Allow snapping constraint labels to grid.

This is pretty much the only way to get a sketch with tidily placed
dimensions.

src/draw.cpp

@@ -299,7 +299,7 @@ void GraphicsWindow::GroupSelection(void) {
             gs.constraint[(gs.constraints)++] = s->constraint;
             Constraint *c = SK.GetConstraint(s->constraint);
             if(c->IsStylable()) gs.stylables++;
-            if(c->type == Constraint::COMMENT) gs.comments++;
+            if(c->HasLabel()) gs.constraintLabels++;
         }
     }
 }
@@ -434,7 +434,7 @@ Vector GraphicsWindow::UnProjectPoint3(Vector p) {
     double w = 1 + p.z * SS.CameraTangent() * scale;
     p.x *= w / scale;
     p.y *= w / scale;
-    
+
     Vector orig = offset.ScaledBy(-1);
     orig = orig.Plus(projRight.ScaledBy(p.x)).Plus(
                      projUp.   ScaledBy(p.y).Plus(

src/drawconstraint.cpp

@@ -1229,3 +1229,21 @@ bool Constraint::IsStylable() {
     return false;
 }
 
+bool Constraint::HasLabel() {
+    switch(type) {
+        case COMMENT:
+        case PT_PT_DISTANCE:
+        case PT_PLANE_DISTANCE:
+        case PT_LINE_DISTANCE:
+        case PT_FACE_DISTANCE:
+        case PROJ_PT_DISTANCE:
+        case LENGTH_RATIO:
+        case LENGTH_DIFFERENCE:
+        case DIAMETER:
+        case ANGLE:
+            return true;
+
+        default:
+            return false;
+    }
+}

src/graphicswin.cpp

@@ -888,9 +888,10 @@ void GraphicsWindow::MenuEdit(int id) {
                 break;
             }
             SS.GW.GroupSelection();
-            if(SS.GW.gs.points == 0 && SS.GW.gs.comments == 0) {
+            if(SS.GW.gs.points == 0 && SS.GW.gs.constraintLabels == 0) {
-                Error("Can't snap these items to grid; select points or "
+                Error("Can't snap these items to grid; select points, "
-                      "text comments. To snap a line, select its endpoints.");
+                      "text comments, or constraints with a label. "
+                      "To snap a line, select its endpoints.");
                 break;
             }
             SS.UndoRemember();
@@ -908,8 +909,6 @@ void GraphicsWindow::MenuEdit(int id) {
                     SS.MarkGroupDirty(ep->group);
                 } else if(s->constraint.v) {
                     Constraint *c = SK.GetConstraint(s->constraint);
-                    if(c->type != Constraint::COMMENT) continue;
-
                     c->disp.offset = SS.GW.SnapToGrid(c->disp.offset);
                 }
             }

src/mouse.cpp

@@ -571,7 +571,7 @@ void GraphicsWindow::MouseRightUp(double x, double y) {
                     CMNU_OTHER_ANGLE);
             }
         }
-        if(gs.comments > 0 || gs.points > 0) {
+        if(gs.constraintLabels > 0 || gs.points > 0) {
             AddContextMenuItem("Snap to Grid", CMNU_SNAP_TO_GRID);
         }
 

src/sketch.h

@@ -682,6 +682,7 @@ public:
     void Draw(void);
     void GetEdges(SEdgeList *sel);
     bool IsStylable();
+    bool HasLabel();
 
     void LineDrawOrGetDistance(Vector a, Vector b);
     bool IsVisible() const;

src/ui.h

@@ -649,7 +649,7 @@ public:
         int         vectors;
         int         constraints;
         int         stylables;
-        int         comments;
+        int         constraintLabels;
         int         withEndpoints;
         int         n;
     } gs;