Tutorial 13: Display Filters
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Contents: Display Filters Filter Scope
Adding & Removing Filters Editing Filters
Common Filter Features Global Filter Data
Author Notes Saving & Loading Filters
Summary
What are Display Filters? Display filters modify the way in which articles are displayed in the group window's article view area. The original article is not modified in any way, only its presentation is affected. Display filters might do things such as trim excess quoted text, colorize various aspects of an article, hide unwanted header fields, and so on. It's possible to make display filters group specific, or to apply them to any subset of groups, such as "comp.*".

Display filters can also modify text streams when saving articles to disk files, printing article text, or generating replies to other people's articles. For example, a filter might remove a large UUencoded block of data in a post that you are replying to.

This section of the documentation discusses general display filter topics. The specifics of each different type of filter are covered in the reference section of this documentation.

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Filter Scope Filters can be defined within the context of a particular group, in which case they apply only to that group, or they can be defined globally to apply to groups matching any particular pattern (set in the Group Patt area of the filter list). Global filters are defined in the configuration editor for NewsRog. Group specific filters are defined from within the group reader window. Generally, if a filter is to apply to more than one group (for example, to comp.*) it is best to define it once in the configuration editor instead of duplicating the filter in each group.

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Adding and Deleting Filters In each filter list there is an Add button that, when pressed, will display a popup list of available filters. Filters are plug-ins, so the list may change depending on which filters are currently installed. The popup filter list looks like this:

A filter may be added by double clicking on it's name in the popup list. You may insert multiple filters at once by drag-selecting several and clicking the Insert Selected button. The list may be closed without adding a filter by clicking the Close button.

Removing filters is a simple matter of selecting those to be removed and using the Delete button.

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Editing Filters Each filter provides a user interface for customizing its operation. For example, a quoted text hilighting filter might let you chose the font and color for text of different quoted indent levels, while a header hiding filter might let you specify a pattern indicating which headers to hide and which to show.

The user interface for any filter may be called up by either double clicking on the name of the filter in the filter list, or by using the Edit button. The user interface for each filter is described in detail in the reference section of this documentation.

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Common Filter Features Certain information is available in every type of display filter. Calling up the editor for a particular filter reveals three main click tabs:

  • Filter Settings - This is where you edit information specific to this particular filter. What appears here will differ depending on the type of filter in question, and the specifics for each filter type is documented in the reference section of this documentation.

  • Global Info - This area edits data common to all types of filters, such as the filter's description.

  • Author Note - This area can be used to edit a longer description for this filter, useful for complex filters that you wish to share with other people.

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    Global Info The global info area looks like this:

    The following features are available here:

    • The filter description is any short string that will remind you of the purpose of this filter. Filters can be toggled on and off individually to change the presentation of articles in the group, and this name can serve to remind you what a particular filter does.

    • The Enable checkbox toggles this filter on or off. Filters that are not enabled have no effect on the displayed article presentation.

    • The Printing checkbox is only present on filters that can modify text streams. This filter will be used to modify article text sent to the printer only if this box is checked.

    • The Saving checkbox is only present on filters that can modify text streams. This filter will be used to modify article text saved to disk files only if this box is checked.

    • The Replies checkbox is only present on filters that can modify text streams. This filter will be used to modify article text used in formulating replies to other people's articles.

    • The Toolbar Button option allows you to define a graphic file which will be used to create a toolbar button for this filter. This toolbar button appears in the Group Window, near the article view area, and clicking a filter's icon will toggle that filter on or off and update the currently displayed article accordingly.

    The filter description may also be changed by typing into the name box in a filter list when a particular filter is selected. The Enabled option may be toggled on and off from the filter list by clicking in the appropriate column of the list.

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    Author Notes The use of the Author Note field is the same as in Selection Filters. Please see that documentation for more details.

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    Saving & Loading Filters Display filters can be saved and loaded in a manner identical to Selection Filters. Please see that documentation for more details.

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    Summary By this point in the tutorial you should understand:

    • What display filters are.
    • That display filters change only the presentation of articles, not the article itself.
    • What filter scope refers to, and the difference between global and group specific filters.
    • How to add and remove filters.
    • How to edit a particular filter's parameters.
    • How to change a filter's description.
    • How to enable and disable filters.
    • How to save and load groups of filters to disk files.
    • How and when filters modify articles sent to the printer, saved to disk files, or used in formulating replies.

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