Re: rethinking interpreter <-> gui interaction

[John W. Eaton]

On 7/1/19 11:57 PM, Daniel J Sebald wrote:
> On 7/1/19 2:47 PM, John W. Eaton wrote:

> There shouldn't be a need to make either side of the link suspend and 
> wait on anything.

Don't functions like inputdlg have to wait for a result?  As I 
understand it, function like that ask the GUI to create a dialog and 
then they can't return until the dialog is closed and a result is 
returned (or an error is thrown).

> To make the GUI wait feels unnatural.  Instead, you'd 
> like to allow the user to edit files and whatnot when a long worker 
> process is running.

Yes, I agree that it should be possible to do something like editing 
files as that doesn't generally require the interpreter to perform any 
action.  But what should happen if the GUI asks the interpreter to 
perform some action when it is already busy executing some other code? 
At what point is it safe for the interpreter to check the command queue 
and call other functions?

> In the patch, that is the key, dynamic connections to a "queue" result. 
> There currently is a queuing mechanism for commands, say "cd" or "pwd". 
> The patch extends that idea to include a broadcaster.  In the latter 
> command, some information is returned in an octave_value class.  In the 
> GUI, the object that wants the information puts the command "pwd" in the 
> queue and dynamically makes a connection to the queue result or 
> "broadcast".  The queue also keeps a record of the requesting object's 
> ID (this) so that on the return trip all the objects that may be 
> connected to the broadcaster can compare their "this" against the ID to 
> recognize, "Hey, that's my data!".  Once the GUI has its data, it can 
> choose to disconnect so that the broadcaster doesn't get too many 
> subscribers--or whatever analogy one wants to use.

OK, I will look again at the patch.  I probably promised to do that in 
the past, maybe more than once.  But I don't think I really understood 
threads and Qt signals and slots well enough until now to be able to 
properly evaluate it.

Thanks,

jwe