git.y1.nz

commit de539e1c9adcaa8acd22ece7a99478b6d7a9a991
parent b02c1dc4c9d77467c569a5b38676396897dbfd38
Author: Toxa <untoxa@mail.ru>
Date:   Thu, 26 Aug 2021 00:52:49 +0300

SMS/GG: scroll_bkg() calculates modulus of 224 by Y to make smooth scroll without "jumps"

Diffstat:
M
gbdk-lib/examples/gg/large_map/large_map.c
4
++--
M
gbdk-lib/include/sms/sms.h
3
++-

2 files changed, 4 insertions(+), 3 deletions(-)
diff --git a/gbdk-lib/examples/gg/large_map/large_map.c b/gbdk-lib/examples/gg/large_map/large_map.c
@@ -21,7 +21,7 @@ uint8_t redraw;
 
 void set_camera() {
     // update hardware scroll position
-    move_bkg(camera_x, camera_y < (8 * 28) ? camera_y: (camera_y - (8 * 28)));
+    move_bkg(camera_x, camera_y % 224);
     // up or down
     map_pos_y = (uint8_t)(camera_y >> 3u);
     if (map_pos_y != old_map_pos_y) { 
@@ -58,7 +58,7 @@ void main(){
 
     redraw = FALSE;
 
-    move_bkg(camera_x, camera_y);
+    move_bkg(camera_x, camera_y % 224);
     while (TRUE) {
         joy = joypad();
         // up or down
diff --git a/gbdk-lib/include/sms/sms.h b/gbdk-lib/include/sms/sms.h
@@ -109,7 +109,8 @@ inline void move_bkg(uint8_t x, uint8_t y) {
 
 inline void scroll_bkg(int8_t x, int8_t y) {
 	__WRITE_VDP_REG(VDP_RSCX, __READ_VDP_REG(VDP_RSCX) - x);
-	__WRITE_VDP_REG(VDP_RSCY, __READ_VDP_REG(VDP_RSCY) + y);
+    int16_t tmp = __READ_VDP_REG(VDP_RSCY) + y;
+	__WRITE_VDP_REG(VDP_RSCY, (tmp < 0) ? 224 + tmp : tmp % 224u);
 }
 
 /** HALTs the CPU and waits for the vertical blank interrupt (VBL) to finish.

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