Using a Common Dialog Box to Print Contents of Various Controls


I am trying to print the contents of a RichTextBox using a Windows Common Dialog Box component.

It works to print, if I select OK. If I select Cancel the program crashes with a run-time error #32755.

The name of the common dialog box is 'cmdEd'. It was coded by another developer, without comments, to print the contents of the rtfDisplay RichTextBox control.

The code is as follows:

cdgEd.Flags = cdlPDReturnDC + cdlPDNoPageNums
  If rtfDisplay.SelLength = 0 Then
     cdgEd.Flags = cdgEd.Flags + cdlPDAllPages
     cdgEd.Flags = cdgEd.Flags + cdlPDSelection
  End If
  rtfDisplay.SelPrint cdgEd.hDC

I presently don't understand these 'Flags'. I know how to code the vbOKOnly or vbCancel on a message box.

How does one properly code this dialog component to insure that clicking on cancel truly does cancel and unload the dialog?

Who is Participating?
AzraSoundConnect With a Mentor Commented:
>>Does this Cancel button need to be coded to Exit Sub when a user clicks it?

Yes, otherwise, you have no idea whether or not to proceed with the print operation.  For example, look at this logic:

'Without having cancel throw an error
Show print dialog
Try to print with the selected printer  <~~ If nothing was selected (e.g., they pressed cancel), you have no printer to print to
When you call:
[RichTextBox.SelPrint dialogSelectedPrinter.hDC]
the selected printer is nothing, thus, no valid hDC (handle to a device context) is passed

'With cancel throwing an error
On Error SkipAllCode
You still have all your code from above, but its bypassed if the user presses cancel, and taken to your error handling routine
   If Err.Number = cdlCancel
      'user pressed cancel, you can do nothing, ask if they are sure they want to cancel the print, etc.
   End If

You should be able to trap otherwise, even with CancelError set to False, by testing to be sure the hDC is not 0 before trying to print with it.  However, using the more popular form of error handling is probably the way to go.
try something like this:

Private Sub Command1_Click()
On Error Goto Problems
  'Other code here
  Exit Sub
  If Err.Number = 32755 Then
    Exit Sub
    MsgBox Err.Description
  End If
End Sub

hope this works!
They have set the CancelError to true.  This allows you to determine when a user presses cancel and take any necessary action, e.g,

Sub PrintStuff()
   On Error Goto PrintStuff_EH


   If Err.Number = cdlCancel Then
      'User pressed cancel
   End If
End Sub
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Sorry, CancelError property of the common dialog control.
Richie_SimonettiIT OperationsCommented:
jnowlin, i would like to ask for which reason do you use a commondialog to print richtrextbox.
If i remember well, it has incorporated that funcionality itself:RichTextBox1.selprint
Richie_SimonettiIT OperationsCommented:
Sorry forget my comment.
jnowlinAuthor Commented:
Hi AzraSound,

I changed the CancelError property of this common dialog control to False. When I ran the program, opened a file into the RichTextBox control, 'rtfDisplay', and selected "Cancel" instead of "Print", I got a different run-time error:

Error #32001
"Invalid HDC"

I don't know what HDC means. It must be some sort of relationship between the common dialog control and the print dialog that opens up within Windows2000 that I'm still unclear about.

Does this Cancel button need to be coded to Exit Sub when a user clicks it?

When dealing with a CommonDialog Control, I always go something like this

With cdgEd
  .CancelError=True  'always usefull
  .Flags = cdlPDReturnDC + cdlPDNoPageNums
  If rtfDisplay.SelLength = 0 Then
    .Flags = .Flags + cdlPDAllPages
    .Flags = .Flags + cdlPDSelection
 End If
 On Error Resume Next 'just for the dialog
 If Err = cdlCancel Then Exit Sub 'user pressed cancel
 On Error Goto 0 'disable error handler
 rtfDisplay.SelPrint .hDC
End With

This is a bit like the examples above, except that Error Handling is only enabled for the Commondialog Control when showing the Printbox.

After showing the Printbox and checking if the user presses cancel, ErrorHandling is disabled so that you can see other errors, should they occur.

Just scream 4 more ;)
jnowlinAuthor Commented:
Thanks AzraSound,

I'm posting another question involving the common dialog control, as this project has code on it (not mine), is poorly commented and I have next to nothing for documentation on this control.

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