Fix forcing NURBS to mesh in a step group when the flag is inherited.

Before this commit, if the source group of a step rotate/translate
group is forced to triangle mesh, the UI would show that the step
rotate/translate group is also forced to triangle mesh, but the group
would in fact contain NURBS surfaces.

CHANGELOG.md

@@ -79,6 +79,8 @@ Bugs fixed:
     spurious changes in the sketch.
   * Points highlighted with "Analyze → Show Degrees of Freedom" are drawn
     on top of all other geometry.
+  * A step rotate/translate group using a group forced to triangle mesh
+    as a source group also gets forced to triangle mesh.
 
 2.3
 ---

src/group.cpp

@@ -318,6 +318,23 @@ void Group::TransformImportedBy(Vector t, Quaternion q) {
     SK.GetParam(qz)->val = qg.vz;
 }
 
+bool Group::IsForcedToMeshBySource() const {
+    const Group *srcg = this;
+    if(type == Type::TRANSLATE || type == Type::ROTATE) {
+        // A step and repeat gets merged against the group's prevous group,
+        // not our own previous group.
+        srcg = SK.GetGroup(opA);
+        if(srcg->forceToMesh) return true;
+    }
+    Group *g = srcg->RunningMeshGroup();
+    if(g == NULL) return false;
+    return g->forceToMesh || g->IsForcedToMeshBySource();
+}
+
+bool Group::IsForcedToMesh() const {
+    return forceToMesh || IsForcedToMeshBySource();
+}
+
 std::string Group::DescriptionString() {
     if(name.empty()) {
         return ssprintf("g%03x-%s", h.v, _("(unnamed)"));

src/groupmesh.cpp

@@ -204,8 +204,14 @@ void Group::GenerateShellAndMesh() {
         srcg = SK.GetGroup(opA);
 
         if(!srcg->suppress) {
-            GenerateForStepAndRepeat<SShell>(&(srcg->thisShell), &thisShell, srcg->meshCombine);
-            GenerateForStepAndRepeat<SMesh> (&(srcg->thisMesh),  &thisMesh, srcg->meshCombine);
+            if(!IsForcedToMesh()) {
+                GenerateForStepAndRepeat<SShell>(&(srcg->thisShell), &thisShell, srcg->meshCombine);
+            } else {
+                SMesh prevm = {};
+                prevm.MakeFromCopyOf(&srcg->thisMesh);
+                srcg->thisShell.TriangulateInto(&prevm);
+                GenerateForStepAndRepeat<SMesh> (&prevm, &thisMesh, srcg->meshCombine);
+            }
         }
     } else if(type == Type::EXTRUDE && haveSrc) {
         Group *src = SK.GetGroup(opA);
@@ -317,7 +323,7 @@ void Group::GenerateShellAndMesh() {
 
     Group *prevg = srcg->RunningMeshGroup();
 
-    if(prevg->runningMesh.IsEmpty() && thisMesh.IsEmpty() && !forceToMesh) {
+    if(!IsForcedToMesh()) {
         SShell *prevs = &(prevg->runningShell);
         GenerateForBoolean<SShell>(prevs, &thisShell, &runningShell,
             srcg->meshCombine);
@@ -434,7 +440,7 @@ void Group::GenerateDisplayItems() {
     }
 }
 
-Group *Group::PreviousGroup() {
+Group *Group::PreviousGroup() const {
     int i;
     for(i = 0; i < SK.groupOrder.n; i++) {
         Group *g = SK.GetGroup(SK.groupOrder.elem[i]);
@@ -444,7 +450,7 @@ Group *Group::PreviousGroup() {
     return SK.GetGroup(SK.groupOrder.elem[i - 1]);
 }
 
-Group *Group::RunningMeshGroup() {
+Group *Group::RunningMeshGroup() const {
     if(type == Type::TRANSLATE || type == Type::ROTATE) {
         return SK.GetGroup(opA)->RunningMeshGroup();
     } else {

src/sketch.h

@@ -234,6 +234,8 @@ public:
     void Generate(EntityList *entity, ParamList *param);
     bool IsSolvedOkay();
     void TransformImportedBy(Vector t, Quaternion q);
+    bool IsForcedToMeshBySource() const;
+    bool IsForcedToMesh() const;
     // When a request generates entities from entities, and the source
     // entities may have come from multiple requests, it's necessary to
     // remap the entity ID so that it's still unique. We do this with a
@@ -271,8 +273,8 @@ public:
     void AssembleLoops(bool *allClosed, bool *allCoplanar, bool *allNonZeroLen);
     void GenerateLoops();
     // And the mesh stuff
-    Group *PreviousGroup();
-    Group *RunningMeshGroup();
+    Group *PreviousGroup() const;
+    Group *RunningMeshGroup() const;
     bool IsMeshGroup();
 
     void GenerateShellAndMesh();

src/textscreens.cpp

@@ -395,8 +395,7 @@ void TextWindow::ShowGroupInfo() {
         &TextWindow::ScreenChangeGroupOption,
         g->visible ? CHECK_TRUE : CHECK_FALSE);
 
-    Group *pg; pg = g->PreviousGroup();
-    if(pg && pg->runningMesh.IsEmpty() && g->thisMesh.IsEmpty()) {
+    if(!g->IsForcedToMeshBySource()) {
         Printf(false, " %f%Lf%Fd%s  force NURBS surfaces to triangle mesh",
             &TextWindow::ScreenChangeGroupOption,
             g->forceToMesh ? CHECK_TRUE : CHECK_FALSE);