How to use arc co-ordinates from .slib file to draw an arc in Qt?-CodePudding

I am trying to generate various gate symbols ( AND,NOT,XNOR,MUX etc) by reading .slib file.
But I faced a problem while reading an arc related co-ordinate from .slib file.

I am not understanding how to use those co-ordinates and draw an arc ?
The format of an arc in .slib file is confusing.

Here is the example:

.slib format for an arc and for line

line (66 * SCALE, 80 * SCALE, 0 * SCALE, 80 * SCALE); 
line (94 * SCALE, 70 * SCALE, 62 * SCALE, 70 * SCALE);
              .
              .

arc (145 * SCALE, 100 * SCALE, 94 * SCALE, 70 * SCALE,94.9268 * SCALE,126.774 * SCALE);     
arc (94 * SCALE, 130 * SCALE, 145 * SCALE, 100 * SCALE,94.9268 * SCALE, 73.2256 * SCALE);    
arc (61 * SCALE, 130 * SCALE, 61 * SCALE, 70 * SCALE,8.75 * SCALE, 100 * SCALE);

1st line says draw an arc from O (145,100) to F(94,70)
2nd line says draw an arc from L(94,130) to O(145,100)
3rd line says draw an arc from K(62,30) to E(62,70)

I tried to draw an arc by using 1st 4 co-ordinates from line ( but do not know how to use remaining 2 co-ordinates ? )

 QPainterPath path;  // arc from L --->  F 
 path.moveTo(94,70);
 QRect bound1 (44,70,102,60);
 path.arcTo(bound1,90,-180);
        
 QPainterPath path1;  // arc from K ---> E
 path1.moveTo(62,70);
 QRect bound2 (42,70,40,60);
 path1.arcTo(bound2,90,-180);

And I got following output :

But,

Input lines to OR gate are not attached to 1st arc.
I am using only first four co-ordinates. How to use remaining 2 co-ordinates to draw an arc ?

So how to use all given co-ordinates from.slib to draw an arc ?
Note : SCALE is defined at the start of the file.

CodePudding user response：

It looks like the first two coordinate pairs are two points on an imaginary circle and the third pair is the center of that circle. Together, those describe a circle arc section. For this to work with arcTo, we construct a QRectF bounding the circle, ie with the given center and side 2*radius.

Thus, the following ought to work:

QPointF from, to; // first and second coordinate pair
QPointF center; // third coordinate pair

// Bounding rectangle is a square around center.
QLineF lineFrom{center, from};
QLineF lineTo{center, to};
qreal radius = lineFrom.length();
QRectF bounding{ center - QPointF{radius, radius}, center   QPointF{radius, radius}};

// Use QLineF to calculate angles wrt horizontal axis.
qreal startAngle = lineFrom.angle();
qreal sweep = lineFrom.angleTo(lineTo);

QPainterPath path;
path.moveTo(from);
path.arcTo(bounding, startAngle, sweep);