smooth horizontal scrolling

testbed.c

@@ -9,6 +9,7 @@
 #define setEGAMode() setMode(000Dh)
 #define setTextMode() setMode(0003h)
 
+#define REG_AC   0x03c0
 #define REG_TS   0x03c4
 #define REG_GDC  0x03ce
 #define REG_CRTC 0x03d4
@@ -56,6 +57,12 @@ void setDisplayOffset(unsigned int offset) {
   outport(REG_CRTC, 0x0d | (offset << 8));
 }
 
+void setHorizontalPan(int offset) {
+  inp(0x3da); // INPUT_STATUS_1?
+  outp(REG_AC, 0x13 | 0x20);
+  outp(REG_AC, offset);
+}
+
 #define setLogicalWidth(w) outport(REG_CRTC, 0x13 | (w << 8))
  
 /*** K E Y B O A R D ***/
@@ -462,7 +469,7 @@ int tifLoad(FILE *f, TifImageMeta_t meta, unsigned int *planeBuf, int maxY, int
 // 89ABCDEF 01234567 << 3 => BCDEFXXX 3456789A byteswap => 3456789A BCDEFXXX
 
 #define PAGE_TILES_W 21
-#define PAGE_TILES_H 13
+#define PAGE_TILES_H 12
 #define PAGE_TILES_COUNT (PAGE_TILES_H * PAGE_TILES_W)
 #define PAGE_STRIDE (PAGE_TILES_W << 1)
 
@@ -504,7 +511,7 @@ typedef struct {
   unsigned char firstBuffer;
 } TiledScreen_t;
 
-TiledScreen_t screen = { 0, 0, 0, 0, { 0x0400, 0x2620 }, 0, 0, NULL, NULL,
+TiledScreen_t screen = { 0, 0, 0, 0, { 0x0400, 0x2400 }, 0, 0, NULL, NULL,
   0, 0, 0, 0, 0 };
 
 void loadTiles(unsigned int tilesOffset, unsigned int *memTiles) {
@@ -578,8 +585,8 @@ void drawSpriteToBuf(unsigned int *sprite, int pageX, int pageY, int shift, int
 }
 
 void drawSprite(unsigned int *sprite, int x, int y) {
-  int pageX = (x - (screen.scrollX & 0xfff0)) >> 4;
-  int pageY = (y - (screen.scrollY & 0xfff0)) >> 4;
+  int pageX = (int)(x - (screen.scrollX & 0xfff0)) >> 4;
+  int pageY = (int)(y - (screen.scrollY & 0xfff0)) >> 4;
   int pageOffsetX = x & 0x0f;
   int pageOffsetY = y & 0x0f;
 
@@ -656,6 +663,8 @@ void drawScreen() {
   }
   setAllPlanes();
   setDisplayOffset(scrollOffset);
+  setHorizontalPan(screen.scrollX & 0x07);
+
   screen.currentPage ^= 1;
   screen.firstBuffer = screen.nextBuffer;
   for (di = 0; di < PAGE_TILES_COUNT; di ++) {
@@ -720,25 +729,22 @@ void game_init() {
 }
 
 int main() {
-  int x = 100;
-  int y = 100;
-  int z = 0;
+  int x = -1;
+  int y = -1;
+  int dir = 0;
 
   game_init();
   kbd_init();
 
   while (!keyPressed(K_ESC)) {
 
-    if (keyPressed(K_LEFT))  x -= 3;
-    if (keyPressed(K_RIGHT)) x += 3;
-    if (keyPressed(K_UP))    y -= 3;
-    if (keyPressed(K_DOWN))  y += 3;
+    if (keyPressed(K_LEFT))  { x -= 3; dir = 2; }
+    if (keyPressed(K_RIGHT)) { x += 3; dir = 0; }
+    if (keyPressed(K_UP))    { y -= 3; dir = 1; }
+    if (keyPressed(K_DOWN))  { y += 3; dir = 3; }
     scroll(x - 152, y - 90);
-    drawSprite(&sprites[0 * SPRITE_STRIDE], 50, 50);
-    drawSprite(&sprites[1 * SPRITE_STRIDE], x, y);
+    drawSprite(&sprites[dir * SPRITE_STRIDE], x, y);
     drawScreen();
-
-    z++;
   }
 
   return 0;