Qt for Android Environment Variables
Enabling or disabling workarounds
Qt Android uses some environment variables to enable/disable certain workarounds:
Commonly used variables
| Variable | Description |
|---|---|
| QT_ANDROID_NO_EXIT_CALL | In some cases, an Android app might not be able to safely clean all threads while calling 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 exit() and lets the Android system handle this, at the cost of not attempting to run global destructors. |
| QT_ANDROID_ENABLE_WORKAROUND_TO_DISABLE_PREDICTIVE_TEXT | Allows the hiding of predictive text suggestions, mainly from password fields. Certain devices don’t handle this properly. For more information, see Predictive Text. |
| QT_ANDROID_ENABLE_RIGHT_MOUSE_FROM_LONG_PRESS | Interprets a long touch press as a right mouse click event. |
| QT_ANDROID_DISABLE_ACCESSIBILITY | Disable Accessibility. This prevents the processing of accessibility events. |
Less commonly used variables
| Variable | Description |
|---|---|
| QT_ANDROID_FONT_LOCATION | Sets a custom path for system fonts. |
| QT_ANDROID_MAX_ASSETS_CACHE_SIZE | Cache size for assets under the assets folder. |
| QT_ANDROID_DISABLE_GLYPH_CACHE_WORKAROUND | See Text Glyph Caching |
| QT_ANDROID_RASTER_IMAGE_DEPTH | |
| QT_ANDROID_MINIMUM_MOUSE_DOUBLE_CLICK_DISTANCE | |
| QT_ANDROID_BACKGROUND_ACTIONS_QUEUE_SIZE | 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. |
Note: Though related, these are not the same as CMake commands or variables used by Qt For Android, see Qt for Android CMake Configuration
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