Testing and Debugging

Testing and debugging

Before you install

qmllint myapp/*.qml                         # mistakes, before running
python3 tools/barry-app check myapp         # would it install?
python3 tools/barry-app run myapp           # try it, hosted as on the Thor

barry-app run prints your app's errors and console.log() output in the terminal.

On a Mac, a Windows PC or Linux, Barry Simulator does the same without a terminal: it finds your apps, opens them with a double-click, shows their log, and reopens them when you save a file.

When it won't start

If main.qml has an error, Barry Launcher shows this instead of a black screen:

The log names the file, line and problem:

file:///home/steamos/.local/share/barry_launcher/apps/io.github.you.broken/main.qml:6:1: Expected token `}'

Reading the log on the Thor

Everything your app prints (errors, warnings, console.log) goes to ~/.cache/barry_launcher/ID.log, started afresh each time the app starts. A service's output goes there too.

• Desktop Mode: open it in Kate, or in Konsole: tail -f ~/.cache/barry_launcher/io.github.you.myapp.log
• Over SSH, the same tail -f from your computer, while you use the app on the Thor.

Install errors

Messages from Install app… (and barry-app install) and what they mean:

Message	Fix
no barry-app.json at the top of the archive, or in its one folder	Zip the app folder itself, or its contents, not a folder of folders. barry-app pack gets it right.
"id" … must be lower case and dotted	Use something like io.github.yourname.myapp.
"name" is N characters; the tile has room for 20	Shorten name.
"main" names X, which is not in the app folder	Check the spelling and the case: Main.qml isn't main.qml on Linux.
the archive has a link	Replace symbolic links with real files.
the archive has a file outside its folder	The archive was made with .. or absolute paths; pack it again with barry-app pack.
Barry Launcher isn't answering; is the bottom screen on?	Turn the bottom screen on (Quick Access → Barry Launcher), then try again.

Common QML mistakes

A line starting with ( or [

JavaScript joins it to the line before:

v.push(randomValue())
(dice.itemAt(i) as Die).roll(v[i])     // runs as randomValue()(...): "is not a function"

Start the line differently, for example with a variable:

v.push(randomValue())
const die = dice.itemAt(i) as Die
die.roll(v[i])

Sizes without the scale

width: 200 is right on the Thor and wrong anywhere else. Write width: 200 * app.s.

Settings without a location

On the device and with barry-app run, a Settings without location still lands in your app's data folder (in .config), but run another way (Qt Creator, the plain qml tool) it goes into Qt's shared settings. Set location: app.barry.dataDirUrl + "settings.ini" and you always know where it is.

Case in file names

Die.qml and die.qml are different files on the Thor (Linux), even if they're the same on your Mac or Windows PC.

Text that's too small

What looks fine in a window on a monitor is tiny on a 3.9-inch screen. Body text at 28 or more (* app.s), and try it on the device.

Performance

The bottom screen shares the GPU with the game on the top screen.

• Keep idle at zero: no animations or Timers running while nothing happens.
• Set sourceSize on big images, so they're decoded at the size shown.
• Qt Creator's QML profiler (see Tools) shows what's slow.