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sw_engine shape: expand the algorithm to draw arcs with negative angles

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The _appendArc function allows to draw angles only in a clockwise direction.
The introduced improvement allows to change this direction by giving the 'sweep' argument
with a negative value.
This commit is contained in:
Mira Grudzinska 2020-12-22 13:12:58 +01:00 • committed by Hermet Park
parent ac43ec591e
commit d3bd55dbc7
1 changed files with 4 additions and 4 deletions
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8
src/lib/tvgShape.cpp
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@ -153,14 +153,15 @@ Result Shape::appendArc(float cx, float cy, float radius, float startAngle, floa
const float M_PI_HALF = M_PI * 0.5f;
//just circle
if (sweep >= 360) return appendCircle(cx, cy, radius, radius);
if (sweep >= 360 || sweep <= -360) return appendCircle(cx, cy, radius, radius);
startAngle = (startAngle * M_PI) / 180;
sweep = sweep * M_PI / 180;
auto nCurves = ceil(abs(sweep / M_PI_HALF));
auto sweepSign = (sweep < 0 ? -1 : 1);
auto fract = fmod(sweep, M_PI_HALF);
fract = (fract < std::numeric_limits<float>::epsilon()) ? M_PI_HALF : fract;
fract = (abs(fract) < std::numeric_limits<float>::epsilon()) ? M_PI_HALF : fract;
//Start from here
Point start = {radius * cos(startAngle), radius * sin(startAngle)};
@ -173,8 +174,7 @@ Result Shape::appendArc(float cx, float cy, float radius, float startAngle, floa
}
for (int i = 0; i < nCurves; ++i) {
auto endAngle = startAngle + ((i != nCurves - 1) ? M_PI_HALF : fract);
auto endAngle = startAngle + ((i != nCurves - 1) ? M_PI_HALF * sweepSign : fract);
Point end = {radius * cos(endAngle), radius * sin(endAngle)};
//variables needed to calculate bezier control points