added a demo of drawing while mouse moves, without ClientDC.

Author: ChrisBarker-NOAA

DrawingWhileMouseMoves.py

@@ -0,0 +1,143 @@
+#!/usr/bin/env python
+
+"""
+A test of drawing while the mouse is moving.
+
+The old way of doing this is with a wxClientDC, but that does
+not work right, or at least not well on OS-X. So this shows how
+to do it with Refresh();Update().
+"""
+
+import wx
+
+print "running with version:", wx.__version__
+import random
+
+
+class DrawWindow(wx.Panel):
+    def __init__(self, parent, id = -1):
+        ## Any data the Draw() function needs must be initialized before
+        ## calling BufferedWindow.__init__, as it will call the Draw
+        ## function.
+        wx.Panel.__init__(self, parent, id)
+        
+        self.Bind(wx.EVT_LEFT_DOWN, self.OnLeftDown)
+        self.Bind(wx.EVT_LEFT_UP, self.OnLeftUp)
+        self.Bind(wx.EVT_MOTION, self.OnMove)
+
+        wx.EVT_PAINT(self, self.OnPaint)
+        wx.EVT_SIZE(self, self.OnSize)
+
+        # OnSize called to make sure the buffer is initialized.
+        # This might result in OnSize getting called twice on some
+        # platforms at initialization, but little harm done.
+
+        self.mouse_line = None
+        self.OnSize(None)
+
+    def OnPaint(self, event):
+        # This draws the buffer to the screen, then optionally the mouse_line
+        dc = wx.PaintDC(self)
+        dc.DrawBitmap(self._Buffer,0,0)
+        if self.mouse_line is not None:
+            dc.SetPen(wx.Pen('WHITE', 2, wx.SHORT_DASH))
+            dc.DrawLinePoint( *self.mouse_line )
+
+
+    def OnSize(self,event):
+        # The Buffer init is done here, to make sure the buffer is always
+        # the same size as the Window
+        Size  = self.GetClientSizeTuple()
+
+        # Make sure we don't try to create a 0 size bitmap
+        Size = (max(Size[0], 1), max(Size[1], 1))
+        self._Buffer = wx.EmptyBitmap(Size[0],Size[1])
+        self.Draw()
+
+    def Draw(self):
+        """
+        This draws the backgound image on the buffer
+
+        """
+        # update the buffer
+        dc = wx.MemoryDC()
+        dc.SelectObject(self._Buffer)
+
+        coords = ((40,40),(200,220),(210,120),(120,300))
+        dc.BeginDrawing()
+        dc.SetBackground( wx.Brush("Blue") )
+        dc.Clear() # make sure you clear the bitmap!
+
+        dc.SetPen(wx.RED_PEN)
+        dc.SetBrush(wx.CYAN_BRUSH)
+
+        dc.DrawPolygon(coords)
+
+
+    def OnLeftDown(self, event):
+        self.CaptureMouse()
+        self.mouse_line = [ event.GetPosition(), None]
+
+    def OnLeftUp(self, event):
+        self.mouse_line = None
+        if self.HasCapture():
+            self.ReleaseMouse()
+        self.Refresh()
+        self.Update()
+
+    def OnMove(self, event):
+        if event.Dragging() and event.LeftIsDown() and (self.mouse_line is not None):
+            self.mouse_line[1] = event.GetPosition()
+        self.Refresh()
+        self.Update()
+
+
+class TestFrame(wx.Frame):
+    def __init__(self):
+        wx.Frame.__init__(self, None, -1, "ClientDC Test",
+                         wx.DefaultPosition,
+                         size=(500,500),
+                         style=wx.DEFAULT_FRAME_STYLE | wx.NO_FULL_REPAINT_ON_RESIZE)
+
+        self.Window = DrawWindow(self)
+
+class DemoApp(wx.App):
+    def OnInit(self):
+        wx.InitAllImageHandlers() # called so a PNG can be saved      
+        frame = TestFrame()
+        frame.Show(True)
+
+        ## initialize a drawing
+        ## It doesn't seem like this should be here, but the Frame does
+        ## not get sized untill Show() is called, so it doesn't work if
+        ## it is put in the __init__ method.
+
+        #frame.NewDrawing(None)
+
+        self.SetTopWindow(frame)
+
+        return True
+
+if __name__ == "__main__":
+    app = DemoApp(0)
+    app.MainLoop()
+
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