Qt executables run without error, but nothing displays

SGaist

Hi and welcome to devnet,

Did you try starting your application from the command line ? That might give you some additional clues about what is happening.

Hope it helps

jkern

@SGaist Yes, I would run the executables from the command line. For example:

$ ./HelloWorld -qws

SGaist

And there's nothing showing up ? Or is the screen blacked ?

jkern

Right, there's no additional windows that pop up and the command line just moves on to the next prompt line.

SGaist

That's strange, it should not do that.

Are you sure app.exec() is called properly ?

jkern

I literally haven't read anything about developing Qt programs yet. But as a trivial example, I created a Qt Widgets Application and just kept the default code. As a test, I compiled it with Qt 5.2.1 on my host machine, and it comes up with an empty window. So you would expect this same code is working on the target if cross-compiled correctly.

SGaist

Good thinking, did you check that you have all the necessary rights to access the devices e.g. the frame buffer ?

jkern

No, how do you do that? (I'm new to Linux as well...)

SGaist

groups to know the groups your user is a member of.
ls -la /dev/fb0 or ls -la /dev/fb/0 to see what permissions are set

jkern

groups shows:
analog adm dialout cdrom audio dip video plugdev admin

ls -la /dev/fb0 shows:
crw-rw---- 1 root video 29, 0 Jan 1 00:00 /dev/fb0

SGaist

Looks good.

Then, you should use gdb to debug your application