Drawing Vector Graphics Faster

Question

In my application I want to draw polygons using Windows Create Graphics method and later edit the polygon by allowing the user to select the points of the polygon and allowing to re-position them.

I use moue move event to get the new position of the point to get the new coordinates of the point being moved and use Paint event to re-draw the polygon. The application is working but when a point is moved the movement is not smooth.

I dont know weather the mouse move or the paint event the performance hindrance.

Can anyone make a suggestion as to how to improve this?

Answer 1

You might not have a real performance problem - it could be that you just need to draw to an off screen DC and then copy that to your window, which will reduce flicker and make the movement seem much smoother.

If you're coding using the Win32 api, look at this for reference.

Answer 2

Make sure that you don't repaint for every mouse move. The proper way to do this is to handle all your input events, modifying the polygon data and setting a flag that a repaint needs to occur (on windows possibly just calling InvalidateRect() without calling UpdateWindow()).

Answer 3

...and of course, make sure you only invalidate the area that needs to be repainted. Since you're keeping track of the polygons, invalidate only the polygon area (the rectangular union of the before and after states).