Change the Font Across Your Entire Application

While working on one of my Xojo projects, I needed a quick way to change the font used by the controls across the entire application.

Opening every window and updating each control individually works, but it gets tedious quickly, especially when testing different fonts or adding new UI elements. So I created a small module that applies a font to all supported controls in a DesktopWindow, including controls placed inside DesktopContainer instances.

Module AppWideFont
  Public Sub SetFont(Extends window As DesktopWindow, fontName As String)
    ApplyFontTo(window.Controls, fontName)
  End Sub

  Protected Function GetMonospaceFont() As String
    #If TargetWindows
      Return "Cascadia Mono"
    #ElseIf TargetMacOS
      Return "Menlo"
    #ElseIf TargetLinux
      Return "DejaVu Sans Mono"
    #Else
      Return "Courier New"
    #EndIf
  End Function

  Private Sub ApplyFontTo(controls As Iterable, fontName As String)
    For Each c As Object In controls
      If c IsA DesktopContainer Then
        ApplyFontTo(DesktopContainer(c).Controls, fontName)
      End If
      
      Select Case c
      Case IsA DesktopLabel
        DesktopLabel(c).FontName = fontName
      Case IsA DesktopTextField
        DesktopTextField(c).FontName = fontName
      Case IsA DesktopTextArea
        DesktopTextArea(c).FontName = fontName
      Case IsA DesktopListBox
        DesktopListBox(c).FontName = fontName
      Case IsA DesktopButton
        DesktopButton(c).FontName = fontName
      Case IsA DesktopCheckBox
        DesktopCheckBox(c).FontName = fontName
      Case IsA DesktopRadioButton
        DesktopRadioButton(c).FontName = fontName
      Case IsA DesktopPopupMenu
        DesktopPopupMenu(c).FontName = fontName
      End Select
    Next
  End Sub

End Module

The SetFont method is an extension method, so I can call it directly on any DesktopWindow.

For example, in a window’s Opening event:

Self.SetFont("Arial")

Or, if I want to use a monospace font:

Self.SetFont(AppWideFont.GetMonospaceFont)

The GetMonospaceFont function is just a simple additional helper that returns a suitable monospace font for Windows, macOS, or Linux.

The module uses the window’s Controls collection and recursively checks any DesktopContainer controls, so I only need one line of code per window. It currently handles labels, text fields, text areas, list boxes, buttons, checkboxes, radio buttons, and popup menus.

If I add another control type later, I can extend the Select Case statement with another branch.

This saved me from repeatedly changing font settings throughout the project and gave me one central place to control the application’s typography.

Gabriel is a digital marketing enthusiast who loves coding with Xojo to create cool software tools for any platform. He is always eager to learn and share new ideas!