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/* -*- Mode: C++; tab-width: 4; indent-tabs-mode: nil; c-basic-offset: 4 -*- */
/*
* This file is part of the LibreOffice project.
*
* This Source Code Form is subject to the terms of the Mozilla Public
* License, v. 2.0. If a copy of the MPL was not distributed with this
* file, You can obtain one at http://mozilla.org/MPL/2.0/.
*
* This file incorporates work covered by the following license notice:
*
* Licensed to the Apache Software Foundation (ASF) under one or more
* contributor license agreements. See the NOTICE file distributed
* with this work for additional information regarding copyright
* ownership. The ASF licenses this file to you under the Apache
* License, Version 2.0 (the "License"); you may not use this file
* except in compliance with the License. You may obtain a copy of
* the License at http://www.apache.org/licenses/LICENSE-2.0 .
*/
#ifndef INCLUDED_DRAWINGLAYER_PROCESSOR2D_BASEPROCESSOR2D_HXX
#define INCLUDED_DRAWINGLAYER_PROCESSOR2D_BASEPROCESSOR2D_HXX
#include <drawinglayer/drawinglayerdllapi.h>
#include <drawinglayer/primitive2d/Primitive2DVisitor.hxx>
#include <drawinglayer/primitive2d/baseprimitive2d.hxx>
#include <drawinglayer/geometry/viewinformation2d.hxx>
namespace drawinglayer::processor2d
{
/** BaseProcessor2D class
Base class for all C++ implementations of instances which process
primitives.
Instances which process primitives can be renderers, but also stuff
for HitTests, BoundRect calculations and/or animation processing. The
main usage are renderers, but they are supposed to handle any primitive
processing.
The base implementation is constructed with a ViewInformation2D which
is accessible throughout the processor implementations. The idea is
to construct any processor with a given ViewInformation2D. To be able
to handle primitives which need to change the current transformation
(as e.g. TransformPrimitive2D) it is allowed for the processor implementation
to change its local value using updateViewInformation.
The basic processing method is process(..) which gets handed over the
sequence of primitives to process. For convenience of the C++ implementations,
the default implementation of process(..) maps all accesses to primitives to
single calls to processBasePrimitive2D(..) where the primitive in question is
already casted to the C++ implementation class.
The process(..) implementation makes a complete iteration over the given
sequence of primitives. If the Primitive is not derived from BasePrimitive2D
and thus not part of the C++ implementations, it converts ViewInformation2D
to the corresponding API implementation (a uno::Sequence< beans::PropertyValue >)
and recursively calls the method process(..) at the primitive with the decomposition
derived from that primitive. This is the preparation to handle unknown implementations
of the css::graphic::XPrimitive2D interface in the future.
So, to implement a basic processor, it is necessary to override and implement the
processBasePrimitive2D(..) method. A minimal renderer has to support the
Basic Primitives (see baseprimitive2d.hxx) and the Grouping Primitives (see
groupprimitive2d.hxx). These are (currently):
Basic Primitives:
- BitmapPrimitive2D (bitmap data, possibly with transparency)
- PointArrayPrimitive2D (single points)
- PolygonHairlinePrimitive2D (hairline curves/polygons)
- PolyPolygonColorPrimitive2D (colored polygons)
Grouping Primitives:
- TransparencePrimitive2D (objects with freely defined transparence)
- InvertPrimitive2D (for XOR)
- MaskPrimitive2D (for masking)
- ModifiedColorPrimitive2D (for a stack of color modifications)
- TransformPrimitive2D (for a transformation stack)
A processor doing so is a minimal processor. Of course a processor may
handle any higher-level primitive (that has a decomposition implementation)
for more direct data access or performance reasons, too.
The main part of a processBasePrimitive2D implementation is a switch..case
construct, looking like the following:
void foo::processBasePrimitive2D(const BasePrimitive2D& rCandidate)
{
switch(rCandidate.getPrimitive2DID())
{
case PRIMITIVE2D_ID_??? :
{
// process PRIMITIVE2D_ID_??? here...
...
break;
}
...
default :
{
// process recursively
process(rCandidate.get2DDecomposition(getViewInformation2D()));
break;
}
}
}
The default case makes the processor work with all complex primitives
by recursively using their decomposition.
You can also add a case for ignoring primitives by using:
case PRIMITIVE2D_ID_...IGNORE.A.. :
case PRIMITIVE2D_ID_...IGNORE.B.. :
case PRIMITIVE2D_ID_...IGNORE.C.. :
{
// ignore these primitives by neither processing nor
// recursively processing their decomposition
break;
}
Another useful case is embedding the processing of a complex primitive by
bracketing it with some actions:
case PRIMITIVE2D_ID_SOME_TEXT :
{
// encapsulate e.g. with changing local variables, e.g.
// sometimes it's good to know if a basic primitive is
// part of a text, especially when not handling the text
// self but by purpose want to handle the decomposed
// geometries in the processor
startText();
process(rCandidate.get2DDecomposition(getViewInformation2D()));
endText();
break;
}
As an example a processor collecting the outlines of a sequence of primitives
only needs to handle some Basic Primitives and create outline and collect
outline polygons e.g. for primitives with area like BitmapPrimitive2D (a
rectangle) and PolyPolygonColorPrimitive2D. When also handling the Grouping
Primitives MaskPrimitive2D (e.g. ignoring its content, using the mask polyPolygon)
and TransformPrimitive2D (to have the correct local transformation), a processor
creating the outline can be written using just four (4) primitives. As a tipp, it can
be helpful to add many for the purpose not interesting higher level primitives
to not force their decomposition to be created and/or parsed.
*/
class DRAWINGLAYER_DLLPUBLIC BaseProcessor2D : public drawinglayer::primitive2d::Primitive2DDecompositionVisitor
{
private:
/// The ViewInformation2D itself. It's private to isolate accesses to it
geometry::ViewInformation2D maViewInformation2D;
protected:
/* access method to allow the implementations to change the current
ViewInformation2D if needed. This allows isolating these accesses
later if needed
*/
void updateViewInformation(const geometry::ViewInformation2D& rViewInformation2D)
{
maViewInformation2D = rViewInformation2D;
}
/* as tooling, the process() implementation takes over API handling and calls this
virtual render method when the primitive implementation is BasePrimitive2D-based.
Default implementation does nothing
*/
virtual void processBasePrimitive2D(const primitive2d::BasePrimitive2D& rCandidate);
void process(const primitive2d::BasePrimitive2D& rCandidate);
// Primitive2DDecompositionVisitor
virtual void visit(const primitive2d::Primitive2DReference&) override final;
virtual void visit(const primitive2d::Primitive2DContainer&) override final;
virtual void visit(primitive2d::Primitive2DContainer&&) override final;
public:
/// constructor/destructor
explicit BaseProcessor2D(const geometry::ViewInformation2D& rViewInformation);
virtual ~BaseProcessor2D();
/// the central processing method
void process(const primitive2d::Primitive2DContainer& rSource);
/// data read access
const geometry::ViewInformation2D& getViewInformation2D() const { return maViewInformation2D; }
};
} // end of namespace drawinglayer::processor2d
#endif //INCLUDED_DRAWINGLAYER_PROCESSOR2D_BASEPROCESSOR2D_HXX
/* vim:set shiftwidth=4 softtabstop=4 expandtab: */
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