canvas: Change to rh coordinate system

CHANGES.md

@@ -4,6 +4,8 @@ CeTZ 0.3.0 requires Typst 0.11.0
 
 ## Canvas
 - Transformation matrices are now rounded
+- The default coordinate system changed to a right-hand side system.
+ Use `scale(z: -1)` if you want to change back to a left-hand system.
 
 ## Plot
 - Added support for automatically adding axis breaks (sawtooth lines) by setting the `break`

src/canvas.typ

@@ -11,10 +11,10 @@
 /// Sets up a canvas for drawing on.
 ///
 /// The default transformation matrix of the canvas is set to:
-/// $mat(1,0,0.5,0;
-/// 0,-1,-0.5,0;
-/// 0,0,0,0;
-/// 0,0,0,1)$
+/// $mat(1, 0,-0.5, 0;
+/// 0,-1, 0.5, 0;
+/// 0, 0, 0, 0;
+/// 0, 0, 0, 1)$
 ///
 /// - 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 `draw.typ` have been called.
@@ -45,12 +45,12 @@
  // Previous element position & bbox
  prev: (pt: (0, 0, 0)),
  style: styles.default,
- // Current transformation matrix, a lhs coordinate system
+ // Current transformation matrix, a rhs coordinate system
  // where z is sheared by a half x and y.
- // +x = right, +y = up, +z = 1/2 (right + up)
+ // +x = right, +y = up, +z = 1/2 (left + down)
  transform:
- ((1, 0,+.5, 0),
- (0,-1,-.5, 0),
+ ((1, 0,-.5, 0),
+ (0,-1,+.5, 0),
  (0, 0, .0, 0),
  (0, 0, .0, 1)),
  // Nodes, stores anchors and paths

tests/projection/default/test.typ

@@ -0,0 +1,22 @@
+#import "/src/lib.typ" as cetz
+#import "/tests/helper.typ": *
+
+// Positive direction
+#test-case({
+ import cetz.draw: *
+
+ set-style(mark: (transform-shape: false))
+ line((0,0,0), (1,0,0), mark: (end: ">"))
+ line((0,0,0), (0,1,0), mark: (end: ">"))
+ line((0,0,0), (0,0,1), mark: (end: ">"))
+})
+
+// Negative direction
+#test-case({
+ import cetz.draw: *
+
+ set-style(mark: (transform-shape: false))
+ line((0,0,0), (-1,0,0), mark: (end: ">"))
+ line((0,0,0), (0,-1,0), mark: (end: ">"))
+ line((0,0,0), (0,0,-1), mark: (end: ">"))
+})