[RESOLVED] PrintPreviewDialog showing last page only

[Aussie]

Hi,
I am using visual basic net on VS2019 windows 10.
Scenario.
Our store has a regular catalogue of specials which can include hundreds of products.
We have pre-printed pages with blank areas for us to print on. These pages are perforated so they separate into tickets (as many as 8 per page).

Prior to the PrintPage event
I have written code which creates a list of pages. (Basically a list of classes showing what to draw)
I have not included this code below because it works fine.
I have set the dialog document property to mdoc after setting the mdoc.defaultpagesettings etc

Problem
The printpreview only displays the last page.
The mdoc_printpage event is fired by my calling the printpreviewdialog.showdialog method after creating my list of pages i.e. _Pages()

Here is my code...

Private Sub mDoc_PrintPage(ByVal sender As Object, ByVal e As System.Drawing.Printing.PrintPageEventArgs) Handles MDoc.PrintPage
        Try
            With e.Graphics
                .TextRenderingHint = Drawing.Text.TextRenderingHint.AntiAlias
                'loop pages in the list
                For i2 = 0 To _Pages.Count - 1
                    'get the elements to draw on this page
                    Dim _Elements As List(Of ClsElement) = _Pages(i2).GetElements
                    'loop elements and draw
                    For i = 0 To _Elements.Count - 1
                        'description
                        Dim Xpos As Integer = _Elements(i).Rect.X + (_Elements(i).Rect.Width / 2)
                        Dim yPos As Integer = _Elements(i).Rect.Top + 3
                        Dim A As New StringFormat
                        A.Alignment = StringAlignment.Center
                        A.LineAlignment = StringAlignment.Near
                        Dim St As Integer = _Elements(i).SetText(e.Graphics)
                        .DrawString(_Elements(i).text, FontMedProp, Brushes.Black, Xpos, yPos, A)
                        'price
                        yPos = _Elements(i).Rect.Top + (_Elements(i).Rect.Height / 2) + 10
                        .DrawString(_Elements(i).price, FontLgeProp, Brushes.Black, Xpos, yPos, A)
                        'barcode
                        yPos = _Elements(i).Rect.Bottom - 20
                        A.Alignment = StringAlignment.Near
                        .DrawString(_Elements(i).barcode, FBarcodeHalf, Brushes.Black, Xpos, yPos, A)
                        A.Alignment = StringAlignment.Far
                        .DrawString(_Elements(i).barcode, FontSmlProp, Brushes.Black, Xpos, yPos, A)
                        .DrawRectangle(Pens.Black, _Elements(i).Rect)
                    Next
                    'start a new page?
                    If i2 = _Pages.Count - 1 Then
                        e.HasMorePages = False
                        Exit Sub
                    Else
                        e.HasMorePages = True
                    End If
                Next
            End With

        Catch ex As Exception
            WriteToErrorFile(ex)
        End Try
    End Sub

I can't see where I have gone wrong.
I suspect e.hasmorepages is the culprit but it looks OK to me.

Any ideas anyone?
Thanks in advance.

[.paul.]

It is overwriting your previous pages, if I’m not mistaken. You need to use a variable outside the print page to hold the current page, so instead of…

For i = 0 To _Elements.Count - 1

You’d use…

For i =  yourExternalVariable To yourExternalVariable

You’d increment yourExternalVariable by one after the loop, and set e.hasmorepages to true, only if yourExternalVariable < pages.count

[.paul.]

I’m not at my computer at the moment, but it looks like it’s the i2 loop you need to change as I suggested…

[jmcilhinney]

If you have a list of N items and you want to print M to a page then your code should look something like this:

Private Const ItemsPerPage As Integer = 8
 
Private items As New List(Of String)
Private startIndexForPage As Integer
 
Private Sub PrintDocument1_BeginPrint(sender As Object, e As PrintEventArgs) Handles PrintDocument1.BeginPrint
    startIndexForPage = 0
End Sub
 
Private Sub PrintDocument1_PrintPage(sender As Object, e As Printing.PrintPageEventArgs) Handles PrintDocument1.PrintPage
    'Print up to the number of items per page or the end of the list, whichever comes first.
    For i = startIndexForPage To Math.Min(items.Count, startIndexForPage + ItemsPerPage) - 1
        'Print item at index i.
    Next
 
    startIndexForPage += ItemsPerPage
 
    'There are more pages to print if and only if the start index is still within the bounds of the list.
    e.HasMorePages = startIndexForPage < items.Count
End Sub

[jmcilhinney]

In the code you posted, is _Pages a list of objects that are to be printed one to a page? If so then why do you have a loop over that list in your PrintPage event handler? As the name suggests, the PrintPage event handler prints a page. If you have a list of pages to print then you process one item from that list each time the PrintPage event is raised. If _Pages is such a list then you need an index into that list stored OUTSIDE the PrintPage event handler. That index needs to be initialised to zero and incremented in the event handler, e.g.

Private items As New List(Of String)
Private itemIndex As Integer
 
Private Sub PrintDocument1_BeginPrint(sender As Object, e As PrintEventArgs) Handles PrintDocument1.BeginPrint
    itemIndex = 0
End Sub
 
Private Sub PrintDocument1_PrintPage(sender As Object, e As Printing.PrintPageEventArgs) Handles PrintDocument1.PrintPage
    'Print the item at itemIndex here.
 
    itemIndex += 1
 
    e.HasMorePages = itemIndex < items.Count
End Sub

[Aussie]

Thanks guys.
You were right jmcilhinney. My mistake was not realising the e.hasmorepages re-triggers the printpage event.
Once I took that first loop out everything fell into place.
I will mark this as resolved.
Thanks again.