Update the renderer to support a text layer

8 files changed, 200 insertions, 31 deletions

diff --git a/src/bd-font.c b/src/bd-font.c
new file mode 100644
index 0000000..5276735
--- /dev/null
+++ b/src/bd-font.c
@@ -0,0 +1,141 @@
+/*
+Copyright (c) 2021 Bad Diode
+
+Permission to use, copy, modify, and distribute this software for any
+purpose with or without fee is hereby granted, provided that the above
+copyright notice and this permission notice appear in all copies.
+
+THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
+WITH REGARD TO THIS SOFTWARE.
+*/
+
+static const u32 bd_font[] = {
+    0x00000000, 0x00000000, 0x00002400, 0x423c0000,
+    0x00002400, 0x3c420000, 0x0000363e, 0x3e1c0800,
+    0x00081c3e, 0x3e1c0800, 0x001c1c3e, 0x363e081c,
+    0x00081c3e, 0x3e3e081c, 0x00000018, 0x18000000,
+    0x7e7e7e66, 0x667e7e7e, 0x00001824, 0x24180000,
+    0x7e7e665a, 0x5a667e7e, 0x00081c3e, 0x081c221c,
+    0x001c221c, 0x08083e08, 0x00183828, 0x08080c0c,
+    0x003c2424, 0x24343606, 0x00082208, 0x1c082208,
+    0x040c1c3c, 0x1c0c0400, 0x2030383c, 0x38302000,
+    0x081c3e08, 0x083e1c08, 0x00141414, 0x14140014,
+    0x003c2a2a, 0x2c282828, 0x0038043c, 0x423c201e,
+    0x00000000, 0x7e000000, 0x081c3e08, 0x3e1c083e,
+    0x081c3e08, 0x08080800, 0x00080808, 0x083e1c08,
+    0x00001030, 0x7e301000, 0x0000080c, 0x7e0c0800,
+    0x00000000, 0x0002023e, 0x00002466, 0xff662400,
+    0x0008081c, 0x1c3e3e00, 0x003e3e1c, 0x1c080800,
+    0x00000000, 0x00000000, 0x00080808, 0x08080008,
+    0x14141400, 0x00000000, 0x0000143e, 0x143e1400,
+    0x00081c02, 0x1c201e08, 0x00002616, 0x08343200,
+    0x00081408, 0x34122c00, 0x08080800, 0x00000000,
+    0x08040404, 0x04040408, 0x08101010, 0x10101008,
+    0x00001408, 0x3e081400, 0x00000808, 0x3e080800,
+    0x00000000, 0x000c0804, 0x00000000, 0x3e000000,
+    0x00000000, 0x000c0c00, 0x00203018, 0x0c060200,
+    0x00001c22, 0x2a221c00, 0x00000c0a, 0x08083e00,
+    0x00001c20, 0x1c023e00, 0x00001c22, 0x18221c00,
+    0x00001018, 0x143e1000, 0x00003e02, 0x1e201e00,
+    0x00001c02, 0x1e221c00, 0x00003e20, 0x10080400,
+    0x00001c22, 0x1c221c00, 0x00001c22, 0x3c201c00,
+    0x00000c0c, 0x000c0c00, 0x00000c0c, 0x000c0804,
+    0x00100804, 0x04081000, 0x0000003e, 0x003e0000,
+    0x00040810, 0x10080400, 0x001c2220, 0x10080008,
+    0x001c322a, 0x1a021c00, 0x001c2222, 0x3e222200,
+    0x001e221e, 0x22221e00, 0x001c2202, 0x02221c00,
+    0x000e1222, 0x22120e00, 0x003e021e, 0x02023e00,
+    0x003e021e, 0x02020200, 0x001c2202, 0x32221c00,
+    0x00222222, 0x3e222200, 0x003e0808, 0x08083e00,
+    0x00202020, 0x22221c00, 0x0022120a, 0x0e122200,
+    0x00020202, 0x02023e00, 0x0022362a, 0x22222200,
+    0x0022262a, 0x32222200, 0x001c2222, 0x22221c00,
+    0x001e2222, 0x1e020200, 0x001c2222, 0x2a122c00,
+    0x001e2222, 0x1e122200, 0x001c021c, 0x20221c00,
+    0x003e0808, 0x08080800, 0x00222222, 0x22221c00,
+    0x00222222, 0x22140800, 0x0022222a, 0x2a2a1400,
+    0x00221408, 0x08142200, 0x00222214, 0x08080800,
+    0x003e1008, 0x04023e00, 0x1c040404, 0x0404041c,
+    0x0002060c, 0x18302000, 0x1c101010, 0x1010101c,
+    0x08142200, 0x00000000, 0x00000000, 0x00003e00,
+    0x00040810, 0x00000000, 0x00001c20, 0x3c223c00,
+    0x0002021e, 0x22221e00, 0x00001c22, 0x02221c00,
+    0x0020203c, 0x22223c00, 0x00001c22, 0x1e023c00,
+    0x00003c02, 0x021e0202, 0x00003c22, 0x223c201c,
+    0x0002021e, 0x22222200, 0x0008000c, 0x08083e00,
+    0x00200020, 0x2020221c, 0x0002120a, 0x060a3200,
+    0x000c0808, 0x08083e00, 0x0000162a, 0x2a2a2a00,
+    0x00000e32, 0x22222200, 0x00001c22, 0x22221c00,
+    0x00001e22, 0x221e0202, 0x00003c22, 0x223c2070,
+    0x00001a26, 0x02020200, 0x00001c02, 0x1c201e00,
+    0x00043e04, 0x04041800, 0x00002222, 0x22221c00,
+    0x00002222, 0x22140800, 0x00002222, 0x2a2a1400,
+    0x00002214, 0x08142200, 0x00002222, 0x223c201c,
+    0x00003e10, 0x08043e00, 0x18040402, 0x02040418,
+    0x00080808, 0x08080808, 0x0c101020, 0x2010100c,
+    0x00002c1a, 0x00000000, 0x00000814, 0x22223e00,
+    0x001c2202, 0x221c080e, 0x00140022, 0x2222221c,
+    0x1008001c, 0x221e023c, 0x0814001c, 0x203c223c,
+    0x0014001c, 0x203c223c, 0x0408001c, 0x203c223c,
+    0x0814081c, 0x203c223c, 0x00001c02, 0x221c080e,
+    0x0814001c, 0x221e023c, 0x0014001c, 0x221e023c,
+    0x0408001c, 0x221e023c, 0x0014000c, 0x0808083e,
+    0x0014000c, 0x0808083e, 0x0408000c, 0x0808083e,
+    0x0014001c, 0x223e2222, 0x0814081c, 0x223e2222,
+    0x1008003e, 0x021e023e, 0x00001628, 0x1c0a3400,
+    0x003c0a1a, 0x0e0a3a00, 0x0814001c, 0x2222221c,
+    0x0014001c, 0x2222221c, 0x0408001c, 0x2222221c,
+    0x08140022, 0x2222221c, 0x04080022, 0x2222221c,
+    0x00140022, 0x223c201c, 0x14001c22, 0x2222221c,
+    0x14002222, 0x2222221c, 0x00081c22, 0x02221c08,
+    0x0018240e, 0x04043e00, 0x00221408, 0x1c081c08,
+    0x0038041e, 0x041e0438, 0x0030081c, 0x08080806,
+    0x1008001c, 0x203c223c, 0x1008000c, 0x0808083e,
+    0x1008001c, 0x2222221c, 0x10080022, 0x2222221c,
+    0x2c1a000e, 0x32222222, 0x2c1a0022, 0x262a3222,
+    0x001c122c, 0x001e0000, 0x000c120c, 0x001e0000,
+    0x08000804, 0x02221c00, 0x0000003e, 0x02020000,
+    0x0000003e, 0x20200000, 0x06241468, 0x4422f000,
+    0x06241468, 0x54f24000, 0x08000808, 0x08080800,
+    0x00482412, 0x24480000, 0x00122448, 0x24120000,
+    0x00880022, 0x00880022, 0x55885522, 0x55885522,
+    0x55aa55aa, 0x55aa55aa, 0x08080808, 0x08080808,
+    0x0808080f, 0x08080808, 0x08080f08, 0x0f080808,
+    0x14141417, 0x14141414, 0x0000001f, 0x14141414,
+    0x00000f08, 0x0f080808, 0x14141710, 0x17141414,
+    0x14141414, 0x14141414, 0x00001f10, 0x17141414,
+    0x14141710, 0x1f000000, 0x1414141f, 0x00000000,
+    0x08080f08, 0x0f000000, 0x0000000f, 0x08080808,
+    0x080808f8, 0x00000000, 0x080808ff, 0x00000000,
+    0x000000ff, 0x08080808, 0x080808f8, 0x08080808,
+    0x000000ff, 0x00000000, 0x080808ff, 0x08080808,
+    0x0808f808, 0xf8080808, 0x141414f4, 0x14141414,
+    0x1414f404, 0xfc000000, 0x0000fc04, 0xf4141414,
+    0x1414f700, 0xff000000, 0x0000ff00, 0xf7141414,
+    0x1414f404, 0xf4141414, 0x0000ff00, 0xff000000,
+    0x1414f700, 0xf7141414, 0x0808ff00, 0xff000000,
+    0x141414ff, 0x00000000, 0x0000ff00, 0xff080808,
+    0x000000ff, 0x14141414, 0x141414fc, 0x00000000,
+    0x0808f808, 0xf8000000, 0x0000f808, 0xf8080808,
+    0x000000fc, 0x14141414, 0x141414ff, 0x14141414,
+    0x0808ff08, 0xff080808, 0x0808080f, 0x00000000,
+    0x000000f8, 0x08080808, 0xffffffff, 0xffffffff,
+    0x00000000, 0xffffffff, 0x0f0f0f0f, 0x0f0f0f0f,
+    0xf0f0f0f0, 0xf0f0f0f0, 0xffffffff, 0x00000000,
+    0x00002c12, 0x12122c00, 0x000c120a, 0x12223a02,
+    0x003e2202, 0x02020200, 0x00003e14, 0x14141400,
+    0x3e220408, 0x04223e00, 0x00003c12, 0x12120c00,
+    0x00002222, 0x221e0202, 0x002c1a08, 0x08281000,
+    0x1c081c22, 0x221c081c, 0x1c22223e, 0x22221c00,
+    0x1c222222, 0x22143600, 0x1e041824, 0x22221c00,
+    0x0000142a, 0x2a140000, 0x0020142a, 0x2a140200,
+    0x00003c02, 0x1c023c00, 0x001c2222, 0x22222202,
+    0x00003e00, 0x3e003e00, 0x0000081c, 0x08001c00,
+    0x04081008, 0x04001c00, 0x10080408, 0x10001c00,
+    0x30480808, 0x08080808, 0x08080808, 0x08080906,
+    0x00000800, 0x3e000800, 0x00004c32, 0x004c3200,
+    0x00182418, 0x00000000, 0x00001c1c, 0x1c000000,
+    0x00000018, 0x18000000, 0x00f01010, 0x10121418,
+    0x0c342424, 0x00000000, 0x1810083c, 0x00000000,
+    0x00003c3c, 0x3c3c0000, 0x00000000, 0x00000000,
+};
diff --git a/src/filesystem.h b/src/filesystem.h
index d50e5e7..6439f83 100644
--- a/src/filesystem.h
+++ b/src/filesystem.h
@@ -1,7 +1,7 @@
 #ifndef FILESYSTEM_H
 #define FILESYSTEM_H
 
-#include "common.h"
+#include "gba/gba.h"
 
 typedef enum {
     FS_OPEN_READ   = (1 << 0),
diff --git a/src/bios_calls.s b/src/gba/bios_calls.s
index 740fa02..740fa02 100644
--- a/src/bios_calls.s
+++ b/src/gba/bios_calls.s
diff --git a/src/common.h b/src/gba/gba.h
index fbe01a4..56c4876 100644
--- a/src/common.h
+++ b/src/gba/gba.h
@@ -1,5 +1,5 @@
-#ifndef COMMON_H
-#define COMMON_H
+#ifndef GBA_H
+#define GBA_H
 
 #include "shorthand.h"
 
@@ -664,4 +664,4 @@ wait_vsync(void) {
 #define EWRAM_CODE __attribute__((section(".ewram"), long_call))
 #define EWRAM_BSS __attribute__((section(".sbss")))
 
-#endif // COMMON_H
+#endif // GBA_H
diff --git a/src/interrupts.c b/src/gba/interrupts.c
index 8e560dc..3b11335 100644
--- a/src/interrupts.c
+++ b/src/gba/interrupts.c
@@ -1,4 +1,4 @@
-#include "common.h"
+#include "gba.h"
 
 IrsFunc irs_table[] = {
     [IRQ_VBLANK ] = NULL,
diff --git a/src/interrupts.s b/src/gba/interrupts.s
index 67b9fe9..67b9fe9 100644
--- a/src/interrupts.s
+++ b/src/gba/interrupts.s
diff --git a/src/main.c b/src/main.c
index e228034..1e1ef11 100644
--- a/src/main.c
+++ b/src/main.c
@@ -9,12 +9,11 @@ THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
 WITH REGARD TO THIS SOFTWARE.
 */
 
-#include "common.h"
-// #include "text.h"
+#include "gba/gba.h"
 
-#include "interrupts.c"
 #include "filesystem.c"
 #include "renderer.c"
+// #include "text.h"
 
 //
 // Config parameters.
@@ -62,6 +61,10 @@ int main(void) {
     irq_init();
     irs_set(IRQ_VBLANK, irs_stub);
 
+    draw_pixel(10, 0, 1);
+    draw_pixel(10, 1, 2);
+    draw_pixel(10, 2, 3);
+    draw_pixel(10, 3, 4);
     draw_pixel(0, 0, 1);
     draw_pixel(0, 1, 2);
     draw_pixel(0, 2, 3);
diff --git a/src/renderer.c b/src/renderer.c
index 9fe55b2..ec54411 100644
--- a/src/renderer.c
+++ b/src/renderer.c
@@ -1,14 +1,28 @@
-// TODO: For now we pack front/backbuffers together but this make it so that we
-// can only use 2 backgrounds. Instead we can move the backbuffer to the end of
-// the VRAM. This will give us 3 backgrounds but eats into the available memory
-// for sprites but should be fine for non sprite intensive applications.
-#define FRONTBUFFER ((u32*)(MEM_VRAM))
-#define BACKBUFFER  ((u32*)(MEM_VRAM + KB(96) - KB(20)))
+#include "bd-font.c"
+
+// The frontbuffer is located at the beginning of the VRAM, and requires 20KB of
+// video memory for 32 * 20 tiles at 4bpp.
+#define FRONTBUF ((u32*)(MEM_VRAM))
 
 // Adjust both of these if the location of the map changes. Each screnblock
-// requires 2K.
-#define FRONTBUFFER_TILEMAP     ((u16*)(MEM_VRAM + KB(20)))
-#define FRONTBUFFER_SCREENBLOCK 10
+// requires less than 2KB.
+#define FRONTBUF_TILEMAP ((u16*)(MEM_VRAM + KB(20)))
+#define FRONTBUF_SB      10
+
+// The backbuffer is located at the end of the VRAM. This can allow us to use
+// more backgrounds but eats into the available memory for sprites. This should
+// be fine for non sprite intensive applications. If more sprite memory is
+// needed, the backbuffer can be located at the end of the background memory
+// instead (64KB - 20KB).
+#define BACKBUF  ((u32*)(MEM_VRAM + KB(96) - KB(20)))
+
+// The font data is located at the end of the frontbuffer memory, after the tile
+// map and requires 8KB for 256 8x8 characters at 4bpp. This, along with the
+// tilemap information allow us to store the frontbuffer and font for a text
+// background in the first 2 charblocks (32KB).
+#define FONT_DATA    ((u32*)(MEM_VRAM + KB(22)))
+#define FONT_TILEMAP ((u16*)(MEM_VRAM + KB(30)))
+#define FONT_SB      15
 
 static u32 dirty_tiles[21] = {0};
 
@@ -29,7 +43,7 @@ draw_pixel(u16 x, u16 y, u8 color) {
 
     // Update backbuffer.
     size_t shift = start_col * sizeof(u32);
-    BACKBUFFER[pos] = (BACKBUFFER[pos] & ~(0xF << shift)) | color << shift;
+    BACKBUF[pos] = (BACKBUF[pos] & ~(0xF << shift)) | color << shift;
 
     // Mark tile as dirty.
     dirty_tiles[tile_y] |= 1 << tile_x;
@@ -39,8 +53,8 @@ IWRAM_CODE
 void
 flip_buffer(void) {
     // Copy dirty tiles from the backbuffer to the frontbuffer.
-    Tile *dst = FRONTBUFFER;
-    Tile *src = BACKBUFFER;
+    Tile *dst = FRONTBUF;
+    Tile *src = BACKBUF;
     for (size_t j = 0; j < 20; ++j) {
         if (dirty_tiles[j] == 0) {
             continue;
@@ -54,19 +68,23 @@ flip_buffer(void) {
     }
 }
 
+static u16 font_map[256] = {0};
+
 void
 renderer_init(void) {
     // Initialize display mode and bg palette.
-    DISP_CTRL = DISP_MODE_0 | DISP_BG_0 | DISP_OBJ;
+    DISP_CTRL = DISP_MODE_0 | DISP_BG_0 | DISP_BG_1 | DISP_OBJ;
 
     // Initialize backgrounds.
-    BG_CTRL(0) = BG_CHARBLOCK(0) | BG_SCREENBLOCK(FRONTBUFFER_SCREENBLOCK);
+    BG_CTRL(0) = BG_CHARBLOCK(0) | BG_SCREENBLOCK(FRONTBUF_SB) | BG_PRIORITY(1);
+    BG_CTRL(1) = BG_CHARBLOCK(1) | BG_SCREENBLOCK(FONT_SB) | BG_PRIORITY(0);
 
-    // TODO: Initialize other backgrounds if needed.
-
-    // Use DMA to clear front and back buffers.
-    dma_fill(FRONTBUFFER, 0, KB(20), 3);
-    dma_fill(BACKBUFFER, 0, KB(20), 3);
+    // Use DMA to clear front and back buffers as well as the font memory map.
+    dma_fill(FRONTBUF, 0, KB(20), 3);
+    dma_fill(FRONTBUF_TILEMAP, 0, KB(2), 3);
+    dma_fill(FONT_DATA, 0, KB(8), 3);
+    dma_fill(FONT_TILEMAP, 0, KB(2), 3);
+    dma_fill(BACKBUF, 0, KB(20), 3);
 
     // Initialize default palette.
     PAL_BUFFER_BG[0] = COLOR_BLACK;
@@ -76,11 +94,18 @@ renderer_init(void) {
     PAL_BUFFER_BG[4] = COLOR_CYAN;
     PAL_BUFFER_BG[5] = COLOR_GREY;
 
-    // Initialize background memory map.
+    // Initialize background memory map for frontbuffer and font backgorund.
     for (size_t i = 0; i < 32 * 20; ++i) {
-        FRONTBUFFER_TILEMAP[i] = i;
+        FRONTBUF_TILEMAP[i] = i;
     }
 
-//     // Load font data into VRAM.
-//     unpack_tiles(&bd_font, FONT_DATA, 256);
+    // Load font data into VRAM.
+    unpack_tiles(&bd_font, FONT_DATA, 256);
+
+    // Initialize the font map translation table. That way we can write
+    // a character on the text background layer with:
+    //     FONT_TILEMAP[tile_x + 32 * tile_y] = font_map['A'];
+    for (size_t i = 0; i < 256; ++i) {
+        font_map[i] = 192 + i;
+    }
 }