Support Content Intersections (#386)

- Adds intersection checking for `content` elements by setting their
`segments` to their frame (defaulting to a rectangle)
- Fixes a bug in `line` intersection checking, taking the furthest
intersection for one side and the nearest for the other

This changes `intersection` to _not_ emit anchors for intersections of
one element's drawables with each other (e.g. an element with 2
drawables or marks did emit self intersections prior to this change!).
See the grid intersection example (ref image), which should _not_ emit
intersections.

src/draw/grouping.typ

@@ -97,34 +97,45 @@
   return (ctx => {
     let ctx = ctx
 
-    let named-drawables = () // List of elements to calc intersections for
-    let drawables = () // List of elements to draw + calc intersections for
+    // List of drawables to calc intersections for;
+    // grouped by element.
+    let named-drawables = ()
+    // List of drawables passed as elements to calc intersections for;
+    // grouped by element.
+    let drawables = ()
 
     for elem in elements.pos() {
       if type(elem) == str {
         assert(elem in ctx.nodes,
           message: "No such element '" + elem + "' in elements " + repr(ctx.nodes.keys()))
-        named-drawables += ctx.nodes.at(elem).drawables
+        named-drawables.push(ctx.nodes.at(elem).drawables)
       } else {
-        let new-drawables = ()
-        (ctx: ctx, drawables: new-drawables, ..) = process.many(ctx, elem)
-        drawables += new-drawables
+        for sub in elem {
+          let sub-drawables = ()
+          (ctx: ctx, drawables: sub-drawables, ..) = process.element(ctx, sub)
+          if sub-drawables != none and sub-drawables != () {
+            drawables.push(sub-drawables)
+          }
+        }
       }
     }
 
-    // Filter out elements that can not intersect
-    let paths = (named-drawables + drawables).filter(d => d.type == "path")
-
+    let elems = named-drawables + drawables
     let pts = ()
-    if paths.len() > 1 { 
-      for (i, path-1) in paths.enumerate() {
-        for path-2 in paths.slice(i+1) {
-          for pt in intersection.path-path(
-            path-1,
-            path-2,
-            samples: samples
-          ) {
-            if pt not in pts { pts.push(pt) }
+    if elems.len() > 1 {
+      for (i, elem-1) in elems.enumerate() {
+        for j in range(i + 1, elems.len()) {
+          let elem-2 = elems.at(j)
+          for path-1 in elem-1 {
+            for path-2 in elem-2 {
+              for pt in intersection.path-path(
+                path-1,
+                path-2,
+                samples: samples
+              ) {
+                if pt not in pts { pts.push(pt) }
+              }
+            }
           }
         }
       }
@@ -145,7 +156,7 @@
         transform: none,
         name: name
       ).last(),
-      drawables: drawables
+      drawables: drawables.flatten()
     )
   },)
 }

src/draw/shapes.typ

@@ -609,7 +609,7 @@
       a
     } else {
       // Find the nearest point
-      let pt = util.sort-points-by-distance(b, pts).first()
+      let pt = util.sort-points-by-distance(tb, pts).first()
 
       // Reverse the transformation
       return util.revert-transform(ctx.transform, pt)
@@ -630,7 +630,7 @@
     }
     if pts-system.last() == "element" {
       let elem = ctx.nodes.at(last-elem)
-      pts.last() = element-line-intersection(ctx, elem, ..pts.slice(-2))
+      pts.last() = element-line-intersection(ctx, elem, ..pts.slice(-2).rev())
     }
 
     let style = styles.resolve(ctx.style, merge: style, root: "line")
@@ -935,43 +935,45 @@
       )
     }
 
-    let drawables = ()
-    if style.frame in ("rect", "circle") {
-      drawables.push(
-        if style.frame == "rect" {
-          drawable.path(
-            path-util.line-segment((
-              anchors.north-west,
-              anchors.north-east,
-              anchors.south-east,
-              anchors.south-west
-            )),
-            close: true,
-            stroke: style.stroke,
-            fill: style.fill
-          )
-        } else if style.frame == "circle" {
-          let (x, y, z) = util.calculate-circle-center-3pt(anchors.north-west, anchors.south-west, anchors.south-east)
-          let r = vector.dist((x, y, z), anchors.north-west)
-          drawable.ellipse(
-            x, y, z,
-            r, r,
-            stroke: style.stroke,
-            fill: style.fill
-          )
-        }
+    let border = if style.frame in (none, "rect") {
+      drawable.path(
+        path-util.line-segment((
+          anchors.north-west,
+          anchors.north-east,
+          anchors.south-east,
+          anchors.south-west
+        )),
+        close: true,
+        stroke: style.stroke,
+        fill: style.fill)
+    } else if style.frame == "circle" {
+      let (x, y, z) = util.calculate-circle-center-3pt(anchors.north-west, anchors.south-west, anchors.south-east)
+      let r = vector.dist((x, y, z), anchors.north-west)
+      drawable.ellipse(
+        x, y, z,
+        r, r,
+        stroke: style.stroke,
+        fill: style.fill
       )
     }
 
     let (aabb-width, aabb-height, ..) = aabb.size(aabb.aabb(
       (anchors.north-west, anchors.north-east,
        anchors.south-west, anchors.south-east)))
 
+    let corners = (anchors.north-east, anchors.north-west,
+                   anchors.south-west, anchors.south-east)
+
+    let drawables = ()
+    if style.frame != none {
+      drawables.push(border)
+    }
     drawables.push(
       drawable.content(
         anchors.center,
         aabb-width,
         aabb-height,
+        border.segments,
         typst-rotate(angle,
           block(
             width: width * ctx.length,

src/drawable.typ

@@ -1,6 +1,7 @@
 #import "path-util.typ"
 #import "vector.typ"
 #import "util.typ"
+#import "path-util.typ"
 
 #let apply-transform(transform, drawables) = {
   if type(drawables) == dictionary {
@@ -46,12 +47,13 @@
   )
 }
 
-#let content(pos, width, height, body) = {
+#let content(pos, width, height, border, body) = {
   return (
     type: "content",
     pos: pos,
     width: width,
     height: height,
+    segments: border,
     body: body,
     hidden: false,
   )

tests/content/intersection/test.typ

@@ -0,0 +1,21 @@
+#set page(width: auto, height: auto)
+#import "/src/lib.typ": *
+#import "/tests/helper.typ": *
+
+#test-case({
+  import draw: *
+  set-style(fill: gray, stroke: gray)
+
+  intersections("i", {
+    content((0,0), [Text])
+    on-layer(-1, {
+      line((1,1), (-1,-1))
+      bezier((-1,0), (1,0), (-.5,.5), (.5,-.5), fill: none)
+    })
+  })
+  on-layer(-1, {
+    for-each-anchor("i", n => {
+      circle("i." + n, radius: .05)
+    })
+  })
+})

tests/intersection/test.typ

@@ -60,14 +60,18 @@
     rotate(45deg)
     line((0,0), (calc.sqrt(2*calc.pow(2,2)),0))
   })
+  test({
+    // The marks must not generate intersections with the line!
+    line((0,0), (2,2), mark: (start: ">", end: ">"))
+  })
 })
 
 #box(stroke: 2pt + red, canvas({
   import draw: *
 
   intersections("i", {
-    content((0, 0), [Das ist\ ein Text!], frame: "circle", name: "a")
-    content((2, 1), [Hallo!], frame: "circle", name: "b")
+    content((0, 0), [This is\ Text!], frame: "circle", name: "a")
+    content((2, 1), [Hello!], frame: "circle", name: "b")
     // Invisible intersection line
     line("a.default", "b.default", stroke: none)
   })

tests/line/element-element/test.typ

@@ -40,8 +40,16 @@
   import draw: *
 
   set-style(content: (padding: .1))
-  test(content((0,0), [Text], frame: "rect", name: "a"),
-       content((1,1), [Text], frame: "rect", name: "b"))
+  test(content((0,0), [Text], name: "a"),
+       content((1,1), [Text], name: "b"))
+}))
+
+#box(stroke: 2pt + red, canvas({
+  import draw: *
+
+  set-style(content: (padding: .1))
+  test(content((0,0), [Text], frame: "circle", name: "a"),
+       content((1,1), [Text], frame: "circle", name: "b"))
 }))
 
 #box(stroke: 2pt + red, canvas({