BUG: Z-Order Behavior Different with OLE (.OCX) Controls

MORE INFORMATION

The following OLE (.OCX) controls act like lightweight (non-windowed) controls at design time in Visual Basic 4.0:

AniPushButton      MAPIMessages      Slider
CommonDialog       MAPISession       SpinButton
CrystalReport      MaskEdBox         SSCheck
DBCombo            MhState           SSCommand
DBGrid             MMControl         SSOption
DBList             MSComm            SSRibbon
Graph              MSRDC             StatusBar
Grid               Outline           TreeView
ImageList          PictureClip
ListView           ProgressBar
				

NOTE: The OLE container control is a lightweight control in Visual Basic 4.0.

The DBGrid control cannot be placed underneath a windowed control at run-time with the z-order method. Use the z-order method of the windowed control to place it on top of the DBGrid control instead.

The 16-bit Graph control places itself on top of windowed controls at run-time. Use its z-order method to place it underneath other windowed controls.

The 32-bit MaskEdBox control places itself on top of windowed controls (except for the DBGrid control as noted above) at run-time. Use its z-order method to place it underneath other windowed controls.

The Toolbar control places itself on top of windowed controls (except for the DBGrid control as noted above) at run-time. Use its z-order method to place it underneath other windowed controls.

Steps to Reproduce Problem

1. Start Visual Basic or click New Project (ALT, F, N) on the File menu if Visual Basic is already running. Form1 is created by default.
2. Place the following controls on Form1 in the ORDER listed and in the POSITIONS diagrammed below: Command1, Command2, Command3, Command4, Command5, Command6, Label1, Grid1 and Picture1:

           ------------------------------
          | --------  --------  -------- |
          ||Command1||Command3||Command5||
          | --------  --------  -------- |
          | --------  --------  -------- |
          ||Command2||Command4||Command6||
          | --------  --------  -------- |
          |  --------------              |
          | |Label1        |             |
          | |           ---------------  |
          | |          |Picture1       | |
          | |   -------|               | |
          | |  |Grid1  |               | |
          |  --|       |               | |
          |    |        ---------------  |
          |    |                |        |
          |     ----------------         |
           ------------------------------
   						

3. Place the following code in Form1:

      Private Sub Form_Load()
          Command1.Caption = "Bring to Front - Label1"
          Command2.Caption = "Send to Back - Label1"
          Label1.BorderStyle = 1
          Command3.Caption = "Bring to Front - Grid1"
          Command4.Caption = "Send to Back - Grid1"
          Command5.Caption = "Bring to Front - Picture1"
          Command6.Caption = "Send to Back - Picture1"
      End Sub
   						

4. Place the following code in Command1:

      Private Sub Command1_Click()
          Label1.ZOrder 0 'Bring to Front
      End Sub
   						

5. Place the following code in Command2:

      Private Sub Command2_Click()
          Label1.ZOrder 1 'Send to Back
      End Sub
   						

6. Place the following code in Command3:

      Private Sub Command3_Click()
          Grid1.ZOrder 0 'Bring to Front
      End Sub
   						

7. Place the following code in Command4:

      Private Sub Command4_Click()
          Grid1.ZOrder 1 'Send to Back
      End Sub
   						

8. Place the following code in Command5:

      Private Sub Command5_Click()
          Picture1.ZOrder 0 'Bring to Front
      End Sub
   						

9. Place the following code in Command6:

      Private Sub Command6_Click()
          Picture1.ZOrder 1 'Send to Back
      End Sub
   						

10. Select the Grid control and choose "Send to Back" from the Edit menu. Notice that the Grid control IS underneath the Label control. In Visual Basic 3.0, the Grid control remains on top of the Label control.
11. Select the PictureBox control and on the Edit menu, click "Send to Back". Notice that the PictureBox control IS NOT underneath the Grid control. In Visual Basic 3.0, the PictureBox control is underneath the Grid control.
12. Run the application. If you left the Grid control underneath the Label control, notice that it IS NOT underneath the Label control now. Click the "Send to Back - Grid1" button. Notice that the Grid control IS NOT underneath the Label control now either. This is the way Visual Basic 3.0 behaves.
13. Click the "Send to Back - Picture1" button. Notice that the PictureBox control IS now underneath the Grid control. This is the way Visual Basic 3.0 behaves.

Experiment with this application at both design and run-time. Notice how at design time most OLE (.OCX) controls act like lightweight or non-windowed controls while at run-time they act like windowed controls. When porting a Visual Basic 3.0 project to Visual Basic 4.0, overlapping controls may no longer appear in the desired z-order. Add code using the z-order method so that the controls overlap in the desired way at run-time. Under Visual Basic 3.0, the Grid control can be placed over the PictureBox control at design time. If that project is then ported to Visual Basic 4.0, the Grid control is placed underneath the PictureBox control. The only way to place the Grid control over the PictureBox control at run-time is to use its z-order method.