Question

The simple curve in this application only appears when it’s dragged off the screen, or the window is resized. When the application just starts up it doesn’t appear, and when the window is maximized or minimized it also disappears. However, all of these times, “Path Drawn” is printed, so all of the painting functions are called. Is there something I’m doing wrong with regards to creating and drawing on the graphicscontext? If not, how can I make the window totally refresh in these special cases?

import wx

class Path(object):
    def paint(self,gc):
        print "Path Drawn"
        gc.SetPen(wx.Pen("#000000",1))
        path=gc.CreatePath()
        path.MoveToPoint(wx.Point2D(10,10))
        path.AddCurveToPoint(wx.Point2D(10,50),
                             wx.Point2D(10,150),
                             wx.Point2D(100,100))
        gc.DrawPath(path)


class TestPane(wx.Panel):
    def __init__(self,parent=None,id=-1):
        wx.Panel.__init__(self,parent,id,style=wx.TAB_TRAVERSAL)
        self.SetBackgroundColour("#FFFFFF")
        self.Bind(wx.EVT_PAINT,self.onPaint)
        self.SetDoubleBuffered(True)
        self.path=Path()

    def onPaint(self, event):
        event.Skip()

        dc=wx.PaintDC(self)
        dc.BeginDrawing()
        gc = wx.GraphicsContext.Create(dc)

        gc.PushState()
        self.path.paint(gc)
        gc.PopState()
        dc.EndDrawing()

    def drawTestRects(self,dc):
        dc.SetBrush(wx.Brush("#000000",style=wx.SOLID))
        dc.DrawRectangle(50,50,50,50)
        dc.DrawRectangle(100,100,100,100)

class TestFrame(wx.Frame):
    def __init__(self, parent, title):
        wx.Frame.__init__(self, parent, title=title, size=(640,480))
        self.mainPanel=TestPane(self,-1)

        self.Show(True)


app = wx.App(False)
frame = TestFrame(None,"Test App")
app.MainLoop()

Answer 1

Comment out the self.SetDoubleBuffered(True) part and it will work, because due to bug http://trac.wxwidgets.org/ticket/11138 window isn’t refreshed correctly if SetDoubleBuffered and GraphicsContext are used together.

If you MUST need double buffering implement it yourselves e.g. first draw to a MeomryDC and then blit or paint bitmap to paint dc.