Show alt text instead of the missing image in the Markdown code

generators/markdown/converter.cpp

@@ -186,23 +186,29 @@ void Converter::convertImages(const QTextBlock &parent, const QDir &dir, QTextDo
         if (textFragment.isValid()) {
             const QTextCharFormat textCharFormat = textFragment.charFormat();
             if (textCharFormat.isImageFormat()) {
-                // TODO: Show images from http URIs
-
                 QTextImageFormat format;
 
                 const qreal specifiedHeight = textCharFormat.toImageFormat().height();
                 const qreal specifiedWidth = textCharFormat.toImageFormat().width();
 
-                format.setName(QDir::cleanPath(dir.absoluteFilePath(textCharFormat.toImageFormat().name())));
-                const QImage img = QImage(format.name());
-
-                setImageSize(format, specifiedWidth, specifiedHeight, img.width(), img.height());
-
                 QTextCursor cursor(textDocument);
                 cursor.setPosition(textFragment.position(), QTextCursor::MoveAnchor);
                 cursor.setPosition(textFragment.position() + textFragment.length(), QTextCursor::KeepAnchor);
                 cursor.removeSelectedText();
-                cursor.insertImage(format);
+
+                const QString imageFilePath = QDir::cleanPath(dir.absoluteFilePath(textCharFormat.toImageFormat().name()));
+                if (QFile::exists(imageFilePath)) {
+                    format.setName(imageFilePath);
+                    const QImage img = QImage(format.name());
+
+                    setImageSize(format, specifiedWidth, specifiedHeight, img.width(), img.height());
+
+                    cursor.insertImage(format);
+#if QT_VERSION >= QT_VERSION_CHECK(5, 14, 0)
+                } else if ((!textCharFormat.toImageFormat().property(QTextFormat::ImageAltText).toString().isEmpty())) {
+                    cursor.insertText(textCharFormat.toImageFormat().property(QTextFormat::ImageAltText).toString());
+#endif
+                }
             }
         }
     }