Debug: Show name of root sprite group shown in vehicle debug window

src/newgrf_debug_gui.cpp

@@ -561,7 +561,7 @@ struct NewGRFInspectWindow : Window {
 				if (group != nullptr) const_cast<NewGRFInspectWindow *>(this)->sprite_group_lines[offset] = group;
 				if (highlight_tag != 0) const_cast<NewGRFInspectWindow *>(this)->highlight_tag_lines[offset] = highlight_tag;
 
-				TextColour colour = (this->selected_sprite_group == group) ? TC_LIGHT_BLUE : TC_BLACK;
+				TextColour colour = (this->selected_sprite_group == group && group != nullptr) ? TC_LIGHT_BLUE : TC_BLACK;
 				if (highlight_tag != 0 && this->selected_highlight_tag == highlight_tag) colour = TC_YELLOW;
 				::DrawString(r.left + LEFT_OFFSET, r.right - RIGHT_OFFSET, r.top + TOP_OFFSET + (scroll_offset * this->resize.step_height), buf, colour);
 			});

src/newgrf_engine.cpp

@@ -1621,14 +1621,28 @@ void AnalyseEngineCallbacks()
 
 void DumpVehicleSpriteGroup(const Vehicle *v, DumpSpriteGroupPrinter print)
 {
+	char buffer[512];
 	const SpriteGroup *root_spritegroup = nullptr;
-	if (v->IsGroundVehicle()) root_spritegroup = GetWagonOverrideSpriteSet(v->engine_type, v->cargo_type, v->GetGroundVehicleCache()->first_engine);
+	if (v->IsGroundVehicle()) {
+		root_spritegroup = GetWagonOverrideSpriteSet(v->engine_type, v->cargo_type, v->GetGroundVehicleCache()->first_engine);
+		if (root_spritegroup != nullptr) {
+			seprintf(buffer, lastof(buffer), "Wagon Override for cargo: %u, engine type: %u", v->cargo_type, v->GetGroundVehicleCache()->first_engine);
+			print(nullptr, DSGPO_PRINT, 0, buffer);
+		}
+	}
 
 	if (root_spritegroup == nullptr) {
 		const Engine *e = Engine::Get(v->engine_type);
 		CargoID cargo = v->cargo_type;
 		assert(cargo < lengthof(e->grf_prop.spritegroup));
-		root_spritegroup = e->grf_prop.spritegroup[cargo] != nullptr ? e->grf_prop.spritegroup[cargo] : e->grf_prop.spritegroup[CT_DEFAULT];
+		if (e->grf_prop.spritegroup[cargo] != nullptr) {
+			root_spritegroup = e->grf_prop.spritegroup[cargo];
+			seprintf(buffer, lastof(buffer), "Cargo: %u", cargo);
+		} else {
+			root_spritegroup = e->grf_prop.spritegroup[CT_DEFAULT];
+			seprintf(buffer, lastof(buffer), "CT_DEFAULT");
+		}
+		print(nullptr, DSGPO_PRINT, 0, buffer);
 	}
 	DumpSpriteGroup(root_spritegroup, std::move(print));
 }