Q186429: HOWTO: Create Scrollable Viewports
Article: Q186429
Product(s): Microsoft Visual Basic for Windows
Version(s): WINDOWS:4.0,5.0,6.0
Operating System(s):
Keyword(s): kbCtrl kbVBp400 kbVBp500 kbDSupport
Last Modified: 11-JAN-2001
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The information in this article applies to:
- Microsoft Visual Basic Learning Edition for Windows, versions 5.0, 6.0
- Microsoft Visual Basic Professional Edition for Windows, versions 5.0, 6.0
- Microsoft Visual Basic Enterprise Edition for Windows, versions 5.0, 6.0
- Microsoft Visual Basic Standard Edition, 32-bit, for Windows, version 4.0
- Microsoft Visual Basic Professional Edition, 16-bit, for Windows, version 4.0
- Microsoft Visual Basic Professional Edition, 32-bit, for Windows, version 4.0
- Microsoft Visual Basic Enterprise Edition, 16-bit, for Windows, version 4.0
- Microsoft Visual Basic Enterprise Edition, 32-bit, for Windows, version 4.0
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SUMMARY
=======
This article demonstrates how you can create a scrollable viewport by using the
properties of two picture box controls. You can use this information to display
pictures that are larger than your default form size.
MORE INFORMATION
================
This article assumes that you are familiar with using the picture box control.
To create a scrollable viewport, you will need a picture box control inside
another picture box control. The outside picture box control acts as a
stationary parent picture box control. The inside picture box becomes the
movable child picture box control within the boundaries of the parent picture
box.
When you move the child picture box control during run-time, a clipping effect
bound by the parent picture control is created.
The next section shows you how to create a sample project that demonstrates how
to create a movable viewport. The sample requires a picture image, such as the
bitmap files stored in the following directory:
c:\Program Files\DevStudio\VB\samples\PGuide\Optimize
Steps to Create Sample Project
------------------------------
1. Start a new Standard EXE project in Visual Basic. Form1 is created by
default.
2. Add two Picture boxes to Form1. Make sure that Picture2 is sited inside
Picture1.
3. Add a horizontal scroll bar and a vertical scroll bar to Form1.
4. Copy the following code to the Code window of Form1.
NOTE: Add the path and filename to your picture file in the appropriate
section of the Form_Load event:
Option Explicit
Private Sub Form_Load()
Picture1.Move 0, 0, ScaleWidth - VScroll1.Width, _
ScaleHeight - HScroll1.Height
With Picture2
' Expand the boundaries of Picture2 picture box to the size
' of the actual bitmap.
.AutoSize = True
' Enter the path and file name as the argument to the
' LoadPicture method.
.Picture = LoadPicture("splash.bmp")
' Initialize location of both pictures.
.Move 0, 0
End With
' Position the horizontal scroll bar.
With HScroll1
.Top = Picture1.Height
.Left = 0
.Width = Picture1.Width
End With
' Position the vertical scroll bar.
With VScroll1
.Top = 0
.Left = Picture1.Width
.Height = Picture1.Height
End With
' Set the Max value for the scroll bars.
HScroll1.Max = Picture2.Width - Picture1.Width
VScroll1.Max = Picture2.Height - Picture1.Height
HScroll1.LargeChange = HScroll1.Max / 10
VScroll1.LargeChange = VScroll1.Max / 10
HScroll1.SmallChange = HScroll1.Max / 25
VScroll1.SmallChange = VScroll1.Max / 25
' Determine if child picture will fill up screen.
' If so, then there is no need to use scroll bars.
VScroll1.Visible = (Picture1.Height < Picture2.Height)
HScroll1.Visible = (Picture1.Width < Picture2.Width)
End Sub
Private Sub HScroll1_Change()
' Picture2.Left is set to the negative of the value because
' as you scroll the scroll bar to the right, the display
' should move to the Left, showing more of the right
' of the display, and vice-versa when scrolling to the
' left.
Picture2.Left = -HScroll1.Value
End Sub
Private Sub VScroll1_Change()
' Picture2.Top is set to the negative of the value because
' as you scroll the scroll bar down, the display
' should move up, showing more of the bottom
' of the display, and vice-versa when scrolling up.
Picture2.Top = -VScroll1.Value
End Sub
Private Sub Form_Resize()
' The Picture1 picture box dimensions are changed when the form
' size is changed.
With Picture1
.Height = Form1.Height
.Width = Form1.Width
End With
' Re-Initializes picture positions & scroll bars.
Picture1.Move 0, 0, ScaleWidth - VScroll1.Width, _
ScaleHeight - HScroll1.Height
Picture2.Move 0, 0
With HScroll1
.Top = Picture1.Height
.Left = 0
.Width = Picture1.Width
.Max = Picture2.Width - Picture1.Width
End With
With VScroll1
.Top = 0
.Left = Picture1.Width
.Height = Picture1.Height
.Max = Picture2.Height - Picture1.Height
End With
' Checks to see if scroll bars are needed
VScroll1.Visible = (Picture1.Height < Picture2.Height)
HScroll1.Visible = (Picture1.Width < Picture2.Width)
End Sub
5. On the Run menu, click Start or press the F5 key to start the program. If you
do not see any scroll bars, reduce the size of the form until you see the
scroll bars.
Additional query words:
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Keywords : kbCtrl kbVBp400 kbVBp500 kbDSupport
Technology : kbVBSearch kbAudDeveloper kbZNotKeyword6 kbZNotKeyword2 kbVB500Search kbVB600Search kbVBA500 kbVBA600 kbVB500 kbVB600 kbVB400Search kbVB400 kbVB16bitSearch
Version : WINDOWS:4.0,5.0,6.0
Issue type : kbhowto
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