Extrude: a symmetric distance is the total thickness (#1260)

A symmetric solid extrude of 10 mm is now 10 mm thick, 5 mm each side of the sketch plane, and switching from One Side to Symmetric keeps the thickness entered. Under format 21 the extent records its convention; designs saved without it keep the per-side reading, so their geometry and parameters don't change. Fixes #1236.

Co-authored-by: Karl-VonRichter <[email protected]>

crates/doc/src/document.rs

@@ -134,7 +134,7 @@ pub enum Direction {
     #[default]
     Positive,
     Negative,
-    /// Both sides; `distance` per side.
+    /// Both sides; the extent convention determines whether `distance` is total or per side.
     Symmetric,
 }
 
@@ -186,12 +186,33 @@ pub enum RevolveConvention {
     SketchNormal,
 }
 
+/// Symmetric distance semantics. Missing markers preserve existing designs' thickness.
+#[derive(Clone, Copy, Debug, PartialEq, Eq, Default, Serialize, Deserialize)]
+#[serde(rename_all = "snake_case")]
+pub enum ExtrudeConvention {
+    #[default]
+    LegacyPerSide,
+    TotalDistance,
+}
+
+impl ExtrudeConvention {
+    /// Distance from the mid-plane to either cap for a distance-limited extent.
+    pub fn symmetric_half_distance(self, distance: f64) -> f64 {
+        match self {
+            Self::LegacyPerSide => distance,
+            Self::TotalDistance => distance * 0.5,
+        }
+    }
+}
+
 /// Extent of an extrude.
 #[derive(Clone, Debug, PartialEq, Serialize, Deserialize, solidcraft_derive::Walk)]
 pub struct Extent {
     #[walk(length = "Distance")]
     pub distance: String,
     #[serde(default)]
+    pub convention: ExtrudeConvention,
+    #[serde(default)]
     pub direction: Direction,
     /// Optional second side distance (two-sided extrude), along the negative normal.
     #[serde(default, skip_serializing_if = "Option::is_none")]

crates/doc/src/eval.rs

@@ -3291,7 +3291,11 @@ pub(crate) fn extent_sides(vals: &BTreeMap<String, Value>, extent: &crate::Exten
         (Some(d2), _) => (-val(vals, d2, Kind::Length)?, d),
         (None, crate::Direction::Positive) => (0.0, d),
         (None, crate::Direction::Negative) => (-d, 0.0),
-        (None, crate::Direction::Symmetric) => (-d, d),
+        (None, crate::Direction::Symmetric) => {
+            // Through All is a reach computed from target bodies, not an entered total.
+            let half = if extent.through_all { d } else { extent.convention.symmetric_half_distance(d) };
+            (-half, half)
+        }
     })
 }
 

crates/doc/src/format.rs

@@ -179,6 +179,11 @@
 //!   neighbouring edges as they are (`neighbours: false`). An Extend without them builds the
 //!   planar extension it always did and saves as before; 0.11.0 asks for an update instead of
 //!   dropping them and extending a plane by the distance.
+//!   Under the same version, an extrude's extent records how a symmetric `distance` is read
+//!   (`convention`: `total_distance`, split evenly around the start plane, which new solid
+//!   extrudes save; or `legacy_per_side`). An extent without it keeps the per-side reading
+//!   designs always had, so their thickness and parameters don't change; 0.11.0 asks for an
+//!   update instead of doubling a total-distance extrude.
 
 use serde_json::Value;
 
@@ -1131,6 +1136,7 @@ mod tests {
                     sketch,
                     profiles: ProfileSel::All,
                     extent: Extent {
+                        convention: crate::ExtrudeConvention::LegacyPerSide,
                         distance: "10".into(),
                         direction: Direction::Negative,
                         distance2: None,

crates/doc/src/format_offsets.rs

@@ -427,6 +427,7 @@ mod tests {
                         sketch: if missing_sketch { 999_999 } else { id },
                         profiles: ProfileSel::OffsetBoundaries { associations: vec!["deleted-o1".into()] },
                         extent: crate::Extent {
+                            convention: crate::ExtrudeConvention::LegacyPerSide,
                             distance: "2".into(),
                             direction: crate::Direction::Positive,
                             distance2: None,

crates/doc/src/profile_refs.rs

@@ -312,6 +312,7 @@ mod tests {
                     sketch: feature,
                     profiles: selection.clone(),
                     extent: crate::Extent {
+                        convention: crate::ExtrudeConvention::LegacyPerSide,
                         distance: "2".into(),
                         direction: crate::Direction::Positive,
                         distance2: None,
@@ -438,6 +439,7 @@ mod tests {
                     sketch: feature,
                     profiles: selection.clone(),
                     extent: crate::Extent {
+                        convention: crate::ExtrudeConvention::LegacyPerSide,
                         distance: "2".into(),
                         direction: crate::Direction::Positive,
                         distance2: None,

crates/doc/src/tests.rs

@@ -33,6 +33,7 @@ fn plate_doc() -> (Document, u64) {
             sketch: s,
             profiles: ProfileSel::All,
             extent: Extent {
+                convention: crate::ExtrudeConvention::LegacyPerSide,
                 distance: "20".into(),
                 direction: Direction::Positive,
                 distance2: None,
@@ -125,6 +126,7 @@ fn box_fillet_cut_timeline() {
             sketch: s2,
             profiles: ProfileSel::Points { points: vec![Vec2::new(20.0, 15.0)] },
             extent: Extent {
+                convention: crate::ExtrudeConvention::LegacyPerSide,
                 distance: "20".into(),
                 direction: Direction::Positive,
                 distance2: None,

crates/doc/src/walk.rs

@@ -53,6 +53,7 @@ impl Walk for crate::document::ThinSide {}
 impl Walk for crate::document::ExtendMode {}
 impl Walk for crate::document::RuledMode {}
 impl Walk for crate::document::RuledCorners {}
+impl Walk for crate::document::ExtrudeConvention {}
 
 /// Containers walk what they hold, in order.
 macro_rules! walk_each {