mark: Support position override

src/mark.typ

@@ -24,6 +24,7 @@
     scale: auto,
     length: auto,
     sep: auto,
+    pos: auto,
     offset: auto,
     flex: auto,
     xy-up: auto,
@@ -74,10 +75,15 @@
     }
 
     // Path length relative attributes
-    style.offset = if type(style.offset) == ratio {
-      style.offset * path-length / 100%
-    } else {
-      util.resolve-number(ctx, style.offset)
+    for k in ("offset", "pos",) {
+      let v = style.at(k)
+      if v != none and v != auto {
+        style.insert(k, if type(v) == ratio {
+          v * path-length / 100%
+        } else {
+          util.resolve-number(ctx, v)
+        })
+      }
     }
 
     out.push(style)
@@ -151,6 +157,11 @@
       continue
     }
 
+    // Override position, if set
+    if style.pos != none {
+      distance = style.pos
+    }
+
     // Apply mark offset
     distance += style.offset
 

src/styles.typ

@@ -21,7 +21,8 @@
     width: 0.15cm,    // The size of the mark along the normal of its direction
     inset: .05cm,     // The inner length of some mark shapes, like triangles and brackets
     sep: .1cm,        // The distance between multiple marks along their path
-    offset: 0cm,
+    pos: none,        // Position override on the path (none, number or path-length ratio)
+    offset: 0,        // Mark extra offset (number or path-length ratio)
     start: none,      // Mark start symbol(s)
     end: none,        // Mark end symbol(s)
     symbol: none,     // Mark symbol

tests/mark/pos/test.typ

@@ -0,0 +1,28 @@
+#set page(width: auto, height: auto)
+#import "/src/lib.typ": *
+#import "/tests/helper.typ": *
+
+// No Position
+#test-case({
+  import draw: *
+  set-style(mark: (fill: white))
+  line((-1,0), (1,0), mark: (start: ">", end: ">"))
+})
+
+// Absolute Position
+#test-case({
+  import draw: *
+  set-style(mark: (fill: white))
+  line((-1,1), (1,1), mark: (start: ">", end: ">", pos: .25, shorten-to: none))
+})
+
+
+// Relative Offset
+#test-case({
+  import draw: *
+  set-style(mark: (fill: white))
+  line((-1,0), (1,0), mark: (start: ">", end: ">", pos: 25%, shorten-to: none))
+  line((-1,1), (1,1), mark: (end: ">", pos: 50%, shorten-to: none))
+  line((-1,2), (1,2), mark: (start: ">", pos: 50%, shorten-to: none))
+  line((-1,3), (1,3), mark: (start: (">", (symbol: "|", pos: 50%)), end: ">", shorten-to: 0))
+})