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// Copyright (C) 2023 The Qt Company Ltd.
// SPDX-License-Identifier: LicenseRef-Qt-Commercial OR GFDL-1.3-no-invariants-only
/*!
\page android-environment-variables.html
\title Qt for Android Environment Variables
\brief Lists some useful environment variables used by the Qt For Android toolchain.
\ingroup android-platform-extra-topics
\section1 Enabling or disabling workarounds
Qt for Android uses some environment variables to enable/disable certain workarounds:
\section2 Commonly used variables
\table 80%
\header \li Variable \li Description
\row
\li QT_ANDROID_NO_EXIT_CALL
\li In some cases, an Android app might not be able to safely clean all
threads while calling \c exit() and it might crash. This is because there
are C++ threads running and destroying these without joining them terminates
an application. These threads cannot be joined because it's not possible
to know if they are running. This flag avoids calling \c exit() and lets
the Android system handle this, at the cost of not attempting to run
global destructors.
\row
\li QT_ANDROID_ENABLE_WORKAROUND_TO_DISABLE_PREDICTIVE_TEXT
\li Allows the hiding of predictive text suggestions, mainly from password
fields. Certain devices don’t handle this properly. For more information,
see \l {Android Platform Notes}{Predictive Text}.
\row
\li QT_ANDROID_ENABLE_RIGHT_MOUSE_FROM_LONG_PRESS
\li Interprets a long touch press as a right mouse click event.
\row
\li QT_ANDROID_DISABLE_ACCESSIBILITY
\li Disable \l{Assistive Tools}{Accessibility}. This prevents the processing
of accessibility events.
\endtable
\section2 Less commonly used variables
\table 80%
\header \li Variable \li Description
\row
\li QT_ANDROID_FONT_LOCATION
\li Sets a custom path for system fonts.
\row
\li QT_ANDROID_MAX_ASSETS_CACHE_SIZE
\li Cache size for assets under the assets folder.
\row
\li QT_ANDROID_DISABLE_GLYPH_CACHE_WORKAROUND
\li See \l{Text Glyph Caching}{Text Glyph Caching}
\row
\li QT_ANDROID_RASTER_IMAGE_DEPTH
\li
\row
\li QT_ANDROID_MINIMUM_MOUSE_DOUBLE_CLICK_DISTANCE
\li
\row
\li QT_ANDROID_BACKGROUND_ACTIONS_QUEUE_SIZE
\li When an Android app is paused or inactive, it may continue to receive
UI updates from components like a BroadcastReceiver or Service. These updates
are queued until the app resumes. The queue can grow indefinitely, leading
to extra memory usage and latency when processing these updates once the app is
active again.
This environment variable addresses this issue by introducing a size limit
for the queue. Once the specified limit is reached, the oldest entry is
discarded to add the newest entry, therefore preventing unbound growth.
By default, the queue is unbound and this environment variable is not set.
Additionally, if set to any negative number the queue remains unbound.
For example, QT_ANDROID_BACKGROUND_ACTIONS_QUEUE_SIZE=100 limits the queue
to 100 actions.
\endtable
\note Though related, these are not the same as CMake commands or variables used
by Qt For Android, see \l{Qt for Android CMake Configuration}
*/
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