From 74d6b52636ecdd560995f22dff5b29a59fc62d5d Mon Sep 17 00:00:00 2001
From: Bad Diode <bd@badd10de.dev>
Date: Thu, 22 Apr 2021 17:34:38 +0200
Subject: Test background scrolling with input control

---
 src/main.c | 72 +++++++++++++++++++++++++++++++++++++++++++++++++++++++-------
 1 file changed, 64 insertions(+), 8 deletions(-)

(limited to 'src/main.c')

diff --git a/src/main.c b/src/main.c
index 0af41f8..4dd2554 100644
--- a/src/main.c
+++ b/src/main.c
@@ -1,6 +1,7 @@
 #include "shorthand.h"
 #include "bd-font.c"
 #include "gba-buttons.c"
+#include "background-tiles.c"
 
 //
 // Memory sections.
@@ -46,10 +47,34 @@
 #define DISP_ENABLE_SPRITES DISP_OBJ | DISP_OBJ_1D
 
 // Registers to control of BG layers.
-#define BG_CTRL_0 *((vu16*)(0x04000008 + 0x0000))
-#define BG_CTRL_1 *((vu16*)(0x04000008 + 0x0002))
-#define BG_CTRL_2 *((vu16*)(0x04000008 + 0x0004))
-#define BG_CTRL_3 *((vu16*)(0x04000008 + 0x0006))
+#define BG_CTRL_0 *((vu16*)(0x04000008 + 0x0002 * 0))
+#define BG_CTRL_1 *((vu16*)(0x04000008 + 0x0002 * 1))
+#define BG_CTRL_2 *((vu16*)(0x04000008 + 0x0002 * 2))
+#define BG_CTRL_3 *((vu16*)(0x04000008 + 0x0002 * 3))
+
+// Bits to control the background.
+#define BG_PRIORITY_0     0x0
+#define BG_PRIORITY_1     0x1
+#define BG_PRIORITY_2     0x2
+#define BG_PRIORITY_3     0x3
+#define BG_CHARBLOCK(N)   ((N) << 2)
+#define BG_MOSAIC         (1 << 6)
+#define BG_HIGH_COLOR     (1 << 7)
+#define BG_SCREENBLOCK(N) ((N) << 8)
+#define BG_AFFINE         (1 << 0xD)
+#define BG_SIZE(N)        ((N) << 0xE)
+
+// BG registers for horizontal displacement.
+#define BG_H_SCROLL_0 *((vu16*)(0x04000010 + 0x0004 * 0))
+#define BG_H_SCROLL_1 *((vu16*)(0x04000010 + 0x0004 * 1))
+#define BG_H_SCROLL_2 *((vu16*)(0x04000010 + 0x0004 * 2))
+#define BG_H_SCROLL_3 *((vu16*)(0x04000010 + 0x0004 * 3))
+
+// BG registers for vertical displacement.
+#define BG_V_SCROLL_0 *((vu16*)(0x04000012 + 0x0004 * 0))
+#define BG_V_SCROLL_1 *((vu16*)(0x04000012 + 0x0004 * 1))
+#define BG_V_SCROLL_2 *((vu16*)(0x04000012 + 0x0004 * 2))
+#define BG_V_SCROLL_3 *((vu16*)(0x04000012 + 0x0004 * 3))
 
 // Screen settings.
 #define SCREEN_WIDTH 240
@@ -69,9 +94,11 @@ typedef struct Tile {
 } Tile;
 
 typedef Tile TileBlock[512];
-
 #define TILE_MEM ((TileBlock*) MEM_VRAM)
 
+typedef u16 ScreenBlock[1024];
+#define SCREENBLOCK_MEM ((ScreenBlock*)MEM_VRAM)
+
 // We can treat the screen as a HxW matrix. With the following macro we can
 // write a pixel to the screen at the (x, y) position using:
 //
@@ -524,9 +551,6 @@ load_packed_sprite_data(u32 *sprite_data, size_t n_tiles, size_t n_frames) {
 }
 
 int main(void) {
-    // Configure the display in mode 0 to show OBJs, where tile memory is
-    // sequential.
-    DISP_CTRL = DISP_MODE_0 | DISP_ENABLE_SPRITES | DISP_BG_2;
 
     // Add colors to the sprite color palette. Tiles with color number 0 are
     // treated as transparent.
@@ -543,6 +567,21 @@ int main(void) {
     sprite_tile_counter = 0;
     sprite_memory = &TILE_MEM[4][sprite_tile_counter];
 
+    // Load background palette.
+    memcpy(&PAL_BUFFER_BG[0], &bg_palette, 512);
+    memcpy(&TILE_MEM[0][0], bg_data, 3168);
+    memcpy(&SCREENBLOCK_MEM[30][0], bg_map, 2048);
+
+    // Configure BG0 to use 4bpp, 64x32 tile map in charblock 0 and screenblock
+    // 31.
+    BG_CTRL_0 = BG_CHARBLOCK(0) | BG_SCREENBLOCK(30) | BG_SIZE(0);
+    BG_H_SCROLL_0 = 0;
+    BG_V_SCROLL_0 = 0;
+
+    // Configure the display in mode 0 to show OBJs, where tile memory is
+    // sequential.
+    DISP_CTRL = DISP_ENABLE_SPRITES | DISP_MODE_0 | DISP_BG_0;
+
     // Initialize the A/B button sprites.
     int buttons_x = SCREEN_WIDTH / 2;
     int buttons_y = SCREEN_HEIGHT / 2;
@@ -635,6 +674,8 @@ int main(void) {
     OBJ_ATTR_2(btn_r.id) = sprites[btn_r.id].tile_start;
 
     int frame_counter = 0;
+    int x = 0;
+    int y = 0;
     while(true) {
         wait_vsync();
         poll_keys();
@@ -784,6 +825,19 @@ int main(void) {
             }
         }
 
+        if (key_hold(KEY_DOWN)) {
+            y += 3;
+        }
+        if (key_hold(KEY_UP)) {
+            y -= 3;
+        }
+        if (key_hold(KEY_LEFT)) {
+            x -= 3;
+        }
+        if (key_hold(KEY_RIGHT)) {
+            x += 3;
+        }
+
         OBJ_ATTR_2(btn_b.id) = sprites[btn_b.id].tile_start + animation_states[btn_b.state]->tile_offsets[btn_b.frame];
         OBJ_ATTR_2(btn_a.id) = sprites[btn_a.id].tile_start + animation_states[btn_a.state]->tile_offsets[btn_a.frame];
         OBJ_ATTR_2(btn_up.id) = sprites[btn_up.id].tile_start + animation_states[btn_up.state]->tile_offsets[btn_up.frame];
@@ -793,6 +847,8 @@ int main(void) {
         OBJ_ATTR_2(btn_l.id) = sprites[btn_l.id].tile_start + animation_states[btn_l.state]->tile_offsets[btn_l.frame];
         OBJ_ATTR_2(btn_r.id) = sprites[btn_r.id].tile_start + animation_states[btn_r.state]->tile_offsets[btn_r.frame];
         frame_counter++;
+        BG_H_SCROLL_0 = x;
+        BG_V_SCROLL_0 = y;
     };
 
     return 0;
-- 
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