unit kktListBox; {========================================================================
DESIGN BY : 彭国辉
DATE: 2004-12-24
SITE: http://kacarton.yeah.net/
BLOG: http://blog.csdn.net/nhconch
EMAIL: kacarton#sohu.com 文章为作者原创，转载前请先与本人联系，转载请注明文章出处、保留作者信息，谢谢支持！
=========================================================================}
interface uses
Windows, Messages, SysUtils, Classes, Controls, StdCtrls, Commctrl; type
TkktListBox = class(TListBox)
private
MaxLenItemIndex: Integer;
FScrollWidth: Integer;
procedure LBAddString(var Message: TMessage); message LB_ADDSTRING;
procedure LBInsertString(var Message: TMessage); message LB_INSERTSTRING;
procedure LBDeleteString(var Message: TMessage); message LB_DELETESTRING;
procedure CMFontChanged(var Message: TMessage); message CM_FONTCHANGED;
procedure AdjuctScrollWidth(Message: TMessage);
procedure ResetScrollWidth; protected public
constructor Create(AOwner: TComponent); override;
procedure CreateWnd; override;
end; procedure Register; implementation { TkktListBox } constructor TkktListBox.Create(AOwner: TComponent);
begin
inherited Create(AOwner);
MaxLenItemIndex := -1;
FScrollWidth := 0;
end; procedure TkktListBox.CreateWnd;
begin
inherited CreateWnd;
Canvas.Font := Font;
end;
procedure TkktListBox.LBAddString(var Message: TMessage);
begin
inherited;
if Message.Result = LB_ERR then Exit;
AdjuctScrollWidth(Message);
end; procedure TkktListBox.LBInsertString(var Message: TMessage);
begin
inherited;
if Message.Result = LB_ERR then Exit;
if Message.WParam <= MaxLenItemIndex then MaxLenItemIndex := MaxLenItemIndex + 1;
AdjuctScrollWidth(Message);
end; procedure TkktListBox.LBDeleteString(var Message: TMessage);
begin
inherited;
if Message.Result = LB_ERR then Exit;
if Message.WParam = MaxLenItemIndex then ResetScrollWidth;
end; procedure TkktListBox.CMFontChanged(var Message: TMessage);
var
sz: SIZE;
begin
inherited;
if MaxLenItemIndex = -1 then Exit;
//这里没有使用TextWidth，而是用GetTextExtentPoint32函数，如果你有兴趣的话
//可以跟踪一个TextWidth函数，它最终是调用GetTextExtentPoint32实现的
GetTextExtentPoint32(Canvas.Handle, PChar(Items[MaxLenItemIndex]), Length(Items[MaxLenItemIndex]), sz);
FScrollWidth := sz.cx + 4;
Perform(LB_SETHORIZONTALEXTENT, FScrollWidth, 0);
end; procedure TkktListBox.AdjuctScrollWidth(Message: TMessage);
var
sz: SIZE;
begin
GetTextExtentPoint32(Canvas.Handle, PChar(Message.LParam), StrLen(PChar(Message.LParam)), sz);
if sz.cx + 4 > FScrollWidth then begin
FScrollWidth := sz.cx + 4;
Perform(LB_SETHORIZONTALEXTENT, FScrollWidth, 0);
MaxLenItemIndex := Message.Result;
end;
end; procedure TkktListBox.ResetScrollWidth;
var
i, MaxWidth: Integer;
sz: SIZE;
begin
MaxWidth := 0;
i := Items.Count - 1;
MaxLenItemIndex := -1;
while i>=0 do begin
sz.cx := 0;
GetTextExtentPoint32(Canvas.Handle, PChar(Items[i]), Length(Items[i]), sz);
if sz.cx + 4 > MaxWidth then begin
MaxWidth := sz.cx + 4;
MaxLenItemIndex := i;
end;
Dec(i);
end;
FScrollWidth := MaxWidth;
Perform(LB_SETHORIZONTALEXTENT, FScrollWidth, 0);
end; procedure Register;
begin
RegisterComponents('Kacarton', [TkktListBox]);
end; end. |
