python - 在 wxpython 中使用 cairo 绘图

Question

我对 python 相当陌生，正在尝试使用 cairo 和 wxpython 编写一个简单的程序。我习惯于将 cairo 与 gtk 和 C 一起使用，但我发现自己很困惑。

我使用以下代码为自己构建了一个简单的用户界面:

import wx

class Frame(wx.Frame):

    def __init__(self, *args, **kwargs):
        super(Frame, self).__init__(*args, **kwargs) 
        self.InitUI()

    def InitUI(self):
        #----------------------------------------------------
        # Build menu bar and submenus   
        menubar = wx.MenuBar()
        # file menu containing quit menu item
        fileMenu = wx.Menu() 
        quit_item = wx.MenuItem(fileMenu, wx.ID_EXIT, '&Quit\tCtrl+W')
        fileMenu.AppendItem(quit_item)
        self.Bind(wx.EVT_MENU, self.OnQuit, quit_item)
        menubar.Append(fileMenu, '&File')      

        # help menu containing about menu item
        helpMenu = wx.Menu() 
        about_item = wx.MenuItem(helpMenu, wx.ID_ABOUT, '&About\tCtrl+A')
        helpMenu.AppendItem(about_item)
        self.Bind(wx.EVT_MENU, self.OnAboutBox, about_item)
        menubar.Append(helpMenu, '&Help')     

        self.SetMenuBar(menubar)

        #----------------------------------------------------
        # Build window layout

        panel = wx.Panel(self)        
        #panel.SetBackgroundColour('yellow')
        vbox = wx.BoxSizer(wx.VERTICAL)
        panel.SetSizer(vbox)        

        midPan = wx.Panel(panel)
        #midPan.SetBackgroundColour('blue')
        hbox = wx.BoxSizer(wx.HORIZONTAL)
        vbox.Add(midPan, 1, wx.EXPAND | wx.ALL, 12)
        midPan.SetSizer(hbox)      

        smallPan = wx.Panel(panel)
        #smallPan.SetBackgroundColour('red')
        hbox2 = wx.BoxSizer(wx.HORIZONTAL)
        vbox.Add(smallPan, 0, wx.ALIGN_RIGHT|wx.LEFT|wx.RIGHT|wx.BOTTOM, 12)
        smallPan.SetSizer(hbox2)   

        #----------------------------------------------------
        # Place buttons in correct box corresponding with panel

        close_button = wx.Button(smallPan, wx.ID_CLOSE)
        self.Bind(wx.EVT_BUTTON, self.OnQuit, close_button)

        hbox2.Add(close_button)
        #----------------------------------------------------
        # Set window properties

        self.SetSize((1600, 1200))
        self.SetTitle('PROGRAM NAME')
        self.Centre()

    def OnQuit(self, e):
        self.Close()

def main():
    ex = wx.App()
    f = Frame(None)
    f.Show(True)  
    ex.MainLoop()  

if __name__ == '__main__':
    main()

我希望能够在名为 midPan 的面板中绘图。如何添加 OnDraw 函数并链接信号处理程序？

非常感谢您的帮助。

Answer 1

如果您习惯了过程式编程，那么您会感到困惑是自然的。 Python 是一种 OOP 语言，并且采用 OOP 进行编码语言完全不同。我已经清理并更新了提供的例子。用作绘图区域的面板绘制三个彩色矩形。您还没有提供OnAboutBox() 方法的实现，因此，我有注释掉该行。

#!/usr/bin/python

import wx
import wx.lib.wxcairo
import cairo

class DrawingArea(wx.Panel):
    
    def __init__ (self , *args , **kw):
        super(DrawingArea , self).__init__ (*args , **kw)
        
        self.SetDoubleBuffered(True)
        self.Bind(wx.EVT_PAINT, self.OnPaint)
        
    def OnPaint(self, e):
        
        dc = wx.PaintDC(self)
        cr = wx.lib.wxcairo.ContextFromDC(dc)
        self.DoDrawing(cr)     
        
    def DoDrawing(self, cr):
        
        cr.set_source_rgb (0.2 , 0.23 , 0.9)
        cr.rectangle(10 , 15, 90, 60)
        cr.fill()
        
        cr.set_source_rgb(0.9 , 0.1 , 0.1)
        cr.rectangle(130 , 15, 90, 60)
        cr.fill()
        
        cr.set_source_rgb(0.4 , 0.9 , 0.4)
        cr.rectangle(250 , 15, 90, 60)       
        cr.fill()     


class Frame(wx.Frame):

    def __init__(self, *args, **kwargs):
        super(Frame, self).__init__(*args, **kwargs) 
        
        self.InitUI()

    def InitUI(self):
        #----------------------------------------------------
        # Build menu bar and submenus   
        
        menubar = wx.MenuBar()
        # file menu containing quit menu item
        fileMenu = wx.Menu() 
        quit_item = wx.MenuItem(fileMenu, wx.ID_EXIT, '&Quit\tCtrl+W')
        fileMenu.AppendItem(quit_item)
        self.Bind(wx.EVT_MENU, self.OnQuit, quit_item)
        menubar.Append(fileMenu, '&File')      

        # help menu containing about menu item
        helpMenu = wx.Menu() 
        about_item = wx.MenuItem(helpMenu, wx.ID_ABOUT, '&About\tCtrl+A')
        helpMenu.AppendItem(about_item)
        #~ self.Bind(wx.EVT_MENU, self.OnAboutBox, about_item)
        menubar.Append(helpMenu, '&Help')     

        self.SetMenuBar(menubar)

        #----------------------------------------------------
        # Build window layout

        panel = wx.Panel(self)        
        vbox = wx.BoxSizer(wx.VERTICAL)
        panel.SetSizer(vbox)        

        midPan = DrawingArea(panel)
        vbox.Add(midPan, 1, wx.EXPAND | wx.ALL, 12)
    

        smallPan = wx.Panel(panel)
        hbox2 = wx.BoxSizer(wx.HORIZONTAL)
        vbox.Add(smallPan, 1, wx.EXPAND|wx.ALL, 12)
        smallPan.SetSizer(hbox2)   

        #----------------------------------------------------
        # Place buttons in correct box corresponding with panel

        close_button = wx.Button(smallPan, wx.ID_CLOSE)
        self.Bind(wx.EVT_BUTTON, self.OnQuit, close_button)

        hbox2.Add(close_button)
        
        #----------------------------------------------------
        # Set window properties

        #~ self.SetSize((1600, 1200))
        self.SetSize((400, 250))
        #~ self.Maximize()
        self.SetTitle('PROGRAM NAME')
        self.Centre()

    def OnQuit(self, e):
        self.Close()

def main():
    ex = wx.App()
    f = Frame(None)
    f.Show(True)  
    ex.MainLoop()  

if __name__ == '__main__':
    main()

To do the drawing, we create a custom class that will serve as adrawing area. It inherits from a wx.Panel widget.

class DrawingArea(wx.Panel):
    
    def __init__ (self , *args , **kw):
        super(DrawingArea , self).__init__ (*args , **kw)
        
        self.SetDoubleBuffered(True)
        self.Bind(wx.EVT_PAINT, self.OnPaint)
...

这是我们用于绘图的自定义类。在构造函数中我们将绘制事件绑定(bind)到 OnPaint() 方法。

def OnPaint(self, e):
        
    dc = wx.PaintDC(self)
    cr = wx.lib.wxcairo.ContextFromDC(dc)
    self.DoDrawing(cr)  

在OnPaint()方法中我们创建了一个开罗绘图上下文并将实际绘图代码委托(delegate)给 DoDrawing()方法。

midPan = DrawingArea(panel)
vbox.Add(midPan, 1, wx.EXPAND | wx.ALL, 12)

绘图区域已创建并添加到垂直框中。

#~ self.SetSize((1600, 1200))
self.SetSize((400, 250))
#~ self.Maximize()

最后一点:如果您想最大化显示窗口，请调用Maximize()方法。计算机屏幕有不同的尺寸。