做一个打字程序，用richedit的onchange中判断无法改变自身汉字的颜色,英文的可以.

Question

做一个打字程序，r1,r2为两个richedit控件,r2与r1中的汉字相比较,用richedit的onchange中判断无法改变自身汉字的颜色,英文的可以.
源程序如下:procedure TForm1.r2Change(Sender: TObject);/r1,r2为Trichedit组件x:=r2.SelStart ;//x,y为全局变量,初始值为0
if(copy(r2.Lines.Text ,y+1,x-y)=copy(r1.Lines.Text,y+1,x-y) ) then
   begin
   r1.SelStart :=y;
   r1.SelLength :=x-y;
   r1.SelAttributes.Color:=clblue;//颜色能改变成功
   r2.SelStart :=y;
   r2.SelLength :=x-y;    
   r2.SelAttributes.Color:=clblue;//颜色不能改变?????为什么?????   r2.SelStart :=x;
   y:=x;
   end
   else begin
    r1.SelStart :=y;
    r1.SelLength :=x-y;
    r1.SelAttributes.Color:=clred;   r2.SelStart :=y;
   r2.SelLength :=x-y;      
   r2.SelAttributes.Color:=clred;
   r2.SelStart :=x; 
   y:=x;
   endend;

Answer 1

换个思路吧，参考下面代码，我没有优化，只是为了实现功能 
procedure TForm1.RichEdit1Change(Sender: TObject);
var
  dStr:string;
  StrLength,i:Integer;
begin
  dStr:=RichEdit1.Text;
  StrLength:=Length(dStr);
  richedit1.SelStart:=StrLength-1;
  richedit1.SelLength:=1;
  for i:=1 to StrLength do
  begin
    RichEdit1.SelStart:=i-1;
    RichEdit1.SelLength:=1;
    if RichEdit1.Text[i]=Memo1.Text[i] then
      RichEdit1.SelAttributes.Color:=clBlue
    else
      RichEdit1.SelAttributes.Color:=clRed;
  end;
  RichEdit1.SelStart:=StrLength;
end;

Answer 2

优化后的代码：
procedure TForm1.RichEdit1Change(Sender: TObject);
var
  StrLength, i: Integer;
begin
  with RichEdit1 do
  begin
    StrLength := Length(Text);GetPixel
    for i := StrLength downto 1 do
    begin
      SelStart := i - 1;
      SelLength := 1;
      if (SelAttributes.Color =clBlue)or(SelAttributes.Color =clRed) then
        Break;
      if Text[i] = Memo1.Text[i] then
        SelAttributes.Color := clBlue
      else
        SelAttributes.Color := clRed;
    end;
    SelStart := StrLength;
    SelAttributes.Color:=clBlack;
  end;
end;