Debugging.md

Debugging Techniques

In no particular order, here is a list of tricks for debugging gowid applications.

Run on a different tty

• Make a local clone of the tcell repo:

git clone https://github.com/gdamore/tcell
cd tcell

• Apply the patch from this gist: https://gist.github.com/gcla/29628006828e57ece336554f26e0bde9

patch -p1 < gowidtty.patch

• Make your gowid application compile against your local clone of tcell. Adjust your application's go.mod like this, replacing <me> with your username (or adjust to where you cloned tcell)

replace github.com/gdamore/tcell => /home/<me>/tcell

• Run your application in tmux - make a split screen.
  • On one side, determine the tty, then block input
  • On the other side, set the environment variable GOWID_TTY

• Run your gowid application e.g. using tm.sh

tm.sh 1 go run examples/gowid-fib/fib.go

Then you can add fmt.Printf(...) calls to quickly debug and not have them interfere with your application's tty.

Watch Flow of User Input Events

Gowid widgets are arranged in a hierarchy, with outer widgets passing events through to inner widgets for processing, possibly altering them or handling them themselves on the way. Outer widgets could call

child.UserInput(ev, ...)

to determine whether or not the child is handling the event. But instead, all gowid widgets currently call

gowid.UserInput(child, ev, ...)

instead. This has the same effect, but means that gowid.UserInput() can be used to inspect events flowing through the application. For example, you can modify the function in support.go:

func UserInput(w IWidget, ev interface{}, size IRenderSize, focus Selector, app IApp) bool {
  if evm, ok := ev.(*tcell.EventMouse); ok {
    // Do something
    fmt.Printf("Sending event %v of type %T to widget %v", ev, ev, w)
  }
  return w.UserInput(ev, size, focus, app)
}