Add bitmap collision detection unit tests

coresdk/src/test/unit_tests/unit_test_bitmap.cpp

@@ -134,3 +134,141 @@ TEST_CASE("bitmap bounding details can be retrieved", "[bitmap]")
     }
     free_bitmap(bmp);
 }
+
+TEST_CASE("bitmaps can detect point collisions", "[bitmap][collision]")
+{
+    // Create a 2x2 bitmap for testing
+    // P1 P2
+    // P3 P4
+    // Where P1 is Opaque, P2 is Transparent (alpha < 0x7F), P3 is Opaque, P4 is Transparent
+    bitmap test_bmp = create_bitmap("collision_test", 2, 2);
+    clear_bitmap(test_bmp, COLOR_TRANSPARENT);
+
+    // Set pixels
+    draw_pixel_on_bitmap(test_bmp, COLOR_RED, 0, 0); // P1 Opaque
+    draw_pixel_on_bitmap(test_bmp, rgba_color(255, 0, 0, 100), 1, 0); // P2 Transparent
+    draw_pixel_on_bitmap(test_bmp, COLOR_RED, 0, 1); // P3 Opaque
+    draw_pixel_on_bitmap(test_bmp, rgba_color(255, 0, 0, 50), 1, 1); // P4 Transparent
+
+    setup_collision_mask(test_bmp);
+
+    SECTION("point collision with bitmap at origin")
+    {
+        // P1
+        REQUIRE(bitmap_point_collision(test_bmp, 0, 0, 0.5, 0.5));
+        // P2
+        REQUIRE_FALSE(bitmap_point_collision(test_bmp, 0, 0, 1.5, 0.5));
+        // P3
+        REQUIRE(bitmap_point_collision(test_bmp, 0, 0, 0.5, 1.5));
+        // P4
+        REQUIRE_FALSE(bitmap_point_collision(test_bmp, 0, 0, 1.5, 1.5));
+    }
+
+    SECTION("point collision with bitmap at offset")
+    {
+        double offset_x = 100.0;
+        double offset_y = 50.0;
+        // P1
+        REQUIRE(bitmap_point_collision(test_bmp, offset_x, offset_y, offset_x + 0.5, offset_y + 0.5));
+        // P2
+        REQUIRE_FALSE(bitmap_point_collision(test_bmp, offset_x, offset_y, offset_x + 1.5, offset_y + 0.5));
+        // Outside bitmap
+        REQUIRE_FALSE(bitmap_point_collision(test_bmp, offset_x, offset_y, offset_x - 1, offset_y));
+        REQUIRE_FALSE(bitmap_point_collision(test_bmp, offset_x, offset_y, offset_x + 3, offset_y + 1));
+    }
+
+    free_bitmap(test_bmp);
+}
+
+TEST_CASE("bitmaps can detect rectangle and circle collisions", "[bitmap][collision]")
+{
+    // Create a 4x4 bitmap for testing with an opaque 2x2 square at the center
+    bitmap test_bmp = create_bitmap("rect_collision_test", 4, 4);
+    clear_bitmap(test_bmp, COLOR_TRANSPARENT);
+
+    // Draw opaque 2x2 square from (1,1) to (2,2)
+    draw_pixel_on_bitmap(test_bmp, COLOR_RED, 1, 1);
+    draw_pixel_on_bitmap(test_bmp, COLOR_RED, 2, 1);
+    draw_pixel_on_bitmap(test_bmp, COLOR_RED, 1, 2);
+    draw_pixel_on_bitmap(test_bmp, COLOR_RED, 2, 2);
+
+    setup_collision_mask(test_bmp);
+
+    SECTION("rectangle collisions")
+    {
+        // Transparent region overlap only
+        REQUIRE_FALSE(bitmap_rectangle_collision(test_bmp, 0, 0, rectangle_from(0, 0, 1, 1)));
+        // Opaque region overlap
+        REQUIRE(bitmap_rectangle_collision(test_bmp, 0, 0, rectangle_from(0.5, 0.5, 1, 1)));
+        // Entirely outside
+        REQUIRE_FALSE(bitmap_rectangle_collision(test_bmp, 0, 0, rectangle_from(5, 5, 2, 2)));
+        // Rectangle contains the whole bitmap
+        REQUIRE(bitmap_rectangle_collision(test_bmp, 0, 0, rectangle_from(-1, -1, 6, 6)));
+    }
+
+    SECTION("circle collisions")
+    {
+        // Transparent region overlap only
+        REQUIRE_FALSE(bitmap_circle_collision(test_bmp, 0, 0, circle_at(0.5, 0.5, 0.4)));
+        // Opaque region overlap
+        REQUIRE(bitmap_circle_collision(test_bmp, 0, 0, circle_at(1.5, 1.5, 0.1)));
+        // Touching the edge of opaque pixel
+        REQUIRE(bitmap_circle_collision(test_bmp, 0, 0, circle_at(0.5, 1.5, 0.6)));
+        // Entirely outside
+        REQUIRE_FALSE(bitmap_circle_collision(test_bmp, 0, 0, circle_at(10, 10, 1)));
+    }
+
+    free_bitmap(test_bmp);
+}
+
+TEST_CASE("bitmaps can detect bitmap-to-bitmap collisions", "[bitmap][collision]")
+{
+    // Create two 2x2 bitmaps
+    // B1: 2x2 opaque
+    bitmap bmp1 = create_bitmap("bmp1", 2, 2);
+    clear_bitmap(bmp1, COLOR_RED);
+    setup_collision_mask(bmp1);
+
+    // B2: 2x2 with only one opaque pixel at (0,0)
+    bitmap bmp2 = create_bitmap("bmp2", 2, 2);
+    clear_bitmap(bmp2, COLOR_TRANSPARENT);
+    draw_pixel_on_bitmap(bmp2, COLOR_RED, 0, 0);
+    setup_collision_mask(bmp2);
+
+    SECTION("collision when pixels overlap")
+    {
+        // Overlap (0,0) of bmp2 with (1,1) of bmp1
+        REQUIRE(bitmap_collision(bmp1, 0, 0, bmp2, 1, 1));
+    }
+
+    SECTION("no collision when bounding boxes overlap but pixels don't")
+    {
+        // B3: 2x2 with only one opaque pixel at (1,1)
+        bitmap bmp3 = create_bitmap("bmp3", 2, 2);
+        clear_bitmap(bmp3, COLOR_TRANSPARENT);
+        draw_pixel_on_bitmap(bmp3, COLOR_RED, 1, 1);
+        setup_collision_mask(bmp3);
+
+        // Position bmp2 and bmp3 such that their bounding boxes overlap at (1,1) relative to world
+        // bmp2 at (1,1) -> its opaque pixel (0,0) is at world (1,1)
+        // bmp3 at (0,0) -> its opaque pixel (1,1) is at world (1,1)
+        // They should collide.
+        REQUIRE(bitmap_collision(bmp2, 1, 1, bmp3, 0, 0));
+
+        // Position bmp2 and bmp3 such that they overlap but transparent pixels meet
+        // bmp2 at (0,0) -> opaque (0,0), transparent (1,1)
+        // bmp3 at (0,0) -> transparent (0,0), opaque (1,1)
+        // Bounding boxes are identical but pixels (0,0) and (1,1) don't overlap.
+        REQUIRE_FALSE(bitmap_collision(bmp2, 0, 0, bmp3, 0, 0));
+
+        free_bitmap(bmp3);
+    }
+
+    SECTION("no collision when entirely separate")
+    {
+        REQUIRE_FALSE(bitmap_collision(bmp1, 0, 0, bmp2, 10, 10));
+    }
+
+    free_bitmap(bmp1);
+    free_bitmap(bmp2);
+}