Complain about missing custom elements when opening online saves

The complaint manifests as a button in the bottom right corner of the half-size preview.

Also convert the loading error popup to such a button.

src/client/ThumbnailRendererTask.cpp

@@ -29,7 +29,7 @@ ThumbnailRendererTask::~ThumbnailRendererTask()
 
 bool ThumbnailRendererTask::doWork()
 {
-	thumbnail = std::unique_ptr<VideoBuffer>(SaveRenderer::Ref().Render(save.get(), decorations, fire));
+	std::tie(thumbnail, std::ignore) = SaveRenderer::Ref().Render(save.get(), decorations, fire);
 	if (thumbnail)
 	{
 		thumbnail->ResizeToFit(size, true);

src/gui/game/GameView.cpp

@@ -1958,7 +1958,7 @@ void GameView::NotifyTransformedPlaceSaveChanged(GameModel *sender)
 {
 	if (sender->GetTransformedPlaceSave())
 	{
-		placeSaveThumb = SaveRenderer::Ref().Render(sender->GetTransformedPlaceSave(), true, true, sender->GetRenderer());
+		std::tie(placeSaveThumb, std::ignore) = SaveRenderer::Ref().Render(sender->GetTransformedPlaceSave(), true, true, sender->GetRenderer());
 		selectMode = PlaceSave;
 		selectPoint2 = mousePosition;
 	}

src/gui/preview/PreviewView.cpp

@@ -93,6 +93,22 @@ PreviewView::PreviewView(std::unique_ptr<VideoBuffer> newSavePreview):
 	browserOpenButton->SetActionCallback({ [this] { c->OpenInBrowser(); } });
 	AddComponent(browserOpenButton);
 
+	loadErrorButton = new ui::Button({ 0, 0 }, ui::Point(148, 19), "Error loading save");
+	loadErrorButton->Appearance.HorizontalAlign = ui::Appearance::AlignCentre;
+	loadErrorButton->Appearance.VerticalAlign = ui::Appearance::AlignMiddle;
+	loadErrorButton->SetIcon(IconDelete);
+	loadErrorButton->SetActionCallback({ [this] { ShowLoadError(); } });
+	loadErrorButton->Visible = false;
+	AddComponent(loadErrorButton);
+
+	missingElementsButton = new ui::Button({ 0, 0 }, ui::Point(148, 19), "Missing custom elements");
+	missingElementsButton->Appearance.HorizontalAlign = ui::Appearance::AlignCentre;
+	missingElementsButton->Appearance.VerticalAlign = ui::Appearance::AlignMiddle;
+	missingElementsButton->SetIcon(IconReport);
+	missingElementsButton->SetActionCallback({ [this] { ShowMissingCustomElements(); } });
+	missingElementsButton->Visible = false;
+	AddComponent(missingElementsButton);
+
 	if(showAvatars)
 		saveNameLabel = new ui::Label(ui::Point(39, (YRES/2)+4), ui::Point(100, 16), "");
 	else
@@ -387,9 +403,9 @@ void PreviewView::OnTick(float dt)
 	c->Update();
 	if (doError)
 	{
-		new ErrorMessage("Error loading save", doErrorMessage, { [this]() {
-			c->Exit();
-		} });
+		openButton->Enabled = false;
+		loadErrorButton->Visible = true;
+		UpdateLoadStatus();
 	}
 
 	if (reportSaveRequest && reportSaveRequest->CheckDone())
@@ -464,6 +480,36 @@ void PreviewView::OnKeyPress(int key, int scan, bool repeat, bool shift, bool ct
 		openButton->DoAction();
 }
 
+void PreviewView::ShowLoadError()
+{
+	new ErrorMessage("Error loading save", doErrorMessage, {});
+}
+
+void PreviewView::ShowMissingCustomElements()
+{
+	StringBuilder sb;
+	sb << "This save uses custom elements that are not currently available. Make sure that you use the mod and/or have all the scripts the save requires to fully load. A list of identifiers of missing custom elements follows, which may help you determine how to fix this problem.\n";
+	for (auto &identifier : missingElementTypes)
+	{
+		sb << "\n - " << identifier.FromUtf8();
+	}
+	new InformationMessage("Missing custom elements", sb.Build(), true);
+}
+
+void PreviewView::UpdateLoadStatus()
+{
+	auto y = YRES / 2 - 22;
+	auto showButton = [&y](ui::Button *button) {
+		if (button->Visible)
+		{
+			button->Position = { XRES / 2 - button->Size.X - 3, y };
+			y -= button->Size.Y + 3;
+		}
+	};
+	showButton(missingElementsButton);
+	showButton(loadErrorButton);
+}
+
 void PreviewView::NotifySaveChanged(PreviewModel * sender)
 {
 	auto *save = sender->GetSaveInfo();
@@ -510,9 +556,11 @@ void PreviewView::NotifySaveChanged(PreviewModel * sender)
 
 		if(save->GetGameSave())
 		{
-			savePreview = SaveRenderer::Ref().Render(save->GetGameSave(), false, true);
+			std::tie(savePreview, missingElementTypes) = SaveRenderer::Ref().Render(save->GetGameSave(), false, true);
 			if (savePreview)
 				savePreview->ResizeToFit(RES / 2, true);
+			missingElementsButton->Visible = missingElementTypes.size();
+			UpdateLoadStatus();
 		}
 		else if (!sender->GetCanOpen())
 			openButton->Enabled = false;

src/gui/preview/PreviewView.h

@@ -26,25 +26,28 @@ class PreviewModel;
 class PreviewController;
 class PreviewView: public ui::Window
 {
-	PreviewController * c;
+	PreviewController *c{};
+	std::vector<ByteString> missingElementTypes;
 	std::unique_ptr<VideoBuffer> savePreview;
-	ui::Button * openButton;
-	ui::Button * browserOpenButton;
-	ui::Button * favButton;
-	ui::Button * reportButton;
-	ui::Button * submitCommentButton;
-	ui::Textbox * addCommentBox;
-	ui::Label * commentWarningLabel;
-	ui::Label * saveNameLabel;
-	ui::Label * authorDateLabel;
-	ui::AvatarButton * avatarButton;
-	ui::Label * pageInfo;
-	ui::Label * saveDescriptionLabel;
-	ui::Label * viewsLabel;
-	ui::Label * saveIDLabel;
-	ui::Label * saveIDLabel2;
-	ui::CopyTextButton * saveIDButton;
-	ui::ScrollPanel * commentsPanel;
+	ui::Button *openButton{};
+	ui::Button *browserOpenButton{};
+	ui::Button *favButton{};
+	ui::Button *reportButton{};
+	ui::Button *submitCommentButton{};
+	ui::Button *loadErrorButton{};
+	ui::Button *missingElementsButton{};
+	ui::Textbox *addCommentBox{};
+	ui::Label *commentWarningLabel{};
+	ui::Label *saveNameLabel{};
+	ui::Label *authorDateLabel{};
+	ui::AvatarButton *avatarButton{};
+	ui::Label *pageInfo{};
+	ui::Label *saveDescriptionLabel{};
+	ui::Label *viewsLabel{};
+	ui::Label *saveIDLabel{};
+	ui::Label *saveIDLabel2{};
+	ui::CopyTextButton *saveIDButton{};
+	ui::ScrollPanel *commentsPanel{};
 	std::vector<ui::Component*> commentComponents;
 	std::vector<ui::Component*> commentTextComponents;
 	int votesUp;
@@ -70,6 +73,9 @@ class PreviewView: public ui::Window
 	void submitComment();
 	bool CheckSwearing(String text);
 	void CheckComment();
+	void ShowMissingCustomElements();
+	void ShowLoadError();
+	void UpdateLoadStatus();
 
 	std::unique_ptr<http::AddCommentRequest> addCommentRequest;
 	std::unique_ptr<http::ReportSaveRequest> reportSaveRequest;

src/simulation/SaveRenderer.cpp

@@ -20,7 +20,7 @@ void SaveRenderer::Flush(int begin, int end)
 	std::fill(ren->graphicscache + begin, ren->graphicscache + end, gcache_item());
 }
 
-std::unique_ptr<VideoBuffer> SaveRenderer::Render(const GameSave *save, bool decorations, bool fire, Renderer *renderModeSource)
+std::pair<std::unique_ptr<VideoBuffer>, std::vector<ByteString>> SaveRenderer::Render(const GameSave *save, bool decorations, bool fire, Renderer *renderModeSource)
 {
 	std::lock_guard<std::mutex> gx(renderMutex);
 
@@ -32,11 +32,9 @@ std::unique_ptr<VideoBuffer> SaveRenderer::Render(const GameSave *save, bool dec
 		ren->SetColourMode(renderModeSource->GetColourMode());
 	}
 
-	std::unique_ptr<VideoBuffer> tempThumb;
-
 	sim->clear_sim();
 
-	sim->Load(save, true, { 0, 0 });
+	auto missingElementTypes = sim->Load(save, true, { 0, 0 });
 	ren->decorations_enable = true;
 	ren->blackDecorations = !decorations;
 	ren->ClearAccumulation();
@@ -57,10 +55,10 @@ std::unique_ptr<VideoBuffer> SaveRenderer::Render(const GameSave *save, bool dec
 	ren->RenderBegin();
 	ren->RenderEnd();
 
-	tempThumb = std::make_unique<VideoBuffer>(save->blockSize * CELL);
+	auto tempThumb = std::make_unique<VideoBuffer>(save->blockSize * CELL);
 	tempThumb->BlendImage(ren->Data(), 0xFF, ren->Size().OriginRect());
 
-	return tempThumb;
+	return { std::move(tempThumb), missingElementTypes };
 }
 
 SaveRenderer::~SaveRenderer()

src/simulation/SaveRenderer.h

@@ -1,7 +1,10 @@
 #pragma once
 #include <memory>
 #include <mutex>
+#include <utility>
+#include <vector>
 #include "common/ExplicitSingleton.h"
+#include "common/String.h"
 
 class GameSave;
 class VideoBuffer;
@@ -15,7 +18,7 @@ class SaveRenderer: public ExplicitSingleton<SaveRenderer> {
 	std::mutex renderMutex;
 public:
 	SaveRenderer();
-	std::unique_ptr<VideoBuffer> Render(const GameSave *save, bool decorations = true, bool fire = true, Renderer *renderModeSource = nullptr);
+	std::pair<std::unique_ptr<VideoBuffer>, std::vector<ByteString>> Render(const GameSave *save, bool decorations = true, bool fire = true, Renderer *renderModeSource = nullptr);
 	void Flush(int begin, int end);
 	virtual ~SaveRenderer();
 };

src/simulation/Simulation.cpp

@@ -19,8 +19,9 @@ extern int Element_LOLZ_lolz[XRES/9][YRES/9];
 extern int Element_LOVE_RuleTable[9][9];
 extern int Element_LOVE_love[XRES/9][YRES/9];
 
-void Simulation::Load(const GameSave *save, bool includePressure, Vec2<int> blockP) // block coordinates
+std::vector<ByteString> Simulation::Load(const GameSave *save, bool includePressure, Vec2<int> blockP) // block coordinates
 {
+	std::vector<ByteString> missingElementTypes;
 	auto partP = blockP * CELL;
 	unsigned int pmapmask = (1<<save->pmapbits)-1;
 
@@ -44,8 +45,15 @@ void Simulation::Load(const GameSave *save, bool includePressure, Vec2<int> bloc
 				// if this is a custom element, set the ID to the ID we found when comparing identifiers in the palette map
 				// set type to 0 if we couldn't find an element with that identifier present when loading,
 				//  unless this is a default element, in which case keep the current ID, because otherwise when an element is renamed it wouldn't show up anymore in older saves
-				if (myId != 0 || !pi.first.BeginsWith("DEFAULT_PT_"))
+				if (myId != 0)
+				{
 					partMap[pi.second] = myId;
+				}
+				else if (!pi.first.BeginsWith("DEFAULT_PT_"))
+				{
+					missingElementTypes.push_back(pi.first);
+					partMap[pi.second] = myId;
+				}
 			}
 		}
 	}
@@ -318,6 +326,8 @@ void Simulation::Load(const GameSave *save, bool includePressure, Vec2<int> bloc
 	{
 		air->ApproximateBlockAirMaps();
 	}
+
+	return missingElementTypes;
 }
 
 std::unique_ptr<GameSave> Simulation::Save(bool includePressure, Rect<int> partR) // particle coordinates

src/simulation/Simulation.h

@@ -121,7 +121,7 @@ public:
 	uint64_t frameCount;
 	bool ensureDeterminism;
 
-	void Load(const GameSave *save, bool includePressure, Vec2<int> blockP); // block coordinates
+	std::vector<ByteString> Load(const GameSave *save, bool includePressure, Vec2<int> blockP); // block coordinates
 	std::unique_ptr<GameSave> Save(bool includePressure, Rect<int> partR); // particle coordinates
 	void SaveSimOptions(GameSave &gameSave);
 	SimulationSample GetSample(int x, int y);