partially done work on total source tree rework, separation of engine context and game context, generalization of renderer for different backends as well as web platform target

src/rendering/twn_circles.c

@@ -0,0 +1,87 @@
+#include "townengine/util.h"
+#include "townengine/context.h"
+#include "twn_rendering_c.h"
+
+#include <SDL2/SDL.h>
+#include <stb_ds.h>
+
+
+void push_circle(t_fvec2 position, float radius, t_color color) {
+    struct circle_primitive circle = {
+        .radius = radius,
+        .color = color,
+        .position = position,
+    };
+
+    struct primitive_2d primitive = {
+        .type = PRIMITIVE_2D_CIRCLE,
+        .circle = circle,
+    };
+
+    arrput(ctx.render_queue_2d, primitive);
+}
+
+/* TODO: caching and reuse scheme */
+/* vertices_out and indices_out MUST BE FREED */
+void create_circle_geometry(t_fvec2 position,
+                                   t_color color,
+                                   float radius,
+                                   size_t num_vertices,
+                                   SDL_Vertex **vertices_out,
+                                   int **indices_out)
+{
+    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);
+
+    vertices[0].position.x = (float)position.x;
+    vertices[0].position.y = (float)position.y;
+    vertices[0].color.r = color.r;
+    vertices[0].color.g = color.g;
+    vertices[0].color.b = color.b;
+    vertices[0].color.a = color.a;
+    vertices[0].tex_coord = (SDL_FPoint){ 0, 0 };
+
+    /* this point will rotate around the center */
+    float start_x = 0.0f - radius;
+    float start_y = 0.0f;
+
+    for (size_t i = 1; i < num_vertices + 1; ++i) {
+        float final_seg_rotation_angle = (float)i * seg_rotation_angle;
+
+        vertices[i].position.x =
+            cosf(final_seg_rotation_angle) * start_x -
+            sinf(final_seg_rotation_angle) * start_y;
+        vertices[i].position.y =
+            cosf(final_seg_rotation_angle) * start_y +
+            sinf(final_seg_rotation_angle) * start_x;
+
+        vertices[i].position.x += position.x;
+        vertices[i].position.y += position.y;
+
+        vertices[i].color.r = color.r;
+        vertices[i].color.g = color.g;
+        vertices[i].color.b = color.b;
+        vertices[i].color.a = color.a;
+
+        vertices[i].tex_coord = (SDL_FPoint){ 0, 0 };
+
+
+        size_t triangle_offset = 3 * (i - 1);
+
+        /* center point index */
+        indices[triangle_offset] = 0;
+        /* generated point index */
+        indices[triangle_offset + 1] = (int)i;
+
+        size_t index = (i + 1) % num_vertices;
+        if (index == 0)
+            index = num_vertices;
+        indices[triangle_offset + 2] = (int)index;
+    }
+
+    *vertices_out = vertices;
+    *indices_out = indices;
+}