简单组合框与位图 [英] ComboBox Simple with Bitmap

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

  

...也是位图仅在项目可见。

要绘制位图的所有者绘制组合框的编辑，在主人检查 odComboBoxEdit 绘制状态：

 键入
  TComboBox =类（StdCtrls.TComboBox）
  私人的
    FBmp：TBitmap;
    FBmpPos：TPoint;
  保护
    程序DRAWITEM（索引：整数;矩形：TRect;
      状态：TOwnerDrawState）;覆盖;
  上市
    构造函数创建（AOwner：TComponent）;覆盖;
    析构函数销毁;覆盖;
  结束;构造TComboBox.Create（AOwner：TComponent）;
开始
  继承创建（AOwner）;
  FBmp：= TBitmap.Create;
  FBmp.Canvas.Brush.Color：= clGreen;
  FBmp.Width：= 16;
  FBmp.Height：= 16;
结束;析构函数TComboBox.Destroy;
开始
  FBmp.Free;
  继承破坏;
结束;程序TComboBox.DrawItem（索引：整数;矩形：TRect;
  状态：TOwnerDrawState）;
开始
  TControlCanvas（Canvas）的.UpdateTextFlags;
  如果分配（的OnDrawItem），然后
    的OnDrawItem（自考，指数，矩形，州）
  其他
  开始
    Canvas.FillRect（矩形）;
    如果索引＆gt; = 0，则
      Canvas.TextOut（Rect.Left + 2，Rect.Top，项目[指数]）;
    如果odComboBoxEdit在状态，那么
    开始
      DEC（Rect.Right，FBmp.Width + Rect.Left）;
      FBmpPos.X：= Rect.Right + Rect.Left;
      FBmpPos.Y：=（身高 -  FBmp.Height）DIV 2;
      如果的ItemIndex＆GT;然后-1
        Canvas.TextOut（Rect.Left + 2，Rect.Top，项目[的ItemIndex]）;
      Canvas.Draw（FBmpPos.X，FBmpPos.Y，FBmp）;
    结束;
  结束;
结束;
 

为了吸取非所有者绘制组合框的位图，你将不得不使用一个定制的 WM_NCPAINT 处理组合框本身的窗口作画。

How do I put a bitmap in a combobox with style set to simple? For example, Google Chrome has the star on the right, Firefox has the arrow on the right. I tried this code:

procedure TForm2.ComboBox1DrawItem(Control: TWinControl; Index: Integer;
Rect: TRect; State: TOwnerDrawState);
var
ComboBox: TComboBox;
bitmap: TBitmap;
begin
ComboBox := (Control as TComboBox);
Bitmap := TBitmap.Create;
try
ImageList1.GetBitmap(0, Bitmap);
with ComboBox.Canvas do
begin
  FillRect(Rect);
  if Bitmap.Handle <> 0 then Draw(Rect.Left + 2, Rect.Top, Bitmap);
  Rect := Bounds(Rect.Left + ComboBox.ItemHeight + 2, Rect.Top, Rect.Right - Rect.Left, Rect.Bottom - Rect.Top);
  DrawText(handle, PChar(ComboBox.Items[0]), length(ComboBox.Items[0]), Rect, DT_VCENTER+DT_SINGLELINE);
end;
finally
Bitmap.Free;
  end;
end;

works, but only with style: csOwnerDrawFixed and csOwnerDrawVariable, also the bitmaps are only visible on the items.

Thanks.

解决方案

... also the bitmaps are only visible on the items.

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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