From: John Tsiombikas <nuclear@member.fsf.org>
Date: Sun, 17 Mar 2024 19:02:05 +0000 (+0200)
Subject: double buffering
X-Git-Url: http://git.mutantstargoat.com/user/nuclear/?a=commitdiff_plain;h=4328f63283ecf1de957e5a8fb6da861894724934;p=psx_test1

double buffering
---

diff --git a/src/gpu.c b/src/gpu.c
index bc2f1a4..6a4823e 100644
--- a/src/gpu.c
+++ b/src/gpu.c
@@ -51,6 +51,11 @@ void gpu_display(int en)
 	REG_GP1 = GPCMD(GP1_DISPEN) | (en ? 0 : 1);
 }
 
+void gpu_dispstart(int x, int y)
+{
+	REG_GP1 = GPCMD(GP1_START) | x | (y << 10);
+}
+
 void gpu_cliprect(int x, int y, int w, int h)
 {
 	REG_GP0 = GPCMD(GP0_CLIP_TL) | x | (y << 10);
diff --git a/src/gpu.h b/src/gpu.h
index 4bfe724..b8e2119 100644
--- a/src/gpu.h
+++ b/src/gpu.h
@@ -18,6 +18,7 @@ struct gpu_gvert {
 void gpu_reset(void);
 void gpu_setmode(int xsz, int ysz, int bpp, int rate);
 void gpu_display(int en);
+void gpu_dispstart(int x, int y);
 void gpu_cliprect(int x, int y, int w, int h);
 void gpu_origin(int x, int y);
 
diff --git a/src/main.c b/src/main.c
index 073ea1c..3850c99 100644
--- a/src/main.c
+++ b/src/main.c
@@ -18,6 +18,7 @@ int main(void)
 	int16_t rotmat[9] = {0x1000, 0, 0, 0, 0x1000, 0, 0, 0, 0x1000};
 	int trans[3] = {160, 120, 0};
 	int resv[3];
+	int yoffs = 0;
 
 	gte_init();
 
@@ -25,10 +26,7 @@ int main(void)
 	gpu_setmode(320, 264, 15, 50);
 	gpu_display(1);
 
-	REG_GP0 = GPCMD(GP0_TEXPG) | TEXPG_DRAWDISP | TEXPG_DITHER;
-
-	gpu_cliprect(0, 0, 320, 264);
-	gpu_origin(0, 0);
+	REG_GP0 = GPCMD(GP0_TEXPG) | TEXPG_DITHER;
 
 	for(;;) {
 		rotmat[0] = rotmat[4] = COS(frame);
@@ -42,19 +40,26 @@ int main(void)
 			gte_cmd_rot();
 			gte_getvec(resv);
 
-			triangle[i].x = (resv[0] >> 6) + 160;
-			triangle[i].y = (resv[1] >> 6) + 130;
+			triangle[i].x = (resv[0] >> 6);
+			triangle[i].y = (resv[1] >> 6);
 		}
 
-		gpu_fillrect(0, 0, 320, 264, 0x202020);
+		/* use previous frame yoffs as display area */
+		gpu_dispstart(0, yoffs);
+
+		/* set yoffs to the new back buffer */
+		yoffs = (frame++ & 1) ? 0 : 264;
+
+		gpu_cliprect(0, yoffs, 320, 264 + yoffs);
+		gpu_origin(160, 130 + yoffs);
+
+		gpu_fillrect(0, yoffs, 320, 264, 0x202020);
 
 		gpu_draw_gouraud(GP0_GTRI, triangle, 3);
 
-		for(i=0; i<100000; i++) {
+		for(i=0; i<8192; i++) {
 			asm volatile("nop; nop; nop; nop");
 		}
-
-		frame++;
 	}
 	return 0;
 }