Author: Jonas Bilinkevicius

I would like to change the font color on all components on a form at runtime (and 
the components owned by the components etc). I devised a recursive algorithm using 
RTTI that accepts a TComponent as a parameter. It works to some extent, but I still 
have to use 'if' statements to cast the object to a particular descendant, 
resulting in about 30 lines of code to test for all of the components I use. Also, 
some objects (TColumnTitle), are not descended from TComponent, even though they 
have a font property.

Answer:

This may do the trick (with D6 and maybe D5):

1   uses
2     TypInfo;
3   
4   { ... }
5   var
6     i: integer;
7     aFont: TFont;
8   begin
9     for i := 0 to aComponent.ComponentCount - 1 do
10    begin
11      aFont := TFont(GetOrdProp(aComponent.Components[i], 'Font'));
12      if assigned(aFont) then
13        aFont.Color := clWhite;
14    end;
15  end;
16  
17  
18  //With D4:
19  
20  { ... }
21  var
22    i: integer;
23    aFont: TFont;
24    pi: PPropInfo;
25  begin
26    for i := 0 to aComponent.ComponentCount - 1 do
27    begin
28      pi := GetPropInfo(aComponent.Components[i].ClassInfo, 'Font');
29      if assigned(pi) then
30        TFont(GetOrdProp(aComponent.Components[i], pi)).Color := clWhite;
31    end;
32  end;