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41 lines
2.1 KiB
Plaintext
41 lines
2.1 KiB
Plaintext
chapter.of: UI and Rendering Pipeline
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created: 20140717174120958
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modified: 20140717202324456
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sub.num: 2
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tags: doc
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title: Parser
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The first stage of WikiText processing is the parser.
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A Parser is provided by a module with ``module-type: parser`` and is responsible to transform block of text to a parse-tree.
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The parse-tree consists of nested nodes like
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```js
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{type: "element", tag: <string>, attributes: {}, children: []} - an HTML element
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{type: "text", text: <string>} - a text node
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{type: "entity", entity: <string>} - an HTML entity like © for a copyright symbol
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{type: "raw", html: <string>} - raw HTML
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```
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The core plug-in provides a recursive descent WikiText parser which loads it's individual rules from individual modules.
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Thus a developer can provide additional rules by using ``module-type: wikirule``. Each rule can produce a list of parse-tree nodes.
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A simple example for a wikirule producing a ``<hr>`` from ``---`` can be found in [[horizrule.js|$:/core/modules/parsers/wikiparser/rules/horizrule.js]]
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HTML tags can be embedded into WikiText because of the [[html rule|$:/core/modules/parsers/wikiparser/rules/html.js]].
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This rule matches HTML tag syntax and creates ``type: "element"`` nodes.
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But the html-rule has another special purpose. By parsing the HTML tag syntax it implicitly parses WikiText widgets.
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It the recognises them by the $ character at the beginning of the tag name and instead of producing "element" nodes
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it uses the tag name for the type:
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```js
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{type: "list", tag: "$list", attributes: {}, children: []} - a list element
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```
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The [[Widgets]] part will reveal why this makes sense and how each node is transformed into a widget.
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Another special characteristic of the html-rule or the parse nodes in general is the attributes property.
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Attributes in the parse-tree are not stored as simple strings but they are nodes of its own to make indirect text references available as attributes as described in [[Widgets]]:
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```js
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{type: "string", value: <string>} - literal string
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{type: "indirect", textReference: <textReference>} - indirect through a text reference
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```
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