Fix performance of vline

1 files changed, 17 insertions, 4 deletions

diff --git a/src/renderer_m0.c b/src/renderer_m0.c
index c0416ea..8f23376 100644
--- a/src/renderer_m0.c
+++ b/src/renderer_m0.c
@@ -129,10 +129,23 @@ void
 draw_vline(size_t x0, size_t y0, size_t y1, u8 clr) {
     BOUNDCHECK_SCREEN(x0, y0);
     BOUNDCHECK_SCREEN(x0, y1);
-
-    // TODO: perf
-    for (size_t y = y0; y <= y1; y++) {
-        draw_pixel(x0, y, clr);
+    size_t tile_x = x0 / 8;
+    size_t tile_y = y0 / 8;
+    size_t start_row = y0 % 8;
+    size_t start_col = x0 % 8;
+    size_t shift_left = start_col * 4;
+    u32 *dst = &backbuf[tile_x * 8 + tile_y * 8 * 32 + start_row];
+    u32 cur_row = start_row;
+    u32 mask = 0x0000000F;
+    for (size_t i = 0; i <= y1 - y0; i++) {
+        *dst = (*dst & ~(mask << shift_left)) | (clr << shift_left);
+        if (cur_row == 7) {
+            dst += 8 * 31 + 1;
+            cur_row = 0;
+        } else {
+            cur_row++;
+            dst++;
+        }
     }
 }