canvas: Add runtime version check for add-ons (#595)

* canvas: Add version number to ctx

This allows other libs checking the cetz version number
at runtime.

* draw: Add assert-version function

* draw: Default to cetz 0.2.0

Author: johannes-wolf

CHANGES.md

@@ -4,6 +4,7 @@ CeTZ 0.3.0 requires Typst 0.11.0
 The licence changed from Apache-2.0 to GPLv3.
 
 ## Canvas
+- Add runtime cetz version check support (see `assert-version`)
 - Fixed a bug with `#set place(float: true)` affecting the canvas.
 - Transformation matrices are now rounded
 - The default coordinate system changed to a right-hand side system.

manual.typ

@@ -294,6 +294,10 @@ line(..c)
 == Grouping
 #doc-style.parse-show-module("/src/draw/grouping.typ")
 
+#pagebreak()
+== Utility
+#doc-style.parse-show-module("/src/draw/util.typ")
+
 #pagebreak()
 == Transformations
 All transformation functions push a transformation matrix onto the current transform stack. To apply transformations scoped use a `group(...)` object.

src/canvas.typ

@@ -5,6 +5,7 @@
 #import "aabb.typ"
 #import "styles.typ"
 #import "process.typ"
+#import "version.typ"
 
 #import util: typst-length
 
@@ -40,6 +41,7 @@
     message: "Canvas length must be != 0!")
 
   let ctx = (
+    version: version.version,
     length: length,
     debug: debug,
     // Previous element position & bbox

src/draw.typ

@@ -3,3 +3,4 @@
 #import "draw/styling.typ": set-style, fill, stroke
 #import "draw/shapes.typ": circle, circle-through, arc, arc-through, mark, line, grid, content, rect, bezier, bezier-through, catmull, hobby, merge-path
 #import "draw/projection.typ": ortho, on-xy, on-xz, on-yz
+#import "draw/util.typ": assert-version

src/draw/util.typ

@@ -0,0 +1,21 @@
+/// Assert that the cetz version of the canvas
+/// matches the given version (range).
+///
+/// min (version): Minimum version (current >= min)
+/// max (none, version): First unsupported version (current < max)
+/// hint (string): Name of the function/module this assert is called from
+#let assert-version(min, max: none, hint: "") = {
+  if hint != "" { hint = " by " + hint }
+  (ctx => {
+    /* Default to 2.0.0, as this is the first version that had elements as single functions. */
+    let v = ctx.at("version", default: version(0,2,0))
+    assert(min <= v,
+      message: "CeTZ canvas version is " + str(v) + ", but the minimum required version" + hint + " is " + str(min))
+    if max != none {
+      assert(max > v,
+        message: "CeTZ canvas version is " + str(v) + ", but the maximum supported version" + hint + " is " + str(min))
+    }
+
+    return (ctx: ctx)
+  },)
+}

src/lib.typ

@@ -1,4 +1,4 @@
-#let version = version((0,2,2))
+#import "version.typ": version
 
 #import "canvas.typ": canvas
 #import "draw.typ"

src/version.typ

@@ -0,0 +1 @@
+#let version = version(0,2,2)