[okular] [Bug 464716] New: Very slow render time on restaurant menu

[Reuben]

https://bugs.kde.org/show_bug.cgi?id=464716

            Bug ID: 464716
           Summary: Very slow render time on restaurant menu
    Classification: Applications
           Product: okular
           Version: 22.08.1
          Platform: Other
                OS: Linux
            Status: REPORTED
          Severity: normal
          Priority: NOR
         Component: PDF backend
          Assignee: okular-devel at kde.org
          Reporter: kde at flavor8.com
  Target Milestone: ---

Created attachment 155544
  --> https://bugs.kde.org/attachment.cgi?id=155544&action=edit
restaurant menu

SUMMARY

I've attached a 2.5MB 7 "page" restaurant menu. It looks like it's just one
long image rather than properly encoded.

Scrolling through this menu using the pager in the sidebar, there are 5-6
second pauses where the page that is scrolled to just displays as a white
screen before it renders (on an 8 core i7). There appears to be no caching of
previously rendered content (despite 32GB of ram being available) so scrolling
up a previous page has the same issue, even if it was rendered just 30 seconds
before. This seems to happen less when the app isn't full screened, so there
may be some upscaling happening that slows it down.


STEPS TO REPRODUCE
1. Open attached document
2. Scroll using the sidebar (you may need to scroll up and down fast to trigger
it)
3. 

OBSERVED RESULT
White screen for extensive period while rendering happens

EXPECTED RESULT
No delay in rendering

SOFTWARE/OS VERSIONS
Windows: 
macOS: 
Linux/KDE Plasma: Ubuntu 22.10
Operating System: Kubuntu 22.10
KDE Plasma Version: 5.25.5
KDE Frameworks Version: 5.98.0
Qt Version: 5.15.6
Kernel Version: 5.19.0-29-generic (64-bit)
Graphics Platform: X11
Processors: 8 × Intel® Core™ i7-6700K CPU @ 4.00GHz
Memory: 30.8 GiB of RAM
Graphics Processor: Mesa Intel® HD Graphics 530
Manufacturer: MSI
Product Name: MS-7978
System Version: 1.0

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