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digitalmars.D - std.signals non-object delegates

reply Jacob Shtokolov <jacob.100205 gmail.com> writes:
Hello,

I'd like to start a discussion about the standard std.signals 
library.

Currently it has a strange limitation - you can't pass delegates 
that don't belong to an object.

I reviewed the source code an came to conclusion that it can be 
easily fixed.

However, the thing that concerns me more is how to deal with 
delegates whose allocated frame pointer (context) was disposed by 
GC.

In the case of object's delegate, the library places dispose 
handlers via the `rt_attachDisposeEvent`, so if GC just freed an 
object, all related callbacks will be unregistered automatically.

But I'm not really sure how to do the same for a bare frame 
pointer.

I'd like to attract some attention to this topic, because I see 
that people tend to re-implement the same functionality over and 
over again in their projects.

For example, look at the DLangUI by Vadim Lopatin: 
https://github.com/buggins/dlangui/blob/master/src/dlangui/core/signals.d - the
same functionality, but without this stupid limitation (in terms of user
experience).

Any suggestions?
Jun 07 2018
parent reply Jacob Shtokolov <jacob.100205 gmail.com> writes:
On Thursday, 7 June 2018 at 12:56:55 UTC, Jacob Shtokolov wrote:

 Hello,

 I'd like to start a discussion about the standard std.signals 
 library.

 [...]


5 days passed and no one answered 😒

Maybe the guys who are contributing to DRuntime could answer: is 
that possible to attach GC dispose event handlers to the delegate 
context?
Jun 12 2018
parent reply Steven Schveighoffer <schveiguy yahoo.com> writes:
On 6/12/18 9:04 AM, Jacob Shtokolov wrote:

 On Thursday, 7 June 2018 at 12:56:55 UTC, Jacob Shtokolov wrote:

 Hello,

 I'd like to start a discussion about the standard std.signals library.

 [...]


 
 5 days passed and no one answered 😒


I'll respond to say that I don't know a lot of people who use signals 
and slots. It's a very old part of Phobos, and I think a lot of people 
here aren't familiar with it.


 
 Maybe the guys who are contributing to DRuntime could answer: is that 
 possible to attach GC dispose event handlers to the delegate context?


I've never heard of this functionality. Looking it up, it's not used 
anywhere in druntime, only from phobos, and only from this std.signals 
implementation (literally a search through all code finds the function 
rt_attachDisposeEvent in 2 places -- the definition, and the one usage 
in std.signals).

Looking at the implementation, it depends on having an Object with a 
Monitor, as the event is stored in the monitor. So you couldn't attach 
it to any specific piece of memory, it HAS to be an Object.

But like I said, it's not used pretty much anywhere. So I think nobody 
would miss it if you ripped it out and made it better :)

feel free to open a bug report and/or PR and get some more discussion going.

-Steve
Jun 12 2018
parent reply Jacob Shtokolov <jacob.100205 gmail.com> writes:
On Tuesday, 12 June 2018 at 14:33:57 UTC, Steven Schveighoffer 
wrote:

 On 6/12/18 9:04 AM, Jacob Shtokolov wrote:

 [...]


 I'll respond to say that I don't know a lot of people who use 
 signals and slots. It's a very old part of Phobos, and I think 
 a lot of people here aren't familiar with it.


 [...]


 I've never heard of this functionality. Looking it up, it's not 
 used anywhere in druntime, only from phobos, and only from this 
 std.signals implementation (literally a search through all code 
 finds the function rt_attachDisposeEvent in 2 places -- the 
 definition, and the one usage in std.signals).

 Looking at the implementation, it depends on having an Object 
 with a Monitor, as the event is stored in the monitor. So you 
 couldn't attach it to any specific piece of memory, it HAS to 
 be an Object.

 But like I said, it's not used pretty much anywhere. So I think 
 nobody would miss it if you ripped it out and made it better :)

 feel free to open a bug report and/or PR and get some more 
 discussion going.

 -Steve


Thank you Steve!

Then I'll try to fire a bug report and propose my own solution to 
this problem.
Probably there is no need to track down the non-object dispose 
events.

Good to hear that not so many people are affected by this 😏
Jun 12 2018
parent reply Zoadian <no no.no> writes:
On Tuesday, 12 June 2018 at 15:21:49 UTC, Jacob Shtokolov wrote:

 On Tuesday, 12 June 2018 at 14:33:57 UTC, Steven Schveighoffer 
 wrote:

 [...]


 Thank you Steve!

 Then I'll try to fire a bug report and propose my own solution 
 to this problem.
 Probably there is no need to track down the non-object dispose 
 events.

 Good to hear that not so many people are affected by this 😏


i remember someone was working on a std.signals replacement a few 
years ago.
don't know where that went.
it might be this:
https://wiki.dlang.org/Review/std.signal
https://github.com/phobos-x/phobosx/blob/master/source/phobosx/signal.d
Jun 12 2018
parent Jacob Shtokolov <jacob.100205 gmail.com> writes:
On Tuesday, 12 June 2018 at 15:39:52 UTC, Zoadian wrote:

 On Tuesday, 12 June 2018 at 15:21:49 UTC, Jacob Shtokolov wrote:

 On Tuesday, 12 June 2018 at 14:33:57 UTC, Steven Schveighoffer 
 wrote:

 [...]


 Thank you Steve!

 Then I'll try to fire a bug report and propose my own solution 
 to this problem.
 Probably there is no need to track down the non-object dispose 
 events.

 Good to hear that not so many people are affected by this 😏


 i remember someone was working on a std.signals replacement a 
 few years ago.
 don't know where that went.
 it might be this:
 https://wiki.dlang.org/Review/std.signal
 https://github.com/phobos-x/phobosx/blob/master/source/phobosx/signal.d


Many thanks! I didn't see this topic at all. This is very 
helpful, will try to check this implementation.
Jun 12 2018