From f6686f1e86927f038086023362251ebe78ce5ad6 Mon Sep 17 00:00:00 2001
From: Bad Diode <bd@badd10de.dev>
Date: Wed, 2 Jun 2021 17:26:08 +0200
Subject: Init repo with basic BG framebuffer renderer

---
 src/renderer.c | 86 ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 86 insertions(+)
 create mode 100644 src/renderer.c

(limited to 'src/renderer.c')

diff --git a/src/renderer.c b/src/renderer.c
new file mode 100644
index 0000000..9fe55b2
--- /dev/null
+++ b/src/renderer.c
@@ -0,0 +1,86 @@
+// 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)))
+
+// 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
+
+static u32 dirty_tiles[21] = {0};
+
+// TODO: Allow disable bound checking at compile time.
+#define BOUNDCHECK_SCREEN() if (x >= SCREEN_WIDTH || y >= SCREEN_HEIGHT) return;
+
+IWRAM_CODE
+void
+draw_pixel(u16 x, u16 y, u8 color) {
+    BOUNDCHECK_SCREEN();
+
+    // 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);
+    BACKBUFFER[pos] = (BACKBUFFER[pos] & ~(0xF << shift)) | color << shift;
+
+    // Mark tile as dirty.
+    dirty_tiles[tile_y] |= 1 << tile_x;
+}
+
+IWRAM_CODE
+void
+flip_buffer(void) {
+    // Copy dirty tiles from the backbuffer to the frontbuffer.
+    Tile *dst = FRONTBUFFER;
+    Tile *src = BACKBUFFER;
+    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_OBJ;
+
+    // Initialize backgrounds.
+    BG_CTRL(0) = BG_CHARBLOCK(0) | BG_SCREENBLOCK(FRONTBUFFER_SCREENBLOCK);
+
+    // 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);
+
+    // 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 (size_t i = 0; i < 32 * 20; ++i) {
+        FRONTBUFFER_TILEMAP[i] = i;
+    }
+
+//     // Load font data into VRAM.
+//     unpack_tiles(&bd_font, FONT_DATA, 256);
+}
-- 
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