Pebble bitmap cache

bitmap-cache.c

static BitmapLayer *s_graph_layer;
static GBitmap *s_cache_bitmap;

static void init_bitmap(Window *window) {
  Layer *window_layer = window_get_root_layer(window);
  GRect bounds = layer_get_bounds(window_layer);
  s_graph_layer = bitmap_layer_create(bounds);
  s_cache_bitmap = gbitmap_create_blank(bounds.size, GBitmapFormat8Bit);
}

static void graphics_copy_frame_buffer_to_bitmap(GContext *ctx, GBitmap *bitmap) {
    GBitmap *buffer = graphics_capture_frame_buffer(ctx);
    
    GBitmapDataRowInfo source, dest;
    GRect bounds = gbitmap_get_bounds(buffer);
    for (int i = 0; i < bounds.size.h; i++) {
        source = gbitmap_get_data_row_info(buffer, i);
        dest = gbitmap_get_data_row_info(bitmap, i);
        memcpy(dest.data, source.data, source.max_x + 1);
    }

    graphics_release_frame_buffer(ctx, buffer);
}

static void layer_update(Layer *layer, GContext* ctx) {
  // Use cache if available and relevant
  graphics_draw_bitmap_in_rect(ctx, s_cache_bitmap, layer_get_bounds(layer));
}