title: vcl combobox doesn't always show that it has focus
body: <p>When I tab from another control to a combo box it shows the box with a dotted line around the text, but when I set the control to be active programmatically, it doesn't show the same focus indicator.</p>
  
  <p>Is there a work-around for this behaviour?</p>
  
  <p>I have Delphi XE6</p>
  
  <hr>
  
  <p>MCVE</p>
  
  <pre><code>unit Unit27;
  interface
  uses
    Winapi.Windows, Winapi.Messages, System.SysUtils, System.Variants, System.Classes, Vcl.Graphics,
    Vcl.Controls, Vcl.Forms, Vcl.Dialogs, Vcl.ComCtrls, Vcl.StdCtrls, Vcl.ExtCtrls;
  
  type
    TForm27 = class(TForm)
      Edit1: TEdit;
      Button1: TButton;
      ComboBox1: TComboBox;
      procedure Button1Click(Sender: TObject);
    private
    public
    end;
  
  var
    Form27: TForm27;
  
  implementation
  {$R *.dfm}
  
  procedure TForm27.Button1Click(Sender: TObject);
  begin
    ComboBox1.SetFocus;
  end;
  
  end.
  
  object Form27: TForm27
    Left = 0
    Top = 0
    Caption = 'Form27'
    ClientHeight = 90
    ClientWidth = 246
    Color = clBtnFace
    Font.Charset = DEFAULT_CHARSET
    Font.Color = clWindowText
    Font.Height = -11
    Font.Name = 'Tahoma'
    Font.Style = []
    OldCreateOrder = False
    PixelsPerInch = 96
    TextHeight = 13
    object Edit1: TEdit
      Left = 16
      Top = 8
      Width = 121
      Height = 21
      TabOrder = 0
      Text = 'Edit1'
    end
    object Button1: TButton
      Left = 152
      Top = 8
      Width = 75
      Height = 25
      Caption = 'Button1'
      TabOrder = 1
      OnClick = Button1Click
    end
    object ComboBox1: TComboBox
      Left = 16
      Top = 39
      Width = 145
      Height = 21
      Style = csDropDownList
      ItemIndex = 2
      TabOrder = 2
      Text = '2'
      Items.Strings = (
        '0'
        '1'
        '2'
        '3')
    end
  end
  </code></pre>
  
  <p><a href="https://i.stack.imgur.com/7fP6w.png" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/7fP6w.png" alt="enter image description here"></a></p>
  
  <p>Start the app and left-click on <code>Button1</code>, which calls</p>
  
  <pre><code>  ComboBox1.SetFocus;
  </code></pre>
  
  <p>Notice that <strong>no focus rectangle is drawn</strong>, but the combo has focus as the following shows:
  Hit keyboard arrow up or arrow down. The combo item changes and now the focus rectangle becomes visible.
  After the focus rectangle once is shown, it is also drawn on the combo after a mouse click on Button1. So to repeat the problem, restart the app.</p>