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180 lines
6.2 KiB
180 lines
6.2 KiB
A Perspective on Chalk's Design
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Chalk's codebase has been through as many changes as the app's name
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itself. It started with KImageShop (hence the 'kis' prefix one finds
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everwhere, and which would have been unnessary had Chalk used
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namespaces, one fancies), then became Krayon to end up as Chalk. The
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stated design goal was to create a application geared towards the
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more artistic user; the kind of user who settles down with his
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tablet to create a spot of Art. It ended up as a Gimp-clone, a Kimp,
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so to say.
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This document was the basis for a discussion on the chalk mailinglist:
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http://lists.kde.org/?l=kde-kimageshop&m=106530035202770&w=2. See the
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answer for some answers to the questions at the end.
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Design Patterns
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Patrick Julien restructured Chalk to use a lot design patterns. Chalk
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appears to have a very solid base for blasting pixels to the screen,
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zooming, selecting and moving. These are what I recognize as his
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changes:
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* Change brushes handling to a generic Mediator pattern
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(kis_resource_mediator). Resources are brush shapes,
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patterns (and colours, too?) Patrick intended a Flyweight
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here.
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* The composite pattern is used in paint devices, layers, channels,
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etc. (What about masks?)
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* Change colourspace handling to a Strategy pattern
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(strategy/kis_strategy_color)
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* Change moving chunks of painting to a Strategy pattern
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(strategy/kis_strategy_move)
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* kis_factory points towards a Factory pattern Creates the
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pluginserver and resourceserver.
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* Tools are created by a Factory pattern (but it isn't
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dynamic yet): kis_tool_factory. Tools are intended to
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become tdeparts.
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* There's the start of a Memento pattern for tools, but it
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doesn't seem to be used (kis_tool_memento). It was an
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experiment that didn't pan out.
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* The Builder pattern is used to do conversion to and/or
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from ImageMagick. I guess this is used for importing
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images in other file-formats than .chalk. An idea at one
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was to use Koffice filters, but that didn't work because
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images are rather different from other office documents.
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* Flyweight pattern used for background tiles.
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kis_background.
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* Nameserver. Perhaps not a pattern -- at least not one
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with an obvious GOF name. Appears to be computing a
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number for new layers and new documents.
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* kis_render. Interface implemented by kis_paint_device
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and kis_image.
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* Rename kisTool to kisToolInterface -- but the file is
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still called kis_tool. (This is intentional, and should
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be kept in the style guide.)
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* Addition of kis_types. Defines shared pointer pointers
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to core chalk objects: image, paintdevice, channel,
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mask, layer etc.
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* Tile architecture. There's Mediator and a Singleton
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pattern here at least. This stuff seems to work, doesn't
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need hacking at the moment.
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* Visitor pattern used to flatten an image or merge
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layers. Merging exposes a funny bug where the tiles
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are re-arranged in an interesting mosaic pattern.
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User interface
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Chalk uses a fairly ugly side-panel to collect what are palettes
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in other applications. I would prefer dockable, attachable
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palettes myself. Doesn't KDE have a lib for that already?
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ui/labels
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These classes are used in the statusbar.
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ui
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The dialogs appear to be created by hand, not with Qt
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Designer. Besides, many are inoperational.
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other
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The canvas, rules and sidebar panels are defined here, too,
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nicely separated.
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Tools
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Working: select_rectangular, test, zoom, colorpicker, paste, move
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Not working: airbrush, brush, colorchanger (no idea what it should
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do), ellipse, eraser, fill, line, pen, polygon, polyline,
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rectangle, select_contiguous, select_elliptical, select_freehand,
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select_polygonal, stamp
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Missing tools: convolve, smear, smudge, whirl, charcoal, chalk,
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oils, clone, select_by_colour
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Plugins
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The single plugin example has been present in chalk since about day
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one, as far as I can see. It doesn't show anything about what one
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can do with plugins.
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To judge from the code in kis_plugin_server, it never got beyond
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an idea. (kdDebug() << "hallo\n"...)
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(This code should be removed.)
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ImageMagick
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There still appear to be some dependencies upon ImageMagick (builder
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subdir). What are these for, and should they stay? Is it for
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importing/exporting foreign file formats?
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Undo/Redo
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Undo and Redo make use of the standard KDE mechanism, which I don't
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really understand either.
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Obsolete files
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The following files appear to be unused:
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core/helper/kis_timer
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core/helper/kis_scopedlock (Replaced with QMutexlocker)
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core/kis_krayon (was predecessor of kis_resource)
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core/kis_mask
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core/kis_util
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ui/kis_krayon_widget
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Random head-scratchings
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- Why the QUANTUM redefinition: the number of bits per channel,
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8 for 32-bit colour, 16 for 64-bit colour.
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- is_mask unimplemented? What was it meant to do, or is it an
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interface?
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- nameserver presents unique numbers for new layers and images.
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- what does 'upscale' do? in 8 bit/channel color mode, upscale
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doesn't do anything. However, downscale and upscale in > 8 bit,
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this is needed to covert the color for the actual display
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rendering, i.e. X, etc, only do 8 bit color. Using this
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everywhere you work on color will keep chalk color channel
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bit depth independent.
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- Is KisVector only used in obsolete tools?
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- I take it that the two tests that are present in chalk/test
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are obsolete?
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- what with the dummmmmy.cc?
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- which bits of the chalk/ui files are still relevant?
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- kis_selection.h needs to be included to compile code that
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uses kis_paint_device, and I wonder why.
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- what is paint-offset?
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