QML apps take long time to load

aaronwg

Hi. I have a QML app and when deploying release builds it takes a long time to start up. I've tried it on a bunch of machines and VMs and it seems to range between 3 and 10 seconds for anything to appear depending on the machine.

I tried precompiling all my QML using the CMAKE code specified by Qt documentation but the launch time appears to remain unchanged.

This is the CMAKE code I'm using for non-precompiled qml:

find_package(Qt5Core)
find_package(Qt5Network)
find_package(Qt5Gui)
find_package(Qt5Qml)
find_package(Qt5Quick)
find_package(Qt5QuickControls2)
find_package(Qt5QuickCompiler)

set(HEADERS
    ...
    ...
    ...
)

set(SOURCES
    main.cpp
    ...
    ...
    ...
    qml.qrc
)

add_executable(${PROJECT_NAME} WIN32 ${SOURCES} ${HEADERS})
target_compile_definitions(${PROJECT_NAME} PRIVATE $<$<OR:$<CONFIG:Debug>,$<CONFIG:RelWithDebInfo>>:QT_QML_DEBUG>)

target_link_libraries(${PROJECT_NAME}
    Qt5::Core
    Qt5::Network
    Qt5::Gui
    Qt5::Qml
    Qt5::Quick
    Qt5::QuickControls2
)

and this is the CMAKE code I'm using to precompile the QML:

find_package(Qt5Core)
find_package(Qt5Network)
find_package(Qt5Gui)
find_package(Qt5Qml)
find_package(Qt5Quick)
find_package(Qt5QuickControls2)
find_package(Qt5QuickCompiler)

set(HEADERS
    ...
    ...
    ...
)

set(SOURCES
    main.cpp
    ...
    ...
    ...
)

qtquick_compiler_add_resources(RESOURCES qml.qrc)
add_executable(${PROJECT_NAME} WIN32 ${SOURCES} ${RESOURCES} ${HEADERS})
target_compile_definitions(${PROJECT_NAME} PRIVATE $<$<OR:$<CONFIG:Debug>,$<CONFIG:RelWithDebInfo>>:QT_QML_DEBUG>)

target_link_libraries(${PROJECT_NAME}
    Qt5::Core
    Qt5::Network
    Qt5::Gui
    Qt5::Qml
    Qt5::Quick
    Qt5::QuickControls2
)

I'm led to believe by Qt documentation (https://doc.qt.io/qt-5/qtquick-deployment.html#ahead-of-time-compilation) that the second should result in a faster to load QML application when deployed but this doesn't appear to be the case.

On my current machine (pretty beefy threadripper 2920X with a GTX 1070) both the precompiled and non-precompiled versions of the app are taking around 4 seconds to display a Window from the point of double clicking the exe, and this is a pretty small application.

Is there anything I can do to speed up that initial load time? (Qt 5.12.3)