Fix bugs: problem drag-rotating normals with the mouse, a failure

to save our registry stuff (because we were calling exit() instead
of doing a PostQuitMessage()), and a misclassification of triangles
coplanar with the test surface, when the test surface contained
zero-area triangles.

[git-p4: depot-paths = "//depot/solvespace/": change = 1773]

graphicswin.cpp

@@ -649,17 +649,17 @@ void GraphicsWindow::MouseMoved(double x, double y, bool leftDown,
                 double theta = atan2(orig.mouse.y-p2.y, orig.mouse.x-p2.x);
                 theta -= atan2(y-p2.y, x-p2.x);
 
-                Vector normal = orig.projRight.Cross(orig.projUp);
+                Vector normal = projRight.Cross(projUp);
                 u = u.RotatedAbout(normal, -theta);
                 v = v.RotatedAbout(normal, -theta);
             } else {
                 double dx = -(x - orig.mouse.x);
                 double dy = -(y - orig.mouse.y);
                 double s = 0.3*(PI/180); // degrees per pixel
-                u = u.RotatedAbout(orig.projUp, -s*dx);
-                u = u.RotatedAbout(orig.projRight, s*dy);
-                v = v.RotatedAbout(orig.projUp, -s*dx);
-                v = v.RotatedAbout(orig.projRight, s*dy);
+                u = u.RotatedAbout(projUp, -s*dx);
+                u = u.RotatedAbout(projRight, s*dy);
+                v = v.RotatedAbout(projUp, -s*dx);
+                v = v.RotatedAbout(projRight, s*dy);
             }
             orig.mouse = mp;
             normal->NormalForceTo(Quaternion::From(u, v));

polygon.cpp

@@ -7,6 +7,10 @@ Vector STriangle::Normal(void) {
 
 bool STriangle::ContainsPoint(Vector p) {
     Vector n = Normal();
+    if(n.Magnitude() < LENGTH_EPS*LENGTH_EPS) {
+        // shouldn't happen; zero-area triangle
+        return false;
+    }
     return ContainsPointProjd(n.WithMagnitude(1), p);
 }
 

solvespace.cpp

@@ -459,7 +459,7 @@ void SolveSpace::MenuFile(int id) {
 
         case GraphicsWindow::MNU_EXIT:
             if(!SS.OkayToStartNewFile()) break;
-            exit(0);
+            ExitNow();
             break;
 
         default: oops();

solvespace.h

@@ -79,6 +79,7 @@ void dbp(char *str, ...);
         CO((tri).a), CO((tri).b), CO((tri).c))
 
 void Error(char *str, ...);
+void ExitNow(void);
 
 void *AllocTemporary(int n);
 void FreeAllTemporary(void);

win32/w32main.cpp

@@ -67,6 +67,10 @@ void Error(char *str, ...)
     MessageBox(h, buf, "SolveSpace Error", MB_OK | MB_ICONERROR);
 }
 
+void ExitNow(void) {
+    PostQuitMessage(0);
+}
+
 //-----------------------------------------------------------------------------
 // A separate heap, on which we allocate expressions. Maybe a bit faster,
 // since no fragmentation issues whatsoever, and it also makes it possible