add an overdraw buffer to allow for layered rendering

src/engine/engine.c

@@ -42,9 +42,15 @@ mark_dirty_rect(int x, int y, int w, int h)
         .h = h
     };
 
-    if (!game_state->framebuffer_dirty) {
+    if (!game_state->framebuffer_base_dirty) {
         game_state->dirty_rect = rect;
-        game_state->framebuffer_dirty = true;
+        game_state->framebuffer_base_dirty = true;
+        return;
+    }
+    
+    if (!game_state->framebuffer_overdraw_dirty) {
+        game_state->dirty_rect = rect;
+        game_state->framebuffer_overdraw_dirty = true;
         return;
     }
 
@@ -83,9 +89,24 @@ mark_dirty_rect(int x, int y, int w, int h)
 }
 
 bool
-upload_dirty_texture(void)
-{
-    if (!game_state->framebuffer_dirty) {
+upload_dirty_texture(
+    framebuffer_e framebuffer
+) {
+    uint32_t *current_framebuffer;
+    switch (framebuffer) {
+    case BASE:
+        current_framebuffer = game_state->framebuffer_base;
+        break;
+    case OVERDRAW:
+        current_framebuffer = game_state->framebuffer_overdraw;
+        break;
+    default:
+        break;
+    }
+
+    if (!game_state->framebuffer_base_dirty &&
+        !game_state->framebuffer_overdraw_dirty
+    ) {
         return true;
     }
 
@@ -117,7 +138,7 @@ upload_dirty_texture(void)
         (size_t)rect.w * sizeof(uint32_t);
 
     const uint8_t *source =
-        (const uint8_t *)game_state->framebuffer +
+        (const uint8_t *)current_framebuffer +
         (size_t)rect.y * source_pitch +
         (size_t)rect.x * sizeof(uint32_t);
 
@@ -134,7 +155,16 @@ upload_dirty_texture(void)
 
     SDL_UnlockTexture(texture);
 
-    game_state->framebuffer_dirty = false;
+    switch (framebuffer) {
+    case BASE:
+        game_state->framebuffer_base_dirty = false;
+        break;
+    case OVERDRAW:
+        game_state->framebuffer_overdraw_dirty = false;
+        break;
+    default:
+        break;
+    }
 
     return true;
 }
@@ -152,7 +182,8 @@ engine_start() {
 		internal_state->engine_update_framebuffer();
 
 		// update the texture with the modified framebuffer
-		upload_dirty_texture();
+		upload_dirty_texture(BASE);
+		upload_dirty_texture(OVERDRAW);
 
 		SDL_RenderClear(
 			internal_state->sdl_state->renderer
@@ -174,6 +205,7 @@ void
 engine_stop() {
 	engine_sdl_destroy(internal_state->sdl_state);
 	free(internal_state);
-	free(game_state->framebuffer);
+	free(game_state->framebuffer_base);
+	free(game_state->framebuffer_overdraw);
     free(game_state);
-}
+}

src/engine/engine_init.c

@@ -160,14 +160,23 @@ engine_init(
 		return RCODE_FAILURE;
 	}
 
-	game_state->framebuffer = (uint32_t *)
+	game_state->framebuffer_base = (uint32_t *)
 		malloc(sizeof(uint32_t) * window_width * window_height);
-	if (game_state->framebuffer == NULL) {
+	if (game_state->framebuffer_base == NULL) {
 		free(internal_state);
 		free(game_state);
 		return RCODE_FAILURE;
 	}
 
+	game_state->framebuffer_overdraw = (uint32_t *)
+		malloc(sizeof(uint32_t) * window_width * window_height);
+	if (game_state->framebuffer_overdraw == NULL) {
+		free(internal_state);
+        free(game_state->framebuffer_base);
+		free(game_state);
+		return RCODE_FAILURE;
+	}
+
 	internal_state->engine_poll_events
 		= engine_poll_events;
 
@@ -181,13 +190,15 @@ engine_init(
 	);
 	if (internal_state->sdl_state == NULL) {
 		free(internal_state);
-		free(game_state->framebuffer);
+		free(game_state->framebuffer_base);
+		free(game_state->framebuffer_overdraw);
 		free(game_state);
 		return RCODE_FAILURE;
 	}
 
 	game_state->is_running = true;
-	game_state->framebuffer_dirty = true;
+	game_state->framebuffer_base_dirty = true;
+	game_state->framebuffer_overdraw_dirty = true;
 	game_state->dirty_rect = (SDL_Rect) {
 	    .x = 0,
 	    .y = 0,
@@ -198,4 +209,4 @@ engine_init(
 	game_state->height = internal_state->sdl_state->height;
 
 	return RCODE_SUCCESS;
-}
+}

src/engine/render/anim.c

@@ -0,0 +1,22 @@
+#include <dangerzone/render/anim.h>
+
+void
+anim_rect_pos(
+    uint32_t x0,
+    uint32_t y0,
+    uint32_t x1,
+    uint32_t y1,
+    uint32_t w,
+    uint32_t h,
+    uint32_t color
+) {
+    // TODO: I THINK I NEED LAYERED BUFFERS
+
+    // one step is one pixel
+    uint32_t stepsx = x1 - x0;
+    uint32_t stepsy = y1 - y0;
+
+    /**
+     * 1. get the row / column in the direction of the movement
+     */
+}

src/engine/render/misc.c

@@ -2,16 +2,36 @@
 #include <dangerzone/render/misc.h>
 #include <dangerzone/render/rect.h>
 
+#include "internal/engine_internal.h"
 #include "internal/util/error.h"
+
 #include <stdint.h>
 
+// helper function to return the correct pointer to a framebuffer for drawing selection
+uint32_t*
+get_framebuffer(
+    framebuffer_e framebuffer
+) {
+    switch (framebuffer) {
+    case BASE:
+        return game_state->framebuffer_base;
+    case OVERDRAW:
+        return game_state->framebuffer_overdraw;
+    default:
+        return game_state->framebuffer_base;
+    }
+}
+
 // alter a pixel at an imaginary x & y coordinates
 void 
 put_pixel(
+    framebuffer_e framebuffer,
 	unsigned int x, 
 	unsigned int y, 
 	uint32_t color
 ) {
+    uint32_t *current_framebuffer = get_framebuffer(framebuffer);
+
 	uint16_t w = game_state->width;
 	uint16_t h = game_state->height;
 
@@ -21,7 +41,7 @@ put_pixel(
 			"at x = %d, y = %d", x, y
 		);
 	} else {
-		game_state->framebuffer[game_state->width * y + x]
+		current_framebuffer[game_state->width * y + x]
 			= color;
 
 	    mark_dirty_rect(x, y, 1, 1);
@@ -31,12 +51,15 @@ put_pixel(
 // fill the entire framebuffer with a given color
 void
 clear_framebuffer(
+    framebuffer_e framebuffer,
 	uint32_t color
 ) {
+    uint32_t *current_framebuffer = get_framebuffer(framebuffer);
+    
     for (size_t i = 0;
          i < (size_t)game_state->width * game_state->height;
          ++i) {
-        game_state->framebuffer[i] = color;
+        current_framebuffer[i] = color;
     }
 
     mark_dirty_rect(
@@ -45,4 +68,4 @@ clear_framebuffer(
         game_state->width,
         game_state->height
     );
-}
+}

src/engine/render/rect.c

@@ -10,20 +10,22 @@
  */ 
 void
 put_rect(
+    framebuffer_e framebuffer,
 	uint32_t x, 
 	uint32_t y, 
 	uint32_t w, 
 	uint32_t h,
 	uint32_t color
-) {
+) { 
 	for (int i = x; i < x + w; i++) {
 		for (int j = y; j < y + h; j++) {
-			put_pixel(i, j, color);
+			put_pixel(framebuffer, i, j, color);
 		}
 	}
 	mark_dirty_rect(x, y, w, h);
 }
 
+// TODO: remove, see rect.h
 void
 clear_rect(int x, int y, int w, int h, uint32_t color)
 {
@@ -33,7 +35,7 @@ clear_rect(int x, int y, int w, int h, uint32_t color)
                 px < game_state->width &&
                 py >= 0 &&
                 py < game_state->height) {
-                game_state->framebuffer[
+                game_state->framebuffer_base[
                     py * game_state->width + px
                 ] = color;
             }

src/engine/render/text.c

@@ -81,6 +81,7 @@ static const uint8_t font[128][FONT_ROWS] = {
  */
 void
 put_char(
+    framebuffer_e framebuffer,
     char c,
     uint32_t x,
     uint32_t y,
@@ -107,6 +108,7 @@ put_char(
                     ? fg_color : bg_color;
 
             put_rect(
+                framebuffer,
                 x + col * size,
                 y + row * size,
                 size,
@@ -121,6 +123,7 @@ put_char(
 
 void
 put_string(
+    framebuffer_e framebuffer,
     const char *text,
     uint32_t x,
     uint32_t y,
@@ -137,7 +140,7 @@ put_string(
             x = start_x;
             y += (FONT_ROWS + line_spacing) * size;
         } else {
-            put_char(*text, x, y, size, fg_color, bg_color);
+            put_char(framebuffer, *text, x, y, size, fg_color, bg_color);
             x += (FONT_COLS + spacing) * size;
         }