PRB: Form Cannot Get Focus After You Use SetParent to Move Controls to Another Form (289498)

SetParent Text1.hwnd, Form2.hwnd
SetWindowLong Text1.hwnd, GWL_STYLE, WS_CHILD
Text1.Visible = True
				

MORE INFORMATION

This problem only occurs for certain controls. For example, the Frame, Toolbar, Tabstrip, Statusbar, Progressbar, Dbgrid, Mmcontrol, Sstab, Coolbar, Updown and Flatscrollbar controls do not require the SetWindowLong workaround. Other controls, such as the Label, Image, Timer, Data, Shape, Imagelist, Adodc, Calender, and Forms 2.0 controls do not have a window handle and, thus, cannot be moved. All of the other controls exhibit the same behavior as the TextBox control.

Important: It is much more complicated to change a control and its container relationship than to change the windows relationship. Thus, Microsoft does not recommend that you use the SetParent function to change the relationship of controls or the parent window in Visual Basic.

Steps to Reproduce Behavior

1. Create a new Standard EXE project. Form1 is created by default.
2. Add a Frame control, TextBox control, and two command buttons (Command1 and Command2) to Form1.
3. On the Project menu, click Add Form to add another form (Form2) to the project.
4. On the Project menu, click Add Module to add a new module (Module1) to the project.
5. Copy the following code into Module1:

   Public Declare Function SetParent Lib "user32" Alias "SetParent" _
      (ByVal hWndChild As Long, ByVal hWndNewParent As Long) As Long
   
   Public Declare Function SetWindowLong Lib "user32" Alias "SetWindowLongA" _
      (ByVal hwnd As Long, ByVal nIndex As Long, ByVal dwNewLong As Long) _
      As Long
   
   Public Const GWL_STYLE = (-16)
   Public Const WS_CHILD = &H40000000
   					

6. Copy the following code in the general declarations for Form1:

   Option Explicit
   
   Private Sub Command1_Click()
       SetParent Frame1.hwnd, Form2.hwnd
   End Sub
   
   Private Sub Command2_Click()
       SetParent Text1.hwnd, Form2.hwnd
       ' Uncomment these two lines to work around the problem.
       'SetWindowLong Text1.hwnd, GWL_STYLE, WS_CHILD
       'Text1.Visible = True
   End Sub
   
   Private Sub Form_Load()
       Form2.Show
   End Sub
   					

7. Press the F5 key to run the project.
8. Click Command1 to move the Frame control from Form1 to Form2.
9. Click Command2 to move the TextBox control to Form2.
10. Click the Frame control on Form2, and then try to click Form1. Notice that Form1 gets the focus.
11. Click the TextBox control on Form2, and then try to click Form1. Notice that Form1 does not get the focus.
12. On the IDE toolbar, click Stop to stop the project.
13. To work around this problem, uncomment the two indicated lines in Command2_Click, and repeat the test. When you click the TextBox, Form1 gets the focus.