skia2/docs/SkPath_Overview.bmh

#Topic Path_Overview

Path contains Lines and Curves which can be stroked or filled. Contour is
composed of a series of connected Lines and Curves. Path may contain zero,
one, or more Contours.
Each Line and Curve are described by Verb, Points, and optional Path_Conic_Weight.

Each pair of connected Lines and Curves share common Point; for instance, Path
containing two connected Lines are described the Path_Verb sequence:
SkPath::kMove_Verb, SkPath::kLine_Verb, SkPath::kLine_Verb; and a Point sequence
with three entries, sharing
the middle entry as the end of the first Line and the start of the second Line.

Path components Arc, Rect, Round_Rect, Circle, and Oval are composed of
Lines and Curves with as many Verbs and Points required
for an exact description. Once added to Path, these components may lose their
identity; although Path can be inspected to determine if it describes a single
Rect, Oval, Round_Rect, and so on.

#Example
#Height 192
#Description
Path contains three Contours: Line, Circle, and Quad. Line is stroked but
not filled. Circle is stroked and filled; Circle stroke forms a loop. Quad
is stroked and filled, but since it is not closed, Quad does not stroke a loop.
##
void draw(SkCanvas* canvas) {
    SkPaint paint;
    paint.setAntiAlias(true);
    SkPath path;
    path.moveTo(124, 108);
    path.lineTo(172, 24);
    path.addCircle(50, 50, 30);
    path.moveTo(36, 148);
    path.quadTo(66, 188, 120, 136);
    canvas->drawPath(path, paint);
    paint.setStyle(SkPaint::kStroke_Style);
    paint.setColor(SK_ColorBLUE);
    paint.setStrokeWidth(3);
    canvas->drawPath(path, paint);
}
##

Path contains a Path_Fill_Type which determines whether overlapping Contours
form fills or holes. Path_Fill_Type also determines whether area inside or outside
Lines and Curves is filled.

#Example
#Height 192
#Description
Path is drawn filled, then stroked, then stroked and filled.
##
void draw(SkCanvas* canvas) {
    SkPaint paint;
    paint.setAntiAlias(true);
    SkPath path;
    path.moveTo(36, 48);
    path.quadTo(66, 88, 120, 36);
    canvas->drawPath(path, paint);
    paint.setStyle(SkPaint::kStroke_Style);
    paint.setColor(SK_ColorBLUE);
    paint.setStrokeWidth(8);
    canvas->translate(0, 50);
    canvas->drawPath(path, paint);
    paint.setStyle(SkPaint::kStrokeAndFill_Style);
    paint.setColor(SK_ColorRED);
    canvas->translate(0, 50);
    canvas->drawPath(path, paint);
}
##

Path contents are never shared. Copying Path by value effectively creates
a new Path independent of the original. Internally, the copy does not duplicate
its contents until it is edited, to reduce memory use and improve performance.

#Subtopic Contour
#Alias Path_Contour ##
#Alias Contour ##
#Alias Contours ##
#Line # loop of lines and curves ##

Contour contains one or more Verbs, and as many Points as
are required to satisfy Path_Verb_Array. First Path_Verb in Path is always
SkPath::kMove_Verb; each SkPath::kMove_Verb that follows starts a new Contour.

#Example
#Description
Each SkPath::moveTo starts a new Contour, and content after SkPath::close()
also starts a new Contour. Since SkPath::conicTo is not preceded by
SkPath::moveTo, the first Point of the third Contour starts at the last Point
of the second Contour.
##
#Height 192
    SkPaint paint;
    paint.setAntiAlias(true);
    canvas->drawString("1st contour", 150, 100, paint);
    canvas->drawString("2nd contour", 130, 160, paint);
    canvas->drawString("3rd contour", 40, 30, paint);
    paint.setStyle(SkPaint::kStroke_Style);
    SkPath path;
    path.moveTo(124, 108);
    path.lineTo(172, 24);
    path.moveTo(36, 148);
    path.quadTo(66, 188, 120, 136);
    path.close();
    path.conicTo(70, 20, 110, 40, 0.6f);
    canvas->drawPath(path, paint);
##

If final Path_Verb in Contour is SkPath::kClose_Verb, Line connects Path_Last_Point in
Contour with first Point. A closed Contour, stroked, draws
Paint_Stroke_Join at Path_Last_Point and first Point. Without SkPath::kClose_Verb
as final Verb, Path_Last_Point and first Point are not connected; Contour
remains open. An open Contour, stroked, draws Paint_Stroke_Cap at
Path_Last_Point and first Point.

#Example
#Height 160
#Description
Path is drawn stroked, with an open Contour and a closed Contour.
##
void draw(SkCanvas* canvas) {
    SkPaint paint;
    paint.setAntiAlias(true);
    paint.setStyle(SkPaint::kStroke_Style);
    paint.setStrokeWidth(8);
    SkPath path;
    path.moveTo(36, 48);
    path.quadTo(66, 88, 120, 36);
    canvas->drawPath(path, paint);
    path.close();
    canvas->translate(0, 50);
    canvas->drawPath(path, paint);
}
##

#Subtopic Zero_Length
#Alias Zero_Length_Contour ##
#Line # consideration when contour has no length ##
Contour length is distance traveled from first Point to Path_Last_Point,
plus, if Contour is closed, distance from Path_Last_Point to first Point.
Even if Contour length is zero, stroked Lines are drawn if Paint_Stroke_Cap
makes them visible.

#Example
#Height 64
    SkPaint paint;
    paint.setAntiAlias(true);
    paint.setStyle(SkPaint::kStroke_Style);
    paint.setStrokeWidth(8);
    paint.setStrokeCap(SkPaint::kRound_Cap);
    SkPath path;
    path.moveTo(36, 48);
    path.lineTo(36, 48);
    canvas->drawPath(path, paint);
    path.reset();
    paint.setStrokeCap(SkPaint::kSquare_Cap);
    path.moveTo(56, 48);
    path.close();
    canvas->drawPath(path, paint);
##

#Subtopic Zero_Length ##

#Subtopic Contour ##

# ------------------------------------------------------------------------------

#Topic Path_Overview ##