PYMOL-4854: Add cell_color setting for unit cell coloring

Author: JarrettSJohnson

layer1/Setting.cpp

@@ -2481,6 +2481,9 @@ void SettingGenerateSideEffects(PyMOLGlobals * G, int index, const char *sele, i
     ExecutiveInvalidateRep(G, inv_sele, cRepSphere, cRepInvRep);
     SceneInvalidate(G);
     break;
+  case cSetting_cell_color:
+    ExecutiveInvalidateRep(G, inv_sele, cRepCell, cRepInvColor);
+    SceneInvalidate(G);
   case cSetting_cull_spheres:
   case cSetting_sphere_scale:
   case cSetting_sphere_transparency:

layer1/SettingInfo.h

@@ -904,6 +904,7 @@ enum {
   REC_f( 794, halogen_bond_as_acceptor_max_acceptor_angle , global    , 170.0f ),
   REC_f( 795, salt_bridge_distance                        , global    , 5.0f ),
   REC_b( 796, use_tessellation_shaders                , global    , true ),
+  REC_c( 797, cell_color                              , ostate    , "-1" ),
 
 #ifdef SETTINGINFO_IMPLEMENTATION
 #undef SETTINGINFO_IMPLEMENTATION

layer2/CoordSet.cpp

@@ -1287,7 +1287,12 @@ void CoordSet::update(int state)
       UnitCellCGO.reset(CrystalGetUnitCellCGO(&sym->Crystal));
       auto use_shader = SettingGet<bool>(G, cSetting_use_shaders);
       if (use_shader) {
-        auto color = ColorGet(G, Obj->Color);
+        auto cell_color = SettingGet_color(
+            G, this->Setting.get(), Obj->Setting.get(), cSetting_cell_color);
+        if (cell_color < 0) {
+          cell_color = Obj->Color;
+        }
+        auto color = ColorGet(G, cell_color);
         auto preCGO = std::make_unique<CGO>(G);
         CGOColorv(preCGO.get(), color);
         CGOAppendNoStop(preCGO.get(), UnitCellCGO.get());

layer2/ObjectSurface.cpp

@@ -870,7 +870,12 @@ static void ObjectSurfaceRenderCell(PyMOLGlobals *G, ObjectSurface * I,
    * TODO: Ray with primitive CGO
    */
 
-  const float *color = ColorGet(G, I->Color);
+  // TODO: Surface-state level color?
+  auto cell_color = SettingGet_color(*I, cSetting_cell_color);
+  if (cell_color < 0) {
+    cell_color = I->Color;
+  }
+  const float *color = ColorGet(G, cell_color);
   if (use_shader != ms->UnitCellCGO->has_draw_buffers){
     if (use_shader){
       auto preCGO = std::make_unique<CGO>(G);