在为所选文本设置背景颜色后，将字体分配给TRichEdit

Question

I have a TRichEdit control on my Delphi form, and I'm assigning a background colour to certain parts of the text using the perform method to send a windows message to the control. (Text is selected using SelStart and SelLength before calling this code).

FillChar(Format, SizeOf(Format), 0);
with Format do
begin
  cbSize := SizeOf(Format);
  dwMask := CFM_BACKCOLOR;
  crBackColor := AColor;
  fRichEdit.Perform(EM_SETCHARFORMAT, SCF_SELECTION, Longint(@Format));
end;

I'm also wanting the font to be changeable by the user (the ENTIRE font, it's not selective like the background highlighting), so I'm presenting a TFontDialog to the user when they'd like to modify the font for the edit box, and I'm assigning the font to the font of the TRichEdit control.

RichEdit.Font.Assign(SelectedFont);

However, using a windows message seems to stop the font from updating. When I comment out the perform method, everything works fine, but when I uncomment the line, the font doesn't update.

I'm new to windows messages, please explain why this is happening.

Answer 1

The Font property you are setting will set the font for the entire RichEdit as a whole, not the current text selection. If you want to set a per-selection font, you need to use the szFaceName , yHeight , and bCharset fields of the CHARFORMAT record that you pass via EM_SETCHARFORMAT . There is no way to assign a TFont object, or even an HFONT handle, on a per-selection basis.