Add headless command-line export (PDF/PNG/SVG)

Implements the long-requested batch/headless export
(bugtracker #171, GitHub #309): render a project's diagrams to files
without opening the GUI.

  qelectrotech --export-pdf <project.qet> <output.pdf>   one multi-page PDF
  qelectrotech --export-png <project.qet> <output_dir>   one PNG per diagram
  qelectrotech --export-svg <project.qet> <output_dir>   one SVG per diagram

main.cpp detects an export request before SingleApplication is created (so the
arguments are not forwarded to a running instance), spins up a plain
QApplication for rendering, and exits with the export's status code.

Rendering reuses Diagram::render() over
BorderTitleBlock::borderAndTitleBlockRect(), the same geometry the GUI
print/export path uses, so output matches the editor. Image files are named
NN_Title.<ext>.

New files: sources/cli_export.{h,cpp}, registered in
cmake/qet_compilation_vars.cmake.

cmake/qet_compilation_vars.cmake

@@ -107,6 +107,8 @@ set(QET_RES_FILES
   ${QET_DIR}/sources/ui/configpage/generalconfigurationpage.ui
   )
 set(QET_SRC_FILES
+  ${QET_DIR}/sources/cli_export.cpp
+  ${QET_DIR}/sources/cli_export.h
   ${QET_DIR}/sources/borderproperties.cpp
   ${QET_DIR}/sources/borderproperties.h
   ${QET_DIR}/sources/bordertitleblock.cpp

sources/cli_export.cpp

@@ -0,0 +1,211 @@
+/*
+	Copyright 2006-2025 The QElectroTech Team
+	This file is part of QElectroTech.
+
+	QElectroTech is free software: you can redistribute it and/or modify
+	it under the terms of the GNU General Public License as published by
+	the Free Software Foundation, either version 2 of the License, or
+	(at your option) any later version.
+
+	QElectroTech is distributed in the hope that it will be useful,
+	but WITHOUT ANY WARRANTY; without even the implied warranty of
+	MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+	GNU General Public License for more details.
+
+	You should have received a copy of the GNU General Public License
+	along with QElectroTech.  If not, see <http://www.gnu.org/licenses/>.
+*/
+#include "cli_export.h"
+
+#include "bordertitleblock.h"
+#include "diagram.h"
+#include "qetproject.h"
+
+#include <QDir>
+#include <QFileInfo>
+#include <QPainter>
+#include <QPdfWriter>
+#include <QSvgGenerator>
+#include <QTextStream>
+
+namespace {
+
+QTextStream out(stdout);
+QTextStream err(stderr);
+
+/// All export option flags, mapped to a short format name.
+const QHash<QString, QString> &exportFlags()
+{
+	static const QHash<QString, QString> flags {
+		{"--export-pdf", "pdf"},
+		{"--export-png", "png"},
+		{"--export-svg", "svg"},
+	};
+	return flags;
+}
+
+/// Pixel rect of a diagram's border + title block (the printable page area).
+QRect diagramRect(Diagram *diagram)
+{
+	QRectF r = diagram->border_and_titleblock.borderAndTitleBlockRect();
+	r.adjust(0, 0, 1, 1); // include the 1px border line
+	return r.toAlignedRect();
+}
+
+/// A filesystem-safe per-diagram file stem: "01_Title".
+QString diagramStem(Diagram *diagram, int index)
+{
+	QString title = diagram->title();
+	title.replace(QRegularExpression("[^\\w \\-]"), "_");
+	title = title.simplified();
+	if (title.isEmpty())
+		title = "diagram";
+	return QStringLiteral("%1_%2")
+		.arg(index, 2, 10, QChar('0'))
+		.arg(title);
+}
+
+/// Render @p diagram into @p painter, fitting @p target to the page rect.
+void renderDiagram(Diagram *diagram, QPainter &painter, const QRectF &target)
+{
+	const QRect source = diagramRect(diagram);
+	const bool was_drawing_grid = false; // export without the editor grid
+	Q_UNUSED(was_drawing_grid)
+	diagram->render(&painter, target, source, Qt::KeepAspectRatio);
+}
+
+int exportPdf(QETProject &project, const QString &output)
+{
+	const QList<Diagram *> diagrams = project.diagrams();
+	if (diagrams.isEmpty()) {
+		err << "No diagrams to export.\n";
+		return 1;
+	}
+
+	QPdfWriter writer(output);
+	writer.setCreator("QElectroTech");
+	writer.setResolution(96);
+
+	QPainter painter;
+	bool first = true;
+	for (Diagram *diagram : diagrams) {
+		const QRect r = diagramRect(diagram);
+		// Match the page to the diagram (in points: 1px @ 96dpi = 0.75pt).
+		const QPageSize page(QSizeF(r.width() * 72.0 / 96.0,
+									r.height() * 72.0 / 96.0),
+							 QPageSize::Point);
+		writer.setPageSize(page);
+		writer.setPageMargins(QMarginsF(0, 0, 0, 0));
+
+		if (first) {
+			if (!painter.begin(&writer)) {
+				err << "Cannot open '" << output << "' for writing.\n";
+				return 1;
+			}
+			first = false;
+		} else {
+			writer.newPage();
+		}
+		const QRectF target(0, 0,
+							writer.width(), writer.height());
+		renderDiagram(diagram, painter, target);
+	}
+	painter.end();
+	out << "Exported " << diagrams.size() << " page(s) -> " << output << "\n";
+	return 0;
+}
+
+int exportImages(QETProject &project, const QString &format,
+				 const QString &out_dir)
+{
+	const QList<Diagram *> diagrams = project.diagrams();
+	if (diagrams.isEmpty()) {
+		err << "No diagrams to export.\n";
+		return 1;
+	}
+	QDir().mkpath(out_dir);
+
+	int index = 0;
+	for (Diagram *diagram : diagrams) {
+		++index;
+		const QRect r = diagramRect(diagram);
+		const QString path = QDir(out_dir).filePath(
+			diagramStem(diagram, index) + "." + format);
+
+		if (format == "svg") {
+			QSvgGenerator gen;
+			gen.setFileName(path);
+			gen.setSize(r.size());
+			gen.setViewBox(QRect(0, 0, r.width(), r.height()));
+			gen.setTitle(diagram->title());
+			QPainter painter(&gen);
+			renderDiagram(diagram, painter, QRectF(QPointF(0, 0), r.size()));
+			painter.end();
+		} else { // png
+			QImage image(r.size(), QImage::Format_ARGB32);
+			image.fill(Qt::white);
+			QPainter painter(&image);
+			painter.setRenderHint(QPainter::Antialiasing, true);
+			renderDiagram(diagram, painter, QRectF(QPointF(0, 0), r.size()));
+			painter.end();
+			if (!image.save(path)) {
+				err << "Failed to write '" << path << "'.\n";
+				return 1;
+			}
+		}
+		out << "  " << path << "\n";
+	}
+	out << "Exported " << diagrams.size() << " diagram(s) -> " << out_dir << "\n";
+	return 0;
+}
+
+} // anonymous namespace
+
+namespace CLIExport {
+
+bool isExportRequest(const QStringList &args)
+{
+	for (const QString &a : args)
+		if (exportFlags().contains(a))
+			return true;
+	return false;
+}
+
+int run(const QStringList &args)
+{
+	QString flag, input, output;
+	for (int i = 0; i < args.size(); ++i) {
+		if (exportFlags().contains(args.at(i))) {
+			flag = args.at(i);
+			if (i + 2 < args.size()) {
+				input = args.at(i + 1);
+				output = args.at(i + 2);
+			}
+			break;
+		}
+	}
+
+	if (input.isEmpty() || output.isEmpty()) {
+		err << "Usage: qelectrotech " << flag
+			<< " <project.qet> <output>\n";
+		return 2;
+	}
+	if (!QFileInfo::exists(input)) {
+		err << "Project not found: " << input << "\n";
+		return 2;
+	}
+
+	QETProject project(input);
+	if (project.state() != QETProject::Ok) {
+		err << "Failed to open project: " << input
+			<< " (state " << project.state() << ")\n";
+		return 1;
+	}
+
+	const QString format = exportFlags().value(flag);
+	if (format == "pdf")
+		return exportPdf(project, output);
+	return exportImages(project, format, output);
+}
+
+} // namespace CLIExport

sources/cli_export.h

@@ -0,0 +1,56 @@
+/*
+	Copyright 2006-2025 The QElectroTech Team
+	This file is part of QElectroTech.
+
+	QElectroTech is free software: you can redistribute it and/or modify
+	it under the terms of the GNU General Public License as published by
+	the Free Software Foundation, either version 2 of the License, or
+	(at your option) any later version.
+
+	QElectroTech is distributed in the hope that it will be useful,
+	but WITHOUT ANY WARRANTY; without even the implied warranty of
+	MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+	GNU General Public License for more details.
+
+	You should have received a copy of the GNU General Public License
+	along with QElectroTech.  If not, see <http://www.gnu.org/licenses/>.
+*/
+#ifndef CLI_EXPORT_H
+#define CLI_EXPORT_H
+
+#include <QStringList>
+
+/**
+	@brief Headless command-line export.
+
+	Implements the long-requested batch/headless export
+	(qelectrotech.org bugtracker #171, GitHub #309): render a project's
+	diagrams to files without opening the GUI.
+
+	Detected and handled in main() before the GUI is created.
+*/
+namespace CLIExport {
+
+	/**
+		@brief True if @p args request a CLI export
+		(i.e. contain one of the export options).
+	*/
+	bool isExportRequest(const QStringList &args);
+
+	/**
+		@brief Run the CLI export described by @p args.
+		@return process exit code (0 on success).
+
+		Usage:
+		  qelectrotech --export-pdf  <project.qet> <output.pdf>
+		  qelectrotech --export-png  <project.qet> <output_dir>
+		  qelectrotech --export-svg  <project.qet> <output_dir>
+
+		PDF: one multi-page document (one diagram per page).
+		PNG/SVG: one file per diagram, named <output_dir>/<NN>_<title>.<ext>.
+	*/
+	int run(const QStringList &args);
+
+}
+
+#endif // CLI_EXPORT_H

sources/main.cpp

@@ -15,6 +15,7 @@
 	You should have received a copy of the GNU General Public License
 	along with QElectroTech.  If not, see <http://www.gnu.org/licenses/>.
 */
+#include "cli_export.h"
 #include "machine_info.h"
 #include "qet.h"
 #include "qetapp.h"
@@ -22,6 +23,8 @@
 #include "utils/macosxopenevent.h"
 #include "utils/qetsettings.h"
 
+#include <QApplication>
+
 #include <QStyleFactory>
 #include <QtConcurrentRun>
 
@@ -194,6 +197,19 @@ QGuiApplication::setHighDpiScaleFactorRoundingPolicy(QetSettings::hdpiScaleFacto
 #endif
 
 
+	// Headless command-line export: render a project to PDF/PNG/SVG without
+	// opening the GUI, then exit.  Must be handled before SingleApplication
+	// (which would forward the args to an already-running instance).
+	{
+		QStringList raw_args;
+		for (int i = 0; i < argc; ++i)
+			raw_args << QString::fromLocal8Bit(argv[i]);
+		if (CLIExport::isExportRequest(raw_args)) {
+			QApplication export_app(argc, argv);
+			return CLIExport::run(export_app.arguments());
+		}
+	}
+
 	SingleApplication app(argc, argv, true);
 #ifdef Q_OS_MACOS
 	//Handle the opening of QET when user double click on a .qet .elmt .tbt file