Wxpython with matplotlib - resize plot

Question

I’m using matplotlib in wxpython, and here is what I’m trying to do…

I’d like to define my figure to be a specific (user chosen) size…say 8 inches wide by 6 inches high.

Then, I’d like the user to be able to size the window and resize/scale the plot to fit the window, but the underlying figure still be 8x6 (to ensure fonts stay the right size and such).

What I’m currently doing is this:

    size = self.GetClientSize()
    self.canvas.SetSize(size)
    self.figure.set_size_inches(8, 6)
    self.figure.set_dpi(min(size.width/8, size.height/6))
    # my plot configuration code is here
    self.canvas.draw_idle()

This works great from a sizing standpoint, but if you size up the plot and back down, I end up with clutter on the right or bottom. Like this:

Any suggestions? I saw something about wxDC.SetLogicalScale, but couldn’t figure out how to get a DC or how to custom paint the background.

Headcrab · Accepted Answer · 2025-08-04 20:21:24Z

Should it keep the exact size of 8x6 inches or the width to height ratio as 8 to 6?

If it's the former, wouldn't it work to put it in the center of a 3x3 FlexGridSizer and make all cells except the central one growable? You didn't provide a minimal reproducible example, showing what you're drawing and how, so I made my own, loosely based on the first example from here:

from numpy import arange, sin, pi
from matplotlib.figure import Figure
from matplotlib.backends.backend_wxagg import FigureCanvasWxAgg as FigureCanvas
import wx

class MyCanvasPanel(wx.Panel):
    def __init__(self, parent):
        wx.Panel.__init__(self, parent, size=(800, 600))

        self.figure = Figure()
        self.figure.set_size_inches(8, 6)
        self.axes = self.figure.add_subplot(111)
        self.canvas = FigureCanvas(self, -1, self.figure)

        sizer = wx.FlexGridSizer(3, 3, 0, 0)
        for i in range(4): sizer.AddStretchSpacer()
        sizer.Add(self.canvas, 1, wx.EXPAND)
        for i in range(4): sizer.AddStretchSpacer()
        
        sizer.AddGrowableRow(0, 1)
        sizer.AddGrowableRow(2, 1)
        sizer.AddGrowableCol(0, 1)
        sizer.AddGrowableCol(2, 1)
        
        self.SetSizer(sizer)
        self.Fit()

    def Draw(self):
        t = arange(0.0, 3.0, 0.01)
        s = sin(2 * pi * t)
        self.axes.plot(t, s)


class MyFrame(wx.Frame):
    def __init__(self, title):
        wx.Frame.__init__(self, None, -1, title, size=(800, 600))

        self.panel = MyCanvasPanel(self)
        self.panel.Draw()


class MyApp(wx.App):
    def OnInit(self):
        frame = MyFrame("8x6 inches")
        self.SetTopWindow(frame)
        frame.Show(True)

        return True


if __name__ == "__main__" :
    app = MyApp(False)
    app.MainLoop()

If it's the latter - the plot should grow and shrink, but proportionally - then wouldn't it work to simply set aspect to 'equal' with matplotlib, e. g.:

class MyCanvasPanel(wx.Panel):
    def __init__(self, parent):
        wx.Panel.__init__(self, parent)

        self.figure = Figure()
        self.axes = self.figure.add_subplot(111)
        self.axes.set_aspect('equal', 'box')
        self.canvas = FigureCanvas(self, -1, self.figure)

        sizer = wx.BoxSizer()
        sizer.Add(self.canvas, 1, wx.EXPAND)
        
        self.SetSizer(sizer)
        self.Fit()

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