[squeak-dev] What is the task of NullEncoder?Nicolas Cellier nicolas.cellier.aka.nice at gmail.comFri Sep 29 15:54:17 UTC 2017
The target inst. var. is used exclusively by the PostscriptCanvas.
And IMO it is a classical mistake of inheritance versus composition.
A PostScript canvas will have to encode the sequence of graphics
instruction into a stream of PostScript instructions written into a
PostScript file.
For this purpose, it has a target PostscriptEncoder, which is itself an
encoder already.
An Encoder implements a processing unit that transform a stream by using a
kind of generic double dispatching.
Why the PostscriptCanvas has to be considered as an Encoder itself is very
suspect, unless we ask
canvas write: aMorph.
Do we really want to do that, have a stream of Morphs (or other graphical
objects)?
2017-09-29 17:33 GMT+02:00 H. Hirzel <hannes.hirzel at gmail.com>:
> Tobias
>
> You write that NullEncoder and subclasses could be summarized as
>
> "Put objects onto another thing with encoding inbetween".
>
> which I think is helpful for understanding.
>
> Maybe we consider for the class comment of NullEncoder
>
> "Put objects onto another thing with encoding/transformation
> inbetween".
>
>
> But also note that this is not only related to PostscriptCanvas as we have
>
>
> NullEncoder
> FlattenEncoder
> Canvas
> FormCanvas
>
> FormCanvas has some nice usage examples.
>
> #test1 is
>
> test1
> "FormCanvas test1"
>
> | canvas |
> canvas := FormCanvas extent: 200 at 200.
> canvas fillColor: (Color black).
> canvas line: 10 at 10 to: 50 at 30 width: 1 color: (Color red).
> canvas frameRectangle: ((20 at 20) corner: (120 at 120)) width: 4 color:
> (Color green).
> canvas point: 100 at 100 color: (Color black).
> canvas drawString: 'Hello, World!' at: 40 at 40 font: nil color:
> (Color cyan).
> canvas fillRectangle: ((10 at 80) corner: (31 at 121)) color: (Color
> magenta).
> canvas fillOval: ((10 at 80) corner: (31 at 121)) color: (Color cyan).
> canvas frameOval: ((40 at 80) corner: (61 at 121)) color: (Color blue).
> canvas frameOval: ((70 at 80) corner: (91 at 121)) width: 3 color:
> (Color
> red alpha: 0.2).
> canvas fillRectangle: ((130 at 30) corner: (170 at 80)) color: (Color
> lightYellow).
> canvas showAt: 0 at 0.
>
>
> This works fine in an MVC project
>
> --Hannes
>
> On 9/29/17, Tobias Pape <Das.Linux at gmx.de> wrote:
> > Hi Hannes
> >
> >> On 29.09.2017, at 15:21, H. Hirzel <hannes.hirzel at gmail.com> wrote:
> >>
> >> And there is no 'FlattenEncoder' in Pharo 6
> >
> >>
> >>
> >> On 9/29/17, H. Hirzel <hannes.hirzel at gmail.com> wrote:
> >>> We have
> >>>
> >>> NullEncoder
> >>> FlattenEncoder
> >>> Canvas
> >
> > So here's the Thing: I looked in 3.8, and there's:
> >
> > Object
> > NullEncoder - Morphic-Postscript Filters
> > FlattenEncoder - Morphic-Postscript Filters
> > Canvas - Morphic-Support
> > PostscriptCanvas - Morphic-Postscript Canvases
> >
> > But also note that they all have a callback via class>>filterSelector:
> >
> > NullEncoder>>filterSelector ^ #writeOnFilterStream:
> > FlattenEncoder>>filterSelector ^ #flattenOnStream:
> > Canvas>>filterSelector ^ #drawOnCanvas:
> > PostscriptCanvas>>filterSelector ^ #fullDrawPostscriptOn:
> >
> > I think part of that happened because this all shared common
> functionallity,
> > In the sense that all those things "Put objects onto another thing with
> > encoding inbetween".
> > Thinking of things like a n-dimensonal stream or so…
> >
> > I checked and It is like that even in Squeak 3.6, 3.0, 2.8.
> > Squeak 1.13 does not have any of those, and it has no Morphic.
> >
> > Self Morphic does not have such Encoders, tho.
> >
> > In the end it all seems to be related to the PostScript Canvas, which,
> > understandably, has to have access to certain objects and actually has to
> > "encode" them into a file.
> >
> > Best regards
> > -Tobias
> >
> >
> >
> >>>
> >>> there are no direct users of NullEncoder and FlattenEncoder.
> >>>
> >>> FlattenEncoder class comment is just
> >>>
> >>> 'The simplest possible encoding: leave the objects as is.'
> >>>
> >>> a bit terse. Does not really say what the issue is about.
> >>>
> >>>
> >>>
> >>> On 9/29/17, H. Hirzel <hannes.hirzel at gmail.com> wrote:
> >>>> P.S.
> >>>>
> >>>> There is no NullEncoder in Pharo.
> >>>>
> >>>> The class Canvas is not in a package 'Morphic-Support' but in a
> >>>> package 'Graphics-Canvas'.
> >>>>
> >>>> There is no 'Graphics-Canvas' package in Squeak. [2]
> >>>>
> >>>> Seems like a good idea to move Canvas and subclasses to a package
> >>>> 'Graphics-Canvas' as well.
> >>>>
> >>>>
> >>>> [2] Graphics package in Squeak 6.0a-17405
> >>>>
> >>>> Graphics-Display Objects
> >>>> Graphics-External-Ffenestri
> >>>> Graphics-Files
> >>>> Graphics-Fonts
> >>>> Graphics-Primitives
> >>>> Graphics-Text
> >>>> Graphics-Transformations
> >>>> GraphicsTests-Files
> >>>> GraphicsTests-Primitives
> >>>> GraphicsTests-Text
> >>>>
> >>>> On 9/29/17, H. Hirzel <hannes.hirzel at gmail.com> wrote:
> >>>>> Hello
> >>>>>
> >>>>> NullEncoder is subclass of object ([1] for full hierachy). It is a
> >>>>> superclass of Canvas.
> >>>>>
> >>>>> What is the function of NullEncoder. No class comment so far?
> >>>>>
> >>>>> Regards
> >>>>> Hannes
> >>>>>
> >>>>>
> >>>>> ------------------------------------------------------------
> -------------------------------------------------------------------
> >>>>>
> >>>>> [1] NullEncoder printHierarchy '
> >>>>> ProtoObject #()
> >>>>> Object #()
> >>>>> NullEncoder #(''target'' ''filterSelector'')
> >>>>> FlattenEncoder #()
> >>>>> ByteEncoder #()
> >>>>> PrintableEncoder #()
> >>>>> PostscriptEncoder #()
> >>>>>
> PostscriptEncoderToDisk #()
> >>>>> PropertyListEncoder #()
> >>>>> Canvas #()
> >>>>> ColorMappingCanvas #(''myCanvas'')
> >>>>> AlphaBlendingCanvas
> #(''alpha'')
> >>>>> ShadowDrawingCanvas
> #(''shadowColor'')
> >>>>> FormCanvas #(''origin''
> ''clipRect'' ''form'' ''port''
> >>>>> ''shadowColor'')
> >>>>> BalloonCanvas
> #(''transform'' ''colorTransform'' ''engine''
> >>>>> ''aaLevel'' ''deferred'')
> >>>>> BlueFormCanvas #()
> >>>>> ColorPatchCanvas
> #(''stopMorph'' ''foundMorph'' ''doStop'')
> >>>>> MultiResolutionCanvas
> #(''deferredMorphs'')
> >>>>> PluggableCanvas #()
> >>>>> BufferedCanvas
> #(''remote'' ''previousVersion'' ''lastTick''
> >>>>> ''dirtyRect'' ''mirrorOfScreen'')
> >>>>> CachingCanvas
> #(''cacheCanvas'' ''mainCanvas'')
> >>>>> ClippingCanvas
> #(''canvas'' ''clipRect'')
> >>>>> MultiCanvas #(''canvases''
> ''extent'' ''depth'')
> >>>>> NullCanvas #()
> >>>>> PostscriptCanvas #(''origin''
> ''clipRect'' ''currentColor''
> >>>>> ''shadowColor'' ''currentFont'' ''morphLevel'' ''gstateStack''
> >>>>> ''fontMap'' ''usedFonts'' ''psBounds'' ''topLevelMorph''
> >>>>> ''initialScale'' ''savedMorphExtent'' ''currentTransformation''
> >>>>> ''printSpecs'' ''pages'')
> >>>>> DSCPostscriptCanvas #()
> >>>>>
> DSCPostscriptCanvasToDisk #()
> >>>>> EPSCanvas #()
> >>>>> RemoteCanvas #(''innerClipRect''
> ''outerClipRect'' ''transform''
> >>>>> ''connection'' ''shadowColor'')'
> >>>>>
> >>>>
> >>>
> >>
> >
> >
> >
>
>
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