If a Boolean fails, then make a note of it in the group's text

window screen, and remind the user that they could 'fix' the
problem by working with meshes instead.

[git-p4: depot-paths = "//depot/solvespace/": change = 1962]

groupmesh.cpp

@@ -149,6 +149,9 @@ void Group::GenerateForBoolean(T *prevs, T *thiss, T *outs) {
 }
 
 void Group::GenerateShellAndMesh(void) {    
+    bool prevBooleanFailed = booleanFailed;
+    booleanFailed = false;
+
     thisShell.Clear();
     thisMesh.Clear();
     runningShell.Clear();
@@ -292,6 +295,13 @@ void Group::GenerateShellAndMesh(void) {
     if(pg->runningMesh.IsEmpty() && thisMesh.IsEmpty() && !forceToMesh) {
         SShell *prevs = &(pg->runningShell);
         GenerateForBoolean<SShell>(prevs, &thisShell, &runningShell);
+
+        // If the Boolean failed, then we should note that in the text screen
+        // for this group.
+        booleanFailed = runningShell.booleanFailed;
+        if(booleanFailed != prevBooleanFailed) {
+            SS.later.showTW = true;
+        }
     } else {
         SMesh prevm, thism;
         ZERO(&prevm);

sketch.h

@@ -145,6 +145,8 @@ public:
         Vector          errorPointAt;
     }               polyError;
 
+    bool            booleanFailed;
+
     SShell          thisShell;
     SShell          runningShell;
 

srf/boolean.cpp

@@ -454,6 +454,7 @@ SSurface SSurface::MakeCopyTrimAgainst(SShell *agnst, SShell *parent,
     ZERO(&poly);
     final.l.ClearTags();
     if(!final.AssemblePolygon(&poly, NULL, true)) {
+        into->booleanFailed = true;
         DEBUGEDGELIST(&final, &ret);
     }
     poly.Clear();
@@ -530,6 +531,8 @@ void SShell::RewriteSurfaceHandlesForCurves(SShell *a, SShell *b) {
 // much faster than merging as union.
 //-----------------------------------------------------------------------------
 void SShell::MakeFromAssemblyOf(SShell *a, SShell *b) {
+    booleanFailed = false;
+
     Vector t = Vector::From(0, 0, 0);
     Quaternion q = Quaternion::IDENTITY;
     int i = 0;
@@ -571,6 +574,8 @@ void SShell::MakeFromAssemblyOf(SShell *a, SShell *b) {
 }
 
 void SShell::MakeFromBoolean(SShell *a, SShell *b, int type) {
+    booleanFailed = false;
+
     a->MakeClassifyingBsps();
     b->MakeClassifyingBsps();
 

srf/surface.cpp

@@ -626,6 +626,8 @@ void SShell::MakeFromCopyOf(SShell *a) {
 }
 
 void SShell::MakeFromTransformationOf(SShell *a, Vector t, Quaternion q) {
+    booleanFailed = false;
+
     SSurface *s;
     for(s = a->surface.First(); s; s = a->surface.NextAfter(s)) {
         SSurface n;

srf/surface.h

@@ -278,6 +278,8 @@ public:
     IdList<SCurve,hSCurve>      curve;
     IdList<SSurface,hSSurface>  surface;
 
+    bool                        booleanFailed;
+
     void MakeFromExtrusionOf(SBezierLoopSet *sbls, Vector t0, Vector t1,
                              int color);
     void MakeFromRevolutionOf(SBezierLoopSet *sbls, Vector pt, Vector axis,

textscreens.cpp

@@ -475,6 +475,12 @@ void TextWindow::ShowGroupInfo(void) {
             Printf(false,
                 "%FtSURFACES%E %Fsas mesh%E");
         }
+
+        if(g->booleanFailed) {
+            Printf(true,  "The Boolean operation failed. It may be ");
+            Printf(false, "possible to fix the problem by choosing ");
+            Printf(false, "surfaces 'as mesh' instead of 'as NURBS'.");
+        }
     }
 
     // Leave more space if the group has configuration stuff above the req/