Working with comments
This topic discusses the Open XML SDK for Office Comment class and how it relates to the Open XML File Format PresentationML schema. For more information about the overall structure of the parts and elements that make up a PresentationML document, see Structure of a PresentationML Document.
Comments in PresentationML
The ISO/IEC 29500 specification describes the Comments section of the Open XML PresentationML framework as follows:
A comment is a text note attached to a slide, with the primary purpose of allowing readers of a presentation to provide feedback to the presentation author. Each comment contains an unformatted text string and information about its author, and is attached to a particular location on a slide. Comments can be visible while editing the presentation, but do not appear when a slide show is given. The displaying application decides when to display comments and determines their visual appearance.
The ISO/IEC 29500 specification describes the Open XML PresentationML <cm> element used to represent comments in a PresentationML document as follows:
This element specifies a single comment attached to a slide. It contains the text of the comment, its position on the slide, and attributes referring to its author and date.
Example:
<p:cm authorId="0" dt="2006-08-28T17:26:44.129" idx="1">
<p:pos x="10" y="10"/>
<p:text\>Add diagram to clarify.</p:text>
</p:cm>
The following table lists the child elements of the <cm > element used when working with comments and the Open XML SDK classes that correspond to them.
| PresentationML Element | Open XML SDK Class |
|---|---|
| <extLst> | ExtensionListWithModification |
| <pos> | Position |
| <text> | Text |
The following table from the ISO/IEC 29500 specification describes the attributes of the <cm> element.
| Attributes | Description |
|---|---|
| authorId | This attribute specifies the author of the comment.It refers to the ID of an author in the comment author list for the document. The possible values for this attribute are defined by the W3C XML Schema unsignedInt datatype. |
| dt | This attribute specifies the date and time this comment was last modified. The possible values for this attribute are defined by the W3C XML Schema datetime datatype. |
| idx | This attribute specifies an identifier for this comment that is unique within a list of all comments by this author in this document. An author's first comment in a document has index 1. Note: Because the index is unique only for the comment author, a document can contain multiple comments with the same index created by different authors. The possible values for this attribute are defined by the ST_Index simple type (ยง19.7.3). |
Open XML SDK Comment Class
The OXML SDK Comment class represents the <cm> element defined in the Open XML File Format schema for PresentationML documents. Use the Comment class to manipulate individual <cm> elements in a PresentationML document.
Classes that represent child elements of the <cm> element and that are therefore commonly associated with the Comment class are shown in the following list.
ExtensionListWithModification Class
The ExtensionListWithModification class corresponds to the <extLst>element. The following information from the ISO/IEC 29500 specification introduces the <extLst> element:
This element specifies the extension list with modification ability within which all future extensions of element type <ext> are defined. The extension list along with corresponding future extensions is used to extend the storage capabilities of the PresentationML framework. This allows for various new kinds of data to be stored natively within the framework.
Note
Using this extLst element allows the generating application to store whether this extension property has been modified. end note
Position Class
The Position class corresponds to the <pos>element. The following information from the ISO/IEC 29500 specification introduces the <pos> element:
This element specifies the positioning information for the placement of a comment on a slide surface. In LTR versions of the generating application, this position information should refer to the upper left point of the comment shape. In RTL versions of the generating application, this position information should refer to the upper right point of the comment shape.
[Note: The anchoring point on the slide surface is unaffected by a right-to-left or left-to-right layout change. That is the anchoring point remains the same for all language versions. end note]
[Note: Because there is no specified size or formatting for comments, this UI widget used to display a comment can be any size and thus the lower right point of the comment shape is determined by how the viewing application chooses to display comments. end note]
[Example: <p:pos x="1426" y="660"/> end example]
Text class
The Text class corresponds to the <text>element. The following information from the ISO/IEC 29500 specification introduces the <text> element:
This element specifies the content of a comment. This is the text with which the author has annotated the slide.
The possible values for this element are defined by the W3C XML Schema string datatype.
Working with the Comment Class
A comment is a text note attached to a slide, with the primary purpose of enabling readers of a presentation to provide feedback to the presentation author. Each comment contains an unformatted text string and information about its author and is attached to a particular location on a slide. Comments can be visible while editing the presentation, but do not appear when a slide show is given. The displaying application decides when to display comments and determines their visual appearance.
As shown in the Open XML SDK code sample that follows, every instance of the Comment class is associated with an instance of the SlideCommentsPart class, which represents a slide comments part, one of the parts of a PresentationML presentation file package, and a part that is required for each slide in a presentation file that contains comments. Each Comment class instance is also associated with an instance of the CommentAuthor class, which is in turn associated with a similarly named presentation part, represented by the CommentAuthorsPart class. Comment authors for a presentation are specified in a comment author list, represented by the CommentAuthorList class, while comments for each slide are listed in a comments list for that slide, represented by the CommentList class.
The Comment class, which represents the <cm> element, is therefore also associated with other classes that represent the child elements of the <cm> element. Among these classes, as shown in the following code sample, are the Position class, which specifies the position of the comment relative to the slide, and the Text class, which specifies the text content of the comment.
Open XML SDK Code Example
The following code segment from the article How to: Add a comment to a slide in a presentation adds a new comments part to an existing slide in a presentation (if the slide does not already contain comments) and creates an instance of an Open XML SDK Comment class in the slide comments part. It also adds a comment list to the comments part by creating an instance of the CommentList class, if one does not already exist; assigns an ID to the comment; and then adds a comment to the comment list by creating an instance of the Comment class, assigning the required attribute values. In addition, it creates instances of the Position and Text classes associated with the new Comment class instance. For the complete code sample, see the aforementioned article.
// Declare a comments part.
SlideCommentsPart commentsPart;
// Verify that there is a comments part in the first slide part.
if (slidePart1.GetPartsOfType<SlideCommentsPart>().Count() == 0)
{
// If not, add a new comments part.
commentsPart = slidePart1.AddNewPart<SlideCommentsPart>();
}
else
{
// Else, use the first comments part in the slide part.
commentsPart = slidePart1.GetPartsOfType<SlideCommentsPart>().First();
}
// If the comment list does not exist.
if (commentsPart.CommentList is null)
{
// Add a new comments list.
commentsPart.CommentList = new CommentList();
}
// Get the new comment ID.
uint commentIdx = author.LastIndex is null ? 1 : author.LastIndex + 1;
author.LastIndex = commentIdx;
// Add a new comment.
Comment comment = commentsPart.CommentList.AppendChild<Comment>(
new Comment()
{
AuthorId = authorId,
Index = commentIdx,
DateTime = DateTime.Now
});
// Add the position child node to the comment element.
comment.Append(
new Position() { X = 100, Y = 200 },
new Text() { Text = text });