[wxPython-users] Reducing the size of a BufferedDC

[Christopher Barker]

Alexander 'boesi' B=F6secke wrote:
> Am 14.12.2006 20:29:41 schrieb Christopher Barker:
> So GetSize returns now the correct size (of the target DC)?

oops, no, it looks like it's still doing the same thing -- not reducing =

the size when the window is shrunk.

>> In real use, it's likely you want to keep that bitmap around anyway, so =

>> that your OnPaint handler can just blit it to the screen. See the =

>> DoubleBuffer demo in the Wiki.
> =

> Hmm but with BufferedDC this isn't needed, is it?

Sure it is. if you don't keep the bitmap around, then you need to =

re-draw it in every Paint event. With your code, you're getting double =

buffering, but only when drawing, so you don't see the drawing happening =

in progress (I actually generally like to see the drawing in progress -- =

it lets me know something is happening)

> I'm not really interested
> in the size of the DC - but for drawing I need the correct size. Of
> course I can save the size of the DC before doubble buffering, but this
> confuses me somewhat.

Yes, the BufferedDC should return the correct size, if it's using a =

large bitmap under the covers, that shouldn't keep it from returning the =

correct value.

Again, see the DoubleBuffer example in the Wiki.

Enclosed is an example that keeps the off-screen buffer around.

-Chris


-- =

Christopher Barker, Ph.D.
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-------------- next part --------------
# -*- coding: iso8859_15 -*-

import wx

class myFrame(wx.Frame):
    def __init__(self, parent=3DNone):
        wx.Frame.__init__(self, parent, -1, 'Test')
        self.dc =3D None
        self.panel =3D wx.Panel(self, -1)
        self.btnBuffer =3D wx.ToggleButton(self.panel, label=3D'Use Buffere=
d DC', pos=3D(0, 0))
        self.btnDC =3D wx.Button(self.panel, label=3D'Create DC', pos=3D(0,=
 25))
        self.btnDC.Bind(wx.EVT_BUTTON, self.createDC)

        self.Bind(wx.EVT_SIZE, self.OnSize)

    def OnSize(self,event):
        self._buffer =3D wx.EmptyBitmap(*self.GetSize())
        event.Skip()
        =

    def createDC(self, event=3DNone):
            self.dc =3D wx.ClientDC(self.panel)
            print 'Unbuffered Size:', self.dc.GetSize(),
            if self.btnBuffer.GetValue() =3D=3D True:
                self.dc =3D wx.BufferedDC(self.dc, self._buffer)
                print 'Buffered Size:', self.dc.GetSize()
            else:
                print "UnBuffered Size:", self.dc.GetSize()

app =3D wx.PySimpleApp()
frame =3D myFrame()
frame.Show()
app.MainLoop()