How to catch keypress before it reaches a control?

wxPython Users
#1

Hi,

I am using python3 and wxPython 4.1.1. on Fedora 32.

Is there a way how to catch a keypress and prevent it from reaching the RichTextCtrl?
For example I would like to disable the Shift+Enter key combination because it is broken and I want to prevent the user from using it since it may lead to unpredictable results.

I tried binding a method to a key event like this:
self.rtc.Bind(wx.EVT_KEY_UP, self.on_keypress)
I thought that if the event is not skipped, it will not reach the control, but it does.
You can test this by running the code and watching the terminal output, key codes will be printed but also the text in the window will be affected.

What is the right way of doing this?

Thanks a lot.

import wx
import wx.richtext as rt


class RichTextFrame(wx.Frame):
    def __init__(self, *args, **kw):
        wx.Frame.__init__(self, *args, **kw)
        self.rtc = rt.RichTextCtrl(self, style=wx.VSCROLL | wx.HSCROLL | wx.NO_BORDER)
        self.sizer = wx.BoxSizer(wx.VERTICAL)

        # Create style stylesheet and control
        self._stylesheet = rt.RichTextStyleSheet()
        self._stylesheet.SetName('Stylesheet')

        self._style_control = rt.RichTextStyleListBox(self, 1, size=(140, 25))
        self._style_control.SetStyleType(0)
        self._style_control.SetMargins(-5, -5)

        self.rtc.SetStyleSheet(self._stylesheet)
        self._style_control.SetRichTextCtrl(self.rtc)
        self._style_control.SetStyleSheet(self._stylesheet)

        self.sizer.Add(self.rtc, 1, flag=wx.EXPAND)
        self.sizer.Add(self._style_control)
        self.SetSizer(self.sizer)

        self._create_styles()
        self._insert_sample_text()

        self.rtc.Bind(wx.EVT_KEY_UP, self.on_keypress)

    def _create_styles(self) -> None:
        """
        Create styles for rich text control.
        :return: None
        """
        # Paragraph style
        stl_paragraph: rt.RichTextAttr = rt.RichTextAttr()
        stl_paragraph.SetFontSize(Numbers.paragraph_font_size)
        stl_paragraph.SetAlignment(wx.TEXT_ALIGNMENT_LEFT)
        stl_paragraph.SetFontWeight(wx.FONTWEIGHT_NORMAL)
        stl_paragraph.SetParagraphSpacingBefore(Numbers.paragraph_spacing)
        stl_paragraph.SetParagraphSpacingAfter(Numbers.paragraph_spacing)

        style_paragraph: rt.RichTextParagraphStyleDefinition = rt.RichTextParagraphStyleDefinition(Strings.style_par)
        style_paragraph.SetStyle(stl_paragraph)
        style_paragraph.SetNextStyle(Strings.style_par)
        self._stylesheet.AddParagraphStyle(style_paragraph)

        self.rtc.SetStyleSheet(self._stylesheet)
        self._style_control.SetRichTextCtrl(self.rtc)
        self._style_control.SetStyleSheet(self._stylesheet)
        self._style_control.UpdateStyles()

    def _insert_sample_text(self) -> None:
        """
        Insert sample text.
        :return: None
        """
        self.rtc.ApplyStyle(self._stylesheet.FindParagraphStyle(Strings.style_par))
        self.rtc.BeginParagraphStyle(Strings.style_par)
        self.rtc.WriteText('Example paragraph')
        self.rtc.EndParagraphStyle()
        self.rtc.Newline()

    def on_keypress(self, evt: wx.KeyEvent) -> None:
        """
        Capture key presses
        :param evt: Carries the key code.
        :return: None
        """
        print(evt.GetKeyCode())


class Strings:
    """
    Just constants
    """
    style_par: str = 'paragraph'


class Numbers:
    paragraph_font_size: int = 12
    paragraph_spacing: int = 10


class MyApp(wx.App):
    """
    Main class for running the gui
    """

    def __init__(self):
        wx.App.__init__(self)
        self.frame = None

    def OnInit(self):
        self.frame = RichTextFrame(None, -1, "RichTextCtrl", size=(900, 700), style=wx.DEFAULT_FRAME_STYLE)
        self.SetTopWindow(self.frame)
        self.frame.Show()
        return True


if __name__ == "__main__":
    app = MyApp()
    app.MainLoop()
#2

Try EVT_CHAR_HOOK.

P.S.:
Also read the comparison of the events at https://wxpython.org/Phoenix/docs/html/wx.KeyEvent.html#events-events-emitted-by-this-class
EVT_KEY_DOWN might also do what you want.

#3

Thanks, it works.