feat(editor): a slip goes only where the straights cross at the skos of its template: a Rkpd 1:9 was laid at a crossing of 1:7 or 1:14 as well, shaped for the angle of the tracks there into no slip of the catalogue. The straights crossing at a skos more than 0.14 deg off it, half of what keeps 1:9.51 and 1:10 apart, are refused with the skos they cross at and the slip of the same kind made for it, of the same rail and radius first, or none; a double slip replaced by one of another skos likewise. The panel and the hints say the slip goes at its skos. Selftest: a Rkpd 49E1-190-1:9 laid at 1:9 and 1:9.08, refused at 1:7 with no template for it and at 1:9.51 with Rkpd S42-230-1:9,51 fitting

application/editormode.h

@@ -1674,6 +1674,9 @@ class editor_mode : public application_mode, private editor_track::observer, pri
 		std::array<glm::dvec3, 4> points{};
 	};
 	bool plan_double_slip(editor_track::straight const &Line, glm::dvec3 const &Point, editor_track::switch_template const &Shape, slip_plan &Plan) const;
+	// a slip is made for its skos: where the tracks cross at another one, the refusal, which tells the template made for theirs; empty
+	// where it fits, and for a crossing
+	std::string slip_skew(editor_track::switch_template const &Shape, double const Angle) const;
 	// the cursor where it points at the straight, at the height of the straight there
 	glm::dvec3 cursor_on_straight(editor_track::straight const &Line) const;
 	bool insert_double_slip(editor_track::straight const &Line, glm::dvec3 const &Point, editor_track::switch_template const &Shape);

application/editormodeswitchplace.cpp

@@ -44,6 +44,9 @@ http:
 
 using namespace track_mode;
 
+// the name of the template in the language of the editor, editormodeswitchtool.cpp
+std::string switch_name_translated(std::string Title);
+
 std::vector<segment_data> editor_mode::switch_preview() const
 {
 	auto const &tool{m_switch};
@@ -1065,6 +1068,11 @@ bool editor_mode::plan_double_slip(editor_track::straight const &Line, glm::dvec
 		Plan.problem = STR_C("The straights cross at an angle unsuitable for a double slip");
 		return false;
 	}
+	if (auto const skew{slip_skew(Shape, angle)}; false == skew.empty())
+	{
+		Plan.problem = skew;
+		return false;
+	}
 	auto const alongfirst{glm::dot(crossing - plan_of(Line.start), Line.direction)};
 	auto const alongsecond{glm::dot(crossing - plan_of(second.start), second.direction)};
 	auto const available{std::min({alongfirst, Line.length - alongfirst, alongsecond, second.length - alongsecond}) - 0.5};
@@ -1110,6 +1118,33 @@ bool editor_mode::plan_double_slip(editor_track::straight const &Line, glm::dvec
 	return true;
 }
 
+std::string editor_mode::slip_skew(editor_track::switch_template const &Shape, double const Angle) const
+{
+	// rad: the tracks crossing at the skos of the slip to within this, half of what keeps 1:9.51 and 1:10 of the catalogue apart
+	auto const tolerance{glm::radians(0.14)};
+	auto const fits = [&](editor_track::switch_template const &Template) { return Template.ratio > 0.0 && std::abs(Angle - std::atan(1.0 / Template.ratio)) <= tolerance; };
+	if (Shape.type == "Skrz" || false == Shape.double_slip || Shape.ratio <= 0.0 || fits(Shape))
+		return {};
+	// a slip of the same kind made for the skos of the tracks, of the same rail and radius before the others
+	editor_track::switch_template const *fitting{nullptr};
+	auto best{-1};
+	for (auto const &entry : m_switch.templates)
+	{
+		if (false == entry.double_slip || entry.type != Shape.type || false == fits(entry))
+			continue;
+		auto const rank{(entry.rail == Shape.rail ? 2 : 0) + (std::abs(entry.radius - Shape.radius) < 0.5 ? 1 : 0)};
+		if (rank > best)
+		{
+			best = rank;
+			fitting = &entry;
+		}
+	}
+	auto const ratio{1.0 / std::tan(Angle)};
+	if (fitting == nullptr)
+		return format(STR_C("The straights cross at 1:%.2f, %s is made for 1:%.2f and no slip template is made for that"), ratio, switch_name_translated(Shape.title()).c_str(), Shape.ratio);
+	return format(STR_C("The straights cross at 1:%.2f, %s is made for 1:%.2f: %s fits that crossing"), ratio, switch_name_translated(Shape.title()).c_str(), Shape.ratio, switch_name_translated(fitting->title()).c_str());
+}
+
 bool editor_mode::insert_double_slip(editor_track::straight const &Line, glm::dvec3 const &Point, editor_track::switch_template const &Shape)
 {
 	auto &state{m_straights};
@@ -1241,6 +1276,11 @@ bool editor_mode::replace_double_slip(TTrack &Part, editor_track::switch_templat
 	auto const t{cross(plan_of(c.point) - plan_of(a.point), direction) / determinant};
 	glm::dvec2 const crossing{plan_of(a.point) + first * t};
 	auto const angle{std::atan2(std::abs(cross(first, direction)), glm::dot(first, direction))};
+	if (auto const skew{slip_skew(Shape, angle)}; false == skew.empty())
+	{
+		state.status = refused(skew);
+		return false;
+	}
 	auto const oldhalf{glm::distance(plan_of(a.point), crossing)};
 	auto const blade{switch_design::secant_blade(Shape.rail, Shape.radius, Shape.ratio)};
 	auto curve{editor_track::slip_of(Shape.radius, Shape.middle, angle, 0.5 * std::abs(switches[0]->fTrackWidth) + switches[0]->rail_dimensions().head + 0.002, blade.first, blade.second)};

application/editormodeswitchtool.cpp

@@ -139,7 +139,10 @@ std::string template_tooltip(editor_track::switch_template const &Template)
 		text += "\n";
 		text += Template.type == "Rkp" ? STR_C("Single slip (Rkp)") : Template.type == "Rkpd" ? STR_C("Double slip (Rkpd)") : STR_C("Crossing (Skrz)");
 		text += "\n" + format(STR_C("a %.3f m from the middle of the crossing to the joint"), Template.a) + "\n";
-		text += Template.type == "Rkp" ? STR_C("Drag at a crossing of two straights, on the side of the tracks to join") : STR_C("Drag at a crossing of two straights");
+		if (Template.type == "Skrz")
+			text += STR_C("Drag at a crossing of two straights");
+		else
+			text += Template.type == "Rkp" ? STR_C("Drag at a crossing of two straights at its skos, on the side of the tracks to join") : STR_C("Drag at a crossing of two straights at its skos");
 		return text;
 	}
 	text += "\n" + format(STR_C("a %.3f m to the centre of the switch, b %.3f m on to its end"), Template.a, Template.b);
@@ -228,7 +231,7 @@ void editor_mode::render_switch_ui()
 		char const *tooltip;
 	};
 	choice const choices[] = {{switch_kind::single, "Switch", "A switch in a straight or a curve"},
-	                          {switch_kind::slip, "Slip switch", "Rkp or Rkpd at a crossing of two straights"},
+	                          {switch_kind::slip, "Slip switch", "Rkp or Rkpd at a crossing of two straights at its skos"},
 	                          {switch_kind::crossing, "Crossing", "A crossing of two straights"},
 	                          {switch_kind::connection, "Connection", "Crossover, double, scissors, ladder"}};
 	{
@@ -274,7 +277,7 @@ void editor_mode::render_switch_ui()
 	std::vector<std::pair<char const *, char const *>> how;
 	switch (kind)
 	{
-	case switch_kind::slip:
+	case switch_kind::slip: how = {{"Drag at a crossing", "of two straights at the skos of the slip: it goes there"}}; break;
 	case switch_kind::crossing: how = {{"Drag at a crossing", "of two straights: it goes there"}}; break;
 	case switch_kind::connection:
 		how = {{"Drag", "from a straight onto the other track"}, {"Shift+wheel", "the kind"}, {"Ctrl+wheel", "R of the aligning curve"}};

application/editormodetrack.cpp

@@ -1754,6 +1754,8 @@ std::vector<editor_mode::key_hint> editor_mode::track_key_hints(bool const All)
 	}
 	else if (m_track_tab == track_tab::turnout && m_switch.armed < 0)
 		hints = {{"List in the panel", "the type of the switch"}, {"LMB on a track", "another track"}};
+	else if (m_track_tab == track_tab::turnout && current_switch_kind() == switch_kind::slip)
+		hints = {{"Press+drag at a crossing", "of two straights at the skos of the slip"}};
 	else if (m_track_tab == track_tab::turnout)
 		hints = {{"Press+drag on the track", "along: direction, sideways: side"}, {"List in the panel", "the type of the switch"}, {"LMB on another track", "choose it"}};
 	else if (m_track_tab == track_tab::profile && m_profile.route.spans.empty())