How do I reposition "Page X of Y" for different PageTemplates in ReportLab?

Question

This is my first time using ReportLab, and I've been stuck on this problem for a couple days. There are two main components to this issue: 1) Some of my pages are portrait and some are landscape. I'm using two different PageTemplates for this, but since I just learned how to use PageTemplates today, I may not be doing it correctly. 2) I'm including a "Page X of Y" on each page, but that's done with code on the canvas instead of the PageTemplates, since the people who wrote the code I'm using said that PageTemplates can't know how many pages are in the entire document, while the canvas can.

Imports:

from reportlab.pdfgen import canvas
from reportlab.lib.pagesizes import letter, landscape
from reportlab.lib.units import inch
from reportlab.platypus import SimpleDocTemplate, Frame, Table, TableStyle, Image, Paragraph, PageBreak, PageTemplate, NextPageTemplate

Here's the code that numbers the pages in the canvas (as well as a two-part header):

class NumberedCanvas(canvas.Canvas):
    def __init__(self, *args, **kwargs):
        canvas.Canvas.__init__(self, *args, **kwargs)
        self._saved_page_states = []

    def showPage(self):
        self._saved_page_states.append(dict(self.__dict__))
        self._startPage()

    def save(self):
        """add page info to each page (page x of y)"""
        num_pages = len(self._saved_page_states)
        for state in self._saved_page_states:
            self.__dict__.update(state)
            self.draw_page_number(num_pages)
            canvas.Canvas.showPage(self)
        canvas.Canvas.save(self)

    def draw_page_number(self, page_count):
        self.setFont('Helvetica',8)
        self.drawString(x=0.25*inch, y=10.5*inch, text='This is the upper left header')
        self.drawRightString(x=8.25*inch, y=10.5*inch, text='This is the upper right header')
        self.drawRightString(x=8.25*inch, y=0.5*inch, text='Page %d of %d' % (self._pageNumber, page_count))

Here's the code for the document template and the 'portrait' and 'landscape' PageTemplates:

doc = SimpleDocTemplate('output.pdf', pagesize=letter, topMargin=0.5*inch, bottomMargin=0.6*inch)

portrait_frame = Frame(doc.leftMargin, doc.bottomMargin, doc.width, doc.height, id='portrait_frame ')
landscape_frame = Frame(doc.leftMargin, doc.bottomMargin, 
                        width=letter[1]-doc.leftMargin-doc.rightMargin,
                        height=letter[0]-doc.topMargin-doc.bottomMargin, id='landscape_frame ')

doc.addPageTemplates([PageTemplate(id='portrait',frames=portrait_frame),
                      PageTemplate(id='landscape',frames=landscape_frame, pagesize=landscape(letter))
                     ])

Here's how I create the story and build the pdf:

elements = []
# Page 1 is portrait orientation (side question: page 1 and only page 1 defaults to the first AddTemplate created- why is that? I had to create the portrait PageTemplate just because of that.)
elements.append(--generate logo--)
elements.append(--generate paragraph--)
elements.append(PageBreak())
# Page 2 is portrait orientation
elements.append(--generate table--)
elements.append(NextPageTemplate('landscape'))
elements.append(PageBreak())
# Page 3 is landscape orientation
elements.append(--generate table--)

doc.build(elements, canvasmaker=NumberedCanvas)

The problem is that the two header parts and page number are in the same position on the landscape page as they would be on a portrait page, and the reason is obvious- that's how draw_page_number is coded in the NumberedCanvas class (the result is that the page number is an additional 1.25 inches from the right side of the page, and the headers aren't even visible because they're above the top of the page). If I could access the id of the PageTemplate during the for loop in the NumberedCanvas's save function, I could set up a simple if statement, calculate the appropriate x and y locations for the headers and page number, and send those to the draw_page_number function. However, I looked at the contents of the state variable during the loop and couldn't find anything to indicate what kind of page I was on.

Is there a solution to this? Please know that I'm very shaky when it comes to understanding how classes work, so if I have to rewrite some things in there, I'd really appreciate any details and background as you'd care to give me.

score 0 · Answer 1 · answered Dec 15 '20 at 21:00

First, there is a possibly unrelated change I was forced to make. I'm including it in case it's critical to the particular solution to my problem. When I was switching between templates, nextPageTemplate was only working for one page at a time, even if I wanted it to be repeating. i.e. nextPageTemplate('landscape') will result in the next page being landscape, while nextPageTemplate(['landscape']) should have resulted in all following pages being landscape, but only did the next page. This was important to me in case the tables in my document were split. In order to fix this, my document had to be changed from a SimpleDocTemplate to a BaseDocTemplate.

Then I had to keep track of the page templates as the pages were produced, which I did with my page_templates list. This was done by creating my own doc template class, based on BaseDocTemplate, and overwriting the beforePage method.

page_templates = []

class MyDocTemplate(BaseDocTemplate)

     def beforePage(self):
          page_templates.append(self.pageTemplate.id) # tracks 'portrait'/'landscape' pages

I then altered the save method in NumberedCanvas class to count the pages and send 'portrait' or 'landscape' to the draw_page_number method, which used it to properly place the headers and footers. (In hindsight, I should have renamed draw_page_number to draw_headers_footers.)

def save(self):
    """add page info to each page (page x of y)"""
    num_pages = len(self._saved_page_states)
    for i, state in enumerate(self._saved_page_states): # counting pages with i
        self.__dict__.update(state)
        self.draw_page_number(num_pages, page_templates[i]) # send 'portrait'/'landscape'
        canvas.Canvas.showPage(self)
    canvas.Canvas.save(self)

def draw_page_number(self, page_count, pagetemplate): # Includes add'l upgrades from original
    self.setFont('Helvetica',8)
    pwidth, pheight = (letter[0], letter[1]) if pagetemplate=='portrait' else (letter[1], letter[0])
    self.drawString(x=0.25*inch, y=pheight-0.5*inch, text='This is the upper left header')
    self.drawRightString(x=pwidth-0.25*inch, y=pheight-0.5*inch, text='This is the upper right header')
    self.drawRightString(x=pwidth-0.25*inch, y=0.5*inch, text='Page %d of %d' % (self._pageNumber, page_count))

How do I reposition "Page X of Y" for different PageTemplates in ReportLab?

1 Answers1