讲述如何开发一个控件,很有价值(七)


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 windows 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); 
var 

SaveOnChangeIn: TNotifyEvent;  
WasSelStart,WasRow,Row,BeginSelStart,EndSelStart: Integer; 
MyRe : TRichEdit; 
MyPBuff: array[0..255] of char; 
MyTokenStr:string; 
MyTokenState:TTokenState; 
MyRun:PChar; 
MySelStart: Integer; 
begin 

MyRe := TRichEdit(Sender); 
SaveOnChangeIn := MyRe.OnChange; 
MyRe.OnChange  := nil; 
MyRe.Enabled   := False; 
WasSelStart      := MyRE.SelStart; 
WasRow            := MyRE.Perform(EM_LINEFROMCHAR, MyRE.SelStart, 0); 
Row                    := WasRow; 
BeginSelStart    := MyRe.Perform(EM_LINEINDEX, Row, 0); 
EndSelStart       := BeginSelStart + Length(MyRE.Lines.Strings[Row]); 
StrPCopy(MyPBuff,MyRE.Lines.Strings[Row]); 
MYPBuff[Length(MyRE.Lines.Strings[Row])] := #0;  
MySelStart   := BeginSelStart; 
MyRun         := MyPBuff; 
while(MyRun^ <> #0) do 
begin 

MyRun := PasCon.GetToken(MyRun,MyTokenState,MyTokenStr); 
MyRE.SelStart := MySelStart; 
MyRE.SelLength := Length(MyTokenStr); 
If MyRE.SelAttributes.Name <> PasCon.FParseFont[MyTokenState].Name then MyRE.SelAttributes.Name := PasCon.FParseFont[MyTokenState].Name; 
If MyRE.SelAttributes.Color <> PasCon.FParseFont[MyTokenState].Color then MyRE.SelAttributes.Color := PasCon.FParseFont[MyTokenState].Color; 
if MyRE.SelAttributes.Style <> PasCon.FParseFont[MyTokenState].Style then MyRE.SelAttributes.Style := PasCon.FParseFont[MyTokenState].Style; 
MySelStart := MySelStart + Length(MyTokenStr);

end; 
MyRE.SelStart          := WasSelStart; 
MyRE.SelLength      := 0; 
MyRe.OnChange     := SaveOnChangeIn; 
MyRe.Enabled         := True; 
MyRe.SetFocus;
end;
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

补充：软件开发 , Delphi ,