MText support #238
Description
MText import and export is currently broken under netDXF. In an AutoCAD MText entity, the line break is represented by \P. In ImportDXF.cs, the MText value is being retrieved with the PlainText() method which strips the special characters specific to MText style overrides and replaces \P with a standard \r\n line termination.
In ExportDXF.cs, Text GeoObjects are being exported with the line termination intact, creating an invalid DXF. In the below attached example, the text entity will look like this:
AcDbText
1
100932
-02
10
0.1587455459
Where -02 is the second line of the text string but is being interpreted as an invalid group code, causing AutoCAD to fail to open the file.
I have a PR to replace newlines with spaces during export. There's not really a great universal fix to this without a much larger change to somehow support exporting MText entities. I can't think of a good solution off the top of my head. Import could be handled by arranging a list of text objects based on the text height and upward vector of the text which I've done in previous CAD plugins, but I don't know how to maintain their association for export without multi-line support in the Text GeoObject.
Another option is to preserve the newlines on import as-is, then export conditionally as MText when a newline character is found, replacing it with \P, however the interim Text GeoObject will still have no support for the newline while within CADAbility.