Delphi32.com -- FAQ - RichEdit in a COM server is not being correctly created

RichEdit in a COM server is not being correctly created

I have a RichEdit control in my COM Server application that uses the tmFree threading model for COM objects, and the RichEdit control is not being created. How can I get around this?

This is related to a bug in the VCL for Delphi 5 and you can click here to read more about it. (It is also mentioned in the readme file for Delphi 5).

One possible workaround given was to override CreateParams for a TRichEdit and add the ES_EX_NOCALLOLEINIT style to it. However, this may not always work. Another possible solution is to capture the WM_NCCREATE message and set the proper params at that point. Below is a component that will do that for you.

Download FixedRichEdit.pas

Sample Code

unit FixedRichEdit;
interface
uses Windows, Messages, Classes, Controls, RichEdit, ComCtrls;
type TFixedRichEdit = class(TRichEdit) protected procedure WMNCCreate(var message: TWMNCCreate); message WM_NCCREATE; end;
procedure Register;
implementation
procedure TFixedRichEdit.WMNCCreate(var message: TWMNCCreate); var gwlEx : Longint; begin gwlEx := GetWindowLong(WindowHandle, GWL_EXSTYLE); gwlEx := gwlEx or ES_EX_NOCALLOLEINIT; message.CreateStruct^.dwExStyle := gwlEx; inherited; end;
procedure Register; begin RegisterComponents('Samples', ;TFixedRichEdit]); end;
end.

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