Right to left ComboBox in Delphi XE2 with styles

问题

I have problems when I use ComboBox in Delphi XE2 with Custom styles(Emerald Light Slate) and this property:

BiDiMode := bdRightToLeft;
Style := csDropDownList;

That ComboBox without Custom style:

And with Custom styles(Emerald Light Slate):

How i can fix it?

回答1:

The issue it seems located in the DrawItem method of the TComboBoxStyleHook (the vcl style hook of the TComboBox), you can fix this overriding this method.

Try this sample code (this solution is far from being perfect but is a start)

type
  TComboBoxStyleHookFix = class(TComboBoxStyleHook)
  protected
    procedure DrawItem(Canvas: TCanvas; Index: Integer;
      const R: TRect; Selected: Boolean); override;
  end;

{ TComboBoxStyleHookFix }

procedure TComboBoxStyleHookFix.DrawItem(Canvas: TCanvas; Index: Integer;
  const R: TRect; Selected: Boolean);
var
  DIS  : TDrawItemStruct;
  Text : string;
begin
  if Control.BiDiMode<>bdRightToLeft then
   inherited
  else
  begin
    FillChar(DIS, SizeOf(DIS), 0);
    DIS.CtlType := ODT_COMBOBOX;
    DIS.CtlID := GetDlgCtrlID(Handle);
    DIS.itemAction := ODA_DRAWENTIRE;
    DIS.hDC := Canvas.Handle;
    DIS.hwndItem := Handle;
    DIS.rcItem := R;
    Text:=TComboBox(Control).Items[Index];    
    DIS.rcItem.Left:=DIS.rcItem.Left+ (DIS.rcItem.Width-Canvas.TextWidth(Text)-5);    
    DIS.itemID := Index;
    DIS.itemData := SendMessage(ListHandle, LB_GETITEMDATA, 0, 0);
    if Selected then
      DIS.itemState := DIS.itemState {or ODS_FOCUS} or ODS_SELECTED;
    SendMessage(Handle, WM_DRAWITEM, Handle, LPARAM(@DIS));
  end;
end;

and use in this way

 TStyleManager.Engine.RegisterStyleHook(TComboBox, TComboBoxStyleHookFix);

Don't forget report this bug in the QC page of Embarcadero.

来源：https://stackoverflow.com/questions/12152880/right-to-left-combobox-in-delphi-xe2-with-styles