improve sprites and balloon demo

demos/demo/demo_balloon.h

@@ -1,62 +1,136 @@
 #include <font8x8.h>
 
+// the balloon sprite, manually copied from C64 User's guide
 #include "cbm_balloon.h"
 
-void move_balloon(byte x, byte y, byte color) {
-   tms_sprite spr0,spr1;
-   spr0.x = x;
-   spr0.y = y;
-   spr0.name = 0;
-   spr0.color = color;
-   spr1.x = spr0.x;
-   spr1.y = spr0.y + 16*1;
-   spr1.name = spr0.name + 4;
-   spr1.color = spr0.color;
-   tms_set_sprite(0, &spr0);
-   tms_set_sprite(1, &spr1);   
+// a balloon is two 16x16 sprites, one above the other
+typedef struct {
+   int x;                 // x coordinate of the balloon
+   int y;                 // y coordinate of the balloon
+   int dx;                // x velocity of the balloon
+   int dy;                // y velocity of the balloon
+   byte color;            // color of the balloon
+   byte sprite_number;    // sprite number (0-31) of the balloon
+   tms_sprite upper;      // the upper sprite portion of the balloon
+   tms_sprite lower;      // the lower sprite portion of the balloon   
+} balloon;
+
+// move ballon on the screen by its velocity
+// and make it bounce over the borders
+void animate_balloon(balloon *b) {     
+   
+   // use temporary variables as KickC has issues dealing with "->" operator
+   int x = b->x;
+   int y = b->y;
+   int dx = b->dx;
+   int dy = b->dy;
+
+   // border collision detection
+   if(x>=240 || x<=0) dx = -dx; 
+   if(y>=172 || y<=0) dy = -dy; 
+
+   // move the balloon
+   x += dx;
+   y += dy;
+
+   // write back temporary variables
+   b->x = x;
+   b->y = y;
+   b->dx = dx;
+   b->dy = dy;
+
+   // update the sprite part of the balloon
+   b->upper.x = (byte) x;
+   b->upper.y = (signed char) y;
+   b->upper.name = 0;
+   b->upper.color = b->color;   
+   b->lower.x = b->upper.x;
+   b->lower.y = b->upper.y + 16;      // 16 pixels below the upper sprite
+   b->lower.name = b->upper.name + 4;  
+   b->lower.color = b->color;   
+   tms_set_sprite(b->sprite_number, &(b->upper));
+   tms_set_sprite(b->sprite_number+1, &(b->lower));   
 }
 
 void demo_balloon() {
    tms_init_regs(SCREEN2_TABLE);   
-   tms_set_color(COLOR_LIGHT_BLUE);
 
-   byte text_color = FG_BG(COLOR_GREY,COLOR_DARK_BLUE);
+   // we use only 4 sprites, two for each ot the two balloons on the screen
+   tms_set_total_sprites(4);
+   
+   // fake C64 bootup screen colors
+   tms_set_color(COLOR_LIGHT_BLUE);   
+   byte text_color = FG_BG(COLOR_GREY,COLOR_DARK_BLUE);  // alas, COLOR_LIGHT_BLUE doesn't fit well so we use GREY instead
 
    screen2_init_bitmap(text_color);
-              // 12345678901234567890123456789012
+
+   // C64-like screen text              
    screen2_puts("*** COMMODORE-APPLE BASIC V2 ***", 0, 0, text_color);
    screen2_puts("38911 BASIC BYTES FREE"          , 0, 2, text_color);
    screen2_puts("READY."                          , 0, 4, text_color);
-   screen2_puts(" "                               , 0, 5, FG_BG(COLOR_DARK_BLUE,COLOR_GREY));
    
-   // ballon demo
-
-   // define sprites using bitmap fonts
+   // copy the ballon graphic to VRAM
    tms_copy_to_vram(cbm_balloon, 4*8*2, TMS_SPRITE_PATTERNS);
-   tms_set_sprite_double_size(1);   // set 16x16 sprites   
-   tms_set_sprite_magnification(0); // set double pixel sprites
 
-   int x = 200;
-   int y = 80;
-   int dx = 1;
-   int dy = 1;
-   int delay = 0;   
-   byte sprcolor = COLOR_LIGHT_YELLOW;
+   tms_set_sprite_double_size(1);   // set 16x16 sprites   
+   tms_set_sprite_magnification(0); // set single pixel sprites
+
+   // we have two balloons bouncing around the screen
+
+   // first balloon
+   balloon b1;   
+   b1.x = 20;
+   b1.y = 20;
+   b1.dx = 1;
+   b1.dy = 1;
+   b1.color = COLOR_LIGHT_YELLOW;
+   b1.sprite_number = 0;
+
+   // second balloon
+   balloon b2;   
+   b2.x = 150;
+   b2.y = 150;
+   b2.dx = -1;
+   b2.dy = -1;
+   b2.color = COLOR_LIGHT_RED;
+   b2.sprite_number = 2;
+
+   // counter for a fake blinking cursor
+   byte blink_counter=0;
 
    for(;;) {
-      for(delay=0; delay<800; delay++) {
+
+      // delay the animation
+      for(int delay=0; delay<400; delay++) {
          delay = delay+1;
          delay = delay-1;
       }
 
+      // RETURN key ends the demo
       if(apple1_readkey()==0x0d) break;
 
-      if(x>=228 || x<=0) { dx = -dx; sprcolor++; }
-      if(y>=148 || y<=0) { dy = -dy; sprcolor++; }
+      // if there's a collision invert the motion of the balloons
+      if(COLLISION_BIT(TMS_READ_CTRL_PORT)) {      
+         int temp;
+         temp = b1.dx; b1.dx = -temp;   // b1.dx = -b1.dx; // due to KickC issue
+         temp = b1.dy; b1.dy = -temp;   // b1.dy = -b1.dy; // due to KickC issue
+         temp = b2.dx; b2.dx = -temp;   // b2.dx = -b2.dx; // due to KickC issue
+         temp = b2.dy; b2.dy = -temp;   // b2.dy = -b2.dy; // due to KickC issue
+      }
 
-      x += dx;
-      y += dy;
-      move_balloon((byte)x,(byte)y, COLOR_WHITE);     
+      // move the two balloons
+      animate_balloon(&b1);      
+      animate_balloon(&b2);  
+
+      // since a balloon is made of two sprites, sometimes they overlap 
+      // by one line during the move, causing a false collision      
+      // so we clear the collision bit by simply reading the status register
+      tms_clear_collisions();
+
+      // fake a blinking cursor
+      blink_counter++;
+      if(blink_counter == 16) { screen2_puts(" ", 0, 5, FG_BG(COLOR_DARK_BLUE,COLOR_GREY)); }
+      if(blink_counter == 32) { screen2_puts(" ", 0, 5, FG_BG(COLOR_GREY,COLOR_DARK_BLUE)); blink_counter = 0; }      
    }
 }
 

demos/demo/demo_screen2.h

@@ -29,23 +29,5 @@ void demo_screen2() {
    screen2_line(18+5+5,187,232+5+5, 45);
 
    screen2_plot_mode = PLOT_MODE_SET;   
-
-   // define sprites using bitmap fonts
-   tms_copy_to_vram(&FONT[64*8], 32*8, TMS_SPRITE_PATTERNS);
-
-   // set 16x16 sprites
-   tms_set_sprite_double_size(1);
-
-   // set double pixel sprites
-   tms_set_sprite_magnification(1);
-
-   tms_sprite spr;
-   for(byte t=0;t<4;t++) {
-      spr.x = 200;
-      spr.y =  5 + t*32;
-      spr.name = t*4;
-      spr.color = t+1;
-      tms_set_sprite(t, &spr);
-   }
 }
 

lib/screen1.h

@@ -48,12 +48,12 @@ void screen1_scroll_up() {
 }
 
 void screen1_prepare() {
+   // clear all the sprites
+   tms_set_total_sprites(0);
+
    // fill name table with spaces (32)
    screen1_cls();
 
-   // clear all the sprites
-   tms_clear_sprites();
-
    // fill pattern table with 0
    tms_set_vram_write_addr(TMS_PATTERN_TABLE);
    for(word i=256*8;i!=0;i--) {

lib/screen2.h

@@ -10,8 +10,8 @@ const word SCREEN2_SIZE = (32*24);
 
 // prepare the screen 2 to be used as a bitmap
 void screen2_init_bitmap(byte color) {
-   // erases all the sprites
-   tms_clear_sprites();
+   // clear all the sprites
+   tms_set_total_sprites(0);
 
    // fill pattern table with 0 (clear screen)
    tms_set_vram_write_addr(TMS_PATTERN_TABLE);

lib/sprites.h

@@ -2,13 +2,22 @@
 #define SPRITES_H
 
 typedef struct {
-   byte y;
+   signed char y;
    byte x;
    byte name;
    byte color;
 } tms_sprite;
 
 #define SIZEOF_SPRITE 4
+#define SPRITE_OFF_MARKER 0xD0
+#define EARLY_CLOCK 128
+
+void tms_set_total_sprites(byte num) {
+   // write the value 0xD0 as Y coordinate of the first unused sprite
+   word addr = TMS_SPRITE_ATTRS + (word) (num * SIZEOF_SPRITE);
+   tms_set_vram_write_addr(addr);
+   TMS_WRITE_DATA_PORT(SPRITE_OFF_MARKER);  // 0xD0 oi the sprite off indicator
+}
 
 void tms_set_sprite(byte sprite_num, tms_sprite *s) {
    word addr = TMS_SPRITE_ATTRS + (word) (sprite_num * SIZEOF_SPRITE);
@@ -34,21 +43,8 @@ void tms_set_sprite_magnification(byte m) {
    tms_write_reg(1, regval);
 }
 
-// clears all the sprites
-void tms_clear_sprites() {
-   // fills first sprite pattern with 0
-   tms_set_vram_write_addr(TMS_SPRITE_PATTERNS);  
-   for(byte i=0;i<8;i++) {
-      TMS_WRITE_DATA_PORT(0);
-   }
-
-   // set sprite coordinates to (0,0) and set pattern name 0
-   tms_set_vram_write_addr(TMS_SPRITE_ATTRS);       
-   for(byte i=0;i<32;i++) {
-      TMS_WRITE_DATA_PORT(0); NOP; NOP; NOP; NOP; // y coordinate
-      TMS_WRITE_DATA_PORT(0); NOP; NOP; NOP; NOP; // x coordinate
-      TMS_WRITE_DATA_PORT(0); NOP; NOP; NOP; NOP; // name
-      TMS_WRITE_DATA_PORT(0); NOP; NOP; NOP; NOP; // color
-   }
+// clear the collision flag by reading the status register
+inline void tms_clear_collisions() {
+   asm { lda VDP_REG };
 }
 #endif