,19 +179,19 @@ draw_line(size_t x0, size_t y0, size_t x1, size_t y1, u8 clr) {
         draw_vline(x0, y0, y1, clr);
     } else {
 #if 1
-        int precision_bits = 6;
-        int precision_one = (1 << precision_bits);
-        int precision_half = precision_one >> 1;
-        int dx = x0 > x1 ? x0 - x1 : x1 - x0;
-        int dy = y0 > y1 ? y0 - y1 : y1 - y0;
-        int frac_x = x0 > x1 ? ((x0 - x1) << precision_bits) : ((x1 - x0) << precision_bits);
-        int frac_y = y0 > y1 ? ((y0 - y1) << precision_bits) : ((y1 - y0) << precision_bits);
+        int fp_bit = 6;
+        int fp_one = FP_NUM(1, fp_bit);
+        int fp_half = fp_one >> 1;
+        int dx     = x0 > x1 ? x0 - x1 : x1 - x0;
+        int dy     = y0 > y1 ? y0 - y1 : y1 - y0;
+        int frac_x = x0 > x1 ? FP_NUM(x0 - x1, fp_bit) : FP_NUM(x1 - x0, fp_bit);
+        int frac_y = y0 > y1 ? FP_NUM(y0 - y1, fp_bit) : FP_NUM(y1 - y0, fp_bit);
         int x_step = x0 > x1 ? -1 : 1;
         int y_step = y0 > y1 ? -1 : 1;
-        int dxf = (dx << precision_bits);
-        int dyf = (dy << precision_bits);
+        int dxf = (dx << fp_bit);
+        int dyf = (dy << fp_bit);
         if (dx >= dy) {
-            int distance = (frac_y - precision_one) * dx - (frac_x - precision_half) * dy;
+            int distance = (frac_y - fp_one) * dx - (frac_x - fp_half) * dy;
             for (int i = 0; i <= dx; i++) {
                 if (distance >= 0) {
                     distance -= 2 * dxf;
@@ -202,7 +202,7 @@ draw_line(size_t x0, size_t y0, size_t x1, size_t y1, u8 clr) {
                 x0 += x_step;
             }
         } else {
-            int distance = (frac_x - precision_one) * dy - (frac_y - precision_half) * dx;
+            int distance = (frac_x - fp_one) * dy - (frac_y - fp_half) * dx;
             for (int i = 0; i <= dy; i++) {
                 draw_pixel(x0, y0, clr);
                 if (distance >= 0) {