motion: Implement Position/CurPosition returning AxisUnit

These come in handy to avoid manual casts and enforce types at runtime.

src/modules/motion.h

@@ -166,6 +166,14 @@ public:
     /// @param axis axis affected
     pos_t Position(Axis axis) const;
 
+    /// @returns head position of an axis, but in AxisUnit.
+    /// The Axis needs to be supplied as the first template argument: Position<axis>().
+    /// @see Position
+    template <Axis A>
+    constexpr AxisUnit<pos_t, A, Lenght> Position() const {
+        return AxisUnit<pos_t, A, Lenght> { Position(A) };
+    }
+
     /// Fetch the current position of the axis while stepping. This function is expensive!
     /// It's necessary only in exceptional cases. For regular usage, Position() should
     /// probably be used instead.
@@ -173,6 +181,14 @@ public:
     /// @returns the current position of the axis
     pos_t CurPosition(Axis axis) const { return axisData[axis].ctrl.CurPosition(); }
 
+    /// Fetch the current axis position, but in AxisUnit. This function is expensive!
+    /// The Axis needs to be supplied as the first template argument: CurPosition<axis>().
+    /// @see CurPosition
+    template <Axis A>
+    constexpr AxisUnit<pos_t, A, Lenght> CurPosition() const {
+        return AxisUnit<pos_t, A, Lenght> { CurPosition(A) };
+    }
+
     /// Set the position of an axis. Should only be called when the queue is empty.
     /// @param axis axis affected
     /// @param x position to set

tests/unit/modules/motion/test_motion.cpp

@@ -93,6 +93,8 @@ TEST_CASE("motion::unit", "[motion]") {
     motion.PlanMoveTo<Selector>(10.0_S_mm, 100.0_S_mm_s);
     CHECK(stepUntilDone() != -1);
     REQUIRE(motion.Position(Selector) == target);
+    S_pos_t s_target = motion.Position<Selector>();
+    REQUIRE(s_target.v == target);
 
     // move directly with physical units
     motion.PlanMoveTo<Selector>(10.0_mm, 100.0_mm_s);
@@ -103,6 +105,8 @@ TEST_CASE("motion::unit", "[motion]") {
     motion.PlanMove<Selector>(-5.0_S_mm, 100.0_S_mm_s);
     CHECK(stepUntilDone() != -1);
     REQUIRE(motion.Position(Selector) == target / 2);
+    s_target = motion.Position<Selector>();
+    REQUIRE(s_target.v == target / 2);
 
     // relative move with physical unit
     motion.PlanMove<Selector>(-5.0_mm, 100.0_mm_s);