SUCCESS - (Nearly...)
I think youll agree we are pretty close. There is just a little bit of flicker. This flicker is the SelStart jumping the Cursor position around the text. We need to hide this. This "Cursor" is also known as a Caret. Looking throught Win32.Hlp again we find the lovely, and appropriately named, HideCaret() function.
Lets try this then: everytime we change the value of MyRe.SelStart lets call HideCaret(MyRe.Handle) immediately before.
Ill be kind - that doesnt work. I tried 2 x HideCaret(MyRe.Handle), and it still didnt work. Neither did three,four or 25x. So close - but yet - so far. I think its time for another Delphi Rule:
DELPHI RULE #5 - If you bother to get your way through the atrocious index of the Win32.HLP file to find what you are looking for - make sure you really read what you found properly!
The key was the last paragraph in the description of not HideCaret but ShowCaret (which I had also read as I thought we were going to need it, especially to reverse my 25x HideCaret()). You also need another Delphi Rule to understand it:
|The caret is a shared resource; there is only one caret in the system. A window should show a caret only when the window has the keyboard focus or is active.|
DELPHI RULE #6 - Everything (basically) is a Window
You see the RichEdit is a control and is also.. in a weird sense.. a window. It has a Handle, which is why HideCaret would accept it. So re-reading the last line again we get:
|The caret is a shared resource; there is only one caret in the system. A [RichEdit] should show a caret only when the [RichEdit] has the keyboard focus or is active.|
So - in the end - were back to were we started - we have to disable the RichEdit to stop the final bit of flickering. This also (co-incidentially) means that EM_HIDESELECTION is not needed anymore (if HideSelection is set properly during Design time). So in the end everyone gets 10/10 for marks!
ASH Version 0.9b
|procedure TForm1.RichEdit1Change(Sender: TObject);
Towards - ASH Version 1.0b
Couple of problems with the last version if you try it out for size:
- Its slightly inefficient in that everytime SelAttributes is changed it forces a repaint of the same token in the control. We should instead use some variable (e.g var DoFormat:Boolean) to decided if we need to reformat, and then check the value of DoFormat at the end of this chec