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