Implement Analyze → Measure Perimeter.

CHANGELOG.md

@@ -8,6 +8,10 @@ New export/import features:
   * Three.js: allow configuring projection for exported model, and initially
     use the current viewport projection.
 
+Other new features:
+  * New command for measuring total length of selected entities,
+    "Analyze → Measure Perimeter".
+
 2.2
 ---
 

src/graphicswin.cpp

@@ -149,7 +149,8 @@ const GraphicsWindow::MenuEntry GraphicsWindow::menu[] = {
 
 { 0, "&Analyze",                    Command::NONE,             0,       TN, NULL  },
 { 1, "Measure &Volume",             Command::VOLUME,           C|S|'V', TN, mAna  },
-{ 1, "Measure &Area",               Command::AREA,             C|S|'A', TN, mAna  },
+{ 1, "Measure A&rea",               Command::AREA,             C|S|'A', TN, mAna  },
+{ 1, "Measure &Perimeter",          Command::PERIMETER,        C|S|'P', TN, mAna  },
 { 1, "Show &Interfering Parts",     Command::INTERFERENCE,     C|S|'I', TN, mAna  },
 { 1, "Show &Naked Edges",           Command::NAKED_EDGES,      C|S|'N', TN, mAna  },
 { 1, NULL,                          Command::NONE,             0,       TN, NULL  },

src/solvespace.cpp

@@ -749,6 +749,30 @@ void SolveSpaceUI::MenuAnalyze(Command id) {
             break;
         }
 
+        case Command::PERIMETER: {
+            if(gs.n > 0 && gs.n == gs.entities) {
+                double perimeter = 0.0;
+                for(int i = 0; i < gs.entities; i++) {
+                    Entity *e = SK.entity.FindById(gs.entity[i]);
+                    SEdgeList *el = e->GetOrGenerateEdges();
+                    for(const SEdge &e : el->l) {
+                        perimeter += e.b.Minus(e.a).Magnitude();
+                    }
+                }
+
+                double scale = SS.MmPerUnit();
+                Message("The total length of the selected entities is:\n\n"
+                        "    %.3f %s\n\n"
+                        "Curves have been approximated as piecewise linear.\n"
+                        "This introduces error, typically of around 1%%.",
+                    perimeter / scale,
+                    SS.UnitName());
+            } else {
+                Error("Bad selection for perimeter; select line segments, arcs, and curves.");
+            }
+            break;
+        }
+
         case Command::SHOW_DOF:
             // This works like a normal solve, except that it calculates
             // which variables are free/bound at the same time.

src/ui.h

@@ -102,6 +102,7 @@ enum class Command : uint32_t {
     // Analyze
     VOLUME,
     AREA,
+    PERIMETER,
     INTERFERENCE,
     NAKED_EDGES,
     SHOW_DOF,