Linkgraph: Scroll overlay pixel cache instead of clearing it on scroll

Reduce cost of preparing/drawing cache
Improve missing station checks in RefreshDrawCache
Remove need for checks in DrawLinks
Don't rebase overlay cache coordinate to screen in viewport map mode

src/linkgraph/linkgraph_gui.cpp

@@ -116,16 +116,25 @@ void LinkGraphOverlay::RebuildCache(bool incremental)
 		this->cached_links.clear();
 		this->cached_stations.clear();
 		this->last_update_number = GetWindowUpdateNumber();
+		this->rebuild_counter++;
 	}
 	if (this->company_mask == 0) return;
 
+	const Rect old_cached_region = this->cached_region;
 	DrawPixelInfo dpi;
 	bool cache_all = false;
 	if (this->window->viewport) {
 		const Viewport *vp = this->window->viewport;
 		const int pixel_margin = 256;
 		const int vp_margin = ScaleByZoom(pixel_margin, vp->zoom);
+		if (vp->zoom < ZOOM_LVL_DRAW_MAP) {
 			this->GetWidgetDpi(&dpi, pixel_margin);
+		} else {
+			dpi.left = UnScaleByZoomLower(vp->virtual_left - vp_margin, vp->zoom);
+			dpi.top = UnScaleByZoomLower(vp->virtual_top - vp_margin, vp->zoom);
+			dpi.width = UnScaleByZoom(vp->virtual_width + vp_margin * 2, vp->zoom);
+			dpi.height = UnScaleByZoom(vp->virtual_height + vp_margin * 2, vp->zoom);
+		}
 		this->cached_region = Rect({ vp->virtual_left - vp_margin, vp->virtual_top - vp_margin,
 				vp->virtual_left + vp->virtual_width + vp_margin, vp->virtual_top + vp->virtual_height + vp_margin });
 	} else {
@@ -237,6 +246,26 @@ void LinkGraphOverlay::RebuildCache(bool incremental)
 		this->cached_links.push_back({ iter.first.first, iter.first.second, iter.second.from_pt, iter.second.to_pt, iter.second.prop });
 	}
 
+	if (incremental && (this->cached_stations.size() > previous_cached_stations_count || this->cached_links.size() > previous_cached_links_count)) {
+		/* Check if newly added stations/links are visible in previous cached area */
+		DrawPixelInfo old_dpi;
+		old_dpi.left = old_cached_region.left;
+		old_dpi.top = old_cached_region.top;
+		old_dpi.width = old_cached_region.right - old_cached_region.left;
+		old_dpi.height = old_cached_region.bottom - old_cached_region.top;
+
+		auto check_found = [&]() -> bool {
+			for (size_t i = previous_cached_stations_count; i < this->cached_stations.size(); i++) {
+				if (this->IsPointVisible(this->cached_stations[i].pt, &old_dpi)) return true;
+			}
+			for (size_t i = previous_cached_links_count; i < this->cached_links.size(); i++) {
+				if (this->IsLinkVisible(this->cached_links[i].from_pt, this->cached_links[i].to_pt, &old_dpi)) return true;
+			}
+			return false;
+		};
+		if (check_found()) this->rebuild_counter++;
+	}
+
 	if (previous_cached_stations_count > 0) {
 		std::inplace_merge(this->cached_stations.begin(), this->cached_stations.begin() + previous_cached_stations_count, this->cached_stations.end(),
 				[](const StationSupplyInfo &a, const StationSupplyInfo &b) {
@@ -364,17 +393,32 @@ inline bool LinkGraphOverlay::IsLinkVisible(Point pta, Point ptb, const DrawPixe
 
 void LinkGraphOverlay::RefreshDrawCache()
 {
+	static const Point INVALID_POINT = Point{ INT_MIN / 2, INT_MIN / 2 };
+
 	for (StationSupplyList::iterator i(this->cached_stations.begin()); i != this->cached_stations.end(); ++i) {
 		const Station *st = Station::GetIfValid(i->id);
-		if (st == nullptr) continue;
-
-		i->pt = this->GetStationMiddle(st);
+		if (st == nullptr) {
+			i->pt = INVALID_POINT;
+			continue;
 		}
+
+		Point new_pt = this->GetStationMiddle(st);
+		if (i->pt.x != new_pt.x || i->pt.y != new_pt.y) {
+			i->pt = new_pt;
+		}
+	}
+
 	for (LinkList::iterator i(this->cached_links.begin()); i != this->cached_links.end(); ++i) {
 		const Station *sta = Station::GetIfValid(i->from_id);
-		if (sta == nullptr) continue;
+		if (sta == nullptr) {
+			i->from_pt = i->to_pt = INVALID_POINT;
+			continue;
+		}
 		const Station *stb = Station::GetIfValid(i->to_id);
-		if (stb == nullptr) continue;
+		if (stb == nullptr) {
+			i->from_pt = i->to_pt = INVALID_POINT;
+			continue;
+		}
 
 		i->from_pt = this->GetStationMiddle(sta);
 		i->to_pt = this->GetStationMiddle(stb);
@@ -389,7 +433,7 @@ void LinkGraphOverlay::PrepareDraw()
 	if (this->dirty) {
 		this->RebuildCache();
 	}
-	if (this->last_update_number != GetWindowUpdateNumber()) {
+	if (this->last_update_number != GetWindowUpdateNumber() && this->window->viewport->zoom < ZOOM_LVL_DRAW_MAP) {
 		this->last_update_number = GetWindowUpdateNumber();
 		this->RefreshDrawCache();
 	}
@@ -414,8 +458,6 @@ void LinkGraphOverlay::DrawLinks(const DrawPixelInfo *dpi) const
 	int width = ScaleGUITrad(this->scale);
 	for (const auto &i : this->cached_links) {
 		if (!this->IsLinkVisible(i.from_pt, i.to_pt, dpi, width + 2)) continue;
-		if (!Station::IsValidID(i.from_id)) continue;
-		if (!Station::IsValidID(i.to_id)) continue;
 		this->DrawContent(dpi, i.from_pt, i.to_pt, i.prop);
 	}
 }

src/linkgraph/linkgraph_gui.h

@@ -87,10 +87,12 @@ public:
 	void SetDirty() { this->dirty = true; }
 
 	/** Get a bitmask of the currently shown cargoes. */
-	CargoTypes GetCargoMask() { return this->cargo_mask; }
+	CargoTypes GetCargoMask() const { return this->cargo_mask; }
 
 	/** Get a bitmask of the currently shown companies. */
-	CompanyMask GetCompanyMask() { return this->company_mask; }
+	CompanyMask GetCompanyMask() const { return this->company_mask; }
+
+	uint64_t GetRebuildCounter() const { return this->rebuild_counter; }
 
 protected:
 	Window *window;                    ///< Window to be drawn into.
@@ -103,6 +105,7 @@ protected:
 	uint scale;                        ///< Width of link lines.
 	bool dirty;                        ///< Set if overlay should be rebuilt.
 	uint64_t last_update_number = 0;   ///< Last window update number
+	uint64_t rebuild_counter = 0;      ///< Rebuild counter
 
 	Point GetStationMiddle(const Station *st) const;
 

src/viewport.cpp

@@ -566,6 +566,32 @@ static void ScrollPlanPixelCache(Viewport *vp, int offset_x, int offset_y)
 	if (clear) ClearViewportPlanPixelCache(vp);
 }
 
+static void ScrollOrInvalidateOverlayPixelCache(Viewport *vp, int offset_x, int offset_y)
+{
+	if (vp->overlay_pixel_cache.empty()) return;
+
+	if (vp->zoom < ZOOM_LVL_DRAW_MAP || vp->last_overlay_rebuild_counter != vp->overlay->GetRebuildCounter()) {
+		vp->overlay_pixel_cache.clear();
+		return;
+	}
+
+	bool clear = ScrollViewportPixelCacheGeneric(vp, vp->overlay_pixel_cache, offset_x, offset_y, 1, [](Viewport *vp, int x, int y, int width, int height) {
+		DrawPixelInfo overlay_dpi;
+		overlay_dpi.dst_ptr = vp->overlay_pixel_cache.data() + x + (y * vp->width);
+		overlay_dpi.height = height;
+		overlay_dpi.width = width;
+		overlay_dpi.pitch = vp->width;
+		overlay_dpi.zoom = ZOOM_LVL_NORMAL;
+		overlay_dpi.left = UnScaleByZoomLower(vp->virtual_left, vp->zoom) + x;
+		overlay_dpi.top = UnScaleByZoomLower(vp->virtual_top, vp->zoom) + y;
+
+		Blitter_8bppDrawing blitter;
+		BlitterFactory::TemporaryCurrentBlitterOverride current_blitter(&blitter);
+		vp->overlay->Draw(&overlay_dpi);
+	});
+	if (clear) vp->overlay_pixel_cache.clear();
+}
+
 void ClearViewportCache(Viewport *vp)
 {
 	if (vp->zoom >= ZOOM_LVL_DRAW_MAP) {
@@ -870,7 +896,11 @@ static void SetViewportPosition(Window *w, int x, int y, bool force_update_overl
 	vp->virtual_top = y;
 	UpdateViewportDirtyBlockLeftMargin(vp);
 
-	if (force_update_overlay || IsViewportOverlayOutsideCachedRegion(w)) RebuildViewportOverlay(w, true);
+	bool have_overlay = w->viewport->overlay != nullptr &&
+			w->viewport->overlay->GetCompanyMask() != 0 &&
+			w->viewport->overlay->GetCargoMask() != 0;
+
+	if (have_overlay && (force_update_overlay || !w->viewport->overlay->CacheStillValid())) RebuildViewportOverlay(w, true);
 
 	/* Viewport is bound to its left top corner, so it must be rounded down (UnScaleByZoomLower)
 	 * else glitch described in FS#1412 will happen (offset by 1 pixel with zoom level > NORMAL)
@@ -913,6 +943,7 @@ static void SetViewportPosition(Window *w, int x, int y, bool force_update_overl
 			SCOPE_INFO_FMT([&], "DoSetViewportPosition: %d, %d, %d, %d, %d, %d, %s", left, top, width, height, move_offset.x, move_offset.y, scope_dumper().WindowInfo(w));
 			ScrollViewportLandPixelCache(vp, move_offset.x, move_offset.y);
 			ScrollPlanPixelCache(vp, move_offset.x, move_offset.y);
+			if (have_overlay) ScrollOrInvalidateOverlayPixelCache(vp, move_offset.x, move_offset.y);
 			w->viewport->update_vehicles = true;
 			DoSetViewportPosition((Window *) w->z_front, move_offset, left, top, width, height);
 			ClearViewportCache(w->viewport);
@@ -3816,16 +3847,6 @@ static void ViewportProcessParentSprites(ViewportDrawerDynamic *vdd, uint data_i
 	}
 }
 
-static bool CheckViewportOverlayPixelRefresh(Viewport *vp)
-{
-	size_t screen_area = vp->ScreenArea();
-	if (vp->last_overlay_update_number == GetWindowUpdateNumber() && vp->overlay_pixel_cache.size() == screen_area) return false;
-
-	vp->last_overlay_update_number = GetWindowUpdateNumber();
-	vp->overlay_pixel_cache.assign(screen_area, 0xD7);
-	return true;
-}
-
 static void ViewportDoDrawPhase2(Viewport *vp, ViewportDrawerDynamic *vdd);
 static void ViewportDoDrawPhase3(Viewport *vp);
 static void ViewportDoDrawRenderJob(Viewport *vp, ViewportDrawerDynamic *vdd);
@@ -3868,15 +3889,19 @@ void ViewportDoDraw(Viewport *vp, int left, int top, int right, int bottom, uint
 	if (vp->overlay != nullptr && vp->overlay->GetCargoMask() != 0 && vp->overlay->GetCompanyMask() != 0) {
 		vp->overlay->PrepareDraw();
 
-		if (vp->zoom >= ZOOM_LVL_DRAW_MAP && CheckViewportOverlayPixelRefresh(vp)) {
+		if (vp->zoom >= ZOOM_LVL_DRAW_MAP && (vp->overlay_pixel_cache.empty() || vp->last_overlay_rebuild_counter != vp->overlay->GetRebuildCounter())) {
+			vp->last_overlay_rebuild_counter = vp->overlay->GetRebuildCounter();
+
+			vp->overlay_pixel_cache.assign(vp->ScreenArea(), 0xD7);
+
 			DrawPixelInfo overlay_dpi;
 			overlay_dpi.dst_ptr = vp->overlay_pixel_cache.data();
 			overlay_dpi.height = vp->height;
 			overlay_dpi.width = vp->width;
 			overlay_dpi.pitch = vp->width;
 			overlay_dpi.zoom = ZOOM_LVL_NORMAL;
-			overlay_dpi.left = vp->left;
-			overlay_dpi.top = vp->top;
+			overlay_dpi.left = UnScaleByZoomLower(vp->virtual_left, vp->zoom);
+			overlay_dpi.top = UnScaleByZoomLower(vp->virtual_top, vp->zoom);
 
 			Blitter_8bppDrawing blitter;
 			BlitterFactory::TemporaryCurrentBlitterOverride current_blitter(&blitter);
@@ -4283,6 +4308,7 @@ void UpdateViewportSizeZoom(Viewport *vp)
 		} else {
 			vp->land_pixel_cache.assign(vp->ScreenArea(), 0xD7);
 		}
+		vp->overlay_pixel_cache.clear();
 		vp->plan_pixel_cache.clear();
 	} else {
 		vp->map_draw_vehicles_cache.vehicle_pixels.clear();
@@ -5154,17 +5180,6 @@ void RebuildViewportOverlay(Window *w, bool incremental)
 	}
 }
 
-bool IsViewportOverlayOutsideCachedRegion(Window *w)
-{
-	if (w->viewport->overlay != nullptr &&
-			w->viewport->overlay->GetCompanyMask() != 0 &&
-			w->viewport->overlay->GetCargoMask() != 0) {
-		return !w->viewport->overlay->CacheStillValid();
-	} else {
-		return false;
-	}
-}
-
 /**
  * Scrolls the viewport in a window to a given location.
  * @param x       Desired x location of the map to scroll to (world coordinate).
@@ -6567,12 +6582,23 @@ Point GetViewportStationMiddle(const Viewport *vp, const Station *st)
 {
 	int x = TileX(st->xy) * TILE_SIZE;
 	int y = TileY(st->xy) * TILE_SIZE;
-	int z = GetSlopePixelZ(Clamp(x, 0, MapSizeX() * TILE_SIZE - 1), Clamp(y, 0, MapSizeY() * TILE_SIZE - 1));
 
+	/* Be faster/less precise in viewport map mode, sub-pixel precision is not needed.
+	 * Don't rebase point into screen coordinates in viewport map mode.
+	 */
+	if (vp->zoom < ZOOM_LVL_DRAW_MAP) {
+		int z = GetSlopePixelZ(Clamp(x, 0, MapSizeX() * TILE_SIZE - 1), Clamp(y, 0, MapSizeY() * TILE_SIZE - 1));
 		Point p = RemapCoords(x, y, z);
 		p.x = UnScaleByZoom(p.x - vp->virtual_left, vp->zoom) + vp->left;
 		p.y = UnScaleByZoom(p.y - vp->virtual_top, vp->zoom) + vp->top;
 		return p;
+	} else {
+		int z = st->xy < MapSize() ? TILE_HEIGHT * TileHeight(st->xy) : 0;
+		Point p = RemapCoords(x, y, z);
+		p.x = UnScaleByZoomLower(p.x, vp->zoom);
+		p.y = UnScaleByZoomLower(p.y, vp->zoom);
+		return p;
+	}
 }
 
 /** Helper class for getting the best sprite sorter. */

src/viewport_func.h

@@ -103,7 +103,6 @@ bool ScrollWindowTo(int x, int y, int z, Window *w, bool instant = false);
 void UpdateActiveScrollingViewport(Window *w);
 
 void RebuildViewportOverlay(Window *w, bool incremental);
-bool IsViewportOverlayOutsideCachedRegion(Window *w);
 
 bool ScrollMainWindowToTile(TileIndex tile, bool instant = false);
 bool ScrollMainWindowTo(int x, int y, int z = -1, bool instant = false);

src/viewport_type.h

@@ -61,7 +61,7 @@ struct Viewport {
 	bool is_dirty = false;
 	bool is_drawn = false;
 	bool update_vehicles = false;
-	uint64_t last_overlay_update_number = 0;
+	uint64_t last_overlay_rebuild_counter = 0;
 	uint64_t last_plan_update_number = 0;
 	ViewPortMapDrawVehiclesCache map_draw_vehicles_cache;
 	std::vector<byte> land_pixel_cache;