wxPython — drawing a line, relatively slowly

Question

I want to draw a line, but not instantaneously as it usually appears with DrawLine(). I want it to be fast, but just slow enough that you can tell it's being drawn.

I've tried testing a for loop that draws a line a pixel at a time with a sleep of .05 seconds, but it doesn't seem to draw any of it until the for loop ends at which point it draws it all, instantly. I figured this had to do with it not getting drawing actions through the mainloop, so I used CallAfter on the drawline, that didn't work, either.

It seems like there should be a way to simply tell drawline to draw it over the course of x seconds or send it through an animation object in which you can specify # of frames, etc. Not really sure where to look. Any suggestions?

Answer 1

The issue is that time.sleep(...) will also block GUI as the for loop itself. wx.Yield should normally signal "GUI, I have halted the time-consuming process, do whatever you nned to do NOW". But by experience, this basically never works (I have not found out yet why).

So instead of using sleep you could use wx.CallLater ( Link to wxPython Phoenix docs ) which is like wx.CallAfter , but a delay can be specified. By calling it at the end of the inner for loop drawing the line part draw events should not pile up.

Answer 2

You will probably want to draw a series of lines. That would likely be the easiest. I would probably use a wx.Timer. It runs in it's own main loop. You can set up the timer to fire every so often, say every 0.5 second. When it fires, it can call your draw method, which will draw the next line. You can read more about timers here:

• http://wiki.wxpython.org/Timer
• http://www.blog.pythonlibrary.org/2009/08/25/wxpython-using-wx-timers/
• http://www.wxpython.org/docs/api/wx.Timer-class.html