[wxPython-users] Painting How-To [Screwed up last mail list]

[Christopher Barker]

first, a couple style comments:

- it really is better to use spaces than tabs to indent -- it's more or =

less the python standard.

- ID_TOOL_BRUSH=3Dwx.NewId()
   ID_TOOL_LINE=3Dwx.NewId()
   Explicit IDs are kind of ugly, see:
   http://wiki.wxpython.org/wxPython_Style_Guide

Instead of ID_TOOL_whatever, you could have a tool object, or a string, =

or better yet, put your drawing code, etc into a tool object, then you =

wouldn't even need to know what kind of tool object it was.

But now to the real issues:

Your Paint handler should call the same Draw method -- rather than =

duplicating the code there.

One good method for doing this kind of thing is to not actually re-draw =

the whole buffer each time. what you can do instead is draw a "shadow" =

of your object as the mouse moves -- you do this with a ClientDC and set =

the DC mode to XOR -- draw once, you get a reverse color version, draw =

again and it's back to the original bitmap underneath.

However, what you've doing should work OK -- drawing bitmaps to the =

screen is very fast. a few issue though:

         dc=3Dwx.BufferedDC(wx.ClientDC(self), self.buffer)
         dc.DrawBitmap(self.buffer, 0, 0)

you don't want to draw the buffer to a buffered DC, it will draw itself. =

  You want a regular ClientDC. And you want to just draw there, rather =

than in a Paint Handler (you could do it there, but you're kind of doing =

both now)

Then, on mouse-up, you need to draw the final line to the buffer -- note =

that this is why you want your drawing code to be in a Line object -- =

then you can put it in only one place.

By the way, I'd like to discourage you from making a bitmap editor like =

this -- why not make it a vector object editor -- you always save the =

resulting bitmap out later, but if you keep vector objects, then you can =

change them, move them, re-scale, etc, etc.

You might want to look at wx.lib.floatcanvas for some ideas. Or the =

latest version and extra demos here:

http://morticia.cs.dal.ca/FloatCanvas/

Enclosed is my  edited version, which seems to work. It could still use =

some cleaning up.







-- =

Christopher Barker, Ph.D.
Oceanographer

Emergency Response Division
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Chris.Barker at noaa.gov
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