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//
// This Mode 0 renderer provides a way of drawing directly to a framebuffer
// (similar to Mode 3 and 4) while retaining the flexibility of using other
// backgrounds if needed. It also performs double buffering to avoid tearing
// artifacts and tries to only draw tiles that changed on each frame.
//
// In addition to the frontbuffer (displayed on background 0), a tiled text
// layer is displayed on background 1, which can be used for application
// development or for debug information.
//
// These two layers occupy the first and second background charblocks, leaving
// the remaining two available for other background layers. There are 14KB of
// sprite memory available, since the backbuffer is located at the end of the
// VRAM, but if more space is needed it can be moved to the end of the BG
// charblocks instead as described below.
//
#include "text.h"
// 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 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
#define FONT_OFFSET 192
// Keep track of which tiles need to be copied to the frontbuffer.
static u32 dirty_tiles[21] = {0};
// TODO: Allow disable bound checking at compile time.
#define BOUNDCHECK_SCREEN(X,Y) if ((X) >= SCREEN_WIDTH || (Y) >= SCREEN_HEIGHT) return;
IWRAM_CODE
void
draw_pixel(u16 x, u16 y, u8 color) {
BOUNDCHECK_SCREEN(x, y);
// Find row position for the given x/y coordinates.
size_t tile_x = x / 8;
size_t tile_y = y / 8;
size_t start_col = x % 8;
size_t start_row = y % 8;
size_t pos = start_row + (tile_x + tile_y * 32) * 8;
// Update backbuffer.
size_t shift = start_col * sizeof(u32);
BACKBUF[pos] = (BACKBUF[pos] & ~(0xF << shift)) | color << shift;
// Mark tile as dirty.
dirty_tiles[tile_y] |= 1 << tile_x;
}
IWRAM_CODE
void
draw_tile(u16 x, u16 y, Tile *tile, bool merge) {
BOUNDCHECK_SCREEN(x, y);
// Find row position for the given x/y coordinates.
size_t tile_x = x / 8;
size_t tile_y = y / 8;
size_t start_col = x % 8;
size_t start_row = y % 8;
// Get a pointer to the backbuffer and the tile row.
size_t pos = start_row + (tile_x + tile_y * 32) * 8;
u32 *backbuffer = &BACKBUF[pos];
u32 *row = tile;
// This will blend all colors weirdly if using tiles that contain colors
// higher than 1.
size_t shift_left = start_col * 4;
size_t shift_right = (8 - start_col) * 4;
u32 row_mask = merge ? 0 : 0xFFFFFFFF << shift_left;
// Draw the tiles. There are 4 possible cases:
// 1. The tile is exactly at the tile boundary.
// 2. The tile spans 2 tiles horizontally.
// 3. The tile spans 2 tiles vertically.
// 4. The tile spans 4 tiles.
if (start_col == 0 && start_row == 0) {
for (size_t i = 0; i < (8 - start_row); i++, backbuffer++) {
BOUNDCHECK_SCREEN(x, y + i);
backbuffer[0] = (backbuffer[0] & ~row_mask) | row[i];
}
dirty_tiles[tile_y] |= 1 << tile_x;
} else if (start_row == 0) {
for (size_t i = 0; i < 8; i++, backbuffer++) {
BOUNDCHECK_SCREEN(x, y + i);
backbuffer[0] = (backbuffer[0] & ~row_mask) | (row[i] << shift_left);
backbuffer[8] = (backbuffer[8] & row_mask) | (row[i] >> shift_right);
}
dirty_tiles[tile_y] |= 1 << tile_x;
dirty_tiles[tile_y] |= 1 << (tile_x + 1);
} else if (start_col == 0) {
for (size_t i = 0; i < (8 - start_row); i++, backbuffer++) {
BOUNDCHECK_SCREEN(x, y + i);
backbuffer[0] = (backbuffer[0] & ~row_mask) | row[i];
}
backbuffer += 8 * 31;
for (size_t i = (8 - start_row); i < 8; i++, backbuffer++) {
BOUNDCHECK_SCREEN(x, y + i);
backbuffer[0] = (backbuffer[0] & ~row_mask) | row[i];
}
dirty_tiles[tile_y] |= 1 << tile_x;
dirty_tiles[tile_y + 1] |= 1 << tile_x;
} else {
for (size_t i = 0; i < (8 - start_row); i++, backbuffer++) {
BOUNDCHECK_SCREEN(x, y + i);
backbuffer[0] = (backbuffer[0] & ~row_mask) | (row[i] << shift_left);
backbuffer[8] = (backbuffer[8] & row_mask) | (row[i] >> shift_right);
}
backbuffer += 8 * 31;
for (size_t i = (8 - start_row); i < 8; i++, backbuffer++) {
BOUNDCHECK_SCREEN(x, y + i);
backbuffer[0] = (backbuffer[0] & ~row_mask) | (row[i] << shift_left);
backbuffer[8] = (backbuffer[8] & row_mask) | (row[i] >> shift_right);
}
dirty_tiles[tile_y] |= 1 << tile_x;
dirty_tiles[tile_y] |= 1 << (tile_x + 1);
dirty_tiles[tile_y + 1] |= 1 << tile_x;
dirty_tiles[tile_y + 1] |= 1 << (tile_x + 1);
}
}
IWRAM_CODE
void
flip_buffer(void) {
// Copy dirty tiles from the backbuffer to the frontbuffer.
Tile *dst = FRONTBUF;
Tile *src = BACKBUF;
for (size_t j = 0; j < 20; ++j) {
if (dirty_tiles[j] == 0) {
continue;
}
for (size_t i = 0, k = 1; i < 30; ++i, k <<= 1) {
if (dirty_tiles[j] & k) {
dst[i + j * 32] = src[i + j * 32];
}
}
dirty_tiles[j] = 0;
}
}
void
renderer_init(void) {
// Initialize display mode and bg palette.
DISP_CTRL = DISP_MODE_0 | DISP_BG_0 | DISP_BG_1 | DISP_OBJ;
// Initialize backgrounds.
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);
// 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(BACKBUF, 0, KB(20), 3);
dma_fill(FONT_DATA, 0, KB(8), 3);
dma_fill(FONT_TILEMAP, FONT_OFFSET, KB(2), 3);
// Initialize default palette.
PAL_BUFFER_BG[0] = COLOR_BLACK;
PAL_BUFFER_BG[1] = COLOR_WHITE;
PAL_BUFFER_BG[2] = COLOR_RED;
PAL_BUFFER_BG[3] = COLOR_BLUE;
PAL_BUFFER_BG[4] = COLOR_CYAN;
PAL_BUFFER_BG[5] = COLOR_GREY;
// Initialize background memory map for frontbuffer and font backgorund.
for (size_t i = 0; i < 32 * 20; ++i) {
FRONTBUF_TILEMAP[i] = i;
}
// Initialize text engine.
txt_init(FONT_DATA, FONT_TILEMAP, FONT_OFFSET);
}
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