我有：带有图像缓冲区的面板，其中使用Cairo绘制表单。 缓冲区的实现方式与此处的示例类似：http://wiki.wxpython.org/BufferedCanvas
我想：一个线程，在更新缓冲区时执行所有绘图 （创建/调整大小/缩放时）
问题：解决这个问题的好方法是什么？
我已经尝试在线程中进行绘图本身并且因为dc未完成而出现断言错误。 我是否必须在线程中创建dc或在哪里？ 是否有一些关于线程和DC的教程？
编辑：
我尝试将该示例与BufferedCanvas和LongRunningTasks
组合在一起见这里：http://pastebin.com/X9kqSMKT
有时它会产生X Window系统错误，有时候效果不佳
感谢您的帮助
答案 0 :(得分：5)
以下是3个面板的示例。首先使用Paint和Resize事件绘制。其次使用双缓冲，因此不会闪烁。第三个使用另一个线程来绘制位图，在Paint事件中它只显示位图。
import wx
from wx.lib.delayedresult import startWorker
import array
#=============================================================================
class DrawPanel(wx.Panel):
"""
Basic panel with graphics drawn in Pain Event
"""
def __init__(self, *args, **kwargs):
wx.Panel.__init__(self, *args, **kwargs)
self.Bind(wx.EVT_PAINT, self.OnPaint)
self.Bind(wx.EVT_SIZE, self.OnSize)
self.Bind(wx.EVT_ERASE_BACKGROUND, self.OnEraseBackground)
#-------------------------------------------------------------------------
def OnPaint(self, event):
dc = wx.PaintDC(self)
dc.SetBackground(wx.Brush(wx.BLACK))
dc.Clear()
w, h = self.GetClientSizeTuple()
dc.DrawCirclePoint((w / 2, h / 2), 50)
#-------------------------------------------------------------------------
def OnSize(self, event):
self.Refresh()
self.Update()
#-------------------------------------------------------------------------
def OnEraseBackground(self, event):
pass # Or None
#=============================================================================
class DrawPanelDB(wx.Panel):
"""
Basic panel with graphics drawn in Pain Event using Double Buffering
"""
def __init__(self, *args, **kwargs):
wx.Panel.__init__(self, *args, **kwargs)
self.Bind(wx.EVT_PAINT, self.OnPaint)
self.Bind(wx.EVT_SIZE, self.OnSize)
self.Bind(wx.EVT_ERASE_BACKGROUND, self.OnEraseBackground)
#-------------------------------------------------------------------------
def OnPaint(self, event):
# Switches the buffers when 'dc' goes out of scope
dc = wx.BufferedPaintDC(self)
dc.SetBackground(wx.Brush(wx.BLACK))
dc.Clear()
w, h = self.GetClientSizeTuple()
dc.DrawCirclePoint((w / 2, h / 2), 50)
#-------------------------------------------------------------------------
def OnSize(self, event):
self.Refresh()
self.Update()
#-------------------------------------------------------------------------
def OnEraseBackground(self, event):
pass # Or None
#=============================================================================
class DrawPanelDBT(wx.Panel):
"""
Complex panel with its content drawn in another thread
"""
def __init__(self, *args, **kwargs):
wx.Panel.__init__(self, *args, **kwargs)
self.t = None
self.w, self.h = self.GetClientSizeTuple()
self.buffer = wx.EmptyBitmap(self.w, self.h)
self.Bind(wx.EVT_PAINT, self.OnPaint)
self.Bind(wx.EVT_SIZE, self.OnSize)
self.Bind(wx.EVT_ERASE_BACKGROUND, self.OnEraseBackground)
self.timer = wx.Timer(self)
self.Bind(wx.EVT_TIMER, self.OnTimer, self.timer)
self.SizeUpdate()
#-------------------------------------------------------------------------
def OnPaint(self, event):
# Just draw prepared bitmap
wx.BufferedPaintDC(self, self.buffer)
#-------------------------------------------------------------------------
def OnSize(self, event):
self.w, self.h = self.GetClientSizeTuple()
self.buffer = wx.EmptyBitmap(self.w, self.h)
self.Refresh()
self.Update()
# After drawing empty bitmap start update
self.SizeUpdate()
#-------------------------------------------------------------------------
def OnEraseBackground(self, event):
pass # Or None
#-------------------------------------------------------------------------
def OnTimer(self, event):
# Start another thread which will update the bitmap
# But only if another is not still running!
if self.t is None:
self.timer.Stop()
self.t = startWorker(self.ComputationDone, self.Compute)
#-------------------------------------------------------------------------
def SizeUpdate(self):
# The timer is used to wait for last thread to finish
self.timer.Stop()
self.timer.Start(100)
#-------------------------------------------------------------------------
def Compute(self):
# Compute Fractal
MI = 20
def mapme(x, minimal, maximal, newmin, newmax):
return(((float(x) - minimal) / (maximal - minimal))
* (newmax - newmin) + newmin)
def compute(x, y):
z = complex(0, 0)
c = complex(x, y)
for i in range(MI):
z = z**2 + c
if abs(z) > 2:
return i+1
return 0
def color(i):
a = int(mapme(i, 1, MI, 0, 255))
return(a, a, a)
def compute_buff(x1, x2, y1, y2, w, h):
buffer = array.array('B')
for y in range(h):
for x in range(w):
i = compute(mapme(x, 0, w, x1, x2),
mapme(y, 0, h, y2, y1))
if i == 0:
buffer.extend((255, 255, 255))
else:
buffer.extend(color(i))
return buffer
width, height = self.w, self.h
x = -0.5
y = 0.0
w = 2.4
h = w * height / width
data = compute_buff(x - w/2, x + w/2, y - h/2, y + h/2, width, height)
temp_buffer = wx.BitmapFromBuffer(width, height, data)
return temp_buffer
#-------------------------------------------------------------------------
def ComputationDone(self, r):
# When done, take bitmap and place it to the drawing buffer
# Invalidate panel, so it is redrawn
# But not if the later thread is waiting!
temp = r.get()
if not self.timer.IsRunning():
self.buffer = temp
self.Refresh()
self.Update()
self.t = None
#=============================================================================
class MainWindow(wx.Frame):
def __init__(self, *args, **kwargs):
wx.Frame.__init__(self, *args, **kwargs)
self.panel = wx.Panel(self)
self.drawing = DrawPanel(self.panel, size=(300, 300))
self.drawingDB = DrawPanelDB(self.panel, size=(300, 300))
self.drawingDBT = DrawPanelDBT(self.panel, size=(300, 300))
self.sizerPanel = wx.BoxSizer()
self.sizerPanel.Add(self.panel, proportion=1, flag=wx.EXPAND)
self.sizerMain = wx.BoxSizer()
self.sizerMain.Add(self.drawing, 1, wx.ALL | wx.EXPAND, 5)
self.sizerMain.Add(self.drawingDB, 1, wx.ALL | wx.EXPAND, 5)
self.sizerMain.Add(self.drawingDBT, 1, wx.ALL | wx.EXPAND, 5)
self.panel.SetSizerAndFit(self.sizerMain)
self.SetSizerAndFit(self.sizerPanel)
self.Show()
app = wx.App(False)
win = MainWindow(None)
app.MainLoop()