Полосатый TListBox

Delphi , Компоненты и Классы , Списки

Оформил: DeeCo
Автор: http://www.swissdelphicenter.ch

unit Unit1;

 interface

 uses
   Windows, Messages, SysUtils, Classes, Graphics, Controls, Forms, Dialogs,
   StdCtrls;

 type

   TListbox = class(StdCtrls.TListbox)
   private
     procedure wmEraseBkGnd(var Msg: TWMEraseBkGnd); message WM_ERASEBKGND;
   end;

      TForm1 = class(TForm)
     ListBox1: TListBox; // (!) ListBox1.Style := lbOwnerDrawFixed 
    Button1: TButton;
     procedure Button1Click(Sender: TObject);
     procedure ListBox1DrawItem(Control: TWinControl; Index: Integer;
       Rect: TRect; State: TOwnerDrawState);
     { ... }
   end;

 var
   Form1: TForm1;

 implementation

 {$R *.DFM}

 procedure TForm1.Button1Click(Sender: TObject);
 var
   i: Integer;
 begin
   for i := listbox1.Items.Count to listbox1.Items.Count + 5 do
     listbox1.Items.Add(Format('Item %d', [i]));
 end;

 { TListbox }
 const
   colors: array [Boolean] of TColor = ($FFFFC0, $C0FFFF);

 procedure TListbox.wmEraseBkGnd(var Msg: TWMEraseBkGnd);
 var
   cv: TCanvas;
   h, max: Integer;
   r: TRect;
   b: Boolean;
 begin
   Msg.Result := 1;
   h          := Perform(LB_GETITEMHEIGHT, 0, 0);
   if h = LB_ERR then h := ItemHeight;
   cv := TCanvas.Create;
   try
     cv.Handle := Msg.DC;
     r         := Rect(0, 0, ClientWidth, h);
     b         := Odd(TopIndex) and (TopIndex >= 0);
     max       := ClientHeight;
     cv.Brush.Style := bsSolid;
     while r.Top < max do
      begin
       cv.Brush.Color := colors[b];
       b := not b;
       cv.FillRect(r);
       OffsetRect(r, 0, h);
     end;
   finally
     cv.Handle := 0;
     cv.Free;
   end;
 end;

 procedure TForm1.ListBox1DrawItem(Control: TWinControl; Index: Integer;
   Rect: TRect; State: TOwnerDrawState);
 var
   cb, ct: TColor;
 begin
   if not (odSelected in State) then
     with Control as TListbox do
      begin
       Canvas.Brush.Color := colors[Odd(Index)];
       Canvas.Brush.Style := bsSolid;
     end;
   Rect.Right := Control.ClientWidth;
   with Control as TListbox do
    begin
     Canvas.FillRect(Rect);
     Canvas.Brush.Style := bsClear;
     Canvas.TextRect(Rect, Rect.Left + 2, Rect.Top, Items[Index]);
   end;
 end;

 end.

Статья Полосатый TListBox раздела Компоненты и Классы Списки может быть полезна для разработчиков на Delphi и FreePascal.

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