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142 lines
8.1 KiB
142 lines
8.1 KiB
7 months ago
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---
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title: 'SkPath Overview'
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linkTitle: 'SkPath Overview'
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weight: 270
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---
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<a href='https://api.skia.org/classSkPath.html'>Path</a> contains
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<a href='undocumented#Line'>Lines</a> and
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<a href='undocumented#Curve'>Curves</a> which can be stroked or filled.
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<a href='#Contour'>Contour</a> is composed of a series of connected
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<a href='undocumented#Line'>Lines</a> and
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<a href='undocumented#Curve'>Curves</a>.
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<a href='https://api.skia.org/classSkPath.html'>Path</a> may contain zero, one,
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or more <a href='#Contour'>Contours</a>. Each
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<a href='undocumented#Line'>Line</a> and <a href='undocumented#Curve'>Curve</a>
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are described by Verb,
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<a href='https://api.skia.org/structSkPoint.html'>Points</a>, and optional
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<a href='#Path_Conic_Weight'>Path_Conic_Weight</a>.
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Each pair of connected <a href='undocumented#Line'>Lines</a> and
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<a href='undocumented#Curve'>Curves</a> share common
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<a href='https://api.skia.org/structSkPoint.html'>Point</a>; for instance,
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<a href='https://api.skia.org/classSkPath.html'>Path</a> containing two
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connected <a href='undocumented#Line'>Lines</a> are described the
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<a href='#Path_Verb'>Path_Verb</a> sequence:
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<a href='https://api.skia.org/classSkPath.html'>SkPath</a>::<a href='#SkPath_kMove_Verb'>kMove_Verb</a>,
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<a href='https://api.skia.org/classSkPath.html'>SkPath</a>::<a href='#SkPath_kLine_Verb'>kLine_Verb</a>,
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<a href='https://api.skia.org/classSkPath.html'>SkPath</a>::<a href='#SkPath_kLine_Verb'>kLine_Verb</a>;
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and a <a href='https://api.skia.org/structSkPoint.html'>Point</a> sequence with
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three entries, sharing the middle entry as the end of the first
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<a href='undocumented#Line'>Line</a> and the start of the second
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<a href='undocumented#Line'>Line</a>.
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<a href='https://api.skia.org/classSkPath.html'>Path</a> components
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<a href='undocumented#Arc'>Arc</a>,
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<a href='https://api.skia.org/classSkPath.html#af037025a1adad16072abbbcd83b621f2'>Rect</a>,
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<a href='#RRect'>Round_Rect</a>, <a href='undocumented#Circle'>Circle</a>, and
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<a href='undocumented#Oval'>Oval</a> are composed of
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<a href='undocumented#Line'>Lines</a> and
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<a href='undocumented#Curve'>Curves</a> with as many
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<a href='https://api.skia.org/classSkPath.html#ac36f638ac96f3428626e993eacf84ff0'>Verbs</a>
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and <a href='https://api.skia.org/structSkPoint.html'>Points</a> required for an
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exact description. Once added to
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<a href='https://api.skia.org/classSkPath.html'>Path</a>, these components may
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lose their identity; although
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<a href='https://api.skia.org/classSkPath.html'>Path</a> can be inspected to
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determine if it describes a single
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<a href='https://api.skia.org/classSkPath.html#af037025a1adad16072abbbcd83b621f2'>Rect</a>,
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<a href='undocumented#Oval'>Oval</a>, <a href='#RRect'>Round_Rect</a>, and so
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on.
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### Example
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<div><fiddle-embed name="93887af0c1dac49521972698cf04069c"><div><a href='https://api.skia.org/classSkPath.html'>Path</a> contains three <a href='#Contour'>Contours</a>: <a href='undocumented#Line'>Line</a>, <a href='undocumented#Circle'>Circle</a>, and <a href='https://api.skia.org/classSkPath.html#ad75d5a934476ac6543d6d7ddd8dbb90a'>Quad</a>. <a href='undocumented#Line'>Line</a> is stroked but
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not filled. <a href='undocumented#Circle'>Circle</a> is stroked and filled; <a href='undocumented#Circle'>Circle</a> stroke forms a loop. <a href='https://api.skia.org/classSkPath.html#ad75d5a934476ac6543d6d7ddd8dbb90a'>Quad</a>
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is stroked and filled, but since it is not closed, <a href='https://api.skia.org/classSkPath.html#ad75d5a934476ac6543d6d7ddd8dbb90a'>Quad</a> does not stroke a loop.
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</div></fiddle-embed></div>
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<a href='https://api.skia.org/classSkPath.html'>Path</a> contains a
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<a href='#Path_Fill_Type'>Path_Fill_Type</a> which determines whether
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overlapping <a href='#Contour'>Contours</a> form fills or holes.
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<a href='#Path_Fill_Type'>Path_Fill_Type</a> also determines whether area inside
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or outside <a href='undocumented#Line'>Lines</a> and
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<a href='undocumented#Curve'>Curves</a> is filled.
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### Example
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<div><fiddle-embed name="36a995442c081ee779ecab2962d36e69"><div><a href='https://api.skia.org/classSkPath.html'>Path</a> is drawn filled, then stroked, then stroked and filled.
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</div></fiddle-embed></div>
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<a href='https://api.skia.org/classSkPath.html'>Path</a> contents are never
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shared. Copying <a href='https://api.skia.org/classSkPath.html'>Path</a> by
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value effectively creates a new
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<a href='https://api.skia.org/classSkPath.html'>Path</a> independent of the
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original. Internally, the copy does not duplicate its contents until it is
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edited, to reduce memory use and improve performance.
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<a name='Contour'></a>
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---
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<a href='#Contour'>Contour</a> contains one or more
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<a href='https://api.skia.org/classSkPath.html#ac36f638ac96f3428626e993eacf84ff0'>Verbs</a>,
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and as many <a href='https://api.skia.org/structSkPoint.html'>Points</a> as are
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required to satisfy <a href='#Path_Verb_Array'>Path_Verb_Array</a>. First
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<a href='#Path_Verb'>Path_Verb</a> in
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<a href='https://api.skia.org/classSkPath.html'>Path</a> is always
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<a href='https://api.skia.org/classSkPath.html'>SkPath</a>::<a href='#SkPath_kMove_Verb'>kMove_Verb</a>;
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each
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<a href='https://api.skia.org/classSkPath.html'>SkPath</a>::<a href='#SkPath_kMove_Verb'>kMove_Verb</a>
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that follows starts a new <a href='#Contour'>Contour</a>.
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### Example
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<div><fiddle-embed name="0374f2dcd7effeb1dd435205a6c2de6f"><div>Each <a href='https://api.skia.org/classSkPath.html'>SkPath</a>::<a href='#SkPath_moveTo'>moveTo</a> starts a new <a href='#Contour'>Contour</a>, and content after <a href='https://api.skia.org/classSkPath.html'>SkPath</a>::<a href='#SkPath_close'>close()</a>
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also starts a new <a href='#Contour'>Contour</a>. Since <a href='https://api.skia.org/classSkPath.html'>SkPath</a>::<a href='#SkPath_conicTo'>conicTo</a> is not preceded by
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<a href='https://api.skia.org/classSkPath.html'>SkPath</a>::<a href='#SkPath_moveTo'>moveTo</a>, the first <a href='https://api.skia.org/structSkPoint.html'>Point</a> of the third <a href='#Contour'>Contour</a> starts at the last <a href='https://api.skia.org/structSkPoint.html'>Point</a>
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of the second <a href='#Contour'>Contour</a>.
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</div></fiddle-embed></div>
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If final <a href='#Path_Verb'>Path_Verb</a> in <a href='#Contour'>Contour</a> is
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<a href='https://api.skia.org/classSkPath.html'>SkPath</a>::<a href='#SkPath_kClose_Verb'>kClose_Verb</a>,
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<a href='undocumented#Line'>Line</a> connects
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<a href='#Path_Last_Point'>Path_Last_Point</a> in <a href='#Contour'>Contour</a>
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with first <a href='https://api.skia.org/structSkPoint.html'>Point</a>. A closed
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<a href='#Contour'>Contour</a>, stroked, draws
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<a href='#Paint_Stroke_Join'>Paint_Stroke_Join</a> at
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<a href='#Path_Last_Point'>Path_Last_Point</a> and first
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<a href='https://api.skia.org/structSkPoint.html'>Point</a>. Without
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<a href='https://api.skia.org/classSkPath.html'>SkPath</a>::<a href='#SkPath_kClose_Verb'>kClose_Verb</a>
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as final Verb, <a href='#Path_Last_Point'>Path_Last_Point</a> and first
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<a href='https://api.skia.org/structSkPoint.html'>Point</a> are not connected;
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<a href='#Contour'>Contour</a> remains open. An open
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<a href='#Contour'>Contour</a>, stroked, draws
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<a href='#Paint_Stroke_Cap'>Paint_Stroke_Cap</a> at
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<a href='#Path_Last_Point'>Path_Last_Point</a> and first
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<a href='https://api.skia.org/structSkPoint.html'>Point</a>.
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### Example
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<div><fiddle-embed name="7a1f39b12d2cd8b7f5b1190879259cb2"><div><a href='https://api.skia.org/classSkPath.html'>Path</a> is drawn stroked, with an open <a href='#Contour'>Contour</a> and a closed <a href='#Contour'>Contour</a>.
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</div></fiddle-embed></div>
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<a name='Contour_Zero_Length'></a>
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---
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<a href='#Contour'>Contour</a> length is distance traveled from first
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<a href='https://api.skia.org/structSkPoint.html'>Point</a> to
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<a href='#Path_Last_Point'>Path_Last_Point</a>, plus, if
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<a href='#Contour'>Contour</a> is closed, distance from
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<a href='#Path_Last_Point'>Path_Last_Point</a> to first
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<a href='https://api.skia.org/structSkPoint.html'>Point</a>. Even if
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<a href='#Contour'>Contour</a> length is zero, stroked
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<a href='undocumented#Line'>Lines</a> are drawn if
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<a href='#Paint_Stroke_Cap'>Paint_Stroke_Cap</a> makes them visible.
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### Example
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<div><fiddle-embed name="62848df605af6258653d9e16b27d8f7f"></fiddle-embed></div>
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