[Vm-dev] Support for reading and writing JPEGs to/from -32, -16, -8 and 8 bit deep forms on V3

Thu May 26 19:41:22 UTC 2016

Excellent, thanks Laura!

Dave

>  Elliot, Dave,
>
> Thanks for your feedback! I didn't realise the differences between the
> coding practices of JPEGReadWriter2Plugin and other plugins since I
> didn't look at the code of the others. I'll try to get the code of
> JPEGReadWriter2Plugin to bear more resemblance to the rest of the
> codebase. I've taken a brief look at RePlugin's code and the way the C
> code should be placed into external files is still a bit confusing to
> me. Any guidance in this aspect would be greatly appreciated.
>
> As I mentioned earlier, I've been working on handling non-even width
> 16-bit Forms and non-0 modulo 4 width 8 bit Forms. Here are two
> changesets with the implementation of that feature.
>
> Cheers!
> -Laura Perez Cerrato
>
>
> On 19 May 2016 at 23:05, David T. Lewis <lewis at mail.msen.com> wrote:
>>
>> Hi Laura,
>>
>> Thanks very much for posting this. I took a quick look at it and will
>> try to follow up later.
>>
>> To clarify one point: Eliot is using the word "horrible" to refer to
>> some coding practices in the existing JPEGReadWriter2Plugin, and it does
>> not mean that your patches are "horrible".
>>
>>
>> Eliot,
>>
>> Indeed, those giant blocks of #cCode are bad, and somebody (tm) should
>> do something about it. It may not be obvious from looking at the change
>> set, but Laura's updates are are patches against that existing code.
>> So your suggestion is good - either rewrite those portions in proper
>> Smalltalk slang, or just move them out to C code in the platforms
>> support.
>>
>> I think that this is probably beyond the scope of what Laura is trying
>> to
>> do here, although I would encourage anyone with an interest in improving
>> the plugins to take a look at reworking the #cCode portions of
>> JPEGReadWriter2Plugin.
>>
>> Dave
>>
>>
>>
>>
>> On Thu, May 19, 2016 at 04:29:15PM -0700, Eliot Miranda wrote:
>>>
>>> Hi Laura,
>>>
>>>     this isn't your fault, but looking at the body of the plugin
>>> methods,
>>> the code is horrible.  It's essentially 100% C.  The code should really
>>> be
>>> written in C files, not in Smalltalk methods, following the pattern of
>>> separating plugin code into a Smalltalk plugin larger calling platform
>>> functions written in a C layer.  For example, look at the REPlugin
>>> which
>>> does regular expressions.  The source to the machinery is in
>>> platforms/Cross/plugins/RePlugin.  The plugin methods, e.g.
>>> REPlugin>>primPCREExecfromto, do marshalling of Smalltalk objects into
>>> C
>>> parameters and then invoke function implemented in
>>> platforms/Cross/plugins/RePlugin, e.g. pcre_exec.  This approach means
>>> that
>>> there's onlyas much cCode:inSmalltalk: as necessary.  This is far nicer
>>> code to read and fix.
>>>
>>> Do you have energy to rewrite the JPEG plain code to follow this
>>> pattern?
>>> If so, let me encourage you.  It will improve the code hugely.
>>>
>>> On Thu, May 19, 2016 at 7:06 AM, Laura Perez Cerrato <
>>> lauraperezcerrato at gmail.com> wrote:
>>>
>>> >
>>> > Elliot, Dave,
>>> >
>>> > Thanks for your answers! Here go both the changesets requested. The
>>> > JPEGReadWriter2Plugin changeset was generated using a Squeak Spur
>>> > trunk image, whilst the Graphics changeset was generated using the
>>> > latest stable version of Squeak non-Spur (4.6-15102). However, It
>>> > should also work well with a Squeak Spur trunk image, though I
>>> haven't
>>> > tested it's functioning there thoroughly. I haven't yet implemented a
>>> > graceful way for the new primitive to fail if the new version of the
>>> > plugin is absent, so keep that in mind.
>>> >
>>> > I'm currently working on handling non-even width 16-bit Forms and
>>> > non-0 modulo 4 width 8 bit Forms, so I'll hopefully send that to you
>>> > too within this week.
>>> >
>>> > -Laura Perez Cerrato
>>> >
>>> >
>>> > On 18 May 2016 at 22:00, David T. Lewis <lewis at mail.msen.com> wrote:
>>> > >
>>> > > On Wed, May 18, 2016 at 03:56:11PM -0700, Eliot Miranda wrote:
>>> > >>
>>> > >> Hi Laura,
>>> > >>
>>> > >> > On May 18, 2016, at 1:04 PM, Laura Perez Cerrato <
>>> > lauraperezcerrato at gmail.com> wrote:
>>> > >> >
>>> > >> >
>>> > >> > Hello, everyone,
>>> > >> >
>>> > >> > During the past few days I've been working on adding support for
>>> > >> > reading and writing reading and writing JPEGs to/from -32, -16,
>>> -8
>>> > >> > grayscale and 8 grayscale bit deep forms to
>>> JPEGReadWriter2Plugin for
>>> > >> > the Squeak Cog V3 VM. Just chiming in to tell you that the work
>>> is
>>> > >> > done and I'd like to share it with you all. :) I believe this
>>> changes
>>> > >> > should work on Spur VMs too, but haven't tested thoroughly
>>> enough to
>>> > >> > ensure that.
>>> > >> >
>>> > >> > How do you handle contributions to the codebase? I assume I'd
>>> have to
>>> > >> > upload the corresponding changeset to the repository but I'm not
>>> sure
>>> > >> > if there's anything I should do before.
>>> > >> >
>>> > >> > I have also been working on a few changes to the latest non-Spur
>>> > >> > version of Squeak in order to take advantage of the changes to
>>> the
>>> > >> > plugin but, since I added a primitive to it and these changes
>>> use it,
>>> > >> > I think it's prudent to ask you too how those contributions are
>>> > >> > handled. Should I refer to the Squeak-dev mailing list?
>>> > >>
>>> > >> This is indeed a problem.  Talking for myself, until VMs have been
>>> > built that include the code and are generally available one can't
>>> really
>>> > deploy the behaviour to trunk.  But again waiting for the next
>>> release
>>> > feels far too slow.
>>> > >>
>>> > >> One approach is to make the behaviour optional, depending on what
>>> the
>>> > VM provides, eg checking for primitive failure or a plugin version
>>> number,
>>> > or simply making the code fail gracefully.
>>> > >>
>>> > >> Another approach is to provide the functionality in an extension
>>> > package, and merging that extension into trunk at the next release.
>>> > >>
>>> > >> Other suggestions folks?
>>> > >>
>>> > >
>>> > > We should take a look at the image side code too. Laura, perhaps
>>> you can
>>> > > post a change set for that also?
>>> > >
>>> > > Very often a new optional primitive can be handled simply by
>>> providing
>>> > > some suitable fallback code. That provides a smooth transition,
>>> because
>>> > > the new feature is immediately available and the system continues
>>> to work
>>> > > for people who do not yet have the new primitive in their VM.
>>> > >
>>> > > Dave
>>> > >
>>> >
>>> >
>>>
>>>
>>> --
>>> _,,,^..^,,,_
>>> best, Eliot
>>
>