Review Request 129167: Lazy load export image, halving the startup time

[Peter Wu]

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https://git.reviewboard.kde.org/r/129167/
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(Updated Oct. 13, 2016, 4:43 a.m.)


Review request for KDE Graphics and Boudhayan Gupta.


Changes
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Addressed comments, thanks for reviewing


Repository: spectacle


Description
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Conversion of a pixmap to a data URI is quite expensive. On my Skylake
laptop (i7-6500HQ), it took one second to start. A perf trace showed
that 65% of the time was spent in ExportManager::pixmapDataUri.


Diffs (updated)
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  src/Gui/ExportMenu.h 5040fe226bd22baabd8adc408b56fc012bef7d04 
  src/Gui/ExportMenu.cpp 50333e0ffbfa9d382d42c6ee4c00fff1972df9a4 
  src/Gui/KSMainWindow.cpp e0116356a55f205c3be6ce57661f0d754b1a94b0 

Diff: https://git.reviewboard.kde.org/r/129167/diff/


Testing
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Compile spectacle with debug info and obtain a perf trace:

    # close as soon as you see the window
    perf record --call-graph=dwarf src/spectacle
    # open five times, press Escape as soon as you seen the window
    time src/spectacle

Repeat experiment and compare times and perf traces (`perf diff perf.data.old perf.data` and `perf report -i perf.data.old`).

To test that export is still working: open Export menu, hover over Share. The first time there is a small delay, the next time it will be faster due to lazy loading.


Thanks,

Peter Wu

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