LayerOperations Class Reference

#include <tiledbitmapinterface.hh>

Inheritance diagram for LayerOperations:

Collaboration diagram for LayerOperations:

Public Types
using	Ptr = std::shared_ptr< LayerOperations >

Public Member Functions
virtual int	getBpp ()=0
virtual void	initializeCairo (cairo_t *cr)=0
virtual void	draw (cairo_t *cr, const ConstTile::Ptr &tile, Scroom::Utils::Rectangle< double > tileArea, Scroom::Utils::Rectangle< double > viewArea, int zoom, Scroom::Utils::Stuff cache)=0
virtual void	drawState (cairo_t *cr, TileState s, Scroom::Utils::Rectangle< double > viewArea)=0
virtual Scroom::Utils::Stuff	cache (const ConstTile::Ptr &)
virtual Scroom::Utils::Stuff	cacheZoom (const ConstTile::Ptr &, int, Scroom::Utils::Stuff &)
virtual void	reduce (Tile::Ptr target, ConstTile::Ptr source, int x, int y)=0

Additional Inherited Members
Private Member Functions inherited from Interface
	Interface ()=default
	Interface (const Interface &)=delete
Interface &	operator= (const Interface &)=delete
	Interface (Interface &&)=delete
Interface &	operator= (Interface &&)=delete
virtual	~Interface ()=default

Detailed Description

Operations on a layer in the TiledBitmap

Tasks of LayerOperations objects include:

• Reducing the given Layer by a factor of 8, producing data that the LayerOperations object of the next layer will understand
• Draw any portion of the given Layer, at the requested zoom level

See also

Layer

Member Typedef Documentation

Ptr

using LayerOperations::Ptr = std::shared_ptr<LayerOperations>

Member Function Documentation

cache()

virtual Scroom::Utils::Stuff LayerOperations::cache ( const ConstTile::Ptr &  )

inlinevirtual

Cache data for use during later cacheZoom() calls.

This function is called for a given tile, and then the results are passed to the cacheZoom() function. Because draw() is called relatively frequently (i.e. when scrolling), it is recommended to do cpu-intensive work in the cache() and cacheZoom() functions, and then re-use the data to make the draw() faster.

The default implementation returns an empty reference, meaning nothing is cached. As a result, the draw() function will receive an empty reference.

Parameters

tile	the Tile for which caching is requested

Reimplemented in Operations1bpp, Operations8bpp, Operations24bpp, Operations, OperationsColormapped, OperationsCMYK32, OperationsCMYK16, OperationsCMYK8, and OperationsCMYK4.

{ return {}; }

Referenced by CommonOperations::cacheZoom(), and CommonOperations::draw().

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cacheZoom()

virtual Scroom::Utils::Stuff LayerOperations::cacheZoom ( const ConstTile::Ptr &  , int  , Scroom::Utils::Stuff &    )

inlinevirtual

Cache data for use during later draw() calls.

This function is called for a given tile and zoom level, and then the results are passed to the draw() function. Because draw() is called relatively frequently (i.e. when scrolling), it is recommended to do cpu-intensive work in the cache() and cacheZoom() functions, and then re-use the data to make the draw() faster.

The default implementation returns an empty reference, meaning nothing is cached. As a result, the draw() function will receive an empty reference.

Parameters

tile	the Tile for which caching is requested
zoom	the requested zoom level
cache	the output of cache(const ConstTile::Ptr)

Reimplemented in CommonOperations, and Operations1bppClipped.

  {
    return {};
  }

draw()

virtual void LayerOperations::draw ( cairo_t *  cr, const ConstTile::Ptr &  tile, Scroom::Utils::Rectangle< double >  tileArea, Scroom::Utils::Rectangle< double >  viewArea, int  zoom, Scroom::Utils::Stuff  cache  )

pure virtual

Draw the given tileArea into the given viewArea at the requested zoom level

Parameters

cr	The canvas on which to draw
tile	The tile to take data from
tileArea	Area of the tile that needs to be drawn
viewArea	Area of the canvas that the tile needs to be drawn in
zoom	The requested zoom level. One pixel of your presentation should have size 2**zoom when drawn. zoom will be negative for all but the first layer.
cache	Depending on whether the cacheZoom() function finished already, this may either be an empty reference, or a reference to the value returned by cacheZoom()

Implemented in DummyLayerOperations, CommonOperations, Operations1bpp, Operations8bpp, and Operations.

drawState()

virtual void LayerOperations::drawState ( cairo_t *  cr, TileState  s, Scroom::Utils::Rectangle< double >  viewArea  )

pure virtual

Draw the given state into the given viewArea

The associated tile is likely not loaded or not initialized or in whatever other TileState that doesn't allow its contents to be drawn.

Something needs to be drawn in the given viewArea anyway. Implementors might want to just draw an empty rectangle, maybe color-coded to reflect the state of the tile.

Implemented in DummyLayerOperations, and CommonOperations.

getBpp()

virtual int LayerOperations::getBpp ( )

pure virtual

Return the number of bits per pixel that the layer will use.

This number will be used to compute the amount of memory required to store one tile

Implemented in Operations1bpp, Operations8bpp, Operations24bpp, Operations, OperationsColormapped, Operations1bppClipped, OperationsCMYK32, OperationsCMYK16, OperationsCMYK8, OperationsCMYK4, and DummyLayerOperations.

initializeCairo()

virtual void LayerOperations::initializeCairo ( cairo_t *  cr )

pure virtual

Initialize the canvas for drawing the bitmap

When TiledBitmapInterface::redraw() is called, (a portion of) the Layer needs to be redrawn. TiledBitmap will compute which tiles are involved in the redraw, and call draw() or drawState() for each of them, as appropriate. However, before doing so, it will first call initializeCairo(). You can take this opportunity to set various properties that are needed in all subsequent calls to draw() and drawState(), such as anti-aliasing and line caps.

Implemented in DummyLayerOperations, and CommonOperations.

reduce()

virtual void LayerOperations::reduce ( Tile::Ptr  target, ConstTile::Ptr  source, int  x, int  y  )

pure virtual

Reduce the source tile by a factor of 8

The target tile will contain data for 8*8 source tiles. Offsets x and y indicate which of those 64 source tiles is currently being processed

Parameters

target	Tile that will contain the reduced bitmap
source	Tile that is to be reduced
x	x-offset (0..7) of the source tile in the target tile
y	y-offset (0..7) of the source tile in the target tile

Note

The target tile belongs to a different layer, and hence possibly has a different bpp than the current one, depending on the LayerSpec given to createTiledBitmap()

Implemented in Operations1bpp, Operations8bpp, Operations24bpp, Operations, OperationsColormapped, Operations1bppClipped, OperationsCMYK32, OperationsCMYK16, OperationsCMYK8, OperationsCMYK4, and DummyLayerOperations.

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The documentation for this class was generated from the following file:

• libs/tiled-bitmap/inc/scroom/tiledbitmapinterface.hh