In GUI applications, it is often necessary to have multiple panes or sections within a single window. One way to achieve this in wxPython is by using the wx.SplitterWindow class.

Introduction to wx.SplitterWindow

A wx.SplitterWindow is a container widget that can be divided into two or more resizable panes. Users can then adjust the size of the panes by dragging the splitter between them. This layout is commonly used to create a split view, where different sections of the window display different content.

Creating a wx.SplitterWindow

To create a wx.SplitterWindow, we first need to import the necessary classes from the wxPython library:

import wx

Next, we need to define our main application frame. In this example, we will create a simple frame with a wx.SplitterWindow:

class MyFrame(wx.Frame):
    def __init__(self, parent):
        super().__init__(parent, title="SplitterWindow Example")
        
        splitter = wx.SplitterWindow(self)
        panel1 = wx.Panel(splitter)
        panel2 = wx.Panel(splitter)
        
        splitter.SplitVertically(panel1, panel2)
        
        self.Show()

In the above code, we create an instance of wx.SplitterWindow called splitter. We then create two wx.Panel instances, panel1 and panel2, to be used as the content for each pane. The SplitVertically method splits the splitter window vertically, with panel1 on the left and panel2 on the right.

Finally, we create an instance of MyFrame and show it:

if __name__ == "__main__":
    app = wx.App()
    frame = MyFrame(None)
    app.MainLoop()

Setting Pane Sizes

By default, the panes in a wx.SplitterWindow are resized automatically when the window is resized. However, you can also set the initial sizes of the panes by using the SetSashPosition method:

splitter.SetSashPosition(200)

The SetSashPosition method takes the width or height of the first pane as a parameter, in pixels. In the example above, the first pane will have an initial width of 200 pixels.

Handling Events

To respond to user actions, such as resizing the panes, you can bind event handlers to the appropriate events. For example, to handle the event when the splitter position changes, you can use the EVT_SPLITTER_SASH_POS_CHANGING event:

def on_sash_position_change(self, event):
    position = event.GetSashPosition()
    print(f"Sash position changing: {position}")
    event.Skip()

In the above code, we define an event handler called on_sash_position_change that prints the new sash position whenever it changes. The event.Skip() call is necessary to allow the default handling of the event.

To bind the event handler to the wx.SplitterWindow, you can use the Bind method:

splitter.Bind(wx.EVT_SPLITTER_SASH_POS_CHANGING, self.on_sash_position_change)

Conclusion

In this blog post, we have learned about the wx.SplitterWindow class in wxPython. We have seen how to create a split view with resizable panes, set pane sizes, and handle events. With this knowledge, you can now create more dynamic and flexible user interfaces in your wxPython applications.