ocs_doc_api: Phase 4 set_view + viewport-view query

- SetViewportView op + GetViewportView query (append-only).
- backend set_viewport_view (update Viewport.view_target/view_height) + viewport_view.
- facade Entity::set_view/viewport_view (Viewport returns Entity).
- spec Viewport methods; api_reference + binding_schema regenerated; mocks + baseline.
- Test phase4_set_view_and_view_query -> 609 host lib + 3 consistency green.
- Phase 4 complete.

crates/ocs_doc_api/src/backend.rs

@@ -75,6 +75,12 @@ pub trait DocApiBackend {
     /// The entities inside a block definition (read-only traversal), as views.
     fn block_entities(&self, block_name: &str) -> ApiResult<Vec<EntityView>>;
 
+    /// Set a viewport's view target + zoom height in place. Viewport-only.
+    fn set_viewport_view(&mut self, id: ObjectId, view_target: [f64; 3], view_height: f64) -> ApiResult<()>;
+
+    /// A viewport's view (target WCS + zoom height). Viewport-only.
+    fn viewport_view(&self, id: ObjectId) -> ApiResult<([f64; 3], f64)>;
+
     /// Can `id` be modified in place right now (exists, is the expected family,
     /// not on a locked layer)? Read-only pre-check used before mutations.
     /// Default: existence + not-locked (backends narrow the family check).

crates/ocs_doc_api/src/executor.rs

@@ -237,6 +237,16 @@ pub fn apply_op<B: DocApiBackend>(b: &mut B, op: Operation) -> ApiResult<Receipt
             b.finalize_op();
             OpOutcome::Updated(*id)
         }
+        Operation::SetViewportView { id, view_target, view_height } => {
+            b.can_modify(*id).map_err(|e| match e {
+                ApiError::UnknownId(_) => ApiError::validation(name, format!("unknown ObjectId {id:?}")),
+                other => other,
+            })?;
+            b.push_undo(name);
+            b.set_viewport_view(*id, *view_target, *view_height)?;
+            b.finalize_op();
+            OpOutcome::Updated(*id)
+        }
     };
     Ok(Receipt {
         outcome: Some(outcome),
@@ -279,6 +289,10 @@ pub fn apply_queries<B: DocApiBackend>(b: &mut B, queries: Vec<Query>) -> ApiRes
             Query::GetDimensionMeasurement { id } => QueryResult::DimensionMeasurement(b.dimension_measurement(*id)?),
             Query::GetAttributes { id } => QueryResult::Attributes(b.attributes(*id)?),
             Query::GetBlockEntities { block_name } => QueryResult::BlockEntities(b.block_entities(block_name)?),
+            Query::GetViewportView { id } => {
+                let (target, height) = b.viewport_view(*id)?;
+                QueryResult::ViewportView { target, height }
+            }
         };
         results.push(r);
     }

crates/ocs_doc_api/src/facade.rs

@@ -309,6 +309,18 @@ impl Entity {
         self.session.apply_op(Operation::SetAttribute { id: self.id, tag: tag.to_string(), value: value.to_string() })?;
         Ok(())
     }
+    /// This viewport's view (target WCS + zoom height). Viewport-only.
+    pub fn viewport_view(&self) -> ApiResult<([f64; 3], f64)> {
+        match self.session.one_query(Query::GetViewportView { id: self.id })? {
+            QueryResult::ViewportView { target, height } => Ok((target, height)),
+            _ => Err(ApiError::Transport("unexpected viewport-view result".into())),
+        }
+    }
+    /// Retarget / re-zoom this viewport (one undo step). Viewport-only.
+    pub fn set_view(&self, view_target: [f64; 3], view_height: f64) -> ApiResult<()> {
+        self.session.apply_op(Operation::SetViewportView { id: self.id, view_target, view_height })?;
+        Ok(())
+    }
     pub fn as_solid(&self) -> Option<Solid> {
         // Typed downcast is validated by the view's kind.
         matches!(self.view().ok()?.kind.as_str(), "Solid3D").then(|| Solid::new(self.session.clone(), self.id))

crates/ocs_doc_api/src/gen/api_reference.md

@@ -158,6 +158,11 @@ Paper-space viewport: a width×height window at center looking at view_target wi
 
 - **create_viewport**(`center: [f64; 3], width: f64, height: f64, view_target: [f64; 3], view_height: f64`) -> `Entity`
 
+### Methods
+
+- **viewport_view**(``) -> `([f64; 3], f64)` — query `GetViewportView`
+- **set_view**(`view_target: [f64; 3], view_height: f64`) -> `()` — op `SetViewportView`
+
 ## `Entity` (acadrust `RasterImage`, collection `entities`)
 
 Raster image (read-mostly): GetEntity kind + coarse bounds (insertion + u*width + v*height); generic delete. No typed create in v1.

crates/ocs_doc_api/src/gen/binding_schema.json

@@ -339,7 +339,39 @@
       "acadrust_variant": "Viewport",
       "collection": "entities",
       "handle": "Entity",
-      "methods": [],
+      "methods": [
+        {
+          "args": [],
+          "bulk": false,
+          "fixed": null,
+          "kind": "query",
+          "name": "viewport_view",
+          "op": null,
+          "query": "GetViewportView",
+          "read_only": true,
+          "returns": "([f64; 3], f64)"
+        },
+        {
+          "args": [
+            {
+              "name": "view_target",
+              "ty": "[f64; 3]"
+            },
+            {
+              "name": "view_height",
+              "ty": "f64"
+            }
+          ],
+          "bulk": false,
+          "fixed": null,
+          "kind": "op",
+          "name": "set_view",
+          "op": "SetViewportView",
+          "query": null,
+          "read_only": false,
+          "returns": "()"
+        }
+      ],
       "name": "Viewport"
     },
     {

crates/ocs_doc_api/src/gen/ops_gen.rs

@@ -42,4 +42,6 @@ pub enum Operation {
     CreateDimensionLinear(DimensionSpec),
     // attributes
     SetAttribute { id: ObjectId, tag: String, value: String },
+    // viewport view
+    SetViewportView { id: ObjectId, view_target: [f64; 3], view_height: f64 },
 }

crates/ocs_doc_api/src/gen/query_gen.rs

@@ -30,4 +30,6 @@ pub enum Query {
     GetAttributes { id: ObjectId },
     /// The entity ids + kinds inside a block definition (read-only traversal).
     GetBlockEntities { block_name: String },
+    /// A viewport's view (target + zoom height).
+    GetViewportView { id: ObjectId },
 }

crates/ocs_doc_api/src/ops.rs

@@ -170,6 +170,7 @@ impl crate::gen::Operation {
             CreateHatch(_) => "CreateHatch",
             CreateDimensionLinear(_) => "CreateDimensionLinear",
             SetAttribute { .. } => "SetAttribute",
+            SetViewportView { .. } => "SetViewportView",
         }
     }
 }

crates/ocs_doc_api/src/query.rs

@@ -53,6 +53,8 @@ pub enum QueryResult {
     Attributes(Vec<(String, String)>),
     /// The entities inside a block definition (read-only traversal).
     BlockEntities(Vec<EntityView>),
+    /// A viewport's view: target point (WCS) + zoom height.
+    ViewportView { target: [f64; 3], height: f64 },
 }
 
 /// Convenience: the query name for diagnostics.
@@ -71,6 +73,7 @@ impl crate::gen::Query {
             GetDimensionMeasurement { .. } => "GetDimensionMeasurement",
             GetAttributes { .. } => "GetAttributes",
             GetBlockEntities { .. } => "GetBlockEntities",
+            GetViewportView { .. } => "GetViewportView",
         }
     }
 }