SkRegion Reference === # Region Region is a compressed one bit mask. Region describes an aliased clipping area on integer boundaries. Region can also describe an array of integer rectangles. Canvas uses Region to reduce the current clip. Region may be drawn to Canvas; Paint determines if Region is filled or stroked, its Color, and so on. Region may be constructed from IRect array or Path. Diagonal lines and curves in Path become integer rectangle edges. Regions operators compute union, intersection, difference, and so on. Canvas allows only intersection and difference; successive clips can only reduce available Canvas area. # Class SkRegion SkRegion describes the set of pixels used to clip Canvas. SkRegion is compact, efficiently storing a single integer rectangle, or a run length encoded array of rectangles. SkRegion may reduce the current Canvas Clip, or may be drawn as one or more integer rectangles. SkRegion iterator returns the scan lines or rectangles contained by it, optionally intersecting a bounding rectangle. ## Overview
Topic Description
Class Declarations embedded class members
Constants enum and enum class, and their const values
Constructors functions that construct SkRegion
Functions global and class member functions
Operators operator overloading methods
## Constant SkRegion related constants are defined by enum, enum class, #define, const, and constexpr.
Topic Description
Op binary operator combining Regions
kDifference Op target minus operand
kIntersect Op target intersected with operand
kLastOp last operator
kOpCnt number of operators defined
kReplace Op replace target with operand
kReverseDifference Op operand minus target
kUnion Op target unioned with operand
kXOR Op target exclusive or with operand
## Class SkRegion uses C++ classes to declare the public data structures and interfaces.
Topic Description
Cliperator iterator returning IRect within clip
Iterator iterator returning IRect
Spanerator horizontal line segment iterator
## Constructor SkRegion can be constructed or initialized by these functions, including C++ class constructors.
Topic Description
SkRegion() constructs with default values
SkRegion(const SkIRect& rect) constructs Region matching IRect
SkRegion(const SkRegion& region) makes a shallow copy
set makes a shallow copy
setEmpty constructs with default values
setPath constructs Region from clipped Path
setRect constructs Region matching IRect
setRect(const SkIRect& rect)
setRect(int32 t left, int32 t top, int32 t right, int32 t bottom)
setRects sets IRect array
setRegion copies Region
~SkRegion() decreases Reference Count of owned objects
## Operator SkRegion operators inline class member functions with arithmetic equivalents.
Topic Description
operator!=(const SkRegion& other) const compares Regions for inequality
operator=(const SkRegion& region) makes a shallow copy
operator==(const SkRegion& other) const compares Regions for equality
swap exchanges Region pair
## Member Function SkRegion member functions read and modify the structure properties.
Topic Description
computeRegionComplexity returns relative complexity
contains returns true if points are equal or inside
getBoundaryPath appends Region outline to Path
getBounds returns maximum and minimum of IRect array
intersects returns true if areas overlap
isComplex returns true if Region contains more than one IRect
isEmpty returns if bounds has no width or height
isRect returns if Region contains one IRect
op applies binary operator
quickContains returns true quickly if points are equal or inside
quickReject returns true quickly if points are outside
readFromMemory reads from buffer
set makes a shallow copy
setEmpty constructs with default values
setPath constructs Region from clipped Path
setRect constructs Region matching IRect
setRects sets IRect array
setRegion copies Region
swap exchanges Region pair
toString exists for Android framework only
translate translates IPoints in Region
writeToMemory writes to buffer
# Class SkRegion::Iterator ## Constructor SkRegion::Iterator can be constructed or initialized by these functions, including C++ class constructors.
Topic Description
Iterator(const SkRegion& region) constructs Region iterator
## Member_Function SkRegion::Iterator member functions read and modify the structure properties.
Topic Description
Iterator() constructs Region iterator
done returns if data parsing is complete
next advances to next IRect
rect returns part of Region as IRect
reset sets Region to iterate
rewind points Iterator to start
rgn returns original Region 
    class Iterator {
    public:
        Iterator();
        Iterator(const SkRegion& region);
        bool rewind;
        void reset(const SkRegion& region);
        bool done const;
        void next;
        const SkIRect& rect;
        const SkRegion* rgn;
    };
Returns sequence of rectangles, sorted along y-axis, then x-axis, that make up Region. ## Iterator 
Iterator()
Initializes Iterator with an empty Region. done on Iterator returns true. Call reset to initialized Iterator at a later time. ### Return Value empty Region ierator ### Example
#### Example Output ~~~~ rect={1,2,3,4} ~~~~
### See Also reset SkRegion --- ## Iterator 
Iterator(const SkRegion& region)
Sets Iterator to return elements of IRect array in region. ### Parameters
region Region to iterate
### Return Value Region iterator ### Example
#### Example Output ~~~~ rect={1,2,3,4} ~~~~
### See Also reset SkRegion Cliperator Spanerator --- ## rewind 
bool rewind()
Points Iterator to start of Region. Returns true if Region was set; otherwise, returns false. ### Return Value true if Region was set ### Example
#### Example Output ~~~~ #Volatile empty iter rewind success=false empty iter rect={0,0,0,0} empty region rewind success=true empty region rect={0,0,0,0} after set rect rect={1,2,3,4} after rewind rewind success=true after rewind rect={1,2,3,4} ~~~~
### See Also reset --- ## reset 
void reset(const SkRegion& region)
Resets iterator, using the new Region. ### Parameters
region Region to iterate
### Example
#### Example Output ~~~~ empty region: done=true after set rect: done=true after reset: done=false ~~~~
### See Also rewind --- ## done 
bool done() const
Returns true if Iterator is pointing to final IRect in Region. ### Return Value true if data parsing is complete ### Example
#### Example Output ~~~~ done=true done=false ~~~~
### See Also next rect --- ## next 
void next()
Advances Iterator to next IRect in Region if it is not done. ### Example
#### Example Output ~~~~ rect={1,2,3,4} rect={5,6,7,8} ~~~~
### See Also done rect --- ## rect 
const SkIRect& rect() const
Returns IRect element in Region. Does not return predictable results if Region is empty. ### Return Value part of Region as IRect ### Example
#### Example Output ~~~~ #Volatile rect={0,0,0,0} rect={1,2,3,4} ~~~~
### See Also next done --- ## rgn 
const SkRegion* rgn() const
Returns Region if set; otherwise, returns nullptr. ### Return Value iterated Region ### Example
### See Also Iterator reset --- # Class SkRegion::Cliperator ## Constructor SkRegion::Cliperator can be constructed or initialized by these functions, including C++ class constructors.
Topic Description
Cliperator(const SkRegion& region, const SkIRect& clip) constructs Region iterator with clip
## Member_Function SkRegion::Cliperator member functions read and modify the structure properties.
Topic Description
done returns if data parsing is complete
next advances to next IRect within clip
rect returns part of Region as IRect intersected with clip 
    class SK_API Cliperator {
    public:
        Cliperator(const SkRegion& region, const SkIRect& clip);
        bool done;
        void next;
        const SkIRect& rect const;
    };
Returns the sequence of rectangles, sorted along y-axis, then x-axis, that make up Region intersected with the specified clip rectangle. ## Cliperator 
Cliperator(const SkRegion& region, const SkIRect& clip)
Sets Cliperator to return elements of IRect array in Region within clip. ### Parameters
region Region to iterate
clip bounds of iteration
### Return Value Region iterator ### Example
#### Example Output ~~~~ rect={1,2,2,3} ~~~~
### See Also SkRegion Iterator Spanerator --- ## done 
bool done()
Returns true if Cliperator is pointing to final IRect in Region. ### Return Value true if data parsing is complete ### Example
#### Example Output ~~~~ empty region done=true after add rect done=false ~~~~
### See Also next rect --- ## next 
void  next()
Advances iterator to next IRect in Region contained by clip. ### Example
#### Example Output ~~~~ rect={1,3,3,4} rect={5,6,7,7} ~~~~
### See Also done --- ## rect 
const SkIRect& rect() const
Returns IRect element in Region, intersected with clip passed to Cliperator constructor. Does not return predictable results if Region is empty. ### Return Value part of Region inside clip as IRect ### Example
#### Example Output ~~~~ #Volatile empty region rect={1094713344,1065353216,0,-1} after set rect rect={1,2,3,3} ~~~~
### See Also next done --- # Class SkRegion::Spanerator ## Constructor SkRegion::Spanerator can be constructed or initialized by these functions, including C++ class constructors.
Topic Description
Spanerator(const SkRegion& region, int y, int left, int right) constructs Region iterator on scan line
## Member_Function SkRegion::Spanerator member functions read and modify the structure properties.
Topic Description
next advances to next span on horizontal line 
    class Spanerator {
    public:
        Spanerator(const SkRegion& region, int y, int left, int right);
        bool next(int* left, int* right);
    };
Returns the line segment ends within Region that intersect a horizontal line. ## Spanerator 
Spanerator(const SkRegion& region, int y, int left, int right)
Sets Spanerator to return line segments in Region on scan line. ### Parameters
region Region to iterate
y horizontal line to intersect
left bounds of iteration
right bounds of iteration
### Return Value Region iterator ### Example
### See Also SkRegion Iterator Cliperator --- ## next 
bool next(int* left, int* right)
Advances iterator to next span intersecting Region within line segment provided in constructor. Returns true if interval was found. ### Parameters
left pointer to span start; may be nullptr
right pointer to span end; may be nullptr
### Return Value true if interval was found ### Example
#### Example Output ~~~~ empty region: result=false after set rect: result=true left=2 right=3 ~~~~
### See Also done --- ## SkRegion 
SkRegion()
Constructs an empty Region. Region is set to empty bounds at (0, 0) with zero width and height. ### Return Value empty Region ### Example
#### Example Output ~~~~ region bounds: {0, 0, 0, 0} ~~~~
### See Also setEmpty --- ## SkRegion 
SkRegion(const SkRegion& region)
Constructs a copy of an existing region. Copy constructor makes two regions identical by value. Internally, region and the returned result share pointer values. The underlying Rect array is copied when modified. Creating a Region copy is very efficient and never allocates memory. Regions are always copied by value from the interface; the underlying shared pointers are not exposed. ### Parameters
region Region to copy by value
### Return Value copy of Region ### Example
#### Example Output ~~~~ region bounds: {1,2,3,4} region2 bounds: {1,2,3,4} after region set empty: region bounds: {0,0,0,0} region2 bounds: {1,2,3,4} ~~~~
### See Also setRegion operator=(const SkRegion& region) --- ## SkRegion 
explicit SkRegion(const SkIRect& rect)
Constructs a rectangular Region matching the bounds of rect. ### Parameters
rect bounds of constructed Region
### Return Value rectangular Region ### Example
### See Also setRect[2] setRegion --- ## ~SkRegion 
~SkRegion()
Releases ownership of any shared data and deletes data if Region is sole owner. ### Example
delete calls Region Destructor, but copy of original in region2 is unaffected.
#### Example Output ~~~~ region2 bounds: {1,2,3,4} ~~~~
### See Also SkRegion() SkRegion(const SkRegion& region) SkRegion(const SkIRect& rect) operator=(const SkRegion& region) --- ## operator= 
SkRegion& operator=(const SkRegion& region)
Constructs a copy of an existing region. Makes two regions identical by value. Internally, region and the returned result share pointer values. The underlying Rect array is copied when modified. Creating a Region copy is very efficient and never allocates memory. Regions are always copied by value from the interface; the underlying shared pointers are not exposed. ### Parameters
region Region to copy by value
### Return Value Region to copy by value ### Example
#### Example Output ~~~~ region1 bounds: {1,2,3,4} region2 bounds: {1,2,3,4} ~~~~
### See Also set swap SkRegion(const SkRegion& region) --- ## operator== 
bool operator==(const SkRegion& other) _const
Compares Region and other; returns true if they enclose exactly the same area. ### Parameters
other Region to compare
### Return Value true if Region pair are equivalent ### Example
#### Example Output ~~~~ empty one == two set rect one != two set empty one == two ~~~~
### See Also operator!=(const SkRegion& other) const operator=(const SkRegion& region) --- ## operator!= 
bool operator!=(const SkRegion& other) _const
Compares Region and other; returns true if they do not enclose the same area. ### Parameters
other Region to compare
### Return Value true if Region pair are not equivalent ### Example
#### Example Output ~~~~ empty one == two set rect one != two union rect one == two ~~~~
### See Also operator==(const SkRegion& other) const operator=(const SkRegion& region) --- ## set 
bool set(const SkRegion& src)
Sets Region to src, and returns true if src bounds is not empty. This makes Region and src identical by value. Internally, Region and src share pointer values. The underlying Rect array is copied when modified. Creating a Region copy is very efficient and never allocates memory. Regions are always copied by value from the interface; the underlying shared pointers are not exposed. ### Parameters
src Region to copy
### Return Value copy of src ### Example
#### Example Output ~~~~ region1 bounds: {1,2,3,4} region2 bounds: {1,2,3,4} ~~~~
### See Also operator=(const SkRegion& region) swap SkRegion(const SkRegion& region) --- ## swap 
void swap(SkRegion& other)
Exchanges IRect array of Region and other. swap internally exchanges pointers, so it is lightweight and does not allocate memory. swap usage has largely been replaced by operator=(const SkRegion& region). Paths do not copy their content on assignment until they are written to, making assignment as efficient as swap. ### Parameters
other operator=(const SkRegion& region) set
### Example
#### Example Output ~~~~ region1 bounds: {0,0,0,0} region2 bounds: {1,2,3,4} ~~~~
### See Also operator=(const SkRegion& region) set SkRegion(const SkRegion& region) --- ## isEmpty 
bool isEmpty() const
Returns true if Region is empty. Empty Region has bounds width or height less than or equal to zero. SkRegion() constructs empty Region; setEmpty and setRect with dimensionless data make Region empty. ### Return Value true if bounds has no width or height ### Example
#### Example Output ~~~~ initial: region is empty set rect: region is not empty set empty: region is empty ~~~~
### See Also isRect isComplex operator==(const SkRegion& other) const --- ## isRect 
bool isRect() const
Returns true if Region is one IRect with positive dimensions. ### Return Value true if Region contains one IRect ### Example
#### Example Output ~~~~ initial: region is not rect set rect: region is rect set empty: region is not rect ~~~~
### See Also isEmpty isComplex --- ## isComplex 
bool isComplex() const
Returns true if Region is described by more than one rectangle. ### Return Value true if Region contains more than one IRect ### Example
#### Example Output ~~~~ initial: region is not complex set rect: region is not complex op rect: region is complex ~~~~
### See Also isEmpty isRect --- ## getBounds 
const SkIRect& getBounds() const
Returns minimum and maximum axes values of IRect array. Returns (0, 0, 0, 0) if Region is empty. ### Return Value combined bounds of all IRect elements ### Example
#### Example Output ~~~~ bounds: {1,2,4,5} ~~~~
### See Also isEmpty isRect --- ## computeRegionComplexity 
int computeRegionComplexity() const
Returns a value that increases with the number of elements in Region. Returns zero if Region is empty. Returns one if Region equals IRect; otherwise, returns value greater than one indicating that Region is complex. Call to compare Regions for relative complexity. ### Return Value relative complexity ### Example
#### Example Output ~~~~ initial: region complexity 0 set rect: region complexity 1 op rect: region complexity 3 ~~~~
### See Also isRect isComplex --- ## getBoundaryPath 
bool getBoundaryPath(SkPath* path) const
Appends outline of Region to path. Returns true if Region is not empty; otherwise, returns false, and leaves path unmodified. ### Parameters
path Path to append to
### Return Value true if path changed ### Example
### See Also isEmpty isComplex --- ## setEmpty 
bool setEmpty()
Constructs an empty Region. Region is set to empty bounds at (0, 0) with zero width and height. Always returns false. ### Return Value false ### Example
#### Example Output ~~~~ region bounds: {1,2,3,4} after region set empty: region bounds: {0,0,0,0} ~~~~
### See Also SkRegion() --- ## setRect 
bool setRect(const SkIRect& rect)
Constructs a rectangular Region matching the bounds of rect. If rect is empty, constructs empty and returns false. ### Parameters
rect bounds of constructed Region
### Return Value true if rect is not empty ### Example
#### Example Output ~~~~ region is not empty region is empty setEmpty: false ~~~~
### See Also SkRegion(const SkIRect& rect) --- 
bool setRect(int32_t left, int32_t top, int32_t right, int32_t bottom)
Constructs Region with bounds (left, top, right, bottom). Returns true if left is less than right and top is less than bottom; otherwise, constructs empty Region and returns false. ### Parameters
left edge of bounds on x-axis
top edge of bounds on y-axis
right edge of bounds on x-axis
bottom edge of bounds on y-axis
### Return Value rectangular Region ### Example
#### Example Output ~~~~ set to: 1,2,3,4: success:true {1,2,3,4} set to: 3,2,1,4: success:false {0,0,0,0} ~~~~
### See Also SkRegion(const SkIRect& rect) --- ## setRects 
bool setRects(const SkIRect rects[], int count)
Constructs Region as the union of IRect in rects array. If count is zero, constructs empty Region. Returns false if constructed Region is empty. May be faster than repeated calls to op. ### Parameters
rects array of IRects
count array size
### Return Value true if constructed Region is not empty ### Example
### See Also setRect[2] op[2][3][4][5][6] --- ## setRegion 
bool setRegion(const SkRegion& region)
Constructs a copy of an existing region. Makes two regions identical by value. Internally, region and the returned result share pointer values. The underlying Rect array is copied when modified. Creating a Region copy is very efficient and never allocates memory. Regions are always copied by value from the interface; the underlying shared pointers are not exposed. ### Parameters
region Region to copy by value
### Return Value Region to copy by value ### Example
#### Example Output ~~~~ region bounds: {1,2,3,4} region2 bounds: {1,2,3,4} after region set empty: region bounds: {1,2,3,4} region2 bounds: {0,0,0,0} ~~~~
### See Also SkRegion(const SkRegion& region) --- ## setPath 
bool setPath(const SkPath& path, const SkRegion& clip)
Constructs Region to match outline of path within clip. Returns false if constructed Region is empty. Constructed Region draws the same pixels as path through clip when Anti Aliasing is disabled. ### Parameters
path Path providing outline
clip Region containing path
### Return Value true if constructed Region is not empty ### Example
### See Also setRects op[2][3][4][5][6] --- ## intersects 
bool intersects(const SkIRect& rect) const
Returns true if Region intersects rect. Returns false if either rect or Region is empty, or do not intersect. ### Parameters
rect IRect to intersect
### Return Value true if rect and Region have area in common ### Example
### See Also contains[2][3] SkRect::intersects[2] --- 
bool intersects(const SkRegion& other) const
Returns true if Region intersects other. Returns false if either other or Region is empty, or do not intersect. ### Parameters
other Region to intersect
### Return Value true if other and Region have area in common ### Example
### See Also contains[2][3] SkRect::intersects[2] --- ## contains 
bool contains(int32_t x, int32_t y) const
Returns true if IPoint (x, y) is inside Region. Returns false if Region is empty. ### Parameters
x test IPoint x-coordinate
y test IPoint y-coordinate
### Return Value true if (x, y) is inside Region ### Example
### See Also intersects[2] SkRect::contains[2][3] --- 
bool contains(const SkIRect& other) const
Returns true if other is completely inside Region. Returns false if Region or other is empty. ### Parameters
other IRect to contain
### Return Value true if other is inside Region ### Example
### See Also intersects[2] SkRect::contains[2][3] --- 
bool contains(const SkRegion& other) const
Returns true if other is completely inside Region. Returns false if Region or other is empty. ### Parameters
other Region to contain
### Return Value true if other is inside Region ### Example
### See Also intersects[2] SkRect::contains[2][3] --- ## quickContains 
bool quickContains(const SkIRect& r) const
Returns true if Region is a single rectangle and contains r. May return false even though Region contains r. ### Parameters
r IRect to contain
### Return Value true quickly if r points are equal or inside ### Example
#### Example Output ~~~~ quickContains 1: true quickContains 2: true quickContains 3: false ~~~~
### See Also contains[2][3] quickReject[2] intersects[2] --- 
bool quickContains(int32_t left, int32_t top, int32_t right, int32_t bottom) const
Returns true if Region is a single rectangle and contains IRect (left, top, right, bottom). Returns false if Region is empty or IRect (left, top, right, bottom) is empty. May return false even though Region contains (left, top, right, bottom). ### Parameters
left edge of bounds on x-axis
top edge of bounds on y-axis
right edge of bounds on x-axis
bottom edge of bounds on y-axis
### Return Value true quickly if IRect are equal or inside ### Example
#### Example Output ~~~~ quickContains 1: true quickContains 2: true quickContains 3: false ~~~~
### See Also contains[2][3] quickReject[2] intersects[2] --- ## quickReject 
bool quickReject(const SkIRect& rect) const
Returns true if Region does not intersect rect. Returns true if rect is empty or Region is empty. May return false even though Region does not intersect rect. ### Parameters
rect IRect to intersect
### Return Value true if rect does not intersect ### Example
#### Example Output ~~~~ quickReject 1: true quickReject 2: true quickReject 3: false ~~~~
### See Also quickContains[2] contains[2][3] intersects[2] --- 
bool quickReject(const SkRegion& rgn) const
Returns true if Region does not intersect rgn. Returns true if rgn is empty or Region is empty. May return false even though Region does not intersect rgn. ### Parameters
rgn Region to intersect
### Return Value true if rgn does not intersect ### Example
#### Example Output ~~~~ quickReject 1: true quickReject 2: true quickReject 3: false ~~~~
### See Also quickContains[2] contains[2][3] intersects[2] --- ## translate 
void translate(int dx, int dy)
Offsets Region by IVector (dx, dy). Has no effect if Region is empty. ### Parameters
dx x-axis offset
dy y-axis offset
### Example
### See Also SkCanvas::translate SkIRect::offset[2] SkPath::offset[2] --- 
void translate(int dx, int dy, SkRegion* dst) const
Offsets Region by IVector (dx, dy), writing result to dst. Region may be passed as dst parameter, translating Region in place. Has no effect if dst is nullptr. If Region is empty, sets dst to empty. ### Parameters
dx x-axis offset
dy y-axis offset
dst translated result
### Example
### See Also SkCanvas::translate SkIRect::offset[2] SkPath::offset[2] --- ## Enum SkRegion::Op 
    enum Op {
        kDifference Op,
        kIntersect Op,
        kUnion Op,
        kXOR Op,
        kReverseDifference Op,
        kReplace Op,
        kLastOp = kReplace Op,
    };
The logical operations that can be performed when combining two Regions. ### Constants
Const Value Description
SkRegion::kDifference_Op 0 Subtracts operand Region from target Region.
SkRegion::kIntersect_Op 1 Intersects operand Region and target Region.
SkRegion::kUnion_Op 2 Unions operand Region and target Region.
SkRegion::kXOR_Op 3 Replaces target Region with area exclusive to both Regions.
SkRegion::kReverseDifference_Op 4 Subtracts target Region from operand Region.
SkRegion::kReplace_Op 5 Replaces target Region with operand Region.
SkRegion::kLastOp 5 last operator
### Example
### See Also SkPathOp ### Constants
Const Value Description
SkRegion::kOpCnt 6 May be used to verify that Op is a legal value.
## op 
bool op(const SkIRect& rect, Op op)
Replaces Region with the result of Region op rect. Returns true if replaced Region is not empty. ### Parameters
rect IRect operand
op operator, one of: kDifference Op, kIntersect Op, kUnion Op, kXOR Op, kReverseDifference Op, kReplace Op
### Return Value false if result is empty ### Example
### See Also setRects Op --- 
bool op(int left, int top, int right, int bottom, Op op)
Replaces Region with the result of Region op IRect (left, top, right, bottom). Returns true if replaced Region is not empty. ### Parameters
left edge of bounds on x-axis
top edge of bounds on y-axis
right edge of bounds on x-axis
bottom edge of bounds on y-axis
op operator, one of: kDifference Op, kIntersect Op, kUnion Op, kXOR Op, kReverseDifference Op, kReplace Op
### Return Value false if result is empty ### Example
### See Also setRects Op --- 
bool op(const SkRegion& rgn, Op op)
Replaces Region with the result of Region op rgn. Returns true if replaced Region is not empty. ### Parameters
rgn Region operand
op operator, one of: kDifference Op, kIntersect Op, kUnion Op, kXOR Op, kReverseDifference Op, kReplace Op
### Return Value false if result is empty ### Example
### See Also setRects Op --- 
bool op(const SkIRect& rect, const SkRegion& rgn, Op op)
Replaces Region with the result of rect op rgn. Returns true if replaced Region is not empty. ### Parameters
rect IRect operand
rgn Region operand
op operator, one of: kDifference Op, kIntersect Op, kUnion Op, kXOR Op, kReverseDifference Op, kReplace Op
### Return Value false if result is empty ### Example
### See Also setRects Op --- 
bool op(const SkRegion& rgn, const SkIRect& rect, Op op)
Replaces Region with the result of rgn op rect. Returns true if replaced Region is not empty. ### Parameters
rgn Region operand
rect IRect operand
op operator, one of: kDifference Op, kIntersect Op, kUnion Op, kXOR Op, kReverseDifference Op, kReplace Op
### Return Value false if result is empty ### Example
### See Also setRects Op --- 
bool op(const SkRegion& rgna, const SkRegion& rgnb, Op op)
Replaces Region with the result of rgna op rgnb. Returns true if replaced Region is not empty. ### Parameters
rgna Region operand
rgnb Region operand
op operator, one of: kDifference Op, kIntersect Op, kUnion Op, kXOR Op, kReverseDifference Op, kReplace Op
### Return Value false if result is empty ### Example
### See Also setRects Op --- ## toString 
char* toString()
### Return Value string representation of Region --- ## writeToMemory 
size_t writeToMemory(void* buffer) const
Writes Region to buffer, and returns number of bytes written. If buffer is nullptr, returns number number of bytes that would be written. ### Parameters
buffer storage for binary data
### Return Value size of Region ### Example
### See Also readFromMemory --- ## readFromMemory 
size_t readFromMemory(const void* buffer, size_t length)
Constructs Region from buffer of size length. Returns bytes read. Returned value will be multiple of four or zero if length was too small. ### Parameters
buffer storage for binary data
length size of buffer
### Return Value bytes read ### Example
### See Also writeToMemory ---