wxPython - PaintDC not refreshing - python

import wx
class TestDraw(wx.Panel):
def __init__(self,parent=None,id=-1):
wx.Panel.__init__(self,parent,id)
self.SetBackgroundColour("#FFFFFF")
self.Bind(wx.EVT_PAINT,self.onPaint)
def onPaint(self, event):
event.Skip()
dc=wx.PaintDC(self)
dc.BeginDrawing()
width=dc.GetSize()[0]
height=dc.GetSize()[1]
if height<width:
self.drawTestRects(dc)
else:
dc.Clear()
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=TestDraw(self,-1)
self.Show(True)
app = wx.App(False)
frame = TestFrame(None,"Test App")
app.MainLoop()
This code should draw the test rectangles only when the height is less than the width, and otherwise the window should remain clear. However, if you mess with resizing the window, the panel isn't actually redrawn unless it is moved off the window. What am I doing wrong?

You can bind a method to handle wx.EVT_SIZE or the panel and invalidate it there. Alternatively simply use the wx.FULL_REPAINT_ON_RESIZE for the panel.

The documentation for a SizeEvent claims that there may be some complications when drawing depends on the dimensions of the window. I do not know exactly what is going on behind the scenes. I followed the suggestion on the link and added the call self.Refresh() to the top of onPaint() and this seems to give the desired behavior. See mghie's answer for a more efficient example of working code.

Related

Looking for a better way to avoid flickering (wxpython on windows)

I did find SetDoubleBuffered(True) in parent panel would fix the flickering problem(mainly from wx.StaticText), but it slows down the whole UI especially the ObjectListView element when you sort a column. So I searched a bit and according to https://wiki.wxwidgets.org/Flicker-Free_Drawing, get rid of background erasing for wx.StaticText should do the job:
class NoFlickeringTxtCtrl(wx.StaticText):
def __init__(self, parent, id=-1, label="", pos=wx.DefaultPosition,
size=wx.DefaultSize, style=0, name="staticText"):
wx.StaticText.__init__(self, parent, id, label, pos, size,
style, name)
self.Bind(wx.EVT_ERASE_BACKGROUND, self.OnErase)
def OnErase(self, evt):
evt.Skip()
But sadly it does not work, so I was wondering is there a better way to avoid flickering for wx.StaticText?
As far as I can tell, your code does not get rid of background erasing. For that to happen, you would have to replace evt.Skip() by pass.
If that also does not work, try to discard the EVT_ERASE_BACKGROUND for the parent panel of the StaticText (this helped me to get rid of flickering when painting a panel on EVT_PAINT).

wxPython panel SetBackgroundColour on button event

I am trying to add a feature to a calculator i have made with wxpython, i want there to be a button , that when clicked changes the background colour (the panel). To show you my code i have made a smaller program, that should only change colour, and even in this one i get the same outcome:
the background colour doesn't change, nothing happens when i click the button, and i dont even receive any errormessahe.Actually, the calculator does change colour, but not in the way i want it to, it only changes the colour of the text (a wx.StaticText), and it's not really meant to do that.
Anyway, here is the code :
import wx
class calc(wx.Frame):
def __init__(self,parent,id):
wx.Frame.__init__(self,parent,id,"Calculator",size=(400,400))
global panel
panel=wx.Panel(self)
a=wx.Button(panel,label="GO",pos=(100,100),size=(50,50))
self.Bind(wx.EVT_BUTTON, self.change, a)
def change(self,event):
panel.SetBackgroundColour("red")
if __name__=="__main__":
app=wx.App(False)
frame=calc(parent=None,id=-1)
frame.Show()
app.MainLoop()
when i run this, the frame with the button show up, and when i click on the button, nothing happens!! Does anybody know what is wrong with this?
Thanks in advice!!!
While your code worked for me on Xubuntu 14.04, wxPython 2.8.12 and Python 2.7, I went ahead and rewrote it slightly to remove the global and clean it up a bit:
import wx
class calc(wx.Frame):
def __init__(self):
wx.Frame.__init__(self, None, title="Calculator", size=(400,400))
self.panel = wx.Panel(self)
a = wx.Button(self.panel, label="GO", pos=(100,100), size=(50,50))
self.Bind(wx.EVT_BUTTON, self.change, a)
def change(self,event):
self.panel.SetBackgroundColour("red")
self.Refresh() # for windows
if __name__=="__main__":
app = wx.App(False)
frame = calc()
frame.Show()
app.MainLoop()
This also works for me.

wxPython set selected control upon application start

I have a simple wxPython application. It basically has a image and a text-entry field (a wx.TextCtrl).
I want to be able to immediately be able to start entering text as soon as the window opens. Right now, I have to first click in the text control, and then I can start entering text.
Here is a minimal app that demonstrates the issue:
import wx
class MyFrame(wx.Frame):
""" We simply derive a new class of Frame. """
def __init__(self, parent, title):
wx.Frame.__init__(self, parent, title=title, size=(200, 100))
mainSizer = wx.BoxSizer(wx.VERTICAL)
self.control = wx.TextCtrl(self, style=wx.TE_MULTILINE)
mainSizer.Add(self.control, 1, wx.EXPAND)
self.SetSizer(mainSizer)
self.Show(True)
app = wx.App(False)
frame = MyFrame(None, 'Small editor')
app.MainLoop()
I've poked around with wx.SetInsertionPoint, but that does not seem to have any effect.
Ah, derp. I had to look further up the inheritance chain.
You can simply call SetFocus() on the control (in this case, self.control.SetFocus()).
SetFocus() is a member function of wxWindow. I was only looking at the docs for wxTextCtrl.
Of course, I didn't think to look up the inheritance chain until I had already asked the question.
I'm leaving this here, as this is a pretty hard to google issue. Hopefully this will help someone else.

Resizing a wxPython Window

Is it possible to make a wxPython window only re-sizable to a certain ratio? I know you can disable resizing; however, I'd like it so when the window was resized it stuck to a certain width to height ratio.
One obvious way to do this would be to bind wx.EVT_SIZE to a function that constrains the aspect ratio. I'm not certain this is The Right Way to do this, but it works:
import wx
class SizeEvent(wx.Frame):
def __init__(self, parent, id, title):
wx.Frame.__init__(self, parent, id, title)
self.Bind(wx.EVT_SIZE, self.OnSize)
self.Centre()
self.SetSizeWH(400, 300)
self.Show(True)
def OnSize(self, event):
hsize = event.GetSize()[0] * 0.75
self.SetSizeHints(minW=-1, minH=hsize, maxH=hsize)
self.SetTitle(str(event.GetSize()))
app = wx.App()
SizeEvent(None, 1, 'sizeevent.py')
app.MainLoop()
(The boilerplate is borrowed from here.)
I'm not too familiar with wxPython, but can't you just reset the window size to your max/min size that you want once the user pass that? Preferably in the event that detects resizing?

Why does my buffered GraphicsContext application have a flickering problem?

import wx
class MainFrame(wx.Frame):
def __init__(self,parent,title):
wx.Frame.__init__(self, parent, title=title, size=(640,480))
self.mainPanel=DoubleBufferTest(self,-1)
self.Show(True)
class DoubleBufferTest(wx.Panel):
def __init__(self,parent=None,id=-1):
wx.Panel.__init__(self,parent,id,style=wx.FULL_REPAINT_ON_RESIZE)
self.SetBackgroundColour("#FFFFFF")
self.timer = wx.Timer(self)
self.timer.Start(100)
self.Bind(wx.EVT_TIMER, self.update, self.timer)
self.Bind(wx.EVT_PAINT,self.onPaint)
def onPaint(self,event):
event.Skip()
dc = wx.MemoryDC()
dc.SelectObject(wx.EmptyBitmap(640, 480))
gc = wx.GraphicsContext.Create(dc)
gc.PushState()
gc.SetBrush(wx.Brush("#CFCFCF"))
bgRect=gc.CreatePath()
bgRect.AddRectangle(0,0,640,480)
gc.FillPath(bgRect)
gc.PopState()
dc2=wx.PaintDC(self)
dc2.Blit(0,0,640,480,dc,0,0)
def update(self,event):
self.Refresh()
app = wx.App(False)
f=MainFrame(None,"Test")
app.MainLoop()
I've come up with this code to draw double buffered GraphicsContext content onto a panel, but there's a constant flickering across the window. I've tried different kinds of paths, like lines and curves but it's still there and I don't know what's causing it.
You get flicker because each Refresh() causes the background to get erased before calling onPaint. You need to bind to EVT_ERASE_BACKGROUND and make it a no-op.
class DoubleBufferTest(wx.Panel):
def __init__(self,parent=None,id=-1):
# ... existing code ...
self.Bind(wx.EVT_ERASE_BACKGROUND, self.onErase)
def onErase(self, event):
pass
# ... existing code ...
If you're using a relatively modern wxWidgets, you can use wx.BufferedPaintDC and avoid having to muck around with the memory DC and painting and blitting on your own. Also, on windows, FULL_REPAINT_ON_RESIZE often causes flickering even when you're not resizing the window due to funny things going on under the covers - if you don't need it, going with NO_FULL_REPAINT_ON_RESIZE may help. Otherwise, you'll want to simplify your code some to make sure you can get the simplest thing to work, and perhaps take a look at the DoubleBufferedDrawing wiki page at wxpython.org.

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