Proof of concept of UXN on the GBA

1 files changed, 232 insertions, 0 deletions

diff --git a/src/text.h b/src/text.h
new file mode 100644
index 0000000..bfac4e4
--- /dev/null
+++ b/src/text.h
@@ -0,0 +1,232 @@
+#ifndef GBAEXP_TILES_H
+#define GBAEXP_TILES_H
+
+#include <stdarg.h>
+#include <stdio.h>
+
+#include "common.h"
+#include "bitmap.h"
+
+typedef enum {
+    TXT_MODE_TILED_BG,
+    TXT_MODE_MODE3,
+} TextMode;
+
+typedef struct Font {
+    // A pointer to an area of memory containing font data.
+    // TODO: Should we unpack each char everytime or unpack everything into RAM?
+    // Maybe this should be optional?
+    u16 *data;
+    // The char_map stores the index to the character position within the font
+    // array depending on the ascii number we want to render. This allows
+    // the usage reduced font sets, for example just uppercase letters and
+    // numbers.
+    u8 *char_map;
+    // Width and height of each font character. Only monospaced fonts are
+    // currently supported.
+    u8 char_width;
+    u8 char_height;
+    // The color of this font.
+    Color color;
+} Font;
+
+typedef struct TextEngine {
+    // Currently working on tiled backgrounds only. The X and Y positions
+    // correspond to the tile X and Y starting from the top left of the screen.
+    // For a 240x160 screen, we have 30x20 tiles available.
+    size_t cursor_x;
+    size_t cursor_y;
+    // Pointer to the memory being used for writing to the screen.
+    u16 *memory;
+    // TODO: Support other modes and monospaced fonts should be simple but we
+    // need to keep track of a couple of other variables, which may not be
+    // available for all modes. For example, tile modes can't have a font width
+    // smaller than the tile size, although bigger fonts (For example fonts
+    // composed of multiple tiles) should still be possible. This may not be
+    // a good time investment, but can be done in the future if needed.
+    // The mode controls how the text is rendered and how the memory is managed.
+    TextMode mode;
+    // The font used to render the text.
+    Font font;
+} TextEngine;
+
+static TextEngine text_engine = {0};
+
+static u8 default_char_map[256] = {0};
+
+void
+txt_putc_tile(char c) {
+    if (c == '\0') {
+        return;
+    }
+    if (c == '\n') {
+        text_engine.cursor_x = 0;
+        text_engine.cursor_y++;
+    } else {
+        text_engine.memory[text_engine.cursor_x + 32 * text_engine.cursor_y] = c;
+        text_engine.cursor_x++;
+        if (text_engine.cursor_x >= 30) {
+            text_engine.cursor_x = 0;
+            text_engine.cursor_y++;
+        }
+    }
+    if (text_engine.cursor_y >= 20) {
+        text_engine.cursor_y = 0;
+    }
+}
+
+void
+txt_putc_m3(char c) {
+    if (c == '\0') {
+        return;
+    }
+    if (c == '\n') {
+        text_engine.cursor_x = 0;
+        text_engine.cursor_y += text_engine.font.char_height;
+    } else {
+        u8 idx = text_engine.font.char_map[(int)c] * 2;
+        u32 *packed_char = text_engine.font.data;
+        packed_char += idx;
+        Tile tile = {0};
+        unpack_tiles(packed_char, &tile, 1);
+        int x = text_engine.cursor_x;
+        int y = text_engine.cursor_y;
+        for (size_t i = 0; i < text_engine.font.char_height; ++i) {
+            for (size_t j = 0; j < text_engine.font.char_width; ++j) {
+                if ((tile.row[i] >> 4 * j) & 0x1) {
+                    // put_pixel_m4(x + j, y + i, 1, backbuffer);
+                    // TODO: Clean this up please.
+                    put_pixel_m3(x + j,
+                            y + i,
+                            text_engine.font.color,
+                            FRAMEBUFFER);
+                }
+            }
+        }
+        text_engine.cursor_x += text_engine.font.char_width;
+        if (text_engine.cursor_x >= SCREEN_WIDTH) {
+            text_engine.cursor_x = 0;
+            text_engine.cursor_y += text_engine.font.char_height;
+        }
+    }
+    if (text_engine.cursor_y >= SCREEN_HEIGHT) {
+        text_engine.cursor_y = 0;
+    }
+}
+
+void
+txt_putc(char c) {
+    switch (text_engine.mode) {
+        case TXT_MODE_TILED_BG: {
+            txt_putc_tile(c);
+        } break;
+        case TXT_MODE_MODE3: {
+            txt_putc_m3(c);
+        } break;
+    }
+}
+
+static inline void
+txt_puts(char *msg) {
+    while (*msg) {
+        txt_putc(*msg++);
+    }
+}
+
+void
+txt_init_tile(size_t bg, Font font, size_t cb_idx) {
+    // The screenblock for the tile map should start after the tile memory
+    // (MEM_VRAM + 0x2000 for 256 characters). Since each screenblock is
+    // composed of 1024 screenblock entries of u16 (2 bytes), we need an
+    // screenblock index offset of 8192 / (1024 * 2) = 4 screen blocks.
+    size_t sb_idx = cb_idx * 8 + 4;
+
+    // Set the background parameters for the text layer.
+    BG_CTRL(bg) = BG_CHARBLOCK(cb_idx) | BG_SCREENBLOCK(sb_idx) | BG_PRIORITY(3);
+
+    // Load font data in video memory. Each character is unpacked into a tile of
+    // 8 32bit values (4bpp), meaning that for the full ASCII set of 256
+    // characters, we need 8192 bytes of VRAM (8 * 4 * 256).
+    text_engine.font = font;
+    unpack_tiles(font.data, &TILE_MEM[cb_idx], 256);
+
+    // Initialize default values.
+    if (font.color == 0) {
+        font.color = COLOR_WHITE;
+    }
+
+    // Load palette color.
+    PAL_BUFFER_BG[1] = font.color;
+
+    // Update text_engine variables.
+    text_engine.memory = SCREENBLOCK_MEM[sb_idx];
+}
+
+void
+txt_init_bitmap(TextMode mode, Font font) {
+    // NOTE: Only mode 3 is currently supported
+    assert(mode == TXT_MODE_MODE3);
+
+    // If font_map is NULL, initialize the standard 0-255 character map.
+    if (font.char_map == NULL) {
+        for (size_t i = 0; i < 256; ++i) {
+            default_char_map[i] = i;
+        }
+        font.char_map = &default_char_map;
+    }
+
+    // Initialize default values if set to zero.
+    if (font.char_width == 0) {
+        font.char_width = 8;
+    }
+    if (font.char_height == 0) {
+        font.char_height = 8;
+    }
+    if (font.color == 0) {
+        font.color = COLOR_WHITE;
+    }
+
+    // Prepare text engine.
+    text_engine.font = font;
+    text_engine.mode = mode;
+}
+
+// Print text to the screen with formatting.
+void
+txt_printf(char *msg, ...) {
+    va_list arg_list;
+    va_start(arg_list, msg);
+    char buf[512] = {0};
+    vsprintf(buf, msg, arg_list);
+    txt_puts(buf);
+}
+
+// TODO: Update for working on bitmap modes.
+void
+txt_clear_line(void) {
+    for (size_t i = 0; i < 30; ++i) {
+        text_engine.memory[i + 32 * text_engine.cursor_y] = ' ';
+    }
+    text_engine.cursor_x = 0;
+}
+
+// TODO: Update for working on bitmap modes.
+void
+txt_clear_screen(void) {
+    for (size_t j = 0; j < 20; ++j) {
+        for (size_t i = 0; i < 30; ++i) {
+            text_engine.memory[i + 32 * j] = ' ';
+        }
+    }
+    text_engine.cursor_x = 0;
+    text_engine.cursor_y = 0;
+}
+
+void
+txt_position(size_t tile_x, size_t tile_y) {
+    text_engine.cursor_x = tile_x;
+    text_engine.cursor_y = tile_y;
+}
+
+#endif // GBAEXP_TILES_H
+