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APPLE II DEVELOPMENT FORUM CONFERENCE LOG
Tuesday, December 18, 1990  10:00 p.m. Eastern Time
Topic:  Assembly Language Programming
Forum Leader:  Dave Sugar (AFL Dyfet)


AFL Dyfet  Okay, good evening all, and welcome to the Apple II Development
AFL Dyfet  Forum.  Tonight we will be discussing Assembly Language
           Programming
AFL Dyfet  and the latest in Coach Hayden's life :).
AFL Dyfet  I see Scott has snuck in with the first question for tonight
           :)...GA Scott...
AFL Scott  Does anyone have an alternative method of detecting low memory
           situations?   The method in the IIGS
AFL Scott  Technotes and the method in TB Ref Vol3 doesn't really work
AFL Scott  with my application.
AFL Dyfet  GA Dave...
Dave Lyons Why/when doesn't it work?  We can probably come up with some
           refinements.
AFL Scott  Well, basically, when the 32k handle gets purged, some damage has
           already occurred.  This leaves 
AFL Scott  my app in a rotten state (note that this is just for testing
           purposes.  The method I used
AFL Scott  in the final release of Allison is still employed in the release).
            See, I changed things to 
AFL Scott  allow the memory manager to do it's stuff.  The release version of
           Allison _depends_ on memory
AFL Scott  to be fragmented, but this is very wasteful, IMHO.
AFL Scott  I decided to change it to see what happens.  The results weren't
           good. GA.
Dave Lyons I'm missing something--do you know how the damage is occuring?
Dave Lyons I don't see how fragmentation helps.
AFL Scott  Well, for starters, the text in several dialogs gets trashed. 
           Fragmentation ensures Quickdraw has 
AFL Scott  enough memory in most cases.  And the chunks in varied memory
           configurations are 32k.
AFL Scott  On my machine, I've not seen this method fail no matter what I run
           or what I do.  
AFL Scott  I haven't seen it fail on other machines, but I don't trust it. 
           It's very dependant on what the 
Dave Lyons So is the problem that your app can suck up all the big chunks,
           leaving QD insufficient memory?
AFL Scott  user does and has loaded. 
AFL Scott  Big chunks.. in 32k and 85 byte swatches, yup.
Dave Lyons How 'bout this: Keep a *second* chunk of throw-away memory
           allocated,
Dave Lyons and when you notice that your watchdog 32K handle got purged (and
           maybe all got re-used!), you can
Dave Lyons dispose of the second one & be guaranteed enough free memory to
           put up an out-of-memory dialog.
Dave Lyons Does that make sense?
AFL Scott  Yes.  You're saying reserve 64k and use the first 32k as a signal.
            Well, that's fine, except the 
AFL Scott  app has to run in a 1meg ROM03 GS.  The app needs alot of memory
           to do what it has to do.
AFL Scott  It's a toughie, and I don't think there's going to be a good
           answer given the memory requirement of 
AFL Scott  the App.
Dave Lyons Understood, but keeping two chunks would seem to be at least as
           good as creating extra fragmentation,
Dave Lyons no?
AFL Scott  Yes, it would.  I just cannot guarantee there will be 64k at the
           outset.  I'll try it again and see 
AFL Scott  what happens.  
Dave Lyons Maybe both chunks don't have to be 32K--consider
Dave Lyons the relationships of the sizes of handles your app allocates,
           maybe.
AFL Scott  Explain.  I don't follow.
Dave Lyons Well, I'm trying to get at this--
Dave Lyons if you allocate a lot of 32K handles normally, then you're likely
           to
Dave Lyons make your watchdog 32K handle go away *and get completely reused*
           all at once.  So the technote
Dave Lyons is a good starting point, but you can fine-tune it to your
           application by being paranoid & seeing
Dave Lyons how to let the system always have enough memory to put up your
           warning dialogs.
Dave Lyons You could even do stuff like:
Dave Lyons Whenever you allocate a big handle, allocate some slop, allocate
           your handle, and deallocate your
Dave Lyons slop.  Then you haven't sucked up the last available memory if you
           succeed in getting your
Dave Lyons handle.  (If you have a watchdog handle, locking it during your
           big allocation would have the same
Dave Lyons effect, as long as you're prepared for your big NewHandle to
           fail).
Dave Lyons (ga)
AFL Scott  Ok.. that makes sense.  How about trying to allocate memory until
           a failure, counting the handles and 
AFL Scott  using that as a watchdog, instead?
AFL Scott  (should read.. gobble everything, give it back and 
Dave Lyons Not sure I understand--have lots of smaller watchdogs instead of
           one big one??
Dave Lyons Doesn't sound like a plan--if you allocate until failure all the
           time, you'll make everything
Dave Lyons that's purgable get purged, unnecessarily.
AFL Scott  Not really.. Just do it at startup, count the chunks subtract two
           or so from the count, save the count
AFL Scott  then kill all the "count handles".  If I understand you right,
           you're saying that I can purge restart
AFL Scott  able apps doing it this way, right?  I mean if the tools are
           started before this happens, their memory
AFL Scott  shouldn't get purged, right?
Dave Lyons DAs/etc could allocate memory while your app is up, though.
Dave Lyons Yes--not just restartable apps, but other stuff in
Dave Lyons memory that is purgable, like QD's work buffer & who knows what
           else.  If you can avoid purging
Dave Lyons everything, that's good.  That why I'm recommending stuff like
           "allocate with temporary slop".
Dave Lyons ga
AFL Scott  Ok... I see your point.  I'll try your suggestion and see how that
           works.  Thanks, Dave!
AFL Scott  Done.
Dave Lyons okee dokee
AFL Dyfet  Okay, who has the next question for tonight?
Dave Lyons I think Matt does.
Matt DTS   My question:  "Can we talk about something other than Scott's
           memory allocation?"
Matt DTS   :)
AFA Gary J Sure, Matt :)
AFL Scott  (Sounds good to me.  I'm tired of it, too.)
Coach101   What do you want to talk about Matt ?:)
AFL Scott  :)
Matt DTS   Something that more than Dave and Scott can get involved in.  :)
AFL Scott  Printing!:)
AFL Dyfet  GA Scott :)
AFL Scott  Is it necessary for the application to check what type of printer
           is being used?  Serious question.
AFL Scott  (some how I knew he'd answer!:)
AFL Dyfet  Yes, go ahead Matt...
Matt DTS   It depends on what you're going to do with the information. 
           Usually not.
Matt DTS   If you want to use driver-specific features, though, you should
           check the iDev value for the one you
Matt DTS   want (or use some other identification for $8001 iDev values -
           maybe the driver file name).  GA.
AFL Scott  Ok, so Pic Comments shouldn't mess up well behaved
AFL Scott  drivers?
Matt DTS   Most PicComment *numbers* are reserved, so they shouldn't mess up
           well-behaved drivers.  However, if
Matt DTS   you're using driver-specific PicComments, it certainly wouldn't
           hurt to compare the iDev value just to
Matt DTS   be safe.  GA.
AFL Scott  (make PicComments one word :))
AFL Scott  Ok, I think I may have to do that.  Harmonie seems to not like
           PicComments.  Thanks.  Done!:)
Matt DTS   Be sure to tell BurgerBill about it, Scott.
AFL Scott  Wheels are in motion!:) 
AFA Gary J :)
AFA Gary J How are the Seven Hills drivers?
Matt DTS   (Was that fun?)
AFA Gary J Have you tried them?
AFL Scott  Not here, I didn't have time test them at Applefest.
Matt DTS   I've been impressed by what I've seen of the Seven Hills
           drivers.
AFA Gary J That's good to know  :)   
Matt DTS   I'm really impressed with how fast Steve learned how to write
           Printer Drivers for Independence.
AFL Dyfet  Okay, does anyone else have a non memory manager and non printer
           question :)?
AFL Dyfet  GA Scott
AFL Scott  I haven't tried this yet, but it's going to pop up... is it
           possible to start a user toolset using 
AFL Scott  StartTools?  If not, and I wish to use StartTools to start the
           "native" tools, how does one obtain the
AFL Scott  direct page page space necessary for user toolset and does the
           user toolset have to have the same 
AFL Scott  direct page as the "native" tools?
AFL Scott  (dumb question, right?)
AFL Dyfet  GA Dave...(I'm interested in user tools too :)
Dave Lyons LoadOneTool, LoadTools, and StartUpTools only know about system
           tool sets.  So, you have to
Dave Lyons get the code into memory on your own.  For ex:  Imbed it in your
           app (ick), use InitialLoad or
Dave Lyons InitialLoad2, or use LoadResource with the CodeResConverter logged
           in for your resource
Dave Lyons type.
Dave Lyons Once the code is in memory, use SetTSPtr (which *does* have a
           System vs. User tool set flag) to
Dave Lyons tell the system where your tool set's function pointer table (FPT)
           is.
Dave Lyons Direct page space--either have the app allocate it with NewHandle,
           attributes $C015, and pass the
Dave Lyons pointer to the toolset's StartUp function, or have the toolset
           allocate it itself (using its own
Dave Lyons ID, as determined by calling MMStartUp from the
Dave Lyons tool set), or using a memory ID specified by the application (as a
           parameter to the StartUp function,
Dave Lyons or whatever).  The tool set can use its work area pointer (GetWAP,
           SetWAP) to store whatever
Dave Lyons information it wants--usually you'll just have the pointer to your
           direct-page space, if any.
Dave Lyons ga
AFL Scott  Thanks Dave!:)
AFL Scott  done.
Dave Lyons (Of course, see technotes, too.)
AFA Gary J Any more questions, Scott????  :)
AFL Dyfet  Thanks Dave!
AFL Dyfet  Go ahead Coach!
Coach101   If two or more items (app & DA for example) utilize the same Run
           Time Library, will the system
Coach101   have one or two copies of the library in memory?
AFL Dyfet  I don't believe the IIgs loader has a concept of shared code
           images....
AFL Dyfet  (shades of VMS here)
Dave Lyons [I don't know.  Never used run-time libraries.  I thought they
           were there to be shared, but I'm
Dave Lyons not sure.]
AFL Dyfet  GA Winkie...
WinkieJim  SHouldn't be a problem, because almost no one uses them :)
AFA Gary J Q = Coach (WinkieJim)
Coach101   But, they are a real neat idea and do work with the APW linker
           (LinkIIGS).....  done
AFL Dyfet  I think you stumped 'em Coach :)
WinkieJim  Neat idea that never took off...
Dave Lyons (Yeah, you win a prize--you get to write in to DTS and wait until
           the dude responsible for
Coach101   Yeah, I thought for sure Matt would jump on it since it was a ?
           from other than Scott :)
Dave Lyons the Loader comes back from vacation. :)
AFL Scott  :)
Coach101   Nah, its real easy to test.  I was just curious and would rather
           avoid the time to do the test....
Coach101   ga
AFL Dyfet  My guess is that it will load a seperate image :)...I guess we
           will eventually
AFL Dyfet  find out who is right...
AFA Gary J I'd guess the same thing, Dave.
Matt DTS   I *believe* the loader knows about run-time libraries and only
           keeps one copy in memory.
Matt DTS   I would also bet that this part of the Loader hasn't been
           extensively field-tested.  :)
Coach101   I tend to agree with Matt & Dave, but given the ill use of RTLs,
           who knows....
Coach101   the system may even barf in that situation...
WinkieJim  Since the library could change values in itself it would be
           dangerous not to
WinkieJim  have separate copies...I'd think.
AFL Dyfet  I could see the possibility of stomping on data in the RTL if two
           apps are
AFL Dyfet  working with the same image (or as Winkie just said)
Coach101   I know it works fine for the single user RTL though...  (cuts
           linker time too!) 
Dave Lyons (*If* the loader supports shared RTLs, the idea would be that RTLs
           are supposed to be prepared
Dave Lyons to have multiple clients.  Perfectly possible.)
Coach101   But, there is little value to an RTL if it is a single user entity
           (barring the reduction in 
Coach101   linker time).
Coach101   It is kind of like a *callable* user tool set....
Dave Lyons And reduction in disk space, if you have several apps that use the
           same library at different times.
AFL Dyfet  If the library only uses stack reference or dynamically allocated
           work space,
AFL Dyfet  it certainly could function as a shared image if supported by the
           loader in
AFL Dyfet  that manner.  The burden would then simply be on the programmer to
           write it
AFL Dyfet  carefully :)
WinkieJim  Oh, in that case it would always work perfectly...:)
Coach101   A big advantage of them, is that you can have
Coach101   several apps that use a common library.  If you
Coach101   enhance the common library, you do not even need
Coach101   to re-link the apps.  Just reform the library and
Coach101   immediately all the apps are using the new, improved, enhanced,
           faster, less buggy, etc. library
AFL Dyfet  Well, I guess we will have to wait to find out about how RTL's are
           supported...
AFL Dyfet  Okay, do we have any other questions for tonight?
Coach101   I will run the test next week....
AFL Dyfet  GA Winkie...
WinkieJim  I don't suppose there's any other way to put up a modal dialog
           from a resource
WinkieJim  other than using FakeModalDialog?
Dave Lyons Sure, just do part of what FakeModalDialog does, but do it
           yourself.  Call NewWindow2 to create
Dave Lyons your window, and go into a sepaate TaskMaster loop where you only
           turn on the TaskMask bits you
Dave Lyons want.  (For example, leave off the one that brings windows to the
           front when you click on them.)
Dave Lyons If you're doing a complicated dialog, it's probably worth your
           while to use FakeModalDialog instad
Dave Lyons of doing a lot of the work yourself.  ga
WinkieJim  Errr...that would be great for an App, but it's an NDA...
Dave Lyons Why not from an NDA?
WinkieJim  I've always thought NDA's can ony have one window?
Dave Lyons You can do *modal* loops in your NDA--just *don't* allow
           TaskMaster to do window updating for you,
Dave Lyons or you'll make the app's window-update routines get called with
           the wrong CurResourceApp set.  Turn
Dave Lyons off the task-mask update bit & respond to selected updates
           yourself, when the event comes back from
Dave Lyons TaskMaster.
Dave Lyons You can only have one *modeless* window in an NDA--modal ones are
           a different story.  Just
Dave Lyons the main window is special to the system (no need to call
           SetSysWindow on your modal windows, and
Dave Lyons I actually recommend your don't).
WinkieJim  ah....
WinkieJim  Now I just have to decide if it's worth the trouble to use the
           resource window
WinkieJim  or just do it the old fasioned way...
WinkieJim  Wish List: Dialog Resources :)
Dave Lyons I suppose you want all the neat stuff that Extended Controls can
           do added to the Dialog Manager,
Dave Lyons right?)
WinkieJim  Not really, just want to be able to keep the dialog in a resource
           so it can
WinkieJim  be changed and updated easy.
Dave Lyons Well, once you have FakeModalDialog *or* a small collection of
           your own routines, if you don't
Dave Lyons like FMD, existing window/control resources make great dialog
           resources!
Dave Lyons Extended controls are spiffy and will be spiffier.
WinkieJim  I have nothing against FMD, but I didn't realize I could open
           another window
WinkieJim  in a NDA...
WinkieJim  Does FMD handle the updates right?
Dave Lyons (Never seen Memory Bar's about box? :)
Dave Lyons FMD has a flag bit where you tell it whether to update windows
Dave Lyons besides the dialog window.  Just *don't* set that bit when you
           call FMD from a NDA, and life
Dave Lyons is good.
WinkieJim  Sounds good.
Dave Lyons Eventually I would like to make the restriction unnecessary--that
           would
Dave Lyons mean the Window Manager would have to "know" the right resource
           app for each window.  This is
Dave Lyons probably do-able, but not in 5.0.4.
Dave Lyons (ga)
WinkieJim  (and I don't use Memory Bar...I use a better memory bar NDA :)
WinkieJim  IBdone
Dave Lyons (How 'bout the Control Panel's "Help" window?  That's modal.)