Adds a QTGUI edit box block that emits a message when changed.

[trondeau]

Unlike the current QT GUI Entry Widget, this is an actual GNU Radio
block with an output message port 'msg'. When the editing is finished
(enter or change in scope), it triggers the editing_finished method
that publishes the text in the box as a message.

Also allows setting of the value through an input message port.

Adds example test_qtgui_msg.grc to explore this.

[osh]

+1

[jmcorgan]

I like the static key option, but can we make it that when the key is static, it doesn't have it showing next to the entry box? This would make it look just like any other entry widget, except it uses messages instead of calling functions.

[trondeau]

I had considered that, but I left it in to be clear what the edit box was doing. I was considering making it the label, but I think there's value in a user-set label that might me more human readable than the key. But showing the key makes it clear what's happening with that widget. The nice thing is that the block auto-scales the width of the box to just fit the key to reduce wasted space.

Another option might be to have a popup box when you hover over it that displays the key or even the key:value PMT it will create.