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SDL_OpenURL proposal
slvn


Joined: 06 Oct 2012
Posts: 88
Post Posted: Fri Feb 06, 2015 3:31 pm
I have added a first version of "SDL_OpenURL" function for Android and Unix.

It works with URLs, and probably with directories and files.

It would be nice if someone could add MacOSX, IOS, Windows, etc.

see the patch:
https://bugzilla.libsdl.org/show_bug.cgi?id=2783

On Fri, Nov 21, 2014 at 9:42 AM, Eric Wing wrote:
Quote:
Sorry, I'm really late on this one too. But I have useful info I hope.

There are official APIs for opening a URL on Mac, iOS, Android, and
Windows. I don't know about Linux except for the command line
xdg-open.

Mac
NSURL the_url = [NSURL URLWithString:@"http://www.apple.com"];
[[NSWorkspace sharedWorkspace] openURL:the_url];

iOS
NSURL the_url = [NSURL URLWithString:@"http://www.apple.com"];
[[UIApplication sharedApplication] openURL:the_url];

Windows:
LONG r = ShellExecute(NULL, "open", "http://www.microsoft.com", NULL,
NULL, SW_SHOWNORMAL);
(maybe that should be ShellExecuteA)


I forgot the details of Android, but you use Intents.
http://stackoverflow.com/questions/3004515/android-sending-an-intent-to-browser-to-open-specific-url
String url = "http://www.example.com";
Intent i = new Intent(Intent.ACTION_VIEW);
i.setData(Uri.parse(url));
startActivity(i);

Now please don't limit URLs to just http://. It is very common on Mac,
iOS, and Android to use custom URLs to launch specific apps. Sometimes
they are for popular protocols so people spontaneously conform their
apps to URL schemes that get documented so their apps can handle them
too, say like twitter:// (The OS may have an arbitration system if
multiple apps handle the same URL scheme.)
http://wiki.akosma.com/IPhone_URL_Schemes


Particularly in mobile games, I've seen a lot of developers
cross-promote their apps, where one app can launch another and maybe
you win points or something for doing so.

The Mac and iOS code will just work for that case. I think Windows may
work too. Android is a little more involved if I remember and you may
have to add more cases, but I've totally forgotten the details of how
it works.



Also, there is a counterpart system to this. It is also handy to know
when you've been launched via OpenURL. And you need to be able to
parse the URL string for information that was passed. For example,
most text editors on the Mac respond to URL schemes (even MacVim) and
you can tell it to open a specific file at a specific line number. Or
in the cross-promotional example above, you want to know which app
launched you. The receiving app needs a notification that OpenURL was
invoked with a particular string. Also, keep in mind that the app may
or may not have been already running when this even happened.

Thanks,
Eric

--
Beginning iPhone Games Development
http://playcontrol.net/iphonegamebook/
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--
Sylvain Becker
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SDL_OpenURL proposal
Gerry JJ
Guest
Post Posted: Fri Feb 06, 2015 6:21 pm
The Unix code is broken :/

- It may or may not block, depending on the browser

- It doesn't escape the URL in any way. It'll expand variables, lose
quotes, split at & and partially execute the URL, etc. Or just insert a
semicolon and run anything you want.

-g


Den 06. feb. 2015 16:31, skrev Sylvain Becker:
Quote:
I have added a first version of "SDL_OpenURL" function for Android and Unix.

It works with URLs, and probably with directories and files.

It would be nice if someone could add MacOSX, IOS, Windows, etc.

see the patch:
https://bugzilla.libsdl.org/show_bug.cgi?id=2783

On Fri, Nov 21, 2014 at 9:42 AM, Eric Wing wrote:
Quote:
Sorry, I'm really late on this one too. But I have useful info I hope.

There are official APIs for opening a URL on Mac, iOS, Android, and
Windows. I don't know about Linux except for the command line
xdg-open.

Mac
NSURL the_url = [NSURL URLWithString:@"http://www.apple.com"];
[[NSWorkspace sharedWorkspace] openURL:the_url];

iOS
NSURL the_url = [NSURL URLWithString:@"http://www.apple.com"];
[[UIApplication sharedApplication] openURL:the_url];

Windows:
LONG r = ShellExecute(NULL, "open", "http://www.microsoft.com", NULL,
NULL, SW_SHOWNORMAL);
(maybe that should be ShellExecuteA)


I forgot the details of Android, but you use Intents.
http://stackoverflow.com/questions/3004515/android-sending-an-intent-to-browser-to-open-specific-url
String url = "http://www.example.com";
Intent i = new Intent(Intent.ACTION_VIEW);
i.setData(Uri.parse(url));
startActivity(i);

Now please don't limit URLs to just http://. It is very common on Mac,
iOS, and Android to use custom URLs to launch specific apps. Sometimes
they are for popular protocols so people spontaneously conform their
apps to URL schemes that get documented so their apps can handle them
too, say like twitter:// (The OS may have an arbitration system if
multiple apps handle the same URL scheme.)
http://wiki.akosma.com/IPhone_URL_Schemes


Particularly in mobile games, I've seen a lot of developers
cross-promote their apps, where one app can launch another and maybe
you win points or something for doing so.

The Mac and iOS code will just work for that case. I think Windows may
work too. Android is a little more involved if I remember and you may
have to add more cases, but I've totally forgotten the details of how
it works.



Also, there is a counterpart system to this. It is also handy to know
when you've been launched via OpenURL. And you need to be able to
parse the URL string for information that was passed. For example,
most text editors on the Mac respond to URL schemes (even MacVim) and
you can tell it to open a specific file at a specific line number. Or
in the cross-promotional example above, you want to know which app
launched you. The receiving app needs a notification that OpenURL was
invoked with a particular string. Also, keep in mind that the app may
or may not have been already running when this even happened.

Thanks,
Eric

--
Beginning iPhone Games Development
http://playcontrol.net/iphonegamebook/
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SDL_OpenURL proposal
slvn


Joined: 06 Oct 2012
Posts: 88
Post Posted: Sat Feb 07, 2015 8:02 am
You're right !

- I am not sure about how to solve the blocking/non-blocking browser.

- The patch is updated: I changed the call to "system()", by a call to
"execl()" (and fork()) so that the URL argument is protected in a
better way.

thanks,

Sylvain

On Fri, Feb 6, 2015 at 7:21 PM, Gerry JJ wrote:
Quote:
The Unix code is broken :/

- It may or may not block, depending on the browser

- It doesn't escape the URL in any way. It'll expand variables, lose quotes,
split at & and partially execute the URL, etc. Or just insert a semicolon
and run anything you want.

-g


Den 06. feb. 2015 16:31, skrev Sylvain Becker:

Quote:
I have added a first version of "SDL_OpenURL" function for Android and
Unix.

It works with URLs, and probably with directories and files.

It would be nice if someone could add MacOSX, IOS, Windows, etc.

see the patch:
https://bugzilla.libsdl.org/show_bug.cgi?id=2783

On Fri, Nov 21, 2014 at 9:42 AM, Eric Wing wrote:
Quote:

Sorry, I'm really late on this one too. But I have useful info I hope.

There are official APIs for opening a URL on Mac, iOS, Android, and
Windows. I don't know about Linux except for the command line
xdg-open.

Mac
NSURL the_url = [NSURL URLWithString:@"http://www.apple.com"];
[[NSWorkspace sharedWorkspace] openURL:the_url];

iOS
NSURL the_url = [NSURL URLWithString:@"http://www.apple.com"];
[[UIApplication sharedApplication] openURL:the_url];

Windows:
LONG r = ShellExecute(NULL, "open", "http://www.microsoft.com", NULL,
NULL, SW_SHOWNORMAL);
(maybe that should be ShellExecuteA)


I forgot the details of Android, but you use Intents.

http://stackoverflow.com/questions/3004515/android-sending-an-intent-to-browser-to-open-specific-url
String url = "http://www.example.com";
Intent i = new Intent(Intent.ACTION_VIEW);
i.setData(Uri.parse(url));
startActivity(i);

Now please don't limit URLs to just http://. It is very common on Mac,
iOS, and Android to use custom URLs to launch specific apps. Sometimes
they are for popular protocols so people spontaneously conform their
apps to URL schemes that get documented so their apps can handle them
too, say like twitter:// (The OS may have an arbitration system if
multiple apps handle the same URL scheme.)
http://wiki.akosma.com/IPhone_URL_Schemes


Particularly in mobile games, I've seen a lot of developers
cross-promote their apps, where one app can launch another and maybe
you win points or something for doing so.

The Mac and iOS code will just work for that case. I think Windows may
work too. Android is a little more involved if I remember and you may
have to add more cases, but I've totally forgotten the details of how
it works.



Also, there is a counterpart system to this. It is also handy to know
when you've been launched via OpenURL. And you need to be able to
parse the URL string for information that was passed. For example,
most text editors on the Mac respond to URL schemes (even MacVim) and
you can tell it to open a specific file at a specific line number. Or
in the cross-promotional example above, you want to know which app
launched you. The receiving app needs a notification that OpenURL was
invoked with a particular string. Also, keep in mind that the app may
or may not have been already running when this even happened.

Thanks,
Eric

--
Beginning iPhone Games Development
http://playcontrol.net/iphonegamebook/
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http://lists.libsdl.org/listinfo.cgi/sdl-libsdl.org





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--
Sylvain Becker
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SDL_OpenURL proposal
Alexander Sabourenkov
Guest
Post Posted: Sat Feb 07, 2015 5:39 pm
I would recommend using vfork() instead of fork().


Blocking/non-blocking behavior depends on desktop environment, not browser.


xdg-open is just a shell script wrapper, see here - http://cgit.freedesktop.org/xdg/xdg-utils/tree/scripts/xdg-open.in


In absense of a desktop environment it falls back to run-mailcap and mimeopen, in that order. I have no idea if that may block (probably), if any supported DEs' launchers may block (xfce4's does not), and if going asynchonous (waiter thread, success/no-success message/event injected into event queue, quite a bit of code and complexity) is in fact worth it.

Might be better to note that the function may block and leave it at that for now.
SDL_OpenURL proposal
Alexander Sabourenkov
Guest
Post Posted: Sat Feb 07, 2015 5:49 pm
Also please use _exit() instead of exit().
SDL_OpenURL proposal
slvn


Joined: 06 Oct 2012
Posts: 88
Post Posted: Sun Feb 08, 2015 10:53 am
Thanks for the explanation.
I have updated "fork" to "vfork" and "exit" to "_exit".
Just wondering if calling "posix_spawn()" wouldn't be better?

I have also added the MacOSX and IOS part.
Please can someone double-check thoses functions as I don't really
know cocoa/uikit ! (like missing memory release of objects, incudes,
...)



On Sat, Feb 7, 2015 at 6:49 PM, Alexander Sabourenkov
wrote:
Quote:
Also please use _exit() instead of exit().


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--
Sylvain Becker
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Eirik Byrkjeflot Anonsen
Guest
Post Posted: Sun Feb 08, 2015 1:00 pm
Sylvain Becker writes:

Quote:
Thanks for the explanation.
I have updated "fork" to "vfork" and "exit" to "_exit".
Just wondering if calling "posix_spawn()" wouldn't be better?

Actually, fork() is usually preferred over vfork(). The semantics of
fork() are simple, while vfork() can easily get you into undefined
behaviour. ("the behavior is undefined if the process created by vfork()
either modifies any data other than a variable of type pid_t used to
store the return value from vfork(), or returns from the function in
which vfork() was called, or calls any other function before
successfully calling _exit(2) or one of the exec(3) family of
functions.") And the advantages of vfork() are unlikely to be useful in
this case.

posix_spawn() would surely be a potential alternative. I don't think it
really matters which one you use.

When it comes to blocking behaviour, the problem lies in the fact that
you are waiting for the new process to end. Just remove that and you
won't have blocking behaviour any more. However, that creates a new
problem with zombie processes. You do want to wait for the process
eventually. As long as you don't really care about the new process once
you've started it, this can be solved by forking twice. Start the new
process in the grandchild and immediately exit from the child. In the
parent, you wait for the child. Since the child just forks and execs,
that completes quickly and you have no blocking. At this point the child
process is gone, so the grandchild (which is the one doing the exec())
is now orphaned. Orphaned processes are waited for by the init process
(pid 1), so that will be handled automatically.

eirik
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SDL_OpenURL proposal
Alexander Sabourenkov
Guest
Post Posted: Mon Feb 09, 2015 9:41 am
On Sun, Feb 8, 2015 at 4:00 PM, Eirik Byrkjeflot Anonsen wrote:
Quote:
Sylvain Becker writes:

Quote:
Thanks for the explanation.
I have updated "fork" to "vfork" and "exit" to "_exit".
Just wondering if calling "posix_spawn()" wouldn't be better?

Actually, fork() is usually preferred over vfork().


That might be justified if we're talking about small (address-space-wise) throw-away processes. However, that's not that SDL is about.

 
Quote:
The semantics of
fork() are simple, while vfork() can easily get you into undefined
behaviour. ("the behavior is undefined if the process created by vfork()
either modifies any data other than a variable of type pid_t used to
store the return value from vfork(), or returns from the function in
which vfork() was called, or calls any other function before
successfully calling _exit(2) or one of the exec(3) family of
functions.")


The case under consideration certainly shows no potential to trip up on that.
It's a plain simple fork/exec case - the case the vfork() was designed to be used in.

 
Quote:
And the advantages of vfork() are unlikely to be useful in
this case.


Please clarify.

 

Quote:
When it comes to blocking behaviour, the problem lies in the fact that
you are waiting for the new process to end. Just remove that and you
won't have blocking behaviour any more. However, that creates a new
problem with zombie processes. You do want to wait for the process
eventually. As long as you don't really care about the new process once
you've started it, this can be solved by forking twice. Start the new
process in the grandchild and immediately exit from the child. In the
parent, you wait for the child. Since the child just forks and execs,
that completes quickly and you have no blocking. At this point the child
process is gone, so the grandchild (which is the one doing the exec())
is now orphaned. Orphaned processes are waited for by the init process
(pid 1), so that will be handled automatically.


The problem lies not in which pid gets to wait() on spawned processes,
but in the fact that the semantics of xdg-open call are not quite defined.


Life being as it is, I think a double-fork is indeed an acceptable solution
(a setsid() wouldn't hurt either).

Now imagine several gigabytes worth of page tables copied twice over
just so that a tiny shell script can be told to tell the DE to tell a browser to open an URL.


Doesn't it look like an unnecessary waste? Vfork to the rescue!
SDL_OpenURL proposal
Eirik Byrkjeflot Anonsen
Guest
Post Posted: Mon Feb 09, 2015 4:11 pm
Alexander Sabourenkov writes:

Quote:
On Sun, Feb 8, 2015 at 4:00 PM, Eirik Byrkjeflot Anonsen
wrote:

Quote:
Sylvain Becker writes:

Quote:
Thanks for the explanation.
I have updated "fork" to "vfork" and "exit" to "_exit".
Just wondering if calling "posix_spawn()" wouldn't be better?

Actually, fork() is usually preferred over vfork().


That might be justified if we're talking about small (address-space-wise)
throw-away processes. However, that's not that SDL is about.


Quote:
The semantics of
fork() are simple, while vfork() can easily get you into undefined
behaviour. ("the behavior is undefined if the process created by vfork()
either modifies any data other than a variable of type pid_t used to
store the return value from vfork(), or returns from the function in
which vfork() was called, or calls any other function before
successfully calling _exit(2) or one of the exec(3) family of
functions.")


The case under consideration certainly shows no potential to trip up on
that.
It's a plain simple fork/exec case - the case the vfork() was designed to
be used in.

Sure, but code changes. Someone changing the code and not noticing the
"v" could break it. Or someone seeing the "v" might try to exploit the
shared address space effect, something that is bound to break on some
systems. Basically, what I'm saying is that vfork() is usually an
unnecessary complication, for very little gain.

That being said, I agree that the gain depends on the situation at hand,
and I'll accept that SDL might just be one case where vfork() is worth
it.

Quote:
Quote:
And the advantages of vfork() are unlikely to be useful in
this case.


Please clarify.

Without having tested this myself, I assume that the main advantage of
vfork() is that you might be able to spawn thousands of processes per
second rather than a handful. I don't see that as being very useful for
a user-initiated one-off action. Of course, if my intuition about the
performance of fork() is off and it can be expected to take a "long"
time (whatever that is? half a second?) then I'll happily withdraw my
objection Smile

And on second thoughts, I guess if you are trying to have smoothly
animated graphics on the same thread as you are calling fork(), you
could be in trouble. (I might think that you shouldn't be trying to have
smoothly animated graphics on the same thread as arbitrary background
processing, but that's just me.)

Quote:
Quote:
When it comes to blocking behaviour, the problem lies in the fact that
you are waiting for the new process to end. Just remove that and you
won't have blocking behaviour any more. However, that creates a new
problem with zombie processes. You do want to wait for the process
eventually. As long as you don't really care about the new process once
you've started it, this can be solved by forking twice. Start the new
process in the grandchild and immediately exit from the child. In the
parent, you wait for the child. Since the child just forks and execs,
that completes quickly and you have no blocking. At this point the child
process is gone, so the grandchild (which is the one doing the exec())
is now orphaned. Orphaned processes are waited for by the init process
(pid 1), so that will be handled automatically.


The problem lies not in which pid gets to wait() on spawned processes,
but in the fact that the semantics of xdg-open call are not quite defined.

Not sure what you object to here. If you complain about my mentioning
pid 1, I was merely pointing out that some process will indeed be
wait()ing on the created process. Which is kind of important. (I'm sure
you agree that the blocking is precisely because the main process
wait()s synchronously for the potentially long-running child?)

Quote:
Life being as it is, I think a double-fork is indeed an acceptable solution
(a setsid() wouldn't hurt either).

Now imagine several gigabytes worth of page tables copied twice over
just so that a tiny shell script can be told to tell the DE to tell a
browser to open an URL.

If you have several gigabytes worth of page tables, I guess that means
you have many terabytes of allocated memory. I think at that point
the slowness of a fork() is the least of your problems Smile

Quote:
Doesn't it look like an unnecessary waste? Vfork to the rescue!

Small wastes in non-critical code doesn't worry me. Straightforward,
"obviously correct" code is generally more important to me. And I always
have to look up the particulars of vfork() whenever I see it used to be
sure it is used correctly.

But I guess it does depend on exactly how much of an advantage vfork()
is over fork() for the use cases SDL caters for. And exactly how
critical this path really is. Objection (mostly) withdrawn Smile

eirik
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SDL_OpenURL proposal
Sik


Joined: 26 Nov 2011
Posts: 905
Post Posted: Mon Feb 09, 2015 4:53 pm
2015-02-09 13:11 GMT-03:00, Eirik Byrkjeflot Anonsen:
Quote:
And on second thoughts, I guess if you are trying to have smoothly
animated graphics on the same thread as you are calling fork(), you
could be in trouble. (I might think that you shouldn't be trying to have
smoothly animated graphics on the same thread as arbitrary background
processing, but that's just me.)

Having a separate thread may still not be useful if the operating
system is exhausting all the current CPU resources in order to spawn a
new process anyway. Yeah, nitpicking here, just don't think that you
can spawn a new process and not have a serious slow down during the
time it takes to start it Razz

Quote:
If you have several gigabytes worth of page tables, I guess that means
you have many terabytes of allocated memory. I think at that point
the slowness of a fork() is the least of your problems Smile

Sound like bad wording and he just meant gigabytes of pages.

Still, given that games these days demand GBs of RAM in the system
requirements, potentially needing that much copying would be an issue.
I know that Linux only copies when the memory changes, but if the
child process is blocking then that means it could be doing that for a
long time (enough to result in lots of RAM being used up for no real
reason).
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Eirik Byrkjeflot Anonsen
Guest
Post Posted: Mon Feb 09, 2015 7:48 pm
Sik the hedgehog writes:

Quote:
2015-02-09 13:11 GMT-03:00, Eirik Byrkjeflot Anonsen:
Quote:
And on second thoughts, I guess if you are trying to have smoothly
animated graphics on the same thread as you are calling fork(), you
could be in trouble. (I might think that you shouldn't be trying to have
smoothly animated graphics on the same thread as arbitrary background
processing, but that's just me.)

Having a separate thread may still not be useful if the operating
system is exhausting all the current CPU resources in order to spawn a
new process anyway. Yeah, nitpicking here, just don't think that you
can spawn a new process and not have a serious slow down during the
time it takes to start it Razz

I'd still say it is useful. You'll have a lot more chance of reaching
your 16 or 33 ms deadline at degraded performance than when waiting for
a blocking call Smile

Quote:
Quote:
If you have several gigabytes worth of page tables, I guess that means
you have many terabytes of allocated memory. I think at that point
the slowness of a fork() is the least of your problems Smile

Sound like bad wording and he just meant gigabytes of pages.

Possibly. Which I expect would give maybe tens of megabytes of page
tables. Which should take approximately no time at all to copy.

Hmm, I see that I have an iceweasel (aka firefox) running, taking 2.2 GB
of virtual memory, 800 MB of resident memory, and 3968 kB of page
tables. (Unless I'm looking at the wrong numbers)

Quote:
Still, given that games these days demand GBs of RAM in the system
requirements, potentially needing that much copying would be an issue.
I know that Linux only copies when the memory changes, but if the
child process is blocking then that means it could be doing that for a
long time (enough to result in lots of RAM being used up for no real
reason).

Yes, I was assuming that any reasonably modern system would implement
fork() with some form of copy-on-page-required, leaving the process
state and page tables the only thing that fork() actually have to copy
(well, mostly). If SDL supports systems that requires fork() to copy the
whole process's memory space, then by all means use vfork()!

eirik
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Sik


Joined: 26 Nov 2011
Posts: 905
Post Posted: Tue Feb 10, 2015 3:27 am
2015-02-09 16:48 GMT-03:00, Eirik Byrkjeflot Anonsen:
Quote:
I'd still say it is useful. You'll have a lot more chance of reaching
your 16 or 33 ms deadline at degraded performance than when waiting for
a blocking call Smile

What I meant is that you would not even attempt this in a situation
where you don't need to miss the framerate mark in the first place Razz
(and anyway, given the whole point of this function is to open other
program and give focus to it, framerate isn't even relevant here
really)

Quote:
Possibly. Which I expect would give maybe tens of megabytes of page
tables. Which should take approximately no time at all to copy.

But you'd still need to copy the pages themselves too, which is where
the real problem arises...

Quote:
Yes, I was assuming that any reasonably modern system would implement
fork() with some form of copy-on-page-required, leaving the process
state and page tables the only thing that fork() actually have to copy
(well, mostly). If SDL supports systems that requires fork() to copy the
whole process's memory space, then by all means use vfork()!

For that kind of stuff there's usually an #ifdef to select between
both methods. The thing is that as I mentioned the issue can even
arise with copy-on-change, if the two processes stay around for too
long (which is what's bound to happen if the call ends up being
blocking).
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Daniel Gibson
Guest
Post Posted: Tue Feb 10, 2015 4:05 am
On 02/10/2015 04:27 AM, Sik the hedgehog wrote:
Quote:
2015-02-09 16:48 GMT-03:00, Eirik Byrkjeflot Anonsen:
Quote:
I'd still say it is useful. You'll have a lot more chance of reaching
your 16 or 33 ms deadline at degraded performance than when waiting for
a blocking call Smile

What I meant is that you would not even attempt this in a situation
where you don't need to miss the framerate mark in the first place Razz
(and anyway, given the whole point of this function is to open other
program and give focus to it, framerate isn't even relevant here
really)

Quote:
Possibly. Which I expect would give maybe tens of megabytes of page
tables. Which should take approximately no time at all to copy.

But you'd still need to copy the pages themselves too, which is where
the real problem arises...

Quote:
Yes, I was assuming that any reasonably modern system would implement
fork() with some form of copy-on-page-required, leaving the process
state and page tables the only thing that fork() actually have to copy
(well, mostly). If SDL supports systems that requires fork() to copy the
whole process's memory space, then by all means use vfork()!

For that kind of stuff there's usually an #ifdef to select between
both methods. The thing is that as I mentioned the issue can even
arise with copy-on-change, if the two processes stay around for too
long (which is what's bound to happen if the call ends up being
blocking).

Not if the fork()ed process exec()s - after that they shouldn't share
any pages anymore.

I'd suggest stopping to discuss about fork() vs vfork() and concentrate
on how to best run that shellscript savely and reap the child later to
prevent zombies.
As this is a common enough task it shouldn't be that hard?

Cheers,
Daniel

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slvn


Joined: 06 Oct 2012
Posts: 88
Post Posted: Tue Feb 10, 2015 7:52 am
As suggested, I have updated the patch to fork twice so that the
application cannot be blocked.

Notice that the return code does not say anymore something about the
success/failure of xdg-open, but now, is about the success/failure of
the *launching* of xdg-open.

PID should be collected and ended manually at the end probably ?


On Tue, Feb 10, 2015 at 5:05 AM, Daniel Gibson wrote:
Quote:
On 02/10/2015 04:27 AM, Sik the hedgehog wrote:
Quote:

2015-02-09 16:48 GMT-03:00, Eirik Byrkjeflot Anonsen:
Quote:

I'd still say it is useful. You'll have a lot more chance of reaching
your 16 or 33 ms deadline at degraded performance than when waiting for
a blocking call Smile


What I meant is that you would not even attempt this in a situation
where you don't need to miss the framerate mark in the first place Razz
(and anyway, given the whole point of this function is to open other
program and give focus to it, framerate isn't even relevant here
really)

Quote:
Possibly. Which I expect would give maybe tens of megabytes of page
tables. Which should take approximately no time at all to copy.


But you'd still need to copy the pages themselves too, which is where
the real problem arises...

Quote:
Yes, I was assuming that any reasonably modern system would implement
fork() with some form of copy-on-page-required, leaving the process
state and page tables the only thing that fork() actually have to copy
(well, mostly). If SDL supports systems that requires fork() to copy the
whole process's memory space, then by all means use vfork()!


For that kind of stuff there's usually an #ifdef to select between
both methods. The thing is that as I mentioned the issue can even
arise with copy-on-change, if the two processes stay around for too
long (which is what's bound to happen if the call ends up being
blocking).


Not if the fork()ed process exec()s - after that they shouldn't share any
pages anymore.

I'd suggest stopping to discuss about fork() vs vfork() and concentrate on
how to best run that shellscript savely and reap the child later to prevent
zombies.
As this is a common enough task it shouldn't be that hard?

Cheers,
Daniel


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Eirik Byrkjeflot Anonsen
Guest
Post Posted: Tue Feb 10, 2015 7:15 pm
Sylvain Becker writes:

Quote:
As suggested, I have updated the patch to fork twice so that the
application cannot be blocked.

Notice that the return code does not say anymore something about the
success/failure of xdg-open, but now, is about the success/failure of
the *launching* of xdg-open.

PID should be collected and ended manually at the end probably ?

Not sure which pid you are talking about here. If you are thinking about
the pid of xdg-open, you can just ignore it. That's really the point of
forking twice. Since xdg-open is now orphaned, "init" (process 1) will
reap it when it dies. I have not looked carefully at the code, only
quickly read through the unix SDL_OpenURL() code, but it looks sensible
to me.

eirik
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slvn


Joined: 06 Oct 2012
Posts: 88
Post Posted: Wed Feb 11, 2015 7:08 am
Sorry, I did not explain myself correctly.
Yes, I mean't the xdg-open pid, when xdg-open is blocking because of
the system configuration.
For instance, xdg-open is blocking and opening the url/file with no
window/shell/tty attached.
Then those xdg-open process will last forever, because of no user
interaction, even after the main sdl app has exited.

Don't know if this configuration could happen.
(this can be simulated easily, by replacing the launch of xdg-open in
SDL_OpenURL, by the launching of a script that simply does an infinite
loop).


On Tue, Feb 10, 2015 at 8:15 PM, Eirik Byrkjeflot Anonsen
wrote:
Quote:
Sylvain Becker writes:

Quote:
As suggested, I have updated the patch to fork twice so that the
application cannot be blocked.

Notice that the return code does not say anymore something about the
success/failure of xdg-open, but now, is about the success/failure of
the *launching* of xdg-open.

PID should be collected and ended manually at the end probably ?

Not sure which pid you are talking about here. If you are thinking about
the pid of xdg-open, you can just ignore it. That's really the point of
forking twice. Since xdg-open is now orphaned, "init" (process 1) will
reap it when it dies. I have not looked carefully at the code, only
quickly read through the unix SDL_OpenURL() code, but it looks sensible
to me.

eirik
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Eirik Byrkjeflot Anonsen
Guest
Post Posted: Wed Feb 11, 2015 3:43 pm
Sylvain Becker writes:

Quote:
Sorry, I did not explain myself correctly.
Yes, I mean't the xdg-open pid, when xdg-open is blocking because of
the system configuration.
For instance, xdg-open is blocking and opening the url/file with no
window/shell/tty attached.
Then those xdg-open process will last forever, because of no user
interaction, even after the main sdl app has exited.

Don't know if this configuration could happen.
(this can be simulated easily, by replacing the launch of xdg-open in
SDL_OpenURL, by the launching of a script that simply does an infinite
loop).


I see. Yes, that is a point. However, I don't think that is a situation
you want to handle anyway. Consider what would happen if xdg-open
replaces its process with the web browser. The user would probably not
be happy if you kill their web browser.

Also, once you start doing this, you'll have to properly track the
process, which means doing some global work to wait() for the process
again. Which just gets hairy.

I think it is probably better to just assume that xdg-open is sane Smile

eirik
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Gerry JJ
Guest
Post Posted: Wed Feb 11, 2015 3:57 pm
Den 10. feb. 2015 08:52, skrev Sylvain Becker:
Quote:
As suggested, I have updated the patch to fork twice so that the
application cannot be blocked.

I don't think you can vfork twice like that. You can call exec*, or
_exit, and that's it. Just use fork :p

Also, could you use execlp with "xdg-open" as the path instead of execl?

-g

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slvn


Joined: 06 Oct 2012
Posts: 88
Post Posted: Thu Feb 12, 2015 7:46 am
Updated patch.

Yes, you're totally right. The first forking must be done with
"fork()" because it will then try to fork again (so it calls a
function different from _exit and exec*, making "vfork()" not
recommended there).
Second forking can be done either with fork() or vfork().

(Even if it works my Linux distribution, it's seems to have some
problem with others systems).


Thanks for all comments. Also, Thanks to the original posters of this
thread Alex and Eric, because the patch is mainly of copy-paste of
their indications.

I think, now, it needs also the windows patch. Which I can't do as I
have no window platform ready for that.
Would be nice to have someone to look at it.


On Wed, Feb 11, 2015 at 4:56 PM, Gerry JJ wrote:
Quote:
Den 10. feb. 2015 08:52, skrev Sylvain Becker:
Quote:

As suggested, I have updated the patch to fork twice so that the
application cannot be blocked.


I don't think you can vfork twice like that. You can call exec*, or _exit,
and that's it. Just use fork :p

Also, could you use execlp with "xdg-open" as the path instead of execl?

-g


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AntTheAlchemist


Joined: 13 Feb 2015
Posts: 60
Location: UK
Post Posted: Tue Jan 12, 2016 4:56 pm
Has there been any more developments on this? I was hoping to see it included in 2.0.4.

I don't know how to apply a patch...
SDL_OpenURL proposal
slvn


Joined: 06 Oct 2012
Posts: 88
Post Posted: Wed Feb 03, 2016 1:27 pm
I would like also to see this included.
Just to let people know that it currently works on android, ios, windows10, macosx, linux.

But the patch is partially implemented.


On 12 January 2016 at 17:56, AntTheAlchemist wrote:
Quote:
Has there been any more developments on this? I was hoping to see it included in 2.0.4.

I don't know how to apply a patch...


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