Re: Is read_file() always called after an activity __init__?
On Sat, Mar 1, 2008 at 3:12 AM, John Gilmore [EMAIL PROTECTED] wrote: Hmmm, so if my activity needs it's preferences before it can display anything to the user, potential future lazy loading of the data-store (to try and speed up general activity start-up time) is going to leave folks watching my activity with a blank screen for a lazy while? Ouch. Ahem. The Grand Unified Theory of OLPC was that the datastore/journal were going to entirely replace the filesystem (as far as Activites are concerned). Activities aren't permitted to read/write the ordinary Linux filesystem, according to this theory. Not true. The datastore is for recording actions and storing the documents associated to those. In other words: for saving the child's work and allowing for efficient retrieval. Where have you found this theory? See the link below for an explanation of the suggested guidelines for writing to the fs: http://wiki.laptop.org/go/Low-level_Activity_API#Writable_Directories If the datastore isn't just as ready, just as fast, and just as available as the filesystem, e.g. for holding tiny little files that rapidly keep the Activity's configuation options, then there's something terribly wrong here. Can you elaborate? I'm certainly not happy with the current state of the DS, but would like to know more about which problems you see in the current implementation. Thanks, Tomeu ___ Devel mailing list Devel@lists.laptop.org http://lists.laptop.org/listinfo/devel
Re: Is read_file() always called after an activity __init__?
On Thu, Feb 28, 2008 at 10:56 PM, Gary C Martin [EMAIL PROTECTED] wrote: It does seem like read_file() is only triggered if you have previously saved an actual file to filesystem, if you just have metadata, no call is ever made to read_file() so it's a rather bad place to pick-up the metadata. At least this is what I'm seeing here – I've just created a 0 size file in my write_file() and now a resume from that journal entry is triggering read_file() every time. You are right again. Perhaps we should add a read_metadata() method? An alternative would be to have a 'datastore-loaded' method, but that would be less consistent with the current API. Hmmm, so if my activity needs it's preferences before it can display anything to the user, potential future lazy loading of the data-store (to try and speed up general activity start-up time) is going to leave folks watching my activity with a blank screen for a lazy while? Ouch. Well, metadata loading shouldn't be as slow as for the user to notice. But if you add this to all the other initializations, it is significant. Also, the user wouldn't see a blank screen, just startup will be (say) 100ms slower than for an activity that can start without reading the metadata. But the determining reason would be that metadata properties other than the custom ones are not preserved across reboots :/ http://dev.laptop.org/ticket/4662 Oooh thanks, double ouch, I hadn't spotted that gotcha yet! I'm getting the distinct feeling I should avoid current metadata interactions by an activity (too flakey and in transition just now) and just create a custom preference like file format, it only needs to store two key/value pairs at the moment, probably will eventually need only half a dozen at the most for future display options. Though I guess even that's still going to be a problem if lazy data-store loading is ever implemented (though every activity that needs to load a file for display will suffer there). Leave the metadata alone for the Journal and lower level activity class behaviours. Pity, metadata looked like a nice solution for storing simple custom activity state information, maybe in update. 2... Right, metadata in journal entries was thought exactly for that. Using some other kind of preferences file may be the best for now. Regards, Tomeu ___ Devel mailing list Devel@lists.laptop.org http://lists.laptop.org/listinfo/devel
Re: Is read_file() always called after an activity __init__?
Hmmm, so if my activity needs it's preferences before it can display anything to the user, potential future lazy loading of the data-store (to try and speed up general activity start-up time) is going to leave folks watching my activity with a blank screen for a lazy while? Ouch. Ahem. The Grand Unified Theory of OLPC was that the datastore/journal were going to entirely replace the filesystem (as far as Activites are concerned). Activities aren't permitted to read/write the ordinary Linux filesystem, according to this theory. If the datastore isn't just as ready, just as fast, and just as available as the filesystem, e.g. for holding tiny little files that rapidly keep the Activity's configuation options, then there's something terribly wrong here. John ___ Devel mailing list Devel@lists.laptop.org http://lists.laptop.org/listinfo/devel
Re: Is read_file() always called after an activity __init__?
Hi Tomeu, On 28 Feb 2008, at 09:40, Tomeu Vizoso wrote: Well, __init__ is too soon. Well before calling activity.Activity.__init__(self, handle) yes that would be a real bad idea for sure :-) but after that it 'should' be fine shouldn't it, as the activity class is all set up? I can certainly read the metadata in my main __int__ just after the call up to super, and all works well. AFAIK, the API docs say that you can safely access Activity.metadata in the read_file() and write_file() methods. read_file() is called when the user is resuming an existing activity and write_file() when sugar thinks it is a good time to save changes to the journal (probably several times during the life of an activity). It does seem like read_file() is only triggered if you have previously saved an actual file to filesystem, if you just have metadata, no call is ever made to read_file() so it's a rather bad place to pick-up the metadata. At least this is what I'm seeing here – I've just created a 0 size file in my write_file() and now a resume from that journal entry is triggering read_file() every time. Is very probable that the API documentation is lacking, can you point me to the docs you were following? Have you already read the HIG in the wiki? Not an officially maintained page I know, but: http://wiki.laptop.org/go/Beyond_Hello_World Same suggestion comes from the current pydocs: http://xo_running_pydoc-p8080:8080/ sugar.activity.activity.html#Activity-read_file http://www.vrplumber.com/sugar-docs/sugar.activity.activity.html#Activity-read_file (an online version) I also went through a number of activity sources in git looking for examples, but I didn't find one that ONLY used metadata. They all seem to either not bother storing any UI state (so resuming or from new makes no difference), or they save actual files. BTW: I'm quite happy with read_file() not getting called in file-less cases, just a matter of documenting it somewhere (if that is indeed the correct behaviour intended). Thanks for your input. ___ Devel mailing list Devel@lists.laptop.org http://lists.laptop.org/listinfo/devel
Re: Is read_file() always called after an activity __init__?
On Thu, Feb 28, 2008 at 12:45 PM, Gary C Martin [EMAIL PROTECTED] wrote: Hi Tomeu, On 28 Feb 2008, at 09:40, Tomeu Vizoso wrote: Well, __init__ is too soon. Well before calling activity.Activity.__init__(self, handle) yes that would be a real bad idea for sure :-) but after that it 'should' be fine shouldn't it, as the activity class is all set up? I can certainly read the metadata in my main __int__ just after the call up to super, and all works well. You are right, though at some point we would like to defer the fetch of data from the datastore to a later point after construction. In this way some activities will be able to launch faster. AFAIK, the API docs say that you can safely access Activity.metadata in the read_file() and write_file() methods. read_file() is called when the user is resuming an existing activity and write_file() when sugar thinks it is a good time to save changes to the journal (probably several times during the life of an activity). It does seem like read_file() is only triggered if you have previously saved an actual file to filesystem, if you just have metadata, no call is ever made to read_file() so it's a rather bad place to pick-up the metadata. At least this is what I'm seeing here – I've just created a 0 size file in my write_file() and now a resume from that journal entry is triggering read_file() every time. You are right again. Perhaps we should add a read_metadata() method? An alternative would be to have a 'datastore-loaded' method, but that would be less consistent with the current API. Is very probable that the API documentation is lacking, can you point me to the docs you were following? Have you already read the HIG in the wiki? Not an officially maintained page I know, but: http://wiki.laptop.org/go/Beyond_Hello_World Not that we have many officially maintained pages about sugar docs :/ Same suggestion comes from the current pydocs: http://xo_running_pydoc-p8080:8080/ sugar.activity.activity.html#Activity-read_file http://www.vrplumber.com/sugar-docs/sugar.activity.activity.html#Activity-read_file (an online version) Would be nice to have a wiki bot that would update the API docs in the wiki from the sources. Anybody know something like that? I also went through a number of activity sources in git looking for examples, but I didn't find one that ONLY used metadata. They all seem to either not bother storing any UI state (so resuming or from new makes no difference), or they save actual files. I think at some point activities like those realize that they have some data that would be better saved in a file. But the determining reason would be that metadata properties other than the custom ones are not preserved across reboots :/ http://dev.laptop.org/ticket/4662 BTW: I'm quite happy with read_file() not getting called in file-less cases, just a matter of documenting it somewhere (if that is indeed the correct behaviour intended). Thanks for your input. Thanks, Tomeu ___ Devel mailing list Devel@lists.laptop.org http://lists.laptop.org/listinfo/devel
Re: Is read_file() always called after an activity __init__?
It does seem like read_file() is only triggered if you have previously saved an actual file to filesystem, if you just have metadata, no call is ever made to read_file() so it's a rather bad place to pick-up the metadata. At least this is what I'm seeing here – I've just created a 0 size file in my write_file() and now a resume from that journal entry is triggering read_file() every time. You are right again. Perhaps we should add a read_metadata() method? An alternative would be to have a 'datastore-loaded' method, but that would be less consistent with the current API. Hmmm, so if my activity needs it's preferences before it can display anything to the user, potential future lazy loading of the data-store (to try and speed up general activity start-up time) is going to leave folks watching my activity with a blank screen for a lazy while? Ouch. But the determining reason would be that metadata properties other than the custom ones are not preserved across reboots :/ http://dev.laptop.org/ticket/4662 Oooh thanks, double ouch, I hadn't spotted that gotcha yet! I'm getting the distinct feeling I should avoid current metadata interactions by an activity (too flakey and in transition just now) and just create a custom preference like file format, it only needs to store two key/value pairs at the moment, probably will eventually need only half a dozen at the most for future display options. Though I guess even that's still going to be a problem if lazy data-store loading is ever implemented (though every activity that needs to load a file for display will suffer there). Leave the metadata alone for the Journal and lower level activity class behaviours. Pity, metadata looked like a nice solution for storing simple custom activity state information, maybe in update. 2... Thanks again. ___ Devel mailing list Devel@lists.laptop.org http://lists.laptop.org/listinfo/devel
Is read_file() always called after an activity __init__?
Hope this is not too silly a question, but is the read_file() method
always called after the Python activity __init__'? I'm just started
using self.metadata to store some basic preferences to pickup after a
Journal resume, but I'm finding read_file() is never called in my
activity. My write_file() method is correctly called as the activity
is closed. I'm wondering if read_file() is only ever triggered during
a resume if you have a real chunk of filesystem to write/read (my
activity needs/has no file)?
FYI: If I pop a self.read_file('foo.bar') in my activities main
__init__ all works as I'd expect. Should I just be picking up metadata
values in my __init__? All documentation I've seen so far says to
check your metadata in read_file.
Thanks for any help.
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