skia2/include/core/SkPathEffect.h
Michael Ludwig 4e1c1a77ad Implement computeFastBounds for PathEffects
Makes computeFastBounds not part of the public API, it's only accessible
to subclasses of SkPathEffect, GrStyle, and SkPaint. Subclasses can
invoke it other path effects using SkPathEffectPriv::ComputeFastBounds.

Changes the internal function to
  bool computeFastBounds(SkRect* bounds) const;

Subclasses of SkPathEffect must implement this, and can choose to return
false when fast bounds aren't computable.

Provides implementations of computeFastBounds() for path effects
bundled with Skia.

Bug: skia:11974
Change-Id: I545ccf99b4e669d3af9df13acfac28573306fab8
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/406140
Commit-Queue: Michael Ludwig <michaelludwig@google.com>
Reviewed-by: Mike Reed <reed@google.com>
2021-05-11 17:01:59 +00:00

188 lines
7.3 KiB
C++

/*
* Copyright 2006 The Android Open Source Project
*
* Use of this source code is governed by a BSD-style license that can be
* found in the LICENSE file.
*/
#ifndef SkPathEffect_DEFINED
#define SkPathEffect_DEFINED
#include "include/core/SkFlattenable.h"
#include "include/core/SkPath.h"
#include "include/core/SkPoint.h"
#include "include/core/SkRect.h"
class SkPath;
class SkStrokeRec;
/** \class SkPathEffect
SkPathEffect is the base class for objects in the SkPaint that affect
the geometry of a drawing primitive before it is transformed by the
canvas' matrix and drawn.
Dashing is implemented as a subclass of SkPathEffect.
*/
class SK_API SkPathEffect : public SkFlattenable {
public:
/**
* Returns a patheffect that apples each effect (first and second) to the original path,
* and returns a path with the sum of these.
*
* result = first(path) + second(path)
*
*/
static sk_sp<SkPathEffect> MakeSum(sk_sp<SkPathEffect> first, sk_sp<SkPathEffect> second);
/**
* Returns a patheffect that applies the inner effect to the path, and then applies the
* outer effect to the result of the inner's.
*
* result = outer(inner(path))
*/
static sk_sp<SkPathEffect> MakeCompose(sk_sp<SkPathEffect> outer, sk_sp<SkPathEffect> inner);
/**
* Given a src path (input) and a stroke-rec (input and output), apply
* this effect to the src path, returning the new path in dst, and return
* true. If this effect cannot be applied, return false and ignore dst
* and stroke-rec.
*
* The stroke-rec specifies the initial request for stroking (if any).
* The effect can treat this as input only, or it can choose to change
* the rec as well. For example, the effect can decide to change the
* stroke's width or join, or the effect can change the rec from stroke
* to fill (or fill to stroke) in addition to returning a new (dst) path.
*
* If this method returns true, the caller will apply (as needed) the
* resulting stroke-rec to dst and then draw.
*/
bool filterPath(SkPath* dst, const SkPath& src, SkStrokeRec*, const SkRect* cullR) const;
/** \class PointData
PointData aggregates all the information needed to draw the point
primitives returned by an 'asPoints' call.
*/
class PointData {
public:
PointData()
: fFlags(0)
, fPoints(nullptr)
, fNumPoints(0) {
fSize.set(SK_Scalar1, SK_Scalar1);
// 'asPoints' needs to initialize/fill-in 'fClipRect' if it sets
// the kUseClip flag
}
~PointData() {
delete [] fPoints;
}
// TODO: consider using passed-in flags to limit the work asPoints does.
// For example, a kNoPath flag could indicate don't bother generating
// stamped solutions.
// Currently none of these flags are supported.
enum PointFlags {
kCircles_PointFlag = 0x01, // draw points as circles (instead of rects)
kUsePath_PointFlag = 0x02, // draw points as stamps of the returned path
kUseClip_PointFlag = 0x04, // apply 'fClipRect' before drawing the points
};
uint32_t fFlags; // flags that impact the drawing of the points
SkPoint* fPoints; // the center point of each generated point
int fNumPoints; // number of points in fPoints
SkVector fSize; // the size to draw the points
SkRect fClipRect; // clip required to draw the points (if kUseClip is set)
SkPath fPath; // 'stamp' to be used at each point (if kUsePath is set)
SkPath fFirst; // If not empty, contains geometry for first point
SkPath fLast; // If not empty, contains geometry for last point
};
/**
* Does applying this path effect to 'src' yield a set of points? If so,
* optionally return the points in 'results'.
*/
bool asPoints(PointData* results, const SkPath& src,
const SkStrokeRec&, const SkMatrix&,
const SkRect* cullR) const;
/**
* If the PathEffect can be represented as a dash pattern, asADash will return kDash_DashType
* and None otherwise. If a non NULL info is passed in, the various DashInfo will be filled
* in if the PathEffect can be a dash pattern. If passed in info has an fCount equal or
* greater to that of the effect, it will memcpy the values of the dash intervals into the
* info. Thus the general approach will be call asADash once with default info to get DashType
* and fCount. If effect can be represented as a dash pattern, allocate space for the intervals
* in info, then call asADash again with the same info and the intervals will get copied in.
*/
enum DashType {
kNone_DashType, //!< ignores the info parameter
kDash_DashType, //!< fills in all of the info parameter
};
struct DashInfo {
DashInfo() : fIntervals(nullptr), fCount(0), fPhase(0) {}
DashInfo(SkScalar* intervals, int32_t count, SkScalar phase)
: fIntervals(intervals), fCount(count), fPhase(phase) {}
SkScalar* fIntervals; //!< Length of on/off intervals for dashed lines
// Even values represent ons, and odds offs
int32_t fCount; //!< Number of intervals in the dash. Should be even number
SkScalar fPhase; //!< Offset into the dashed interval pattern
// mod the sum of all intervals
};
DashType asADash(DashInfo* info) const;
static void RegisterFlattenables();
static SkFlattenable::Type GetFlattenableType() {
return kSkPathEffect_Type;
}
SkFlattenable::Type getFlattenableType() const override {
return kSkPathEffect_Type;
}
static sk_sp<SkPathEffect> Deserialize(const void* data, size_t size,
const SkDeserialProcs* procs = nullptr) {
return sk_sp<SkPathEffect>(static_cast<SkPathEffect*>(
SkFlattenable::Deserialize(
kSkPathEffect_Type, data, size, procs).release()));
}
protected:
SkPathEffect() {}
virtual bool onFilterPath(SkPath*, const SkPath&, SkStrokeRec*, const SkRect*) const = 0;
virtual bool onAsPoints(PointData*, const SkPath&, const SkStrokeRec&, const SkMatrix&,
const SkRect*) const {
return false;
}
virtual DashType onAsADash(DashInfo*) const {
return kNone_DashType;
}
private:
friend class SkPathEffectPriv;
// Compute a conservative bounds for its effect, given the bounds of the path. 'bounds' is
// both the input and output; if false is returned, fast bounds could not be calculated and
// 'bounds' is undefined.
//
// If 'bounds' is null, performs a dry-run determining if bounds could be computed.
virtual bool computeFastBounds(SkRect* bounds) const = 0;
// illegal
SkPathEffect(const SkPathEffect&);
SkPathEffect& operator=(const SkPathEffect&);
using INHERITED = SkFlattenable;
};
#endif