BUG: Scrollbars Disappear if Objects Placed Past Certain Length

• Microsoft Visual FoxPro for Windows, version 6.0

SYMPTOMS

After placing objects on a form that has scrollbars, the objects will not be seen and the scrollbars will disappear when the form is run. This happens when the objects have been placed too far vertically or horizontally down or across the form.

CAUSE

Visual FoxPro 6.0's forms were designed to have scrollbars that only scroll approximately twice the length or width of the computer's video resolution. Placing any objects past this point will result in the scrollbars disappearing from the form.

RESOLUTION

Do not set the Top and Left properties of any objects past the formula described in the MORE INFORMATION section below.

STATUS

Microsoft has confirmed this to be a bug in the Microsoft products listed at the beginning of this article.

MORE INFORMATION

By design, objects should not be placed beyond the coordinates (video resolution * 2 - object height or width) in a form. For example, if the video resolution is 800x600, then placing a command button's Top property to 1173 (600 * 2 - 27) on a form with vertical scrollbars will allow the user to scroll down the form and select that command button at run-time. If the command button's Top property is set to 1174, then the scrollbars will disappear and the command button cannot be accessed. This number is based on the vertical resolution being 600, and the height of the command button being 27.

The same situation occurs if the command button is positioned on a form with horizontal scrollbars. Setting the Left property of the command button to 1516 (800 * 2 - 84) would allow the user to scroll across the form and select the command button. Any number higher than that will make the scrollbars disappear on the form.

This can be a problem if the form is run on another computer with a lower resolution setting. For example, if a form is created on a computer with 1024x768 resolution and then run on a computer with 800x600 resolution, the scrollbars are not be visible at the lower resolution. To ensure that the scrollbars are visible at all resolutions, any objects placed on the form would have to be set to the above formula using 640x480 as the base for the video resolution.

It is not by design that the scrollbars disappear if an object is placed past these points: the scrollbars should stay active, but the user would not be able to scroll to any object that has been placed past these coordinates.

Steps to Reproduce Behavior

1. Run the following code. It creates a form with vertical and horizontal scrollbars that will have a command button in the bottom-right corner when both scrollbars are scrolled all the way down and right:




     scr_horizontal=SYSMETRIC(1) * 2 - 84 && Add one to the width or height
     scr_vertical=SYSMETRIC(2) * 2 - 27   && and the scrollbars will disappear.
     ? scr_horizontal
     ? scr_vertical
     DO get_form with scr_horizontal, scr_vertical

     PROCEDURE get_form

     PARAMETERS but_width, but_height
     PUBLIC oform1
     oform1=NEWOBJECT("form1")
     oform1.Show
     RETURN

     ****************************************
     DEFINE CLASS form1 AS form
              Top = 0
              Left = 0
              Height = 241
              Width = 209
              ScrollBars = 3
              DoCreate = .T.
              Caption = "Form1"
              Name = "Form1"

                     ADD OBJECT command1 AS commandbutton WITH ;
                            Top = 0, ;
                            Left = 0, ;
                            Height = 27, ;
                            Width = 84, ;
                            Caption = "Command1", ;
                            Name = "Command1"

                       PROCEDURE Init
                             Thisform.Command1.Left = but_width
                             Thisform.Command1.Top = but_height
                      ENDPROC
     ENDDEFINE 

2. Increase the values of either the scr_horizontal or scr_vertical variable by one (1) and note that the scrollbars disappear.

REFERENCES

For additional information about Scrollbars on forms, please see the following article in the Microsoft Knowledge Base:


Q193749 PRB: Setting Scrollbars > 0 Changes Height and Width Property

Additional query words:

Keywords          : kbContainer kbCtrl kbVFp kbVFp600bug kbGrpFox 
Version           : WINDOWS:6.0
Platform          : WINDOWS 
Issue type        : kbbug 

Last Reviewed: May 26, 1999