Building Qt 5.15 LTS for Raspberry Pi on Raspberry Pi OS

28/04/2021 - 13:28
Average: 4.8 (6 votes)

This tutorial will guide you on how to build an up-to-date Qt 5.15 LTS release from source with proper hardware acceleration support for Raspberry Pi on Raspberry Pi OS, both 32-bit and 64-bit.

Pi4 closeup

Raspberry Pi OS (aka Raspbian), based on Debian Buster, comes with an old version of Qt 5.11 that is already outdated. Afaik there are no up-to-date backports so the only way to get an up to date version of Qt with board specific features enabled for running on your Raspberry Pi is to build it yourself.

This tutorial concentrates on the Qt 5.15.2 LTS, the Long Time Support release, the last in the Qt 5 series. Unfortunately later releases of Qt 5.15 are not available as Open Source anymore.

Fortunately KDE provides patches for the Qt 5.15 branch, now.

These instructions will build version of Qt that uses the eglfs interface by default and therefore runs applications fullscreen. You can optionally add X11 and/or Wayland support by installing the required development packages, they are described in the Optional features table below.

You can also choose what graphics drivers you will be using for eglfs, depending on what version of the Raspberry Pi you are using, either the proprietary Broadcom EGL or open source Mesa.

Building Qt for and on the Raspberry Pi is pretty straightforward, there are some Pi specific configurations that needs to be made, but in short it consist of the following steps:

  1. Downloading sources of Qt
  2. Checking the Qt source package integrity
  3. Preparing the sources for building
  4. Setup Qt mkspecs configuration for Raspberry Pi
  5. Installing required dependencies
  6. Installing optional dependencies
  7. Fix for EGL library detection (Not needed for Pi 4)
  8. Configuring the Qt build
  9. Compiling Qt
  10. Installing the Qt build

This tutorial is written for the full source of version 5.15.2, it is fully possible to build only parts using the split up Qt submodule sources packages, but this tutorial will not go into that at this time. Anyway, it is also very easy to skip building of modules that you don't need.

Note: These example builds have been verified to work on both 32-bit and 64-bit Raspberry Pi OS. Just make sure you choose the correct platform!

Tutorial changelog

As this tutorial evolves over time, changes are logged here.

  • 04.04.2021 - 5.15.2 Specific guide, copied from latest 5.12.10 version
  • 28.04.2021 - VC4 needs libdrm-drm, separete table for graphics options, preliminary 64-bit build option

Storage space and memory requirements

Make sure you have enough disk space free on your on your Pi as building Qt requires a lot of storage space. The unpacked full Qt sources itself takes around 3.7GB, the build result around 830MB and the installation from 232MB or more. A minimum of 8GB SD card is highly recommended. USB3 attached HDD or SDD is highly recommended on the Pi 4 as it speeds up compiling. Running out of disk space after hours of compiling can be extremely annoying, trust me.

Qt build storage space requirements
Item Size Note
Qt source archive 560MB qt-everywhere-src-5.15.2.tar.xz
Unpacked Qt Sources 3.7GB qt-everywhere-src-5.15.2
Build result ~830MB Typical, depends on configuration options and enabled features
Install size ~232MB Typical, depends on configuration options and enabled features

Enable swap and adjust CPU/GPU memory split

Compiling Qt takes quite a lot of memory, especially if trying to do a parallel build. Some parts take even too much memory and we need to disable building of them. It is highly recommened to enable at least 200MB of swap and also consider adjusting the Raspberry Pi CPU/GPU memory-split for the time of compilation, especially if parallel building or if you are using a model with limited amount of memory. On the new Raspberry Pi 4 models with 2GB,  4GB or 8GB of memory, swap is not required. If using swap, a USB3 attached HDD or SSD is also highly recommended.

Build Qt for Raspberry Pi

Download the Qt 5.15.2 source archive

Download the single source tar file from download.qt.io, version 5.15.2. The package is relatively large, 560MB, so depending on your bandwidth it might take some time to download, grab a coffe or continue with the dependecies while the Qt source archive is downloading.

wget https://download.qt.io/official_releases/qt/5.15/5.15.2/single/qt-everywhere-src-5.15.2.tar.xz

Check archive MD5 hash

Just to make sure the download was succesfull and is what it should be, check the MD5 hash of the archive with:

md5sum qt-everywhere-src-5.15.2.tar.xz

It should be:

e1447db4f06c841d8947f0a6ce83a7b5 qt-everywhere-src-5.15.2.tar.xz

Un-tar the source archive

Un-tar the source archive in a suitable location, with enough free space (~4GB). This will take around 7-13 minutes on a Raspberry Pi 3+, depending on SD card speed, and even more on an older model, so go grab of coffe again. If you are on a Pi 4, then we highly recommend using fast USB 3 storage (HDD or SSD) for both sources and building. You can of course start installation of the build dependecies while you wait.

tar xf qt-everywhere-src-5.15.2.tar.xz

Setup Qt mkspecs configuration files

Qt build is configured trough the configure script, but platform and device specifc settings are set in mkspecs configuration files. Qt includes mkspecs for the Raspberry Pi but they are unfortunately setup for cross-compilation environments only and can not be used for native building without editing or the need for faking a cross compilation environment and that has its own issues.

Fortunately suitable mkspecs files for the various Pi versions are available in our github, so the next step is to clone that repository and install the mkspecs files into the Qt source tree so that they can be used.

Clone the configuration repository:

git clone https://github.com/oniongarlic/qt-raspberrypi-configuration.git

change into the cloned repository and run (adjust DESTDIR in case your Qt sources are extracted somewhere else):

cd qt-raspberrypi-configuration && make install DESTDIR=../qt-everywhere-src-5.15.2

Install required build dependencies

You will need to install plenty of packages to be able to build Qt 5.15. Some of the Qt 5.15 features are optional and can be either left our or included, depending on your particular needs. For example support for various databases (PostgreSQL, MySQL/MariaDB) and if you don't need a specific feature you can skip building the support (or build the from separate packages later). Or the other way around, if you need a specific feature you might need to install more development packages.

Some features are not strictly required but might still be nice to have, for example support for the webp image format is optional, but these days it is already widely used so might be good to include.

See the table below for a list of some optional features and the required development packages you need to install. But first, start by updating your apt package cache so everything is fresh:

apt update

Then continue with required package installation below.

Install the bare minimum required development packages for building Qt 5.15 with apt:

apt install build-essential libfontconfig1-dev libdbus-1-dev libfreetype6-dev libicu-dev libinput-dev libxkbcommon-dev libsqlite3-dev libssl-dev libpng-dev libjpeg-dev libglib2.0-dev

Graphics driver options

It is possible to use either the proprietary EGL blobs from Broadcom or the Mesa open source drivers. Broadcom drivers can be used on all older Pi variants, but not on any Pi 4 variants (Pi4, 400, Compute Module 4). For those you need to use Mesa.

Graphics driver options
Graphics driver Required package(s) Information

Broadcom EGL

For vintage Pi, Zero, Pi 2, Pi 3, CM 1, CM3

32-bit only

libraspberrypi-dev

Required for all pre-Pi 4 boards if not using open source GL drivers.

EGLFS Rasberry Pi .................... yes
 

VC4 driver

Mandatory on Raspberry Pi 4

Mandatory on 64-bit

libgles2-mesa-dev libgbm-dev libdrm-dev

Use -platform linux-rpi-vc4-g++

Note: If you build with gstreamer support you must also install libwayland-dev

Install optional Qt 5 feature development packages

Qt consist of many modules, depending on your needs you might like to install additional development packages to be able to enable support for these features in Qt 5. Check the table below for any optional features you might need and the required development packages that you need to install to support them. Also make sure that the optional feature you need is found and enabled by the configure script by checking the output of configure run (see config.summary).

Optional features
Optional feature Packages to install Configure option
Bluetooth

bluez libbluetooth-dev

 

gstreamer multimedia framework support

Wayland development packages is required as it is required by a gstreamer header that is used by Qt.

libgstreamer1.0-dev libgstreamer-plugins-base1.0-dev gstreamer1.0-plugins-base gstreamer1.0-plugins-good gstreamer1.0-plugins-ugly gstreamer1.0-plugins-bad libgstreamer-plugins-bad1.0-dev gstreamer1.0-pulseaudio gstreamer1.0-tools gstreamer1.0-alsa

libwayland-dev

 
Linux ALSA Audio support

libasound2-dev

 
Pulseaudio support

pulseaudio libpulse-dev

 
Support for various databases (PostgreSQL, MariaDB/MySQL)

libpq-dev libmariadbclient-dev

 

Printing support using CUPS

libcups2-dev

 
Wayland support

libwayland-dev

 
X11 support

libx11-dev libxcb1-dev  libxext-dev libxi-dev libxcomposite-dev libxcursor-dev libxtst-dev libxrandr-dev libfontconfig1-dev libfreetype6-dev libx11-xcb-dev libxext-dev libxfixes-dev libxi-dev libxrender-dev libxcb1-dev  libxcb-glx0-dev  libxcb-keysyms1-dev libxcb-image0-dev  libxcb-shm0-dev libxcb-icccm4-dev libxcb-sync-dev libxcb-xfixes0-dev libxcb-shape0-dev  libxcb-randr0-dev  libxcb-render-util0-dev  libxcb-util0-dev  libxcb-xinerama0-dev  libxcb-xkb-dev libxkbcommon-dev libxkbcommon-x11-dev

 
QtWebEngine

Required: flex bison gperf libre2-dev libnss3-dev libdrm-dev

Optional: libxml2-dev libxslt1-dev libminizip-dev libjsoncpp-dev liblcms2-dev libevent-dev libprotobuf-dev protobuf-compiler

Optional but unusable versions in raspbian: libopus-dev libvpx-dev

Note: We highly recommend to build QtWebEngine separately from base Qt.

 
libzstd libzstd-dev  
Accessibility

libatspi-dev

 
SCTP [1][2]

libsctp-dev

-sctp

Install any package from the above table with apt install.

Broadcom EGL library filename fix

Note: This is NOT needed when building a Raspberry Pi 4 configuration.

On Raspbian Stretch/Buster the OpenGL library files have been renamed (1, 2) so that they wouldn't conflict with Mesa installed ones. Unfortunately Qt configure script is still looking for the old names. See QTBUG-62216 for details.

If you use the mkspecs configuration files provided in this tutorial you don't need to worry about this as they are setup to reference the libbrcm*.so library names.

Create a shadow build directory outside of the Qt source tree

We will build Qt 5 outside of the source tree, this way you can easily have different build version and easily also start over in case of any issues with configuration or the build itself. Your build location can be anywhere where there is enough space, for example an HDD, SDD or USB stick in case you are running out of spaec on your SD card. Remember to adjust any paths in the example commands.

mkdir build
cd build

Configure the Qt 5 build environment

We configure Qt 5 for a native build and set device specific settings, like libraries, default QPA plugin to use, etc directly on the configure command line. Note that the below configuration is just an example, you might need to adjust it for your particular needs, for example if you do need wayland the remove the "-skip wayland" option. This makes it also easy to optimize for any specific Raspberry Pi board type, see the table for used CFLAGS & CXXFLAGS for your target board. Configure run takes ~10 minutes as it will first compile the Qt build tool qmake and then run various tests and feature checks.

PKG_CONFIG_LIBDIR=/usr/lib/arm-linux-gnueabihf/pkgconfig:/usr/share/pkgconfig \
../qt-everywhere-src-5.15.2/configure -platform linux-rpi-g++ \
-v \
-opengl es2 -eglfs \
-no-gtk \
-opensource -confirm-license -release \
-reduce-exports \
-force-pkg-config \
-nomake examples -no-compile-examples -nomake tests \
-skip qtwayland \
-skip qtwebengine \
-no-feature-geoservices_mapboxgl \
-qt-pcre \
-no-pch \
-ssl \
-evdev \
-system-freetype \
-fontconfig \
-glib \
-prefix /opt/Qt/5.15.2 \
-qpa eglfs

Configuration options explained

Wondering what the options do, let the below table explain:

Qt build configuration options explained
Option Description Why is this option used
-v Verbose configuration output To see what is going on
-opengl es2 -eglfs Use OpenGL ES and use Qt EGLFS platform plugin So we don't need to run X11
-no-gtk Don't use GTK theme support No need for GTK development libraries
-opensource -confirm-license Select open source license build, don't prompt for license License needs to be set
-release Use release build options (optimized libraries and binaries) For speed

-nomake examples -no-compile-examples
-nomake tests

Skip building of example applications and tests. Takes time and space
-qt-pcre Use Qt provided pcre library  
-no-pch Don't use pre-compiled C++ headers Takes a lot of space
-ssl Use OpenSSL, required for crypot and for example https support in Qt networking code Crypto is the new black
-evdev Use Linux generic input subsystem  
-system-freetype Use system provided version of freetype library instead of bundled version Speed up compliation
-fontconfig Use fontconfig for font discovery Fonts are nice to have
-glib Use glib compatible event loop Integrates with glib based event loop users, for example gstreamer
-prefix /opt/Qt/5.15.2 Installation prefix for the Qt framework. Running make install will install Qt at this location. Qt needs to be installed somewhere
-qpa eglfs

Default platform abstraction plugin to use for applications.
Change this if you prefer using something else, for example xcb.

Selects the default platform plugin, on Pi EGLS is nice so you don't need to run X11

Building QtWebEngine support

Building the qtwebengine module takes a lot of time and space, the default configure example above disables it with -skip qtwebengine. The reason being that on older Pi versions with a tiny amount of memory it is pretty much impossible to build. Now with the 4GB or 8GB Raspberry Pi 4 it is fully possible to build, but you might still need to enable swap and also limit the amount of parallel builds the ninja build tool (that qtwebengine uses internally for building) is allowed to use. You can either build qtwebengine at the same time as the rest of Qt, but in case it fails (and it probably will) your whole build has failed, so the recommended way is to first build the base Qt 5 separately, install it and then build qtwebengine separately. But if you so choose, you can enable building of qtwebengine by removing the -skip qtwebengine configure option. Make sure that when you invoke make for building, that you add NINJAJOBS=-j1 to the command line. (make -j4 NINJAJOBS=-j1)

Building QtWebEngine separately

Read the separate guide on how to build qtwebengine.

Raspberry Pi platform options

Select platform according to the Pi model you are going to run Qt on. You can build on a fast Pi 4/3+ and the move the files over to a slower version if needed, just make sure you build for the correct ARM architecture in that case.

Note: For a Qt 5 that will be run on a Raspberry Pi 4 you must use KMS, Broadcom EGL is not supported on that model and never will. Make sure you have installed the packages: libgles2-mesa-dev libgbm-dev

Model specific optimization
Raspberry Pi model ARM architecture version Platform option Compiler FLAGS that will be used

Raspberry Pi 4

32-bit

ARMv8 -platform linux-rpi4-v3d-g++
-march=armv8-a -mtune=cortex-a72 -mfpu=crypto-neon-fp-armv8

Note: Will use VC4 DRM Mesa GL driver, not Broadcom EGL as it is not supported on the Pi 4.

Note: You must install libgles2-mesa-dev libgbm-dev libdrm-dev

Raspberry Pi 4

64-bit
ARMv8 -platform linux-rpi64-vc4-g++

Note: Preliminary, not tested properly yet but should work

Note: You must install libgles2-mesa-dev libgbm-dev libdrm-dev

Raspberry Pi 3, models:
3+, A+, Compute Module 3, Compute Module 3+

Raspberry Pi 2, model:
B v1.2

ARMv8
-platform linux-rpi3-g++
 
-march=armv8-a -mtune=cortex-a53 -mfpu=crypto-neon-fp-armv8

Note: QtScript won't build with these flags. If you need QtScript, then build with ARMv7 options.
And remove -skip qtscript from configure options.

Note: If you will build Qt Creator you will need QtScript!

Raspberry Pi 2, model:
B
ARMv7
-platform linux-rpi2-g++
 
-march=armv7-a -mtune=cortex-a7 -mfpu=neon-vfpv4
Raspberry Pi 1, models:
Original, Zero, Zero W, A, A+, B+, Compute Module 1
ARMv6
-platform linux-rpi-g++
 
-march=armv6zk -mtune=arm1176jzf-s -mfpu=vfp

Check the configure result

When the Qt configuration scripts has finnished succesfully it will print out a configuration summary and store the result in the config.summary file, also all the raw checks will be in the config.log file. Check that all options and features you needed are found and enabled in the summary output. If not, check the config.log file for a reason.

Example configuration summaries for

Broadcom EGLFS

Make sure that the configure script detects Raspberry Pi EGLFS when building for Raspberry Pi 1,2 or 3. Look for the following output or check the log file config.summary:

  EGLFS .................................. yes
  EGLFS details:
...
    EGLFS Rasberry Pi .................... yes

Note: If it says "no", check the configuration run output for reasons. Make sure that you have all required build dependencies installed (check the above table) and fixed the EGLFS library references!

MesaGL

When building for Raspberry Pi 4, check for

  EGLFS .................................. yes
  EGLFS details:
...
    EGLFS EGLDevice ...................... yes
...
    EGLFS Raspberry Pi ................... no

Note: If it says "no" for EGLDevice, check the configuration run output for reasons. Make sure that you have all required build dependencies installed (check the above table), especially the note about Pi 4 packages.

Compile Qt

Now Qt should be configured properly with all features enabled that we need. If you need some of the optional features, make sure to check the configure result that they where properly detected.

To compile Qt run:

make

or if you are using any of the quad-core Pis, append the -j4 parameter to build in parallel. Make sure you have proper cooling in this case, the 3+ this should run fine without getting throttled too much.

Build time

The compilation time depends on the Qt features being built, speed of your SD card, etc. Build time on a Raspberry Pi 3 with two parallel jobs (make -j2) takes roughly 8 hours.

Note: It might happen that parallel build needs too much memory and the compiler will crash. In this case try run with just one process or try -j3 or just -j2. Enabling swap will also help.

Optional: Speed up building with distcc

If you have many Raspberry Pi you can speed up the compilation by using distcc. In that case setup distcc on your machines and invoke make with:

make CC=distcc CXX=distcc -j[Machines in distcc cluster]

Install the build

The compilation should finnish without any errors, if it does not, double check that you have all the dependecies installed and run configure correctly.

If all is well, install Qt by running

make install

You should now have Qt 5.15.2 installed in /opt/Qt/5.15.2 ready for use. To configure your Qt project(s) to build with this version run qmake from the installation directory:

/opt/Qt/5.15.2/bin/qmake

You can of course also add it to your PATH, edit your users ".profile" or system wide in "/etc/profile" .

Choosing platform

As explained in the introduction, this build will default to using the eglfs platform, meaning that no windowing environment is required to run GUI applications. You can choose the platform binaries will run against by suppling the "-platform" paramter when running them.

Qt Platform option examples
Platform Parameter Information
EGLFS -platform eglfs The default if example options are used (qpa eglfs)
 
X11 -platform xcb  
VNC -platform vnc  
WebGL -platform webgl  

Enjoy Qt 5.15 on your Pi, Happy coding!

 

Keywords: 
Qt, Raspberry Pi