fix canvas on hdpi

src/rtt.h

@@ -21,7 +21,7 @@ public:
     void destroy();
     void copy(const RTT& source);
     void resize(int width, int height);
-    bool create(int width, int height, int tex = -1, GLint internal_format = GL_RGBA8);
+    bool create(int width, int height, int tex = -1, GLint internal_format = GL_RGBA8, bool depth_buffer = false);
     bool recreate() { return create(w, h); }
     void clear(glm::vec4 color = glm::vec4(0));
     glm::ivec4 calc_bounds();