Allow creating n-dimensional arrays with translate and rotate groups.

Before this commit, a translate group based on another translate
group would always use the "union" boolean operation, which does not
work at all if one wants an array with a difference operation, and
results in degraded performance if one wants an array with
an assemble operation.

CHANGELOG.md

@@ -7,6 +7,8 @@ Changelog
 New sketch features:
   * Extrude, lathe, translate and rotate groups can now use the "assembly"
     boolean operation, to increase performance.
+  * Translate and rotate groups can create n-dimensional arrays using
+    the "difference" and "assembly" boolean operations.
 
 New export/import features:
   * Three.js: allow configuring projection for exported model, and initially

src/group.cpp

@@ -471,6 +471,9 @@ void Group::Generate(IdList<Entity,hEntity> *entity,
         }
 
         case Type::TRANSLATE: {
+            // inherit meshCombine from source group
+            Group *srcg = SK.GetGroup(opA);
+            meshCombine = srcg->meshCombine;
             // The translation vector
             AddParam(param, h.param(0), gp.x);
             AddParam(param, h.param(1), gp.y);
@@ -498,6 +501,9 @@ void Group::Generate(IdList<Entity,hEntity> *entity,
             return;
         }
         case Type::ROTATE: {
+            // inherit meshCombine from source group
+            Group *srcg = SK.GetGroup(opA);
+            meshCombine = srcg->meshCombine;
             // The center of rotation
             AddParam(param, h.param(0), gc.x);
             AddParam(param, h.param(1), gc.y);

test/CMakeLists.txt

@@ -54,6 +54,7 @@ set(testsuite_SOURCES
     request/line_segment/test.cpp
     request/ttf_text/test.cpp
     group/translate_asy/test.cpp
+    group/translate_nd/test.cpp
 )
 
 add_executable(solvespace_testsuite

test/group/translate_nd/test.cpp

@@ -0,0 +1,7 @@
+#include "harness.h"
+
+TEST_CASE(normal_roundtrip) {
+    CHECK_LOAD("normal.slvs");
+    CHECK_RENDER("normal.png");
+    CHECK_SAVE("normal.slvs");
+}