Qt Lite: Tailoring your Qt build to your needs
The Problem: Getting the smallest functional Qt
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Popular question: How do I minimize my Qt build?
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Particularly relevant for single-purpose static builds for
embedded systems
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Different people have different requirements
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The “essential Qt” is not the same for everybody
Modules
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Coarse-grained
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QtCore, QtNetwork, QtQuick, ...
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Build just the modules you need
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But what if you need some parts of a module only?
Features
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Fine-grained
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Selectively enable/disable parts of the Qt code base
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For instance: QProcess, QSettings, QRegularExpression, state
machine support...
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There are ca. 150 features in qtbase at the moment
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Number will likely increase in the future
Enabling and disabling Qt features
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Happens at configure time
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Relevant options: -feature-* and -no-feature-*
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Opt out of features you don’t need like this:
configure -no-feature-mimetype
-no-feature-openssl
...
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Graphical tool available as part of Qt for Device Creation
Example
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Built Qt statically for the i.MX 6 architecture
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First variant used default configure options
Second variant had several dozen features turned off
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A Qt Quick application showing some animation was built
against both variants
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The executable built against variant two was 30% smaller
Dealing with Qt features in your projects
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Tailor your project to the availability of features:
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In a project file:
qtConfig(openssl):SOURCES += mysslcode.cpp
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In a source file:
#if QT_CONFIG(openssl)
// SSL-specific code goes here
#endif
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You can also declare that your code needs a certain feature:
QT_REQUIRE_CONFIG(openssl)