Streamline Angle API Behaviour (#729)

* angle: Streamline behaviour

* angle: Change inner to direction

src/lib/angle.typ

@@ -15,7 +15,7 @@
   mark: auto,
 )
 
-/// Draw an angle between `a` and `b` through origin `origin`
+/// Draw an angle counter-clock-wise between `a` and `b` through origin `origin`
 ///
 /// ```typc example
 /// line((0,0), (1,1.5), name: "a")
@@ -25,13 +25,13 @@
 /// cetz.angle.angle("a.start", "a.end", "b.end", label: $ alpha $,
 ///   mark: (end: ">"), radius: 1.5)
 /// cetz.angle.angle("a.start", "b.end", "a.end", label: $ alpha' $,
-///   radius: 50%, inner: false)
+///   radius: 50%, direction: "cw")
 /// ```
 ///
 /// - origin (coordinate): Angle origin
 /// - a (coordinate): Coordinate of side `a`, containing an angle between `origin` and `b`.
 /// - b (coordinate): Coordinate of side `b`, containing an angle between `origin` and `a`.
-/// - inner (bool): Draw the smaller (inner) angle if true, otherwise the outer angle gets drawn.
+/// - direction (string): Direction of the angle. Accepts "cw" (clockwise) and "ccw" (counter-clockwise), the latter being the default.
 /// - label (none,content,function): Draw a label at the angles "label" anchor. If label is a function, it gets the angle value passed as argument. The function must be of the format `angle => content`.
 /// - name (none,str): Element name, used for querying anchors.
 /// - ..style (style): Style key-value pairs.
@@ -53,7 +53,7 @@
   origin,
   a,
   b,
-  inner: true,
+  direction: "ccw",
   label: none,
   name: none,
   ..style
@@ -65,32 +65,31 @@
   assert(origin.at(2) == a.at(2) and a.at(2) == b.at(2),
     message: "Angle z coordinates of all three points must be equal")
 
-  let (s, e, ss) = {
+  assert(direction in ("cw", "ccw"),
+    message: "Invalid angle direction " + repr(direction))
+
+  let (start, delta, ccw) = {
+    let ccw = direction == "ccw"
+
     let s = vector.angle2(origin, a)
     if s < 0deg { s += 360deg }
+
     let e = vector.angle2(origin, b)
     if e < 0deg { e += 360deg }
 
-    if s > e {
-      (s, e) = (e, s)
+    if e < s {
+      e += 360deg
     }
 
-    if inner == true {
-      let d = vector.angle(a, origin, b)
-      if e - s > 180deg {
-        (s, e) = (e, e + d)
-      } else {
-        (s, e) = (s, s + d)
-      }
-    } else if inner == false {
-      if e - s < 180deg {
-        let d = 360deg - vector.angle(a, origin, b)
-        (s, e) = (e, e + d)
-      }
+    if ccw {
+      (s, (e - s), ccw)
+    } else {
+      (s, -(360deg - (e - s)), ccw)
     }
-    (s, e, (s + e) / 2)
   }
 
+  let mid = start + delta / 2
+
   // Radius can be relative to the min-distance between origin-a and origin-b
   if type(style.radius) == ratio {
     style.radius = style.radius * calc.min(vector.dist(origin, a), vector.dist(origin, b)) / 100%
@@ -103,28 +102,28 @@
   }
   let (ra, _) = util.resolve-radius(style.label-radius).map(util.resolve-number.with(ctx))
 
-  let label-pt = vector.add(origin, (calc.cos(ss) * ra, calc.sin(ss) * ra, 0))
-  let start-pt = vector.add(origin, (calc.cos(s) * r, calc.sin(s) * r, 0))
-  let end-pt = vector.add(origin, (calc.cos(e) * r, calc.sin(e) * r, 0))
+  let label-pt = vector.add(origin, (calc.cos(mid) * ra, calc.sin(mid) * ra, 0))
+  let start-pt = vector.add(origin, (calc.cos(start) * r, calc.sin(start) * r, 0))
+  let end-pt = vector.add(origin, (calc.cos(start + delta) * r, calc.sin(start + delta) * r, 0))
   draw.anchor("origin", origin)
   draw.anchor("label", label-pt)
   draw.anchor("start", start-pt)
   draw.anchor("end", end-pt)
   draw.anchor("a", a)
   draw.anchor("b", b)
 
-  if s != e {
+  if delta != 0deg {
     if style.fill != none {
-      draw.arc(origin, start: s, stop: e, anchor: "origin",
+      draw.arc(origin, start: start, delta: delta, anchor: "origin",
         name: "arc", ..style, radius: r, mode: "PIE", mark: none, stroke: none)
     }
     if style.stroke != none {
-      draw.arc(origin, start: s, stop: e, anchor: "origin",
+      draw.arc(origin, start: start, delta: delta, anchor: "origin",
         name: "arc", ..style, radius: r, fill: none)
     }
   }
 
-  let label = if type(label) == function { label(e - s) } else { label }
+  let label = if type(label) == function { label(calc.abs(delta)) } else { label }
   if label != none {
     draw.content(label-pt, label)
   }

tests/angle/test.typ

@@ -1,7 +1,8 @@
 #set page(width: auto, height: auto)
 #import "/src/lib.typ": *
+#import "/tests/helper.typ": *
 
-#box(stroke: 2pt + red, canvas(length: 1cm, {
+#test-case({
   import draw: *
   import angle: angle
 
@@ -11,12 +12,12 @@
     group({
       let (o, a, b) = ((0,0), (1,0), (calc.cos(a), calc.sin(a)))
       line(a, o, b)
-      angle(o, a, b, label: $alpha$, inner: true)
+      angle(o, a, b, label: $alpha$)
     })
   }
 }))
 
-#box(stroke: 2pt + red, canvas(length: 1cm, {
+#test-case({
   import draw: *
   import angle: angle
 
@@ -26,12 +27,12 @@
     group({
       let (o, a, b) = ((0,0), (1,0), (calc.cos(a), calc.sin(a)))
       line(a, o, b)
-      angle(o, a, b, label: $alpha$, inner: false)
+      angle(o, a, b, label: $alpha$, direction: "cw")
     })
   }
 }))
 
-#box(stroke: 2pt + red, canvas(length: 1cm, {
+#test-case({
   import draw: *
   import angle: angle
 
@@ -41,12 +42,12 @@
     group({
       let (o, a, b) = ((0,0), (calc.cos(a+90deg), calc.sin(a+90deg)), (calc.cos(a), calc.sin(a)))
       line(a, o, b)
-      angle(o, b, a, label: $alpha$, inner: true)
+      angle(o, b, a, label: $alpha$)
     })
   }
 }))
 
-#box(stroke: 2pt + red, canvas(length: 1cm, {
+#test-case({
   import draw: *
   import angle: angle
 
@@ -56,33 +57,46 @@
     group({
       let (o, a, b) = ((0,0), (calc.cos(a+90deg), calc.sin(a+90deg)), (calc.cos(a), calc.sin(a)))
       line(a, o, b)
-      angle(o, b, a, label: $alpha$, inner: false)
+      angle(o, b, a, label: $alpha$, direction: "cw")
     })
   }
 }))
 
-#box(stroke: 2pt + red, canvas(length: 1cm, {
+#test-case({
   import draw: *
   import angle: angle
 
   let (a, b, c) = ((-1, 1), (0, 0), (1, 2))
 
   line(a, b, c)
   set-style(angle: (stroke: red, label-radius: 1))
-  angle(b, a, c, mark: (start: ">", end: ">"),
-    inner: true, label: $omega$)
+  angle(b, c, a, mark: (start: ">", end: ">"), label: $omega$)
 
   translate((2,0,0))
 
   line(a, b, c)
   set-style(stroke: blue)
   set-style(angle: (stroke: auto, radius: 1, label-radius: .5))
-  angle(b, c, a, mark: (start: ">", end: ">"),
-    inner: false, label: $alpha$, name: "alpha")
+  angle(b, c, a, mark: (start: "|", end: ">"),
+    direction: "cw", label: $alpha$, name: "alpha")
 
   set-style(stroke: black)
   circle("alpha.origin", radius: .15)
   circle("alpha.label", radius: .25)
   circle("alpha.start", radius: .25)
   circle("alpha.end", radius: .25)
 }))
+
+#test-case({
+  import draw: *
+  import angle: *
+
+  angle((0,0), (1,0), (0,1), mark: (end: ">"))
+})
+
+#test-case({
+  import draw: *
+  import angle: *
+
+  angle((0,0), (1,0), (0,1), mark: (end: ">"), direction: "cw")
+})