BackColor Erases Existing Graphics on Form or Picture Control

- Standard and Professional Editions of Microsoft Visual Basic for

  Windows, versions 2.0 and 3.0

SUMMARY

Setting the BackColor property on forms or picture boxes at run time erases all previous printed graphics and output, including a persistent bitmap. This behavior is by design. Setting the ForeColor property does not affect the graphics or print output that are already drawn.

Setting the BackColor property on other controls, such as list boxes, text boxes, or combo boxes, does not erase previously added items.

MORE INFORMATION

NOTE: A persistent bitmap is a bitmap, accessed with the Image property, that stores output from graphics methods in memory. For more information, see the following items in the Visual Basic Help menu:

• AutoRedraw property
• persistent bitmap

Steps to Reproduce Behavior

1. Start a new project in Visual Basic. Form1 is created by default.

2. Add a list box and a picture box to Form1.

3. Double-click the form to open the code window. Add the following code to the Form Load event:

      Sub Form_Load ()
         form1.Show 'In Load event, must show form before Print works
   
         picture1.ForeColor = QBColor(1)
         picture1.BackColor = QBColor(11)
         picture1.Print "color1"
         form1.ForeColor = QBColor(1)
         form1.BackColor = QBColor(12)
         form1.Print "color1"
         list1.ForeColor = QBColor(1)
         list1.BackColor = QBColor(11)
         list1.AddItem "color1"
   
         MsgBox "click to see next color"
         picture1.ForeColor = QBColor(2)
         picture1.BackColor = QBColor(10)  'This BackColor erases picture1
         picture1.Print "color1"
         form1.ForeColor = QBColor(2)
         form1.BackColor = QBColor(13)  'This BackColor erases form1
         form1.Print "color1"
         list1.ForeColor = QBColor(2)
         list1.BackColor = QBColor(10)  'This BackColor doesn't erase List1
         list1.AddItem "color2"
   
         MsgBox "click to see next color"
         picture1.ForeColor = QBColor(4)
         picture1.BackColor = QBColor(14)  'This BackColor erases picture1
         picture1.Print "color1"
         form1.ForeColor = QBColor(4)
         form1.BackColor = QBColor(8)  'This BackColor erases form1
         form1.Print "color1"
         list1.ForeColor = QBColor(4)
         list1.BackColor = QBColor(14)  'This BackColor doesn't erase List1
         list1.AddItem "color3"
   
      End Sub
   
   

4. Start the program or press the F5 key. Click OK to see the next color. To end the program, close the form.

• Changing the Form1.BackColor property erases the text that you previously printed on Form1.
• Changing the Picture1.BackColor property erases the text that you previously printed on Picture1.
• Changing the List1.BackColor property does not erase the text that you previously added to the List1 list box.