简单组合框与位图

问题描述

我如何把一个位图与风格的组合框设置为简单？例如，谷歌Chrome浏览器的右边都有明星，Firefox已经右边的箭头。我想这code：

 程序TForm2.ComboBox1DrawItem（控制：TWinControl;指数：整数;
RECT：TRect;状态：TOwnerDrawState）;
VAR
组合框：TComboBox;
位图：TBitmap;
开始
组合框：=（控制为TComboBox）;
位图：= TBitmap.Create;
尝试
ImageList1.GetBitmap（0，位图）;
与ComboBox.Canvas做
开始
  FillRect（矩形）;
  如果Bitmap.Handle＆LT;＆GT; 0然后绘制（Rect.Left + 2，Rect.Top，位图）;
  矩形：=边界（Rect.Left + ComboBox.ItemHeight + 2，Rect.Top，Rect.Right  -  Rect.Left，Rect.Bottom  -  Rect.Top）;
  DrawText的（手柄，PChar类型（ComboBox.Items [0]），长（ComboBox.Items [0]），矩形，DT_VCENTER + DT_SINGLELINE）;
结束;
最后
Bitmap.Free;
  结束;
结束;
 

的作品，但只有风格：csOwnerDrawFixed和csOwnerDrawVariable，也是位图仅在项目可见

。

感谢。

解决方案

To draw your bitmap in the editor of an owner drawn combo box, check for odComboBoxEdit in the owner draw state:

type
  TComboBox = class(StdCtrls.TComboBox)
  private
    FBmp: TBitmap;
    FBmpPos: TPoint;
  protected
    procedure DrawItem(Index: Integer; Rect: TRect;
      State: TOwnerDrawState); override;
  public
    constructor Create(AOwner: TComponent); override;
    destructor Destroy; override;
  end;

constructor TComboBox.Create(AOwner: TComponent);
begin
  inherited Create(AOwner);
  FBmp := TBitmap.Create;
  FBmp.Canvas.Brush.Color := clGreen;
  FBmp.Width := 16;
  FBmp.Height := 16;
end;

destructor TComboBox.Destroy;
begin
  FBmp.Free;
  inherited Destroy;
end;

procedure TComboBox.DrawItem(Index: Integer; Rect: TRect;
  State: TOwnerDrawState);
begin
  TControlCanvas(Canvas).UpdateTextFlags;
  if Assigned(OnDrawItem) then
    OnDrawItem(Self, Index, Rect, State)
  else
  begin
    Canvas.FillRect(Rect);
    if Index >= 0 then
      Canvas.TextOut(Rect.Left + 2, Rect.Top, Items[Index]);
    if odComboBoxEdit in State then
    begin
      Dec(Rect.Right, FBmp.Width + Rect.Left);
      FBmpPos.X := Rect.Right + Rect.Left;
      FBmpPos.Y := (Height - FBmp.Height) div 2;
      if ItemIndex > -1 then
        Canvas.TextOut(Rect.Left + 2, Rect.Top, Items[ItemIndex]);
      Canvas.Draw(FBmpPos.X, FBmpPos.Y, FBmp);
    end;
  end;
end;

In order to draw a bitmap on non-owner drawn combo boxes, you will have to paint in the window of the combo box itself by using a customized WM_NCPAINT handler.

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