Add a confirmation dialog when the reference viewer is closed

[ejeschke]

• pops up a confirmation dialog that confirms you intend to quit
• adds support across backends
• can be overridden by adding a line to your general.cfg
• example general.cfg updated

[ejeschke]

@pllim, if/when you have time for a quick review. Just adds a pop-up confirmation dialog when you close the reference viewer.

Not sure why we are getting the RTD build failure, but looks like #1060 is the cause. Did I see something go by in my email about a fix for this in stginga?

[pllim]

For the docs, hopefully #1067 will fix it. 🤞

Thanks for the ping. I will review when I get the chance.

[ejeschke]

Rebased to pick up the RTD fix

[ejeschke]

As a user, I cannot tell what is the difference between "close" and "shutdown" in Ginga. Can you please clarify?

It just provides for a 2-step quit sequence. When someplace calls fv.close() the "close" callback is called. Ginga has a function registered for that callback to pop up a confirmation dialog box. If the user confirms, then fv.quit() is called which initiates the "shutdown" of the program. Any code that as registered for the "shutdown" callback will then get called to properly close any resources and terminate the program.

[pllim]

Re: https://github.com/ejeschke/ginga/pull/1066#issuecomment-1712146057

Maybe I am not fully understanding but won't it be simpler to have fv.quit(prompt_dialog=True) instead of a separate fv.close()?

[ejeschke]

The "close" and "shutdown" callbacks allow a flexible way to handle the closure of the program. For example, a plugin might want to register for "shutdown" in order to close a running thread they started or close a database connection, or they could register for "close" to make a checkpoint or pop up their own dialog to say that there are unsaved changes, etc. The reference viewer is basically this core around which there are a large collection of plugins.

Plus, we use the framework for many other programs that are not the reference viewer, but benefit from this style.

[pllim]

Thanks for the clarification! The diff looks reasonable to me and I am okay with this feature's addition. Feel free to merge. 😸

[ejeschke]

Thanks, @pllim!