Add new lcResult class to handle task failures more cleanly.

common/lc_application.cpp

@@ -1156,9 +1156,13 @@ lcStartupMode lcApplication::Initialize(const QList<QPair<QString, bool>>& Libra
 				FileName = FileName.left(FileName.length() - Extension.length() - 1);
 				FileName += ".obj";
 			}
+			
+			lcResult<void> ExportResult = mProject->ExportWavefront(FileName);
 
-			if (mProject->ExportWavefront(FileName))
+			if (ExportResult)
 				StdOut << tr("Saved '%1'.\n").arg(FileName);
+			else if (!ExportResult.error().isEmpty())
+				StdErr << ExportResult.error();
 		}
 
 		if (Options.Save3DS)
@@ -1181,9 +1185,13 @@ lcStartupMode lcApplication::Initialize(const QList<QPair<QString, bool>>& Libra
 				FileName = FileName.left(FileName.length() - Extension.length() - 1);
 				FileName += ".3ds";
 			}
-
-			if (mProject->Export3DStudio(FileName))
+			
+			lcResult<void> ExportResult = mProject->Export3DStudio(FileName);
+			
+			if (ExportResult)
 				StdOut << tr("Saved '%1'.\n").arg(FileName);
+			else if (!ExportResult.error().isEmpty())
+				StdErr << ExportResult.error();
 		}
 
 		if (Options.SaveCOLLADA)
@@ -1206,9 +1214,13 @@ lcStartupMode lcApplication::Initialize(const QList<QPair<QString, bool>>& Libra
 				FileName = FileName.left(FileName.length() - Extension.length() - 1);
 				FileName += ".dae";
 			}
+			
+			lcResult<void> ExportResult = mProject->ExportCOLLADA(FileName);
 
-			if (mProject->ExportCOLLADA(FileName))
+			if (ExportResult)
 				StdOut << tr("Saved '%1'.\n").arg(FileName);
+			else if (!ExportResult.error().isEmpty())
+			    StdErr << ExportResult.error();
 		}
 
 		if (Options.SaveCSV)
@@ -1231,9 +1243,13 @@ lcStartupMode lcApplication::Initialize(const QList<QPair<QString, bool>>& Libra
 				FileName = FileName.left(FileName.length() - Extension.length() - 1);
 				FileName += ".csv";
 			}
-
-			if (mProject->ExportCSV(FileName))
+			
+			lcResult<void> ExportResult = mProject->ExportCSV(FileName);
+			
+			if (ExportResult)
 				StdOut << tr("Saved '%1'.\n").arg(FileName);
+			else if (!ExportResult.error().isEmpty())
+				StdErr << ExportResult.error();
 		}
 
 		if (Options.SaveHTML)
@@ -1243,7 +1259,12 @@ lcStartupMode lcApplication::Initialize(const QList<QPair<QString, bool>>& Libra
 			if (!Options.SaveHTMLName.isEmpty())
 				HTMLOptions.PathName = Options.SaveHTMLName;
 
-			mProject->ExportHTML(HTMLOptions);
+			lcResult<void> ExportResult = mProject->ExportHTML(HTMLOptions);
+			
+			if (ExportResult)
+				StdOut << tr("Saved '%1'.\n").arg(HTMLOptions.PathName);
+			else if (!ExportResult.error().isEmpty())
+				StdErr << ExportResult.error();
 		}
 	}
 

common/lc_bricklink.cpp

@@ -1,7 +1,8 @@
 #include "lc_global.h"
+#include "lc_bricklink.h"
 #include "lc_file.h"
 #include "lc_library.h"
-#include "lc_mainwindow.h"
+#include "lc_application.h"
 #include "lc_string.h"
 #include "pieceinf.h"
 #include "lc_colors.h"
@@ -59,7 +60,7 @@ public:
 	int mCount;
 };
 
-void lcExportBrickLink(const QString& SaveFileName, const lcPartsList& PartsList)
+lcResult<void> lcExportBrickLink(const QString& SaveFileName, const lcPartsList& PartsList)
 {
 	QJsonDocument Document = lcLoadBrickLinkMapping();
 	QJsonObject Root = Document.object();
@@ -70,10 +71,7 @@ void lcExportBrickLink(const QString& SaveFileName, const lcPartsList& PartsList
 	char Line[1024];
 
 	if (!BrickLinkFile.Open(QIODevice::WriteOnly))
-	{
-		QMessageBox::warning(gMainWindow, QObject::tr("LeoCAD"), QObject::tr("Could not open file '%1' for writing.").arg(SaveFileName));
-		return;
-	}
+		return lcUnexpected(QObject::tr("Could not open file '%1' for writing.").arg(SaveFileName));
 
 	std::map<std::string, lcBrickLinkItem> Inventory;
 
@@ -127,4 +125,6 @@ void lcExportBrickLink(const QString& SaveFileName, const lcPartsList& PartsList
 	}
 
 	BrickLinkFile.WriteLine("</INVENTORY>\n");
+	
+	return lcResult<void>();
 }

common/lc_bricklink.h

@@ -1,3 +1,5 @@
 #pragma once
 
-void lcExportBrickLink(const QString& FileName, const lcPartsList& PartsList);
+#include "lc_result.h"
+
+lcResult<void> lcExportBrickLink(const QString& FileName, const lcPartsList& PartsList);

common/lc_mainwindow.cpp

@@ -1321,15 +1321,15 @@ void lcMainWindow::ShowHTMLDialog()
 		return;
 
 	Options.SaveDefaults();
-	lcGetActiveProject()->ExportHTML(Options);
+	ShowResultMessageBox(lcGetActiveProject()->ExportHTML(Options));
 }
 
 void lcMainWindow::ShowExportPOVRayDialog()
 {
-	auto [Success, ErrorMessage] = lcGetActiveProject()->ExportPOVRay(QString());
+	lcResult<void> ExportResult = lcGetActiveProject()->ExportPOVRay(QString());
 
-	if (!Success && !ErrorMessage.isEmpty())
-		QMessageBox::warning(this, tr("POV-Ray Export" ), ErrorMessage);
+	if (!ExportResult && !ExportResult.error().isEmpty())
+		QMessageBox::warning(this, tr("POV-Ray Export" ), ExportResult.error());
 }
 
 void lcMainWindow::ShowRenderDialog(lcRenderDialogMode RenderDialogMode)
@@ -1407,6 +1407,12 @@ void lcMainWindow::ShowSelectDialog()
 	ActiveModel->SetSelectionAndFocusAction(Dialog.mObjects, nullptr, 0, lcSelectionMode::Single);
 }
 
+void lcMainWindow::ShowResultMessageBox(const lcResult<void>& Result)
+{
+	if (!Result && !Result.error().isEmpty())
+		QMessageBox::information(this, tr("LeoCAD"), Result.error());
+}
+
 void lcMainWindow::SetShadingMode(lcShadingMode ShadingMode)
 {
 	lcGetPreferences().mShadingMode = ShadingMode;
@@ -2483,8 +2489,8 @@ void lcMainWindow::ShowMergeDialog()
 	lcSetProfileString(LC_PROFILE_PROJECTS_PATH, QFileInfo(LoadFileNames.first()).absolutePath());
 
 	std::vector<std::unique_ptr<Project>> ProjectsToMerge;
-
-	for (const QString& LoadFileName : LoadFileNames)
+	
+	for (const QString& LoadFileName : std::as_const(LoadFileNames))
 	{
 		std::unique_ptr<Project>& NewProject = ProjectsToMerge.emplace_back(std::make_unique<Project>());
 
@@ -2706,11 +2712,11 @@ void lcMainWindow::HandleCommand(lcCommandId CommandId)
 		break;
 
 	case LC_FILE_EXPORT_3DS:
-		lcGetActiveProject()->Export3DStudio(QString());
+		ShowResultMessageBox(lcGetActiveProject()->Export3DStudio(QString()));
 		break;
 
 	case LC_FILE_EXPORT_COLLADA:
-		lcGetActiveProject()->ExportCOLLADA(QString());
+		ShowResultMessageBox(lcGetActiveProject()->ExportCOLLADA(QString()));
 		break;
 
 	case LC_FILE_EXPORT_HTML:
@@ -2718,11 +2724,11 @@ void lcMainWindow::HandleCommand(lcCommandId CommandId)
 		break;
 
 	case LC_FILE_EXPORT_BRICKLINK:
-		lcGetActiveProject()->ExportBrickLink();
+		ShowResultMessageBox(lcGetActiveProject()->ExportBrickLink());
 		break;
 
 	case LC_FILE_EXPORT_CSV:
-		lcGetActiveProject()->ExportCSV(QString());
+		ShowResultMessageBox(lcGetActiveProject()->ExportCSV(QString()));
 		break;
 
 	case LC_FILE_EXPORT_POVRAY:
@@ -2730,7 +2736,7 @@ void lcMainWindow::HandleCommand(lcCommandId CommandId)
 		break;
 
 	case LC_FILE_EXPORT_WAVEFRONT:
-		lcGetActiveProject()->ExportWavefront(QString());
+		ShowResultMessageBox(lcGetActiveProject()->ExportWavefront(QString()));
 		break;
 
 	case LC_FILE_RENDER_POVRAY:

common/lc_mainwindow.h

@@ -2,6 +2,7 @@
 
 #include "lc_application.h"
 #include "lc_shortcuts.h"
+#include "lc_result.h"
 #include "lc_commands.h"
 #include "lc_model.h"
 
@@ -310,6 +311,7 @@ protected:
 	void ShowPrintDialog();
 	void ShowImageDialog();
 	void ShowSelectDialog();
+	void ShowResultMessageBox(const lcResult<void>& Result);
 	void CreatePreviewWidget();
 
 	bool OpenProjectFile(const QString& FileName);

common/lc_result.h

@@ -0,0 +1,134 @@
+#pragma once
+
+// We can't use std::expected because we only require C++17.
+
+#include <stdexcept>
+
+class lcUnexpected
+{
+public:
+	explicit lcUnexpected(const QString& Error)
+	    : mError(Error)
+	{
+	}
+
+	explicit lcUnexpected(QString&& Error)
+	    : mError(std::move(Error))
+	{
+	}
+
+	const QString& error() const
+	{
+		return mError;
+	}
+	
+	QString& error()
+	{
+		return mError;
+	}
+	
+protected:
+	QString mError;
+};
+
+template <typename T>
+class [[nodiscard]] lcResult
+{
+	using internal_t = std::conditional_t<std::is_void_v<T>, char, T>;
+
+public:
+	template <typename U = T, typename = std::enable_if_t<!std::is_void_v<U> && std::is_convertible_v<U, T>>>
+	lcResult(U&& Value)
+	    : mHasValue(true)
+	{
+		::new (static_cast<void*>(&mValue)) internal_t(std::forward<U>(Value));
+	}
+	
+	template <typename U = T, typename = std::enable_if_t<std::is_void_v<U>>>
+	lcResult()
+	    : mHasValue(true)
+	{
+	}
+	
+	lcResult(lcUnexpected Unexpected)
+	    : mHasValue(false)
+	{
+		::new (static_cast<void*>(&mUnexpected)) lcUnexpected(std::move(Unexpected.error()));
+	}
+	
+	~lcResult() noexcept
+	{
+		if (mHasValue)
+		{
+			if constexpr (!std::is_void_v<T>)
+				mValue.~internal_t();
+		}
+		else
+		{
+			mUnexpected.~lcUnexpected();
+		}
+	}
+	
+	lcResult(const lcResult& Other) :
+	    mHasValue(Other.mHasValue)
+	{
+		if (mHasValue)
+		{
+			if constexpr (!std::is_void_v<T>)
+				::new (static_cast<void*>(&mValue)) internal_t(Other.mValue);
+		}
+		else
+		{
+			::new (static_cast<void*>(&mUnexpected)) lcUnexpected(Other.mUnexpected);
+		}
+	}
+	
+	lcResult(lcResult&& Other) noexcept(std::is_nothrow_move_constructible_v<internal_t> && std::is_nothrow_move_constructible_v<lcUnexpected>) 
+	    : mHasValue(Other.mHasValue)
+	{
+		if (mHasValue)
+		{
+			if constexpr (!std::is_void_v<T>)
+				::new (static_cast<void*>(&mValue)) internal_t(std::move(Other.mValue));
+		}
+		else
+		{
+			::new (static_cast<void*>(&mUnexpected)) lcUnexpected(std::move(Other.mUnexpected));
+		}
+	}
+	
+	bool has_value() const
+	{
+		return mHasValue;
+	}
+
+	explicit operator bool() const
+	{
+		return has_value();
+	}
+
+	template <typename U = T, typename = std::enable_if_t<!std::is_void_v<U>>>
+	constexpr const U& value() const
+	{
+		if (!mHasValue)
+			throw std::logic_error("bad lcResult access");
+		
+		return mValue;
+	}
+	
+	constexpr const QString& error() const
+	{
+		if (mHasValue)
+			throw std::logic_error("bad lcResult access");
+
+		return mUnexpected.error();
+	}
+
+protected:
+	union
+	{
+		internal_t mValue;
+		lcUnexpected mUnexpected;
+	};
+	bool mHasValue;
+};

common/project.cpp

@@ -650,15 +650,12 @@ std::vector<lcModelPartsEntry> Project::GetModelParts()
 	return ModelParts;
 }
 
-bool Project::ExportCurrentStep(const QString& FileName)
+lcResult<void> Project::ExportCurrentStep(const QString& FileName)
 {
 	QFile File(FileName);
 
 	if (!File.open(QIODevice::WriteOnly))
-	{
-		QMessageBox::warning(gMainWindow, tr("Error"), tr("Error writing to file '%1':\n%2").arg(FileName, File.errorString()));
-		return false;
-	}
+		return lcUnexpected(tr("Error writing to file '%1':\n%2").arg(FileName, File.errorString()));
 
 	QStringList Models;
 
@@ -749,8 +746,8 @@ bool Project::ExportCurrentStep(const QString& FileName)
 	File.close();
 
 	lcSetProfileString(LC_PROFILE_PROJECTS_PATH, QFileInfo(FileName).absolutePath());
-
-	return true;
+	
+	return lcResult<void>();
 }
 
 bool Project::ExportModel(const QString& FileName, lcModel* Model) const
@@ -795,28 +792,22 @@ QString Project::GetExportFileName(const QString& FileName, const QString& Defau
 	return QFileDialog::getSaveFileName(gMainWindow, DialogTitle, SaveFileName, DialogFilter);
 }
 
-bool Project::Export3DStudio(const QString& FileName)
+lcResult<void> Project::Export3DStudio(const QString& FileName)
 {
 	std::vector<lcModelPartsEntry> ModelParts = GetModelParts();
 
 	if (ModelParts.empty())
-	{
-		QMessageBox::information(gMainWindow, tr("LeoCAD"), tr("Nothing to export."));
-		return false;
-	}
+		return lcUnexpected(tr("Nothing to export."));
 
 	QString SaveFileName = GetExportFileName(FileName, "3ds", tr("Export 3D Studio"), tr("3DS Files (*.3ds);;All Files (*.*)"));
 
 	if (SaveFileName.isEmpty())
-		return false;
+		return lcUnexpected(QString());
 
 	lcDiskFile File(SaveFileName);
 
 	if (!File.Open(QIODevice::WriteOnly))
-	{
-		QMessageBox::warning(gMainWindow, tr("LeoCAD"), tr("Could not open file '%1' for writing.").arg(SaveFileName));
-		return false;
-	}
+		return lcUnexpected(tr("Could not open file '%1' for writing.").arg(SaveFileName));
 
 	long M3DStart = File.GetPosition();
 	File.WriteU16(0x4D4D); // CHK_M3DMAGIC
@@ -1232,11 +1223,11 @@ bool Project::Export3DStudio(const QString& FileName)
 	File.Seek(M3DStart + 2, SEEK_SET);
 	File.WriteU32(M3DEnd - M3DStart);
 	File.Seek(M3DEnd, SEEK_SET);
-
-	return true;
+	
+	return lcResult<void>();
 }
 
-void Project::ExportBrickLink()
+lcResult<void> Project::ExportBrickLink()
 {
 	lcPartsList PartsList;
 
@@ -1244,41 +1235,32 @@ void Project::ExportBrickLink()
 		mModels[0]->GetPartsList(gDefaultColor, true, false, PartsList);
 
 	if (PartsList.empty())
-	{
-		QMessageBox::information(gMainWindow, tr("LeoCAD"), tr("Nothing to export."));
-		return;
-	}
+		return lcUnexpected(tr("Nothing to export."));
 
 	QString SaveFileName = GetExportFileName(QString(), "xml", tr("Export BrickLink"), tr("XML Files (*.xml);;All Files (*.*)"));
 
 	if (SaveFileName.isEmpty())
-		return;
+		return lcUnexpected(QString());
 
-	lcExportBrickLink(SaveFileName, PartsList);
+	return lcExportBrickLink(SaveFileName, PartsList);
 }
 
-bool Project::ExportCOLLADA(const QString& FileName)
+lcResult<void> Project::ExportCOLLADA(const QString& FileName)
 {
 	std::vector<lcModelPartsEntry> ModelParts = GetModelParts();
 
 	if (ModelParts.empty())
-	{
-		QMessageBox::information(gMainWindow, tr("LeoCAD"), tr("Nothing to export."));
-		return false;
-	}
+		return lcUnexpected(tr("Nothing to export."));
 
 	QString SaveFileName = GetExportFileName(FileName, "dae", tr("Export COLLADA"), tr("COLLADA Files (*.dae);;All Files (*.*)"));
 
 	if (SaveFileName.isEmpty())
-		return false;
+		return lcUnexpected(QString());
 
 	QFile File(SaveFileName);
 
 	if (!File.open(QIODevice::WriteOnly))
-	{
-		QMessageBox::warning(gMainWindow, tr("LeoCAD"), tr("Could not open file '%1' for writing.").arg(SaveFileName));
-		return false;
-	}
+		return lcUnexpected(tr("Could not open file '%1' for writing.").arg(SaveFileName));
 
 	QTextStream Stream(&File);
 
@@ -1525,11 +1507,11 @@ bool Project::ExportCOLLADA(const QString& FileName)
 	Stream << "</scene>\r\n";
 
 	Stream << "</COLLADA>\r\n";
-
-	return true;
+	
+	return lcResult<void>();
 }
 
-bool Project::ExportCSV(const QString& FileName)
+lcResult<void> Project::ExportCSV(const QString& FileName)
 {
 	lcPartsList PartsList;
 
@@ -1537,24 +1519,18 @@ bool Project::ExportCSV(const QString& FileName)
 		mModels[0]->GetPartsList(gDefaultColor, true, false, PartsList);
 
 	if (PartsList.empty())
-	{
-		QMessageBox::information(gMainWindow, tr("LeoCAD"), tr("Nothing to export."));
-		return false;
-	}
+		return lcUnexpected(tr("Nothing to export."));
 
 	QString SaveFileName = GetExportFileName(FileName, "csv", tr("Export CSV"), tr("CSV Files (*.csv);;All Files (*.*)"));
 
 	if (SaveFileName.isEmpty())
-		return false;
+		return lcUnexpected(QString());
 
 	lcDiskFile CSVFile(SaveFileName);
 	char Line[1024];
 
 	if (!CSVFile.Open(QIODevice::WriteOnly))
-	{
-		QMessageBox::warning(gMainWindow, tr("LeoCAD"), tr("Could not open file '%1' for writing.").arg(SaveFileName));
-		return false;
-	}
+		return lcUnexpected(tr("Could not open file '%1' for writing.").arg(SaveFileName));
 
 	CSVFile.WriteLine("Part Name,Color,Quantity,Part ID,Color Code\n");
 
@@ -1571,8 +1547,8 @@ bool Project::ExportCSV(const QString& FileName)
 			CSVFile.WriteLine(Line);
 		}
 	}
-
-	return true;
+	
+	return lcResult<void>();
 }
 
 lcInstructions* Project::GetInstructions()
@@ -1583,7 +1559,7 @@ lcInstructions* Project::GetInstructions()
 	return mInstructions.get();
 }
 
-void Project::ExportHTML(const lcHTMLExportOptions& Options)
+lcResult<void> Project::ExportHTML(const lcHTMLExportOptions& Options)
 {
 	QDir Dir(Options.PathName);
 	Dir.mkpath(QLatin1String("."));
@@ -1641,10 +1617,7 @@ void Project::ExportHTML(const lcHTMLExportOptions& Options)
 			QFile File(FileName);
 
 			if (!File.open(QIODevice::WriteOnly))
-			{
-				QMessageBox::warning(gMainWindow, tr("Error"), tr("Error writing to file '%1':\n%2").arg(FileName, File.errorString()));
-				return;
-			}
+				return lcUnexpected(tr("Error writing to file '%1':\n%2").arg(FileName, File.errorString()));
 
 			QTextStream Stream(&File);
 
@@ -1672,10 +1645,7 @@ void Project::ExportHTML(const lcHTMLExportOptions& Options)
 				QFile File(FileName);
 
 				if (!File.open(QIODevice::WriteOnly))
-				{
-					QMessageBox::warning(gMainWindow, tr("Error"), tr("Error writing to file '%1':\n%2").arg(FileName, File.errorString()));
-					return;
-				}
+					return lcUnexpected(tr("Error writing to file '%1':\n%2").arg(FileName, File.errorString()));
 
 				QTextStream Stream(&File);
 
@@ -1697,10 +1667,7 @@ void Project::ExportHTML(const lcHTMLExportOptions& Options)
 				QFile File(FileName);
 
 				if (!File.open(QIODevice::WriteOnly))
-				{
-					QMessageBox::warning(gMainWindow, tr("Error"), tr("Error writing to file '%1':\n%2").arg(FileName, File.errorString()));
-					return;
-				}
+					return lcUnexpected(tr("Error writing to file '%1':\n%2").arg(FileName, File.errorString()));
 
 				QTextStream Stream(&File);
 
@@ -1731,10 +1698,7 @@ void Project::ExportHTML(const lcHTMLExportOptions& Options)
 				QFile File(FileName);
 
 				if (!File.open(QIODevice::WriteOnly))
-				{
-					QMessageBox::warning(gMainWindow, tr("Error"), tr("Error writing to file '%1':\n%2").arg(FileName, File.errorString()));
-					return;
-				}
+					return lcUnexpected(tr("Error writing to file '%1':\n%2").arg(FileName, File.errorString()));
 
 				QTextStream Stream(&File);
 
@@ -1763,10 +1727,7 @@ void Project::ExportHTML(const lcHTMLExportOptions& Options)
 		QFile File(FileName);
 
 		if (!File.open(QIODevice::WriteOnly))
-		{
-			QMessageBox::warning(gMainWindow, tr("Error"), tr("Error writing to file '%1':\n%2").arg(FileName, File.errorString()));
-			return;
-		}
+			return lcUnexpected(tr("Error writing to file '%1':\n%2").arg(FileName, File.errorString()));
 
 		QTextStream Stream(&File);
 
@@ -1803,24 +1764,26 @@ void Project::ExportHTML(const lcHTMLExportOptions& Options)
 
 		Stream << QLatin1String("</CENTER>\r\n<BR><HR><BR><B><I>Created by <A HREF=\"https://www.leocad.org\">LeoCAD</A></B></I><BR></HTML>\r\n");
 	}
+	
+	return lcResult<void>();
 }
 
-std::pair<bool, QString> Project::ExportPOVRay(const QString& FileName)
+lcResult<void> Project::ExportPOVRay(const QString& FileName)
 {
 	std::vector<lcModelPartsEntry> ModelParts = GetModelParts();
 
 	if (ModelParts.empty())
-		return { false, tr("Nothing to export.") };
+		return lcUnexpected(tr("Nothing to export."));
 
 	QString SaveFileName = GetExportFileName(FileName, QLatin1String("pov"), tr("Export POV-Ray"), tr("POV-Ray Files (*.pov);;All Files (*.*)"));
 
 	if (SaveFileName.isEmpty())
-		return { false, QString() };
+		return lcUnexpected(QString());
 
 	lcDiskFile POVFile(SaveFileName);
 
 	if (!POVFile.Open(QIODevice::WriteOnly))
-		return { false, tr("Could not open file '%1' for writing.").arg(SaveFileName) };
+		return lcUnexpected(tr("Could not open file '%1' for writing.").arg(SaveFileName));
 
 	enum
 	{
@@ -2225,7 +2188,7 @@ std::pair<bool, QString> Project::ExportPOVRay(const QString& FileName)
 		lcDiskFile TableFile(QFileInfo(QDir(LGEOPath), QLatin1String("lg_elements.lst")).absoluteFilePath());
 
 		if (!TableFile.Open(QIODevice::ReadOnly))
-			return { false, tr("Could not find LGEO files in folder '%1'.").arg(LGEOPath) };
+			return lcUnexpected(tr("Could not find LGEO files in folder '%1'.").arg(LGEOPath));
 
 		while (TableFile.ReadLine(Line, sizeof(Line)))
 		{
@@ -2271,7 +2234,7 @@ std::pair<bool, QString> Project::ExportPOVRay(const QString& FileName)
 		lcDiskFile LgeoColorFile(QFileInfo(QDir(LGEOPath), QLatin1String("lg_colors.lst")).absoluteFilePath());
 
 		if (!LgeoColorFile.Open(QIODevice::ReadOnly))
-			return { false, tr("Could not find LGEO files in folder '%1'.").arg(LGEOPath) };
+			return lcUnexpected(tr("Could not find LGEO files in folder '%1'.").arg(LGEOPath));
 
 		while (LgeoColorFile.ReadLine(Line, sizeof(Line)))
 		{
@@ -2487,33 +2450,27 @@ std::pair<bool, QString> Project::ExportPOVRay(const QString& FileName)
 		snprintf(Line, sizeof(Line), "\n#include \"%s\"\n", POVRayOptions.FooterIncludeFile.toLatin1().constData());
 		POVFile.WriteLine(Line);
 	}
-
-	return { true, QString() };
+	
+	return lcResult<void>();
 }
 
-bool Project::ExportWavefront(const QString& FileName)
+lcResult<void> Project::ExportWavefront(const QString& FileName)
 {
 	std::vector<lcModelPartsEntry> ModelParts = GetModelParts();
 
 	if (ModelParts.empty())
-	{
-		QMessageBox::information(gMainWindow, tr("LeoCAD"), tr("Nothing to export."));
-		return false;
-	}
+		return lcUnexpected(tr("Nothing to export."));
 
 	QString SaveFileName = GetExportFileName(FileName, QLatin1String("obj"), tr("Export Wavefront"), tr("Wavefront Files (*.obj);;All Files (*.*)"));
 
 	if (SaveFileName.isEmpty())
-		return false;
+		return lcUnexpected(QString());
 
 	lcDiskFile OBJFile(SaveFileName);
 	char Line[1024];
 
 	if (!OBJFile.Open(QIODevice::WriteOnly))
-	{
-		QMessageBox::warning(gMainWindow, tr("LeoCAD"), tr("Could not open file '%1' for writing.").arg(SaveFileName));
-		return false;
-	}
+		return lcUnexpected(tr("Could not open file '%1' for writing.").arg(SaveFileName));
 
 	quint32 vert = 1;
 
@@ -2526,13 +2483,12 @@ bool Project::ExportWavefront(const QString& FileName)
 	OBJFile.WriteLine(Line);
 
 	lcDiskFile MaterialFile(MaterialFileName);
+	
 	if (!MaterialFile.Open(QIODevice::WriteOnly))
-	{
-		QMessageBox::warning(gMainWindow, tr("LeoCAD"), tr("Could not open file '%1' for writing.").arg(MaterialFileName));
-		return false;
-	}
+		return lcUnexpected(tr("Could not open file '%1' for writing.").arg(MaterialFileName));
 
 	MaterialFile.WriteLine("# Colors used by LeoCAD\n\n");
+	
 	for (const lcColor& Color : gColorList)
 	{
 		if (Color.Translucent)
@@ -2596,8 +2552,8 @@ bool Project::ExportWavefront(const QString& FileName)
 			vert += Mesh->mNumVertices;
 		}
 	}
-
-	return true;
+	
+	return lcResult<void>();
 }
 
 void Project::SaveImage(const lcImageDialogOptions& Options)

common/project.h

@@ -1,6 +1,7 @@
 #pragma once
 
 #include "lc_application.h"
+#include "lc_result.h"
 
 #define LC_HTML_SINGLEPAGE    0x01
 #define LC_HTML_INDEX         0x02
@@ -100,15 +101,15 @@ public:
 	bool ImportInventory(const std::vector<lcSetInventoryItem>& SetInventory, const QString& Name, const QString& Description);
 
 	void SaveImage(const lcImageDialogOptions& Options);
-	bool ExportCurrentStep(const QString& FileName);
+	lcResult<void> ExportCurrentStep(const QString& FileName);
 	bool ExportModel(const QString& FileName, lcModel* Model) const;
-	bool Export3DStudio(const QString& FileName);
-	void ExportBrickLink();
-	bool ExportCOLLADA(const QString& FileName);
-	bool ExportCSV(const QString& FileName);
-	void ExportHTML(const lcHTMLExportOptions& Options);
-	std::pair<bool, QString> ExportPOVRay(const QString& FileName);
-	bool ExportWavefront(const QString& FileName);
+	lcResult<void> Export3DStudio(const QString& FileName);
+	lcResult<void> ExportBrickLink();
+	lcResult<void> ExportCOLLADA(const QString& FileName);
+	lcResult<void> ExportCSV(const QString& FileName);
+	lcResult<void> ExportHTML(const lcHTMLExportOptions& Options);
+	lcResult<void> ExportPOVRay(const QString& FileName);
+	lcResult<void> ExportWavefront(const QString& FileName);
 
 	void UpdatePieceInfo(PieceInfo* Info) const;