wx grid SetCellBackGroundColor() is not working as expected

Question

I have the following program that creates a wx grid, sets the background color of one cell, and then handles a left click event by setting the background color of the cell clicked:

import wx
import wx.grid as gridlib
class MyForm(wx.Frame):

    def __init__(self):
        wx.Frame.__init__(self, None, wx.ID_ANY, "Sample grid")

        self.grid = gridlib.Grid(self)
        self.grid.CreateGrid(5,4)
        self.grid.SetCellSize(4,1,1,2)

        self.grid.SetDefaultCellAlignment(wx.ALIGN_CENTRE, wx.ALIGN_CENTRE)

        self.grid.SetColLabelSize(0)            # eliminates spreadsheet-style row & col headers
        self.grid.SetRowLabelSize(0)

        self.grid.SetCellBackgroundColour(4, 3, wx.LIGHT_GREY)

        rowHeight = 50
        colWidth  = 50
        for i in range(1,5):
            self.grid.SetRowSize(i, rowHeight)
        for i in range(0,4):
            self.grid.SetColSize(i, colWidth)

        self.grid.Bind(gridlib.EVT_GRID_CELL_LEFT_CLICK, self.GridLeftClick, self.grid)

    def GridLeftClick(self, event):
        col = event.GetCol()
        row = event.GetRow()
        print(f"Got col {col} and row {row}")
        self.grid.SetCellBackgroundColour(row, col, wx.LIGHT_GREY)

app = wx.App()
frame = MyForm().Show()
app.MainLoop()

Everything works as I expect except the self.grid.SetCellBackgroundColor(row, col, wx.LIGHT_GREY) statement. The call works when I'm setting up the grid, so I think I have that correct. I get the print statement, so the event binding is working. What else do I have to do for that method to put a background color on the clicked cell?

Answer 1

You just need to refresh the window.
I've added a colour toggle so it will toggle between grey and white on a click.

import wx
import wx.grid as gridlib
class MyForm(wx.Frame):

    def __init__(self):
        wx.Frame.__init__(self, None, wx.ID_ANY, "Sample grid")

        self.grid = gridlib.Grid(self)
        self.grid.CreateGrid(5,4)
        self.grid.SetCellSize(4,1,1,2)

        self.grid.SetDefaultCellAlignment(wx.ALIGN_CENTRE, wx.ALIGN_CENTRE)

        self.grid.SetColLabelSize(0)            # eliminates spreadsheet-style row & col headers
        self.grid.SetRowLabelSize(0)

        self.grid.SetCellBackgroundColour(4, 3, wx.LIGHT_GREY)

        rowHeight = 50
        colWidth  = 50
        for i in range(1,5):
            self.grid.SetRowSize(i, rowHeight)
        for i in range(0,4):
            self.grid.SetColSize(i, colWidth)

        self.grid.Bind(gridlib.EVT_GRID_CELL_LEFT_CLICK, self.GridLeftClick, self.grid)

    def GridLeftClick(self, event):
        col = event.GetCol()
        row = event.GetRow()
        clr = self.grid.GetCellBackgroundColour(row, col)
        if clr != wx.LIGHT_GREY:
            self.grid.SetCellBackgroundColour(row, col, wx.LIGHT_GREY)
        else:
            self.grid.SetCellBackgroundColour(row, col, wx.WHITE)
        self.Refresh()

app = wx.App()
frame = MyForm().Show()
app.MainLoop()