[graphic-properties] Proposal: hint for complex content

1. RATIONALE 1.1 Use cases: Currently a number of ODF implementations expect that the text content of a shape (e.g. <draw:custom-shape>) is simple: it does not contain tables, inline images, table of contents, etc. Help improving these implementations by writing a new boolean attribute inside <style:graphic-properties> to hint if the shape will have such complex content or not. If ODF implementations that previously assumed simple content can get a hint that the content will be complex, then they have a chance to use a more capable rendering engine for the complex content. 1.2 Alternatives considered: Right now it's already valid to write e.g. <draw:frame ... text:anchor-type="as-char" ...> inside <text > inside <draw:custom-shape> (inline picture in shape text), but a number of ODF readers don't expect that. They have to use heuristics to find out if the content is complex or not, in case they have different rendering engines for simple and complex content. 2. REQUESTED CHANGES TO THE ODF STANDARD 2.1 Text changes/additions: In section 17.21 <style:graphic-properties> append to the end of "has the following attributes": style:complex-content 20.x: style:complex-content (new section) The <style:complex-content> attribute gives a hint if the text of the shape (if there is any) is complex or not. 2.2 Schema changes/additions: See attached patch. 3. IMPACTS 3.1 Conformance: This proposal will not add any mandatory features or behaviors. 3.2 Backwards compatibility: This attribute was not used in previous versions and is optional. Existing ODF processors may ignore it. 3.3 Accessibility impact: None.