canvas: Add a padding parameter to canvas (#704)

* canvas: Add a padding parameter to canvas

* changes: Update changelog

* changes: Update changelog

CHANGES.md

@@ -1,3 +1,7 @@
+# 0.3.1
+
+- Added a new `padding` parameter to the canvas element.
+
 # 0.3.0
 
 CeTZ 0.3.0 requires Typst 0.11.0
@@ -243,3 +247,4 @@ CeTZ requires Typst 0.8.0.
 
 ## Plot
 - Added new library `plot` for drawing line charts (of functions), replacing `typst-plot`.
+

src/canvas.typ

@@ -11,12 +11,13 @@
 
 /// Sets up a canvas for drawing on.
 ///
-/// - length (length,ratio): Used to specify what 1 coordinate unit is. If given a ratio, that ratio is relative to the containing elements width!
-/// - body (none,array,element): A code block in which functions from the `draw` module have been called.
-/// - background (none,color): A color to be used for the background of the canvas.
+/// - length (length, ratio): Used to specify what 1 coordinate unit is. If given a ratio, that ratio is relative to the containing elements width!
+/// - body (none, array, element): A code block in which functions from the `draw` module have been called.
+/// - background (none, color): A color to be used for the background of the canvas.
+/// - padding (none, number, array, dictionary) = none: How much padding to add to the canvas. `none` applies no padding. A number applies padding to all sides equally. A dictionary applies padding following Typst's `pad` function: https://typst.app/docs/reference/layout/pad/. An array follows CSS like padding: `(y, x)`, `(top, x, bottom)` or `(top, right, bottom, left)`.
 /// - debug (bool): Shows the bounding boxes of each element when `true`.
 /// -> content
-#let canvas(length: 1cm, debug: false, background: none, body) = context { layout(ly => {
+#let canvas(length: 1cm, debug: false, background: none, padding: none, body) = context { layout(ly => {
   if body == none {
     return []
   }
@@ -73,6 +74,10 @@
     return cmd.at("z-index", default: 0)
   })
 
+  // Apply padding
+  let padding = util.as-padding-dict(padding)
+  bounds = aabb.padded(bounds, padding)
+
   // Final canvas size
   let (width, height, ..) = vector.scale(aabb.size(bounds), length)
 

tests/padding/test.typ

@@ -0,0 +1,14 @@
+#set page(width: auto, height: auto)
+#import "/src/lib.typ": *
+#import "/tests/helper.typ": *
+
+#test-case(padding: 1, background: gray, {
+  import draw: *
+  circle(())
+})
+
+#test-case(padding: (top: 1, left: 2), background: gray, {
+  import draw: *
+  scale(x: -1, y: -.5)
+  circle(())
+})