Add title screen

src/actor.c

@@ -9,6 +9,9 @@
 #define MAX_ACTORS 5
 #define NUM_OAM_ENTRIES 40
 #define TILE_WIDTH 8
+#define FRAMES_PER_ANIM_FRAME 20
+
+static actor_anim_state_t ANIM_TOTAL_FRAMES[] = {2};
 
 static uint8_t mob_ids[MAX_UNIQUE_MOBS];
 static sprite16_mob mob_anim_data[MAX_UNIQUE_MOBS];
@@ -54,12 +57,31 @@ actor_t *actor_create_mob(uint8_t id) {
 
 void actor_remove(actor_t *a) { a->active = 0; }
 
+void actor_update(void) {
+    actor_t *a = &all_actors[0];
+
+    for (uint8_t i = 0; i < ARRSIZE(all_actors); ++i) {
+        if (!a->active) {
+            continue;
+        }
+
+        a->frame_counter++;
+        if (a->frame_counter == FRAMES_PER_ANIM_FRAME) {
+            a->frame_counter = 0;
+            a->frame_idx = (a->frame_idx + 1) % ANIM_TOTAL_FRAMES[a->anim];
+        }
+
+        a++;
+    }
+}
+
 void actor_flush_oam(void) {
     struct oam_entry *oam_ptr = &shadow_oam[0];
     actor_t *a = &all_actors[0];
 
     for (uint8_t i = 0; i < ARRSIZE(all_actors); ++i) {
         if (!a->active) {
+            a++;
             continue;
         }
 
@@ -116,4 +138,4 @@ static uint8_t actor_load_mob_anim_data(uint8_t mob_id) {
     }
 
     return mob_anim_idx;
-}
+}

src/actor.h

@@ -16,6 +16,7 @@ typedef enum {
 
 typedef struct {
     uint8_t active;
+    uint8_t dirty;
     uint8_t mob_anim_idx;
     actor_anim_state_t anim;
     uint8_t frame_idx;
@@ -54,6 +55,11 @@ actor_t *actor_create_mob(mob_id_t id);
  */
 void actor_remove(actor_t *a);
 
+/**
+ * @brief Update the internal state of each actor.
+ */
+void actor_update(void);
+
 /**
  * @brief Flush actor sprite data to OAM.
  */

src/game.h

@@ -0,0 +1,47 @@
+#ifndef IS_GAME_H_
+#define IS_GAME_H_
+
+#define _VRAM 0x8000
+#define _VRAM8000 _VRAM
+#define _VRAM8800 (_VRAM + 0x800)
+#define _VRAM9000 (_VRAM + 0x1000)
+#define _SCRN0 0x9800
+#define _SCRN1 0x9c00
+
+#define SCRN_X 160
+#define SCRN_Y 144
+#define SCRN_X_B 20
+#define SCRN_Y_B 18
+
+#define SCRN_VX 256
+#define SCRN_VY 256
+#define SCRN_VX_B 32
+#define SCRN_VX_Y 32
+
+#define SCREEN_HEIGHT_TILES 18
+#define SCREEN_WIDTH_TILES 20
+
+typedef enum {
+    GAME_STATE_TITLE,
+    GAME_STATE_LEVEL,
+    GAME_STATE_MENU,
+} game_state_t;
+
+extern game_state_t game_state;
+
+/**
+ * @brief Render the title screen.
+ */
+void title(void);
+
+/**
+ * @brief Enable interrupts.
+ */
+void interrupts_enable(void) __preserves_regs(a, b, c, d, e, h, l);
+
+/**
+ * @brief Disable interrupts.
+ */
+void interrupts_disable(void) __preserves_regs(a, b, c, d, e, h, l);
+
+#endif

src/helpers.asm

@@ -0,0 +1,14 @@
+SECTION "vblank", ROM0[$40]
+
+handle_vblank:
+    reti
+
+SECTION "interrupt routines", ROM0
+
+_interrupts_disable::
+    di
+    ret
+
+_interrupts_enable::
+    ei
+    ret

src/main.c

@@ -1,80 +1,34 @@
 #include <string.h>
 
 #include "actor.h"
-#include "sdk/assets.h"
+#include "game.h"
 #include "sdk/hardware.h"
-#include "sdk/joypad.h"
 #include "sdk/oam.h"
-#include "sdk/video.h"
 
-ASSET(tiles, "tiles.2bpp");
-
-uint8_t cursor_x = 0;
-uint8_t cursor_y = 0;
+game_state_t game_state;
 
 void main() {
-    // Load our initial vram (this is slow, but always works, even outside of
-    // vblank)
-    vram_memcpy(0x8000, tiles, tiles_end - tiles);
-    vram_memcpy(0x9000, tiles, tiles_end - tiles);
+    game_state = GAME_STATE_TITLE;
+
     // Setup the OAM for sprite drawing
     oam_init();
 
-    // Set some default DMG palette data
+    // Set up background & sprites
     rBGP = 0b11100100;
     rOBP0 = 0b11100100;
     rOBP1 = 0b11100100;
-
-    // Put some sprites on the screen
-    shadow_oam[0].y = 0x20;
-    shadow_oam[0].x = 0x20;
-    shadow_oam[0].tile = 0x04;
-    shadow_oam[0].attr = 0x00;
-    shadow_oam[1].y = 0x24;
-    shadow_oam[1].x = 0x24;
-    shadow_oam[1].tile = 0x02;
-    shadow_oam[1].attr = 0x00;
-
-    // Make sure sprites and the background are drawn
-    rLCDC = LCDC_ON | LCDC_OBJON | LCDC_BGON;
+    rLCDC = LCDC_OBJON | LCDC_BGON | LCDC_BG8000;
 
     // Setup the VBLANK interrupt, but we don't actually enable interrupt
-    // handling.
-    // We only do this, so HALT waits for VBLANK.
+    // handling. We only do this so HALT waits for VBLANK.
     rIF = 0;
     rIE = IE_VBLANK;
 
-    vram_memset(0x9800, 0x05, 32 * 18);
-    for (uint8_t x = 0; x < 20; x++) {
-        vram_set(0x9800 + x, 0x07);
-        vram_set(0x9A20 + x, 0x07);
-    }
-    for (uint8_t y = 1; y < 18; y++) {
-        vram_set(0x9800 + y * 0x20, 0x07);
-        vram_set(0x9800 + 19 + y * 0x20, 0x07);
-    }
-    vram_set(0x9800 + 3 + 3 * 0x20, 0x01);
-
     while (1) {
-        joypad_update();
-        if (joypad_state & PAD_LEFT) cursor_x--;
-        if (joypad_state & PAD_RIGHT) cursor_x++;
-        if (joypad_state & PAD_UP) cursor_y--;
-        if (joypad_state & PAD_DOWN) cursor_y++;
-        if (joypad_state & (PAD_A | PAD_B)) {
-            vram_set(0x9800 + cursor_x / 8 + cursor_y / 8 * 0x20, 0x03);
+        switch (game_state) {
+            case GAME_STATE_TITLE:
+                title();
+                break;
         }
-
-        // Screen to OAM coordinates
-        shadow_oam[0].y = cursor_y + 16;
-        shadow_oam[0].x = cursor_x + 8;
-
-        // Wait for VBLANK
-        HALT();
-        rIF = 0;  // As global interrupts are not enabled, we need to clear the
-                  // interrupt flag.
-
-        // Copy the sprites into OAM memory
-        oam_dma_copy();
     }
 }

src/title.c

@@ -0,0 +1,44 @@
+#include <string.h>
+
+#include "game.h"
+#include "sdk/assets.h"
+#include "sdk/hardware.h"
+#include "sdk/joypad.h"
+#include "sdk/oam.h"
+#include "sdk/video.h"
+
+ASSET(bg_tiles, "bg/title.2bpp");
+ASSET(bg_map, "bg/title.map");
+
+void title(void) {
+    // NOTE: Replace with lcdc_off() if necessary
+    rLCDC &= ~LCDC_ON;
+
+    // Copy title screen to VRAM
+    memcpy((uint8_t *)_VRAM, &bg_tiles[0], bg_tiles_end - bg_tiles);
+    // vram_memcpy(_VRAM, &bg_tiles[0], bg_tiles_end - bg_tiles);
+
+    uint8_t *vram_ptr = (uint8_t *)_SCRN0;
+    const uint8_t *map_ptr = &bg_map[0];
+
+    for (uint8_t y = 0; y < SCRN_Y_B; ++y) {
+        memcpy(vram_ptr, map_ptr, SCRN_X_B);
+        vram_ptr += SCRN_VX_B;
+        map_ptr += SCRN_X_B;
+    }
+
+    rLCDC |= LCDC_ON;
+    interrupts_enable();
+
+    while (1) {
+        joypad_update();
+        if (joypad_state & PAD_START) {
+            game_state = GAME_STATE_LEVEL;
+            break;
+        }
+
+        // Wait for VBLANK. Clear IF since global interrupts are disabled.
+        HALT();
+        rIF = 0;
+    }
+}