fix brush projection to eliminate seams, still problems with big brushes and need to implement erase

engine/util.h

@@ -8,6 +8,10 @@ uint16_t constexpr const_hash(const char* input)
 }
 
 bool point_in_rect(const glm::vec2& point, const glm::vec4& rect);
+glm::vec4 rect_intersection(glm::vec4 a, glm::vec4 b);
+glm::vec4 rect_union(glm::vec4 a, glm::vec4 b);
+bool segments_intersect(const glm::vec2& p0a, const glm::vec2& p0b,
+    const glm::vec2& p1a, const glm::vec2& p1b, glm::vec2& out_pt);
 glm::vec4 rand_color();
 glm::vec3 convert_hsv2rgb(const glm::vec3 c);
 glm::vec3 convert_rgb2hsv(const glm::vec3 c);