Using Qt5 on PiTFT

Question

I am trying to deploy and run graphical application using Qt 5.3.2 on Raspberry Pi with Debian Whezzy. The goal is to display GUI app on PiTFT 2'8 from Adafruits. To cross compile Qt5 libraries I followed instructions at: https://qt-project.org/wiki/RaspberryPi_Beginners_guide and that seems to work. I can execute console app , I see results on the terminal.

However when I try to run graphical application basing on QMainWindow I see completely no effect on the screen. There is no message about any possible error. I tried to execute my app with with various parameters eg. DISPLAY=:0.0 or -platform eglfs with no effect. Am I missing something?

Answer 1

After executing ./myapp -platform linuxfb:fb=/dev/fb1 I was able to run app based on QWidget and see GUI on the 320x240 TFT display. However in case of having qml objects I get following message:

This plugin does not support createPlatformOpenGLContext! Failed to create OpenGL context for format QSurfaceFormat( ... ). I tried to start an app with: ./myapp -platform eglfs:fb=/dev/fb1 but still no effect. I get nothing on the TFT display. Is it related to some special attribute of OpenGL? and how to workaround this problem?

Answer 2

For completeness: there is a good tutorial about exactly this issue: http://www.jumpnowtek.com/rpi/pitft-displays-and-qt5.html. Basically, you have to copy the GPU output to the TFT framebuffer, as QML needs eglfs and this in turn needs the gpu.

Answer 3

I've the same problem and after a week I found the reason.

https://forums.adafruit.com/viewtopic.php?f=47&t=57557