Title: Change caption font
Use SystemParametersInfo function with SPI_SETNONCLIENTMETRICS parameter. All information, what you may set, are in NONCLIENTMETRICS structure.
procedure TForm1.Button1Click(Sender: TObject);
var
MyStruct: TNonClientMetrics;
begin
MyStruct.cbSize:=SizeOf(TNonClientMetrics);
SystemParametersInfo(
SPI_GETNONCLIENTMETRICS,
SizeOf(TNonClientMetrics),
@MyStruct,
0);
MyStruct.lfCaptionFont.lfHeight:=8;
MyStruct.lfCaptionFont.lfFaceName:='Arial';
SystemParametersInfo(
SPI_SETNONCLIENTMETRICS,
SizeOf(TNonClientMetrics),
@MyStruct,
0);
end;