use static, fixed arrays for circle geometry data instead of allocating for each one

apps/demos/scenery/scenes/title.c

@@ -20,9 +20,9 @@ static void title_tick(State *state) {
             ((float)ctx.resolution.x / 2) - ((float)320 / 2), 64, 320, 128 }));
 
     /* draw the tick count as an example of dynamic text */
-    size_t text_str_len = snprintf(NULL, 0, "%lu", state->ctx->frame_number) + 1;
+    size_t text_str_len = snprintf(NULL, 0, "%llu", state->ctx->frame_number) + 1;
     char *text_str = cmalloc(text_str_len);
-    snprintf(text_str, text_str_len, "%lu", state->ctx->frame_number);
+    snprintf(text_str, text_str_len, "%llu", state->ctx->frame_number);
 
     const char *font = "/fonts/kenney-pixel.ttf";
     int text_h = 32;
@@ -39,7 +39,6 @@ static void title_tick(State *state) {
     );
 
     draw_text(text_str, (Vec2){ 0, 0 }, text_h, (Color) { 255, 255, 255, 255 }, font);
-
     free(text_str);
 }
 

include/twn_draw.h

@@ -22,6 +22,7 @@ TWN_API void draw_sprite(char const *path,
 TWN_API void draw_rectangle(Rect rect, Color color);
 
 /* pushes a filled circle onto the circle render queue */
+/* note that its edges may look jagged with a radius larger than 2048 */
 TWN_API void draw_circle(Vec2 position, float radius, Color color);
 
 /* TODO: have font optional, with something minimal coming embedded */

src/rendering/twn_circles.c

@@ -22,18 +22,14 @@ void draw_circle(Vec2 position, float radius, Color color) {
     arrput(ctx.render_queue_2d, primitive);
 }
 
-/* TODO: caching and reuse scheme */
-/* vertices_out and indices_out MUST BE FREED */
+
 void create_circle_geometry(Vec2 position,
                             Color color,
                             float radius,
                             size_t num_vertices,
-                            SDL_Vertex **vertices_out,
-                            int **indices_out)
+                            SDL_Vertex vertices[],
+                            int indices[])
 {
-    SDL_Vertex *vertices = cmalloc(sizeof *vertices * (num_vertices + 1));
-    int *indices = cmalloc(sizeof *indices * (num_vertices * 3));
-
     /* the angle (in radians) to rotate by on each iteration */
     float seg_rotation_angle = (360.0f / (float)num_vertices) * ((float)M_PI / 180);
 
@@ -82,7 +78,4 @@ void create_circle_geometry(Vec2 position,
             index = num_vertices;
         indices[triangle_offset + 2] = (int)index;
     }
-
-    *vertices_out = vertices;
-    *indices_out = indices;
 }

src/rendering/twn_draw_c.h

@@ -126,12 +126,14 @@ void render(void);
 /* clears all render queues */
 void render_queue_clear(void);
 
+/* fills two existing arrays with the geometry data of a circle */
+/* the size of indices must be at least 3 times the number of vertices */
 void create_circle_geometry(Vec2 position,
                             Color color,
                             float radius,
                             size_t num_vertices,
-                            SDL_Vertex **vertices_out,
-                            int **indices_out);
+                            SDL_Vertex vertices[],
+                            int indices[]);
 
 struct SpriteBatch {
     size_t size;             /* how many primitives are in current batch */

src/rendering/twn_gl_15_rendering.c

@@ -58,6 +58,9 @@ typedef enum {
 static Pipeline pipeline_last_used = PIPELINE_NO;
 
 
+#define CIRCLE_VERTICES_MAX 2048
+
+
 void use_space_pipeline(void) {
     if (pipeline_last_used == PIPELINE_SPACE)
         return;
@@ -164,16 +167,16 @@ void render_rectangle(const RectPrimitive *rectangle) {
 
 
 void render_circle(const CirclePrimitive *circle) {
-    SDL_Vertex *vertices = NULL;
-    int *indices = NULL;
-    int num_vertices = (int)circle->radius;
+    static SDL_Vertex vertices[CIRCLE_VERTICES_MAX];
+    static int indices[CIRCLE_VERTICES_MAX * 3];
+    int num_vertices = MIN((int)circle->radius, CIRCLE_VERTICES_MAX-1);
 
     create_circle_geometry(circle->position,
                            circle->color,
                            circle->radius,
                            num_vertices,
-                           &vertices,
-                           &indices);
+                           vertices,
+                           indices);
 
     glEnableClientState(GL_VERTEX_ARRAY);
     glVertexPointer(2,
@@ -194,9 +197,6 @@ void render_circle(const CirclePrimitive *circle) {
 
     glDisableClientState(GL_COLOR_ARRAY);
     glDisableClientState(GL_VERTEX_ARRAY);
-
-    SDL_free(vertices);
-    SDL_free(indices);
 }