Author: Tomas Rutkauskas

How to change the font of all controls on a form at runtime

Answer:

By default all controls have ParentFont = true, so if you did not change that for 
specific controls you could just change the forms Font property, e.g. in code 
attached to the Screen.OnActiveFormChange event. If you cannot rely on all controls 
having Parentfont = true you would have to loop over all controls on the form and 
set the font property for each or at least for those that have ParentFont set to 
false. You can use the routines from unit TypInfo for that, they allow you to 
access published properties by name. The code, again sitting in a handler for 
Screen.onActiveFormChange, would be something like this:

1   ModifyFontsFor(Screen.ActiveControl);
2   
3   //where
4   
5   procedure ModifyFontsFor(ctrl: TWinControl);
6   
7     procedure ModifyFont(ctrl: TControl);
8     var
9       f: TFont;
10    begin
11      if IsPublishedProp(ctrl, 'Parentfont') and (GetOrdProp(ctrl, 'Parentfont') =
12        Ord(false)) and IsPublishedProp(ctrl, 'font') then
13      begin
14        f := TFont(GetObjectProp(ctrl, 'font', TFont));
15        f.Name := 'Symbol';
16      end;
17    end;
18  
19  var
20    i: Integer;
21  begin
22    ModifyFont(ctrl);
23    for i := 0 to ctrl.controlcount - 1 do
24      if ctrl.controls[i] is TWinControl then
25        ModifyFontsfor(TWinControl(ctrl.controls[i]))
26      else
27        Modifyfont(ctrl.controls[i]);
28  end;


Remember to add TypInfo to your uses clause.