Is this still the best answer for this problem?
I have an app that allows to either see the preview of the report or create and download it as PDF.
Showing the preview works well. It can require many round trips to collect the required data, but it works.
Printing also works well, but only if the total time for starting the headless Chrome and rendering all the forms, each with its own roundtrip, is less than 30 seconds, which is the case the 99% of the times.
I thought about creating many small PDF files and stitching them together at the end, but this would mean spinning a new headless Chrome for each PDF, which would increase the time from 30 seconds to 30 minutes.
I tried passing the data as an argument to the form’s constructor as suggested, but I got an anvil.server.SerializationError error.
My next step will be to try to make my classes portable or create my own serialization and pass a 10MB json string to the form constructor. But it’s frustrating to be sitting in front of an app and thinking "this app is working, but I need to spend a few days on it so I can generate that one large PDF that shows up once every 3 months ".
This is roughly what happens when you click the Print and the Show preview buttons:
def print_click(self, **event_args):
# render the form and show it in an alert
anvil.js.window.location = anvil.server.call(
'create_pdf',
truck_number=self.truck_number,
preview_mode=False # this will hide the PDF footer
)
def show_preview_click(self, **event_args):
# ask the server to render the form as PDF
print_pdf = PrintPDF(
self.truck_number,
preview_mode=True # this will show the footer
)
alert(self.print_pdf, buttons=[], large=True)
And this is how the PDF is generated:
class PrintPDF(PrintPDFTemplate):
def __init__(self, truck_number, preview_mode=False, **properties):
self.truck = Trucks(truck_number) # triggers one round trip
self.init_components(**properties) # uses self.trucks in the databinding
self.add_component(TruckPDF(self.truck, preview_mode))
for crate in self.truck.crates: # generator triggers one round trip per item
self.add_component(PageBreak()) # anvil_extras.PageBreak
self.add_component(CratePDF(crate, preview_mode))