How to build and use an SDK for QT

Coming soon

For internal use only. Not to be published as is.

STMicroelectronics does not distribute an SDK for QT, but it can be built following the information in this article.

1. Prerequisites

Being able to rebuild an OpenSTLinux image

2. Build image QT with EGLFS

after (refrase this or link to another page)

 repo init ...
 repo sync

select the proper machine and distribution

 DISTRO=openstlinux-eglfs MACHINE=stm32mp1 source layers/meta-st/scripts/envsetup.sh

and read and accept EULA.

Then build the QT image and the QT SDK

 bitbake st-example-image-qt
 bitbake meta-toolchain-qt5

The image can be flashed as usual (add link). Install the SDK in a folder (check if we suggest a folder):

 ./tmp-glibc/deploy/sdk/meta-toolchain-qt5-openstlinux-eglfs-stm32mp1-x86_64-toolchain-3.1-snapshot.sh -y -d <install_path_sdk>

3. QT configuration

By default, QT internal data use 64 bit per pixel (16 bit for each R, G, B, A components). It is possible to slightly improve the performance by forcing QT to use 32 bit per pixel (8 bit for each component). This can be achieved by editing the file layers/meta-st/meta-st-openstlinux/recipes-qt/qt5/qtbase_git.bbappend before the build

-QT_CONFIG_FLAGS += " -no-sse2 -no-opengles3"
+QT_CONFIG_FLAGS += " -no-sse2 -no-opengles3 -no-feature-raster-64bit"

The above setup can produce visible artefacts, so has to be evaluated case by case.

4. Build a QT application

Enter in the folder that contains the application, enable the QT SDK and compile the application

 cd <path_of_app>
 . <install_path_sdk>/environment-setup-cortexa7t2hf-neon-vfpv4-ostl-linux-gnueabi
 qmake && make

5. Select the display resolution

When using a display that accepts multiple resolutions, it is possible to specify the preferred resolution by editing the board file /usr/share/qt5/cursor.json. For example, for an HDMI display, change the line

{ "name": "HDMI1", "mode": "1280x720" },

and enter one of the valid resolutions reported by the command

 modetest

6. Hack QT EGLFS display size

The 'FS' of EGLFS means 'Full Screen'. In full-screen conditions it's hard to replicate on standard ST boards the use cases of custom boards with small display. It is possible to modify the QT code to use a custom display size even with an EGLFS build.

Before building the image 'st-example-image-qt', modify the QT code with the following sequence:

 devtool modify qtbase my/qtbase
 cd my/qtbase

Edit the file src/platformsupport/kmsconvenience/qkmsdevice.cpp adding the lines below

  416          framebufferSize.setHeight(modes[selected_mode].vdisplay);
  417      }
     +     int w = qEnvironmentVariableIntValue("ST_W");
     +     int h = qEnvironmentVariableIntValue("ST_H");
     +     if (w && h) {
     +         framebufferSize.setWidth(w);
     +         framebufferSize.setHeight(h);
     +     }
  418
  419      qCDebug(qLcKmsDebug) << "Output" << connectorName << "framebuffer size is " << framebufferSize;

Then compile the image as above with

 bitbake st-example-image-qt

With this modified QT you can set the environment variables 'ST_W' and 'ST_H' to set the desired display size, e.g.:

 ST_W=320 ST_H=200 ./qt-app

Note: This hack will not work if either ST_W or ST_H contains a value that exceed the display size.

Note: The touchscreen is not impacted by this hack, so there would be a mismatch between the coordinates touched and the coordinates reported to the QT application.

7. Text taken from QT framework

Qt is a cross-platform application framework that is used to develop graphical user interfaces (GUIs) and multiplatform applications.

meta-qt5 is a Yocto compatible meta layer that provides recipes for Qt modules.

The OpenSTLinux distribution is ready to link with this meta layer.

The OpenSTLinux distribution offers the possibility to use an example of an image based on the QT framework (st-example-image-qt) as a demonstrator, not for developing products. For Qt-based products, the list of STMicroelectronics partners can be found on STMicroelectronics web site.

Software development kit (A programming package that enables a programmer to develop applications for a specific platform.)

High-definition multimedia interface (HDMI standard)

File system or filesystem, method and data structure that the operating system uses to control how data is stored and retrieved -NEW

The Linux Foundation® and Yocto Project® are registered trademarks of the Linux Foundation. Linux® is a registered trademark of Linux Torvalds