Feature: [Linkgraph] Show a tooltip with statistics when hovering a link

src/lang/english.txt

@@ -2617,6 +2617,11 @@ STR_LINKGRAPH_LEGEND_UNUSED                                     :{TINY_FONT}{BLA
 STR_LINKGRAPH_LEGEND_SATURATED                                  :{TINY_FONT}{BLACK}saturated
 STR_LINKGRAPH_LEGEND_OVERLOADED                                 :{TINY_FONT}{BLACK}overloaded
 
+# Linkgraph tooltip
+STR_LINKGRAPH_STATS_TOOLTIP                                     :{BLACK}{CARGO_LONG} to be transported per month from {STATION} to {STATION} ({COMMA}% of capacity){RAW_STRING}
+STR_LINKGRAPH_STATS_TOOLTIP_RETURN_EXTENSION                    :{}{CARGO_LONG} to be transported back ({COMMA}% of capacity)
+STR_LINKGRAPH_STATS_TOOLTIP_TIME_EXTENSION                      :{}Average travel time: {NUM}{NBSP}day{P "" s}
+
 # Base for station construction window(s)
 STR_STATION_BUILD_COVERAGE_AREA_TITLE                           :{BLACK}Coverage area highlight
 STR_STATION_BUILD_COVERAGE_OFF                                  :{BLACK}Off

src/linkgraph/linkgraph_gui.cpp

@@ -219,8 +219,10 @@ void LinkGraphOverlay::AddLinks(const Station *from, const Station *to)
 		const LinkGraph &lg = *LinkGraph::Get(ge.link_graph);
 		ConstEdge edge = lg[ge.node][to->goods[c].node];
 		if (edge.Capacity() > 0) {
-			this->AddStats(lg.Monthly(edge.Capacity()), lg.Monthly(edge.Usage()),
-					ge.flows.GetFlowVia(to->index), from->owner == OWNER_NONE || to->owner == OWNER_NONE,
+			this->AddStats(c, lg.Monthly(edge.Capacity()), lg.Monthly(edge.Usage()),
+					ge.flows.GetFlowVia(to->index),
+					edge.TravelTime() / DAY_TICKS,
+					from->owner == OWNER_NONE || to->owner == OWNER_NONE,
 					this->cached_links[from->index][to->index]);
 		}
 	}
@@ -236,14 +238,16 @@ void LinkGraphOverlay::AddLinks(const Station *from, const Station *to)
  * @param new_shared If the new link is shared.
  * @param cargo LinkProperties to write the information to.
  */
-/* static */ void LinkGraphOverlay::AddStats(uint new_cap, uint new_usg, uint new_plan, bool new_shared, LinkProperties &cargo)
+/* static */ void LinkGraphOverlay::AddStats(CargoID new_cargo, uint new_cap, uint new_usg, uint new_plan, uint32 time, bool new_shared, LinkProperties &cargo)
 {
 	/* multiply the numbers by 32 in order to avoid comparing to 0 too often. */
 	if (cargo.capacity == 0 ||
-			std::max(cargo.usage, cargo.planned) * 32 / (cargo.capacity + 1) < std::max(new_usg, new_plan) * 32 / (new_cap + 1)) {
+			cargo.Usage() * 32 / (cargo.capacity + 1) < std::max(new_usg, new_plan) * 32 / (new_cap + 1)) {
+		cargo.cargo = new_cargo;
 		cargo.capacity = new_cap;
 		cargo.usage = new_usg;
 		cargo.planned = new_plan;
+		cargo.time = time;
 	}
 	if (new_shared) cargo.shared = true;
 }
@@ -289,7 +293,7 @@ void LinkGraphOverlay::DrawLinks(const DrawPixelInfo *dpi) const
  */
 void LinkGraphOverlay::DrawContent(Point pta, Point ptb, const LinkProperties &cargo) const
 {
-	uint usage_or_plan = std::min(cargo.capacity * 2 + 1, std::max(cargo.usage, cargo.planned));
+	uint usage_or_plan = std::min(cargo.capacity * 2 + 1, cargo.Usage());
 	int colour = LinkGraphOverlay::LINK_COLOURS[_settings_client.gui.linkgraph_colours][usage_or_plan * lengthof(LinkGraphOverlay::LINK_COLOURS[0]) / (cargo.capacity * 2 + 2)];
 	int width = ScaleGUITrad(this->scale);
 	int dash = cargo.shared ? width * 4 : 0;
@@ -354,6 +358,56 @@ void LinkGraphOverlay::DrawStationDots(const DrawPixelInfo *dpi) const
 	GfxDrawLine(x + w2, y - w1, x + w2, y + w2, border_colour);
 }
 
+bool LinkGraphOverlay::ShowTooltip(Point pt, TooltipCloseCondition close_cond)
+{
+	for (auto i(this->cached_links.crbegin()); i != this->cached_links.crend(); ++i) {
+		if (!Station::IsValidID(i->first)) continue;
+		Point pta = this->GetStationMiddle(Station::Get(i->first));
+		for (auto j(i->second.crbegin()); j != i->second.crend(); ++j) {
+			if (!Station::IsValidID(j->first)) continue;
+			if (i->first == j->first) continue;
+
+			/* Check the distance from the cursor to the line defined by the two stations. */
+			Point ptb = this->GetStationMiddle(Station::Get(j->first));
+			float dist = std::abs((ptb.x - pta.x) * (pta.y - pt.y) - (pta.x - pt.x) * (ptb.y - pta.y)) /
+				std::sqrt((ptb.x - pta.x) * (ptb.x - pta.x) + (ptb.y - pta.y) * (ptb.y - pta.y));
+			const auto &link = j->second;
+			if (dist <= 4 && link.Usage() > 0 &&
+					pt.x >= std::min(pta.x, ptb.x) &&
+					pt.x <= std::max(pta.x, ptb.x)) {
+				static char buf[1024];
+				char *buf_end = buf;
+				buf[0] = 0;
+				/* Fill buf with more information if this is a bidirectional link. */
+				auto k = this->cached_links[j->first].find(i->first);
+				const auto &back = k->second;
+				if (k != this->cached_links[j->first].end() && back.Usage() > 0) {
+					SetDParam(0, back.cargo);
+					SetDParam(1, back.Usage());
+					SetDParam(2, back.Usage() * 100 / (back.capacity + 1));
+					buf_end = GetString(buf, STR_LINKGRAPH_STATS_TOOLTIP_RETURN_EXTENSION, lastof(buf));
+				}
+				/* Add information about the travel time if known. */
+				const auto time = link.time ? back.time ? ((link.time + back.time) / 2) : link.time : back.time;
+				if (time > 0) {
+					SetDParam(0, time);
+					buf_end = GetString(buf_end, STR_LINKGRAPH_STATS_TOOLTIP_TIME_EXTENSION, lastof(buf));
+				}
+				SetDParam(0, link.cargo);
+				SetDParam(1, link.Usage());
+				SetDParam(2, i->first);
+				SetDParam(3, j->first);
+				SetDParam(4, link.Usage() * 100 / (link.capacity + 1));
+				SetDParamStr(5, buf);
+				GuiShowTooltips(this->window, STR_LINKGRAPH_STATS_TOOLTIP, 7, nullptr, close_cond);
+				return true;
+			}
+		}
+	}
+	GuiShowTooltips(this->window, STR_NULL, 0, nullptr, close_cond);
+	return false;
+}
+
 /**
  * Determine the middle of a station in the current window.
  * @param st The station we're looking for.

src/linkgraph/linkgraph_gui.h

@@ -19,14 +19,20 @@
 #include <vector>
 
 /**
- * Properties of a link between two stations.
+ * Monthly statistics for a link between two stations.
+ * Only the cargo type of the most saturated linkgraph is taken into account.
  */
 struct LinkProperties {
-	LinkProperties() : capacity(0), usage(0), planned(0), shared(false) {}
+	LinkProperties() : cargo(CT_INVALID), capacity(0), usage(0), planned(0), shared(false) {}
 
+	/** Return the usage of the link to display. */
+	uint Usage() const { return std::max(this->usage, this->planned); }
+
+	CargoID cargo; ///< Cargo type of the link.
 	uint capacity; ///< Capacity of the link.
 	uint usage;    ///< Actual usage of the link.
 	uint planned;  ///< Planned usage of the link.
+	uint32 time;   ///< Travel time of the link.
 	bool shared;   ///< If this is a shared link to be drawn dashed.
 };
 
@@ -50,7 +56,7 @@ public:
 	 * @param company_mask Bitmask of companies to be shown.
 	 * @param scale Desired thickness of lines and size of station dots.
 	 */
-	LinkGraphOverlay(const Window *w, uint wid, CargoTypes cargo_mask, uint32 company_mask, uint scale) :
+	LinkGraphOverlay(Window *w, uint wid, CargoTypes cargo_mask, uint32 company_mask, uint scale) :
 			window(w), widget_id(wid), cargo_mask(cargo_mask), company_mask(company_mask), scale(scale)
 	{}
 
@@ -58,6 +64,8 @@ public:
 	void SetCargoMask(CargoTypes cargo_mask);
 	void SetCompanyMask(uint32 company_mask);
 
+	bool ShowTooltip(Point pt, TooltipCloseCondition close_cond);
+
 	/** Mark the linkgraph dirty to be rebuilt next time Draw() is called. */
 	void SetDirty() { this->dirty = true; }
 
@@ -68,7 +76,7 @@ public:
 	uint32 GetCompanyMask() { return this->company_mask; }
 
 protected:
-	const Window *window;              ///< Window to be drawn into.
+	Window *window;                    ///< Window to be drawn into.
 	const uint widget_id;              ///< ID of Widget in Window to be drawn to.
 	CargoTypes cargo_mask;             ///< Bitmask of cargos to be displayed.
 	uint32 company_mask;               ///< Bitmask of companies to be displayed.
@@ -88,7 +96,7 @@ protected:
 	void GetWidgetDpi(DrawPixelInfo *dpi) const;
 	void RebuildCache();
 
-	static void AddStats(uint new_cap, uint new_usg, uint new_flow, bool new_shared, LinkProperties &cargo);
+	static void AddStats(CargoID new_cargo, uint new_cap, uint new_usg, uint new_flow, uint32 time, bool new_shared, LinkProperties &cargo);
 	static void DrawVertex(int x, int y, int size, int colour, int border_colour);
 };
 

src/main_gui.cpp

@@ -435,6 +435,12 @@ struct MainWindow : Window
 		}
 	}
 
+	bool OnTooltip(Point pt, int widget, TooltipCloseCondition close_cond) override
+	{
+		if (widget != WID_M_VIEWPORT) return false;
+		return this->viewport->overlay->ShowTooltip(pt, close_cond);
+	}
+
 	/**
 	 * Some data on this window has become invalid.
 	 * @param data Information about the changed data.

src/window.cpp

@@ -2873,6 +2873,7 @@ static void MouseLoop(MouseClick click, int mousewheel)
 					_scrolling_viewport = true;
 					_cursor.fix_at = (_settings_client.gui.scroll_mode == VSM_VIEWPORT_RMB_FIXED ||
 							_settings_client.gui.scroll_mode == VSM_MAP_RMB_FIXED);
+					DispatchRightClickEvent(w, x - w->left, y - w->top);
 					return;
 				}
 				break;