refactor(display): trim isolines follow-up comments

src/app/update/file.rs

@@ -356,13 +356,6 @@ impl OpenCADStudio {
     }
 
     /// Write a header variable on the active drawing and mark it modified.
-    ///
-    /// Deliberately does no geometry work. The variables the Options pages
-    /// write differ in what they cost to apply, and treating them alike is
-    /// wrong in both directions: `DISPSILH` is read at render time and needs
-    /// nothing, `SURFU`/`SURFV`/`SURFTYPE` are inputs to PEDIT's smoothing and
-    /// need nothing until it runs, while `ISOLINES` is baked into solid meshes
-    /// at tessellation and needs more than a bump — see `regenerate_meshes`.
     pub(in crate::app) fn set_drawing_var(
         &mut self,
         write: impl FnOnce(&mut acadrust::document::HeaderVariables),
@@ -374,11 +367,7 @@ impl OpenCADStudio {
         }
     }
 
-    /// Re-tessellate the active drawing's solids from the document.
-    ///
-    /// What REGEN does, and the only thing that makes a changed `ISOLINES`
-    /// reach solids that already exist. Costly on a solid-heavy drawing, so
-    /// callers driven by a slider run it when the drag ends, not per tick.
+    /// Re-tessellate active-drawing solids after an ISOLINES change.
     pub(in crate::app) fn regenerate_meshes(&mut self) {
         let i = self.active_tab;
         if let Some(tab) = self.tabs.get_mut(i) {

src/app/update/mod.rs

@@ -6305,15 +6305,7 @@ impl OpenCADStudio {
                 Task::none()
             }
 
-            // Drawing variables: they go into the header of the active
-            // drawing and mark it modified, as SETVAR does. What each one
-            // costs to apply differs, so they are not treated alike.
-            //
-            // ISOLINES is baked into a solid's mesh when it is tessellated, so
-            // an existing solid keeps the density it was born with until the
-            // meshes are rebuilt. That is expensive, and a slider emits on
-            // every pixel of a drag, so the rebuild waits for the release —
-            // and only happens if the value actually moved.
+            // ISOLINES is baked into solid meshes, so rebuild once on release.
             Message::IsolinesChanged(value) => {
                 let value = value.max(0);
                 let changed = self
@@ -6334,14 +6326,11 @@ impl OpenCADStudio {
                 Task::none()
             }
 
-            // Read at render time, so nothing has to be rebuilt for it.
             Message::DispSilhChanged(on) => {
                 self.set_drawing_var(|header| header.display_silhouette = on);
                 Task::none()
             }
 
-            // Inputs to PEDIT's mesh smoothing; they change nothing until it
-            // runs, so writing the header is the whole job.
             Message::SurfaceUChanged(value) => {
                 self.set_drawing_var(|header| header.surface_u_density = value.clamp(0, 200));
                 Task::none()
@@ -6357,14 +6346,11 @@ impl OpenCADStudio {
                 Task::none()
             }
 
-            // Whether history is recorded from now on; nothing to redraw.
             Message::SolidHistChanged(record) => {
                 self.set_drawing_var(|header| header.record_solid_history = record);
                 Task::none()
             }
 
-            // Read while building geometry, so this one does bump — the same
-            // thing the SHOWHIST command does.
             Message::ShowHistChanged(mode) => {
                 self.set_drawing_var(|header| {
                     header.show_solid_history = mode.clamp(0, 2)