https://bugs.documentfoundation.org/show_bug.cgi?id=164627
Bug ID: 164627
Summary: docx export: Drop VML XML_fallback for compat14+
documents
Product: LibreOffice
Version: unspecified
Hardware: All
OS: All
Status: UNCONFIRMED
Keywords: filter:docx
Severity: enhancement
Priority: lowest
Component: Writer
Assignee: [email protected]
Reporter: [email protected]
CC: [email protected]
Blocks: 104442, 131304
DOCX specifies two different "shape" markup languages. VML was the first one
introduced when DOCX was announced for Word 2007. But Word 2010 defined DML and
that has been preferred ever since.
So Word and LO have been writing the following ever since:
<mc:AlternateContent>
<mc:Choice Requires="wps">
<!-- DML content -->
</mc:Choice>
<mc:Fallback>
<!-- VML content -->
</mc:Fallback>
</mc:AlternateContent>
Since LibreOffice has basically always supported DML (since at least 2014), it
always uses that Choice (so our VML import code is rarely exercised, tested,
and therefore is not very good quality).
MS Word of course also uses the DML definition whenever possible.
Since only Word 2007 cannot handle DML, and since Word 2007, 2010, and 2013
(and almost Word 2016) are all end of life, I don't see much value in providing
the VML Fallback content any more. I propose that it should not be written by
default. (The user should be able to control this via a config setting. It also
should be written for any compat12 documents/when writing specifically to Word
2007 format).
The two benefits will probably be minor/insignificant.
-smaller file size
-faster export time
A LO presentation about this topic by Rohit Deshmukh is at
https://prezi.com/vyfyzm_qgmhp/introduction-to-vml-and-dml/
Alternate content
Alternate content is used for adding both VML and DML in office 2010
Alternate content has two parts
Choice : Used in Ms office 2010
Fallback : Used in MS office 2007
VML TO DML in LO
LO import only Choice part (i.e. DML) from alternate content and ignore VML
part
Per the Ecma spec: “VML should be considered a deprecated format included
in Office Open XML for legacy reasons only.”
VML was not entirely replaced by DrawingML before submission to Ecma
Main remaining uses of VML:
WordprocessingML: OfficeArt shapes, textboxes
SpreadsheetML/PresentationML: comments, embedded OLE objects
Referenced Bugs:
https://bugs.documentfoundation.org/show_bug.cgi?id=104442
[Bug 104442] [META] OOXML shape (DrawingML and VML) related issues
https://bugs.documentfoundation.org/show_bug.cgi?id=131304
[Bug 131304] [META] MS Word compatibilityMode = 15
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