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Eclipse Plug-in Developer Guide
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Parsing formatting markup

The most powerful use of the FormText control is when formatting tags are added to the text. The expected root tag is form. It can have one or more children that can either be <p> or <li>. Either of these can have normal text, text between <b> or <span> tags, images, links and SWT controls. Images are declared using <img href="image key"/> (no content), while links are expressed using <a href="href">text</a>.

Some of the tags mentioned above have additional attributes. Tag <a> can accept nowrap="true" to block the link from being wrapped into the new line. Tag <p> can have attribute vspace="false" (true by default) that adds additional space between paragraphs. Tag <li> has more attributes:

  • style - can be text, bullet and image (default is bullet)

  • value - not used for bullet; if style is text, the value will be rendered instead in place of a bullet; if style is image, value represents a key in the image table of an image to be rendered in place of a bullet

  • vspace - the same as for the 'p' tag.

  • indent - the number of pixels to indent text

  • bindent - the number of pixels to indent the bullet (this number is independent from 'indent' - be careful not to overlap them)

Tags that affect appearance of the normal text are <b> (works as expected), and <span>. The later allows you to change font and/or color of the text within the tag. Soft line breaks can be added using <br/> tag. The text is parsed as XML, this means that there must be an end tag for each element so you cannot use open <br> as in HTML). The XML entity &amp; is recognized and replaced with &, and it is required that ampersand (&) characters which are not part of an entity declaration be represented as &amp;. Numeric entities may also be used in formatted text.

Since release 3.1, FormText can be used to mix SWT widgets inside text, hyperlinks and images. SWT controls are created as children of FormText, which makes FormText a layout manager of a sort, with instruction on where to place the control relative to text embedded directly in the XML.

One common theme that can be observed is that FormText is not responsible for loading images, fonts, resolving links or colors. This is not a browser and it is much better to separate concerns and simply assign images and colors managed elsewhere. Both links and images simply have 'href' attribute to reference them. For links, the value of this attribute will be provided in the hyperlink event when listeners are notified. Images need to be registered with the text control using the matching 'href' key. This way, the control does not need to worry about loading the images - it has them in the hash table and can render them immediately.

Similar approach has been used for colors and fonts. Colors are already handled by the toolkit, so you can allocate as many as you want using a unique key and RGB values by calling toolkit.getColors().createColor(). What is left is to set all the colors referenced in the 'span' tag so that the control will be able to use them during rendering.


 
 
  Published under the terms of the Eclipse Public License Version 1.0 ("EPL") Design by Interspire