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area [2014/09/16 14:26] (current)
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 +===== The <area> Element =====
 +==== Definition and Usage ====
 +
 +The [[area|<area>]] element allows for defining a content anchor (a subset of
 +information units of a [[media|<media>]] element's content) that may be used in
 +relationships with other objects in an NCL application.
 +
 +Content anchors may represent:
 +
 +  * spatial portions of images: through the //coords// attribute;
 +  * temporal portions of continuous media content (audio, video, etc.):
 +    through the //begin// and //end// attributes, or based on the
 +    number of audio samples or video frames, through the //first// and
 +    //last// attributes, which indicate the initial and final
 +    sample/frame;
 +  * temporal and spatial portions of videos: through the //coords//,
 +    //begin//, and //end// attributes; or through the
 +    //coords//, //first//, and //last// attributes;
 +  * textual segments: through the //beginText//, //beginPosition//,
 +    //endText//, and //endPosition// attributes, that define the
 +    beginning and end strings, and their occurrence in the text
 +    respectively;
 +  * a string that is used by the media player to identify a content region
 +    (for example, a function or method in an imperative media object, an
 +    interface in a declarative media object, like an HTML anchor, a port in
 +    a media object with an NCL application as a content, etc.): through the
 +    //label// attribute;
 +  * a clip in the content of a declarative hypermedia object: using the
 +    //clip // attribute.
 +
 +Every [[media|<media>]], [[context|<context>]], [[body|<body>]], and [[switch|<switch>]] element
 +has a content anchor with a region representing the whole content of the
 +node defined by default.  This anchor is called "whole content anchor".
 +Except for media objects with imperative code content (for example, those
 +whose MIME type is "application/x-ncl-NCLua"), every time an NCL component
 +is referred without specifying one of its anchors, the whole content anchor
 +is assumed.
 +
 +==== Syntax ====
 +^ Element ^ Attributes ^ Content ^ Parent ^
 +| [[area|<area>]] | __//id//__, //coords//, //begin//, //end//, //beginText//, //endText//, //beginPosition//, //endPosition//, //first//, //last//, //label//, //clip// | -- | [[media|<media>]] |
 +==== Attributes ====
 +
 +^ Name ^ Value ^ Description ^
 +| //id// | It may receive any string value that begins with a letter or an underscore and that only contains letters, digits, <".">, and <"_">. | The //id// attribute uniquely identifies the element within a document. |
 +| //coords// | <html><p></html>A list of values of the form "left-x, top-y, right-x, bottom-y" where each value is either:<html></p></html><html><ol></html><html><li class="level1"><div class="li"></html>a real number in the range [0,100] ending with the character <"%"> (e.g. "30%"), or<html></div></li></html><html><li class="level1"><div class="li"></html>a positive integer specifying the value in pixels. For pixel values, the "px" unit qualifier may be omitted.<html></div></li></html><html></ol></html> | <html><p></html>The //coords// attribute specifies the position of a rectangular area on the screen.<html></p></html><html><p></html>Coordinates are relative to the top, left corner of the object content.<html></p></html><html><p></html>The values are separated by commas.<html></p></html><html><p></html>The order of values is "left-x", "top-y", "right-x", and "bottom-y".<html></p></html><html><p></html>When the "left-x" and "right-x" are expressed as a percentage, the value is relative to the width property of the media object.<html></p></html><html><p></html>When the "top-y" and "bottom-y" are expressed as a percentage, the value is relative to the height property of the media object.<html></p></html> |
 +| //begin// | <html><p></html>Except for the [[media|<media>]] element of the "application/x-ncl-time" type, the //begin// attribute shall be specified according with one of the following syntax:<html></p></html><html><ol></html><html><li class="level1"><div class="li"></html><"<nowiki>Hours:Minutes:Seconds.Fraction</nowiki>">, where "Hours" is an integer in the [0,23] interval, "Minutes" is an integer in the [0,59] interval, "Seconds" is an integer in the 0,59 interval, and "Fraction" is a positive integer,<html></div></li></html><html><li class="level1"><div class="li"></html>Seconds<"s">, where "Seconds" is a positive real number.<html></div></li></html><html></ol></html><html><p></html>For the [[media|<media>]] element of the "application/x-ncl-time" type, the //begin// attribute shall be specified according with the following syntax: <"<nowiki>Year:Month:Day:Hours:Minutes:Seconds.Fraction</nowiki>">, according to the country time zone. The NCL user agent is responsible for translating the value for the country time zone to the one corresponding to the UTC.<html></p></html><html><p></html>If the //end// attribute is defined, but without an explicit definition for the //begin// attribute, the start of the whole media content presentation shall be considered as the anchor beginning.<html></p></html><html><p></html>In the case of a media element of the "application/x-ncl-time" type, the //begin// attribute must always be defined and it assumes an absolute UTC value.<html></p></html> | The //begin// attribute specifies the beginning of the temporal anchor. |
 +| //end// | Same as for //begin//. | The //end// attribute specifies the end of the temporal anchor. |
 +| //beginText// | <html><p></html>String.<html></p></html><html><p></html>If the beginning of the content anchor region is not defined, the beginning of the text content is assumed.<html></p></html> | The //beginText// and //beginPosition// attributes specifies the beginning of the text anchor. The //beginText// defines a string in the text. |
 +| //endText// | String. | The //endText// and //endPosition// attributes specifies the end of the text anchor. The //endText// defines a string in the text. |
 +| //beginPosition// | Positive integer.  The default value is 1. | The //beginText// and //beginPosition// attributes specifies the beginning of the text anchor. The //beginPosition// defines the occurrence of the string in the text. |
 +| //endPosition// | Positive integer.  The default value is the position of the last character in string. | The //endText// and the //endPosition// attributes specifies the end of the text anchor. The //endPosition// defines the occurrence of the string in the text. |
 +| //first// | <html><p></html>The //first// attribute shall be specified according with one of the following syntax:<html></p></html><html><ol></html><html><li class="level1"><div class="li"></html>Samples<"s">, where Samples is a positive integer,<html></div></li></html><html><li class="level1"><div class="li"></html>Frames<"f">, where Frames is a positive integer, or<html></div></li></html><html><li class="level1"><div class="li"></html>NPT<"npt"> where NPT is the Normal Play Time value.<html></div></li></html><html></ol></html><html><p></html>If the //last// attribute is defined, but without an explicit definition for the //first// attribute, the start of the whole media content presentation shall be considered as the anchor beginning.<html></p></html> | -- |
 +| //last// | <html><p></html>The //last// attribute shall be specified according with one of the following syntax:<html></p></html><html><ol></html><html><li class="level1"><div class="li"></html>Samples<"s">, where Samples is a positive integer,<html></div></li></html><html><li class="level1"><div class="li"></html>Frames<"f">, where Frames is a positive integer, or<html></div></li></html><html><li class="level1"><div class="li"></html>NPT<"npt"> where NPT is the Normal Play Time value.<html></div></li></html><html></ol></html><html><p></html>If the //first// attribute is defined, but the //last// attribute is not specified, the end of the whole media content presentation shall be assumed as the anchor ending.<html></p></html> | -- |
 +| //label// | String. | The //label// attribute identifies a content region, for example, a function in an imperative media object, or an interface in a declarative media object, like an HTML anchor, or a port in a media object with an NCL application as content, etc. |
 +| //clip// | <html><p></html>String.<html></p></html><html><p></html>The value depends on the declarative hypermedia object type. For NCL media objects, the clip value is a triple <"(chainId,beginOffset,endOffset)"> that is used by the NCL media player to identify an NCL application [[port|<port>]] through which a temporal chain begins, and the beginning and the end time in this temporal chain.<html></p></html><html><p></html>For [[media|<media>]] elements with NCL code content the following defaults are defined:<html></p></html><html><ol></html><html><li class="level1"><div class="li"></html>"chainId" is the whole content anchor of the [[body|<body>]] element,<html></div></li></html><html><li class="level1"><div class="li"></html>"beginOffset" is "0s", and<html></div></li></html><html><li class="level1"><div class="li"></html>"endOffset" is the end time of the temporal chain.<html></div></li></html><html></ol></html> | The //clip// identifies a stream clip in the content of a declarative hypermedia object |
 +
 +
 +
  
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