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Capture scrolling screenshot on Mac is stuck on processing extremely long pages

Pages: 1
Posted:  05 Sep 2021 01:45
Plugin version: FireShot 0.99.15
OS type and version: Microsoft Windows 10 Professional (x64) Build 19043.1165
Version of browser: Firefox 91.0.2 (64-bit)

Running the latest available version of Fireshot, and I noticed now instead of crashing with an out-of-memory error on extremely long pages, it simply hangs on the "Processing..." progress bar, which never moves. I suspect this is triggered when the capture exceeds 65,536 pixels in height (and probably width too, but I have no examples of any web pages that wide). This happens even if multi-page PDF is the output format. I suspect there is some internal capture buffer that maxes out at 64K pixels. On my 4K display, that's only about 30 screen heights worth of content (each screen is 2160 pixels tall).

I can understand how this would be an issue saving to a single PNG or JPEG, as I believe the file format specifications have a maximum image dimension of 64K pixels. But with a PDF, FireShot should be able to create multiple pages, each up to 64K pixels tall.
Posted:  06 Sep 2021 20:22
Thank you for reporting. Will it remain in "Processing" even if you leave it for 1 hour? It's important for me to distinguish hangup from a slow process of memory swap to find the cause of that problem.
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Posted:  08 Sep 2021 06:24
I have left it running for a very long time because I forget about it and the Processing window is hidden behind some other ones. I can't say exactly for how long, but it could very well have been over an hour. Also, if I capture a slightly shorter page just below the suspected 64K pixel limit, the processing does take several seconds, but it still completes quickly. There is plenty of free RAM while FireShot is stuck processing, so I doubt it is swap/paging activity slowing it down. If it isn't an image buffer size limit, perhaps there is a per-process memory limit?

My particular test case is long Facebook threads, expanding all the comments and replies using the "Expand All" bookmarklet at https://com.hemiola.com/bookmarklet/. If you don't have a long enough thread, use Firefox's viewport zoom feature to artificially enlarge the page until you reach the limit. I will usually zoom to 150% to capture better looking text for high-density displays, but Firefox will go up to 500% zoom.
Pages: 1

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