diff -r 5df69eb50182 -r f116b63c4844 src/documentation.cpp
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/src/documentation.cpp	Sat Aug 29 17:07:39 2015 +0300
@@ -0,0 +1,76 @@
+/*
+ *  LDForge: LDraw parts authoring CAD
+ *  Copyright (C) 2013, 2014 Teemu Piippo
+ *
+ *  This program 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 3 of the License, or
+ *  (at your option) any later version.
+ *
+ *  This program 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 this program.  If not, see <http://www.gnu.org/licenses/>.
+ */
+
+#include <QDialog>
+#include <QTextEdit>
+#include <QDialogButtonBox>
+#include <QBoxLayout>
+#include "main.h"
+#include "basics.h"
+
+// =============================================================================
+// =============================================================================
+class DocumentViewer : public QDialog
+{
+	public:
+		explicit DocumentViewer (QWidget* parent = null, Qt::WindowFlags f = 0) : QDialog (parent, f)
+		{
+			te_text = new QTextEdit (this);
+			te_text->setMinimumSize (QSize (400, 300));
+			te_text->setReadOnly (true);
+
+			QDialogButtonBox* bbx_buttons = new QDialogButtonBox (QDialogButtonBox::Close);
+			QVBoxLayout* layout = new QVBoxLayout (this);
+			layout->addWidget (te_text);
+			layout->addWidget (bbx_buttons);
+
+			connect (bbx_buttons, SIGNAL (rejected()), this, SLOT (reject()));
+		}
+
+		void setText (const char* text)
+		{
+			te_text->setText (text);
+		}
+
+	private:
+		QTextEdit* te_text;
+};
+
+const char* g_docs_overlays =
+	"<h1>Overlay images</h1><br />"
+	"<p>" APPNAME " supports drawing transparent images over the part model. This "
+	"can be used to have, for instance, a photo of the part overlaid on top of the "
+	"model and use it for drawing curves somewhat accurately.</p>"
+	"<p>For this purpose, a specific photo has to be taken of the part; it should "
+	"represent the part as true as possible to the actual camera used for editing. "
+	"The image should be taken from straight above the part, at as an orthogonal "
+	"angle as possible. It is recommended to take a lot of pictures this way and "
+	"select the best candidate.</p>"
+	"<p>The image should then be cropped with the knowledge of the image's LDU "
+	"dimensions in mind. The offset should then be identified in the image in pixels.</p>"
+	"<p>Finally, use the \"Set Overlay Image\" dialog and fill in the details. The "
+	"overlay image should then be ready for use.";
+
+// =============================================================================
+// =============================================================================
+void showDocumentation (const char* text)
+{
+	DocumentViewer dlg;
+	dlg.setText (text);
+	dlg.exec();
+}