Breakage and low performance while viewing RAW files

[luther09]

Environment:

• OS: Windows 10
• qView version: 6.1

Information:

In the file below there are 10 images in .cr2 format. Open one of them and try to move forward with the keyboard right arrow key. The application takes too long to show the next image.

https://1drv.ms/u/c/d3ebeefc2aca61e6/EfhX2HRr9ohJn_Z9P-Uj45IBgSjyU0aLpNzKRFgjz2tIFQ?e=by68Sm

If you keep pressing the right arrow key on the keyboard, the image is distorted and will not be displayed.

Screenshot

Screenshot

Sometimes it shows a blank black screen.

Screenshot

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I cannot reproduce this behavior in an image folder containing multiple jpg, png.
I have also tested these files by opening them with another open source image viewer and found no problems, so the problem is qView-specific.

[jdpurcell]

I can reproduce the corrupt-looking image thing but only reliably on one of the 3 test environments I tried. I believe it's related to the "Preloading" feature somehow, since the problem went away with preloading disabled.

As for performance, the decoder we're using accepts a quality parameter, and when I tried it (e.g. imageReader.setQuality(10);) it helped a bit, but it was still pretty slow (quality 10 took about 3/4 the time vs default quality).

[jdpurcell]

@jurplel Per LibRaw docs, there are thread-safe and single-threaded variants of the library. When we build via vcpkg, both are available:

libraw provides CMake targets:

    find_package(libraw CONFIG REQUIRED)
    # non-thread-safe
    target_link_libraries(main PRIVATE libraw::raw)
    # thread-safe
    target_link_libraries(main PRIVATE libraw::raw_r)

I believe we're linking against the single-threaded version. Do you know what controls that? I see FindLibRaw.cmake has some code mentioning both variants, but then I don't know if or how it's supposed to choose between the two, or if the last ~20 lines are basically forcing it to link to the single-threaded version. EDIT: I figured out how to use the thread-safe version; I'll submit a pull request soon.