Crash when second instance of Pinta is opened

[grofaty]

Pinta 1.8-dev on Ubuntu 20.04:
https://github.com/PintaProject/Pinta/actions/runs/459425971

1. Open Pinta 1.8-dev.
2. Open another instance of Pinta 1.8-dev. Crash window appears in second instance:

System.Reflection.TargetInvocationException: Exception has been thrown by the target of an invocation.
 ---> System.InvalidOperationException: Sequence contains more than one matching element
   at System.Linq.ThrowHelper.ThrowMoreThanOneMatchException()
   at System.Linq.Enumerable.SingleOrDefault[TSource](IEnumerable`1 source, Func`2 predicate)
   at Pinta.Tools.PaintBrushTool.<get_BrushComboBox>b__32_0(Object o, EventArgs e)
   --- End of inner exception stack trace ---
   at System.RuntimeMethodHandle.InvokeMethod(Object target, Object[] arguments, Signature sig, Boolean constructor, Boolean wrapExceptions)
   at System.Reflection.RuntimeMethodInfo.Invoke(Object obj, BindingFlags invokeAttr, Binder binder, Object[] parameters, CultureInfo culture)
   at System.Delegate.DynamicInvokeImpl(Object[] args)
   at System.Delegate.DynamicInvoke(Object[] args)
   at GLib.Signal.ClosureInvokedCB(Object o, ClosureInvokedArgs args)
   at GLib.SignalClosure.MarshalCallback(IntPtr raw_closure, IntPtr return_val, UInt32 n_param_vals, IntPtr param_values, IntPtr invocation_hint, IntPtr marshal_data)

There are several crash like windows one followed after another when trying to close Pinta. I am not posting them here, because there are consequence errors.

[grofaty (grofaty)]

I have tested with Pinta 1.7 snap package and I can have several instances opened. Maybe this is snap specific, because every snap should be in its own container.

I can't test Pinta 1.7 deb package, because I don't want to mess with my current environment. Can't confirm this is regression.

[Cameron White (cameronwhite91)]

Confirmed on Ubuntu 20.04, but it doesn't occur on macOS.
It doesn't seem like it's actually starting a second process, so perhaps what's happening is that the 'activate' signal is being triggered on the original instance and causing some initialization to occur a second time.

[Cameron White (cameronwhite91)]

Should be fixed by https://github.com/PintaProject/Pinta/commit/e4ff9bdcc834101333007a5538003643d44d3b02

[grofaty (grofaty)]

I downloaded Pinta 1.8 on Ubuntu 20.04:
https://github.com/PintaProject/Pinta/actions/runs/459690362

and I can confirm this problem is now fixed. Thanks