move the ui/shaders reload into the ui thread, add rtt region copy, add box/rect conversion

src/util.cpp

@@ -22,6 +22,18 @@ bool point_in_rect(const glm::vec2& p, const glm::vec4& r)
     return p.x > r.x && p.x < r.x+r.z && p.y > r.y && p.y < r.y+r.w;
 }
 
+// from {origin, size} to {min, max}
+glm::vec4 rect_to_box(const glm::vec4& r)
+{
+    return { xy(r), xy(r) + zw(r) };
+}
+
+// from {min, max} to {origin, size}
+glm::vec4 box_to_rect(const glm::vec4& b)
+{
+    return { xy(b), zw(b) - xy(b) };
+}
+
 // params and returns {origin, size} form
 glm::vec4 rect_intersection(glm::vec4 a, glm::vec4 b)
 {