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Fully fixed arcs on the Windows backend, for real this time.

This commit is contained in:
Pietro Gagliardi 2015-10-10 10:48:10 -04:00
parent 22b38accee
commit 5b37dc9fbe
1 changed files with 66 additions and 40 deletions
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106
windows/draw.c
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@ -127,54 +127,82 @@ void uiDrawPathNewFigure(uiDrawPath *p, double x, double y)
p->inFigure = TRUE;
}
static void arcEndpoint(double xCenter, double yCenter, double radius, double startAngle, double *startX, double *startY)
{
FLOAT sinStart, cosStart;
// Direct2D arcs require a little explanation.
// An arc in Direct2D is defined by the chord between the endpoints.
// There are four possible arcs with the same two endpoints that you can draw this way.
// See https://www.youtube.com/watch?v=ATS0ANW1UxQ for a demonstration.
// There is a property rotationAngle which deals with the rotation /of the entire ellipse that forms an ellpitical arc/ - it's effectively a transformation on the arc.
// That is to say, it's NOT THE SWEEP.
// The sweep is defined by the start and end points and whether the arc is "large".
// As a result, this design does not allow for full circles or ellipses with a single arc; they have to be simulated with two.
struct arc {
double xCenter;
double yCenter;
double radius;
double startAngle;
double sweep;
};
static void drawArc(uiDrawPath *p, struct arc *a, void (*startFunction)(uiDrawPath *, double, double))
{
double sinx, cosx;
double startX, startY;
double endX, endY;
D2D1_ARC_SEGMENT as;
// as above, we can't do a full circle with one arc
// simulate it with two half-circles
if (a->sweep >= (2 * M_PI)) {
a->sweep = M_PI;
drawArc(p, a, startFunction);
a->startAngle += M_PI;
drawArc(p, a, NULL);
return;
}
// first, figure out the arc's endpoints
// unfortunately D2D1SinCos() is only defined on Windows 8 and newer
// the MSDN page doesn't say this, but says it requires d2d1_1.h, which is listed as only supported on Windows 8 and newer elsewhere on MSDN
// so we must use sin() and cos() and hope it's right...
sinStart = sin(startAngle);
cosStart = cos(startAngle);
*startX = xCenter + radius * cosStart;
*startY = yCenter - radius * sinStart;
}
sinx = sin(a->startAngle);
cosx = cos(a->startAngle);
startX = a->xCenter + a->radius * cosx;
startY = a->yCenter - a->radius * sinx;
sinx = sin(a->startAngle + a->sweep);
cosx = cos(a->startAngle + a->sweep);
endX = a->xCenter + a->radius * cosx;
endY = a->yCenter - a->radius * sinx;
// An arc in Direct2D is defined by the chord between its endpoints, not solely by the sweep angle.
// There are four possible arcs with the same sweep amount that you can draw this way.
// See https://www.youtube.com/watch?v=ATS0ANW1UxQ for a demonstration.
// TODO clean this up, document it better, and merge it with the above and below functions
static void doDrawArc(ID2D1GeometrySink *sink, double endX, double endY, double radius, double sweep)
{
D2D1_ARC_SEGMENT as;
// now do the initial step to get the current point to be the start point
// this is either creating a new figure, drawing a line, or (in the case of our full circle code above) doing nothing
if (startFunction != NULL)
(*startFunction)(p, startX, startY);
if (sweep > 2 * M_PI)
sweep = 2 * M_PI;
// now we can draw the arc
as.point.x = endX;
as.point.y = endY;
as.size.width = radius;
as.size.height = radius;
as.rotationAngle = sweep * (180.0 / M_PI);
as.size.width = a->radius;
as.size.height = a->radius;
as.rotationAngle = 0; // as above, not relevant for circles
as.sweepDirection = D2D1_SWEEP_DIRECTION_COUNTER_CLOCKWISE;
if (sweep > M_PI)
if (a->sweep > M_PI)
as.arcSize = D2D1_ARC_SIZE_LARGE;
else
as.arcSize = D2D1_ARC_SIZE_SMALL;
ID2D1GeometrySink_AddArc(sink, &as);
ID2D1GeometrySink_AddArc(p->sink, &as);
}
void uiDrawPathNewFigureWithArc(uiDrawPath *p, double xCenter, double yCenter, double radius, double startAngle, double sweep)
{
double startX, startY;
double endX, endY;
struct arc a;
// make the new figure
arcEndpoint(xCenter, yCenter, radius, startAngle, &startX, &startY);
uiDrawPathNewFigure(p, startX, startY);
// draw the arc
arcEndpoint(xCenter, yCenter, radius, startAngle + sweep, &endX, &endY);
doDrawArc(p->sink, endX, endY, radius, sweep);
a.xCenter = xCenter;
a.yCenter = yCenter;
a.radius = radius;
a.startAngle = startAngle;
a.sweep = sweep;
drawArc(p, &a, uiDrawPathNewFigure);
}
void uiDrawPathLineTo(uiDrawPath *p, double x, double y)
@ -188,16 +216,14 @@ void uiDrawPathLineTo(uiDrawPath *p, double x, double y)
void uiDrawPathArcTo(uiDrawPath *p, double xCenter, double yCenter, double radius, double startAngle, double sweep)
{
double startX, startY;
double endX, endY;
struct arc a;
// draw the starting line
arcEndpoint(xCenter, yCenter, radius, startAngle, &startX, &startY);
uiDrawPathLineTo(p, startX, startY);
// draw the arc
arcEndpoint(xCenter, yCenter, radius, startAngle + sweep, &endX, &endY);
doDrawArc(p->sink, endX, endY, radius, sweep);
a.xCenter = xCenter;
a.yCenter = yCenter;
a.radius = radius;
a.startAngle = startAngle;
a.sweep = sweep;
drawArc(p, &a, uiDrawPathLineTo);
}
void uiDrawPathBezierTo(uiDrawPath *p, double c1x, double c1y, double c2x, double c2y, double endX, double endY)