Under Windows, the help viewer and HTML-based info windows use a Microsoft technology called OLE (Object Linking and Embedding) and the Internet Explorer HTML viewer. It actually uses the internals of Internet Explorer to do the HTML rendering. This requires that Internet Explorer 4.0 or newer be installed. Although this technology is admittedly rather nifty, it has rather amazing internal complexity, and when all is said and done, sad and severe limitations. Although the basic functionality is provided, many of the more advanced/obscure features found in the Unix/Linux help system are missing.
If the boolean variable NoHelpDefault is set (with the !set command), pressing the Help button will not bring up the default top-level window. However, clicking on objects and buttons will bring up help topics as usual.
Clicking on a colored HTML reference will bring up the text of the selected topic. If button 1 is used to click, the text will appear in the same window. If button 2 is used to click, a new help window containing the selected topic will appear.
The help system operates in one of two modes. The default mode is to use a single window for each new topic generated by pressing a command or menu button. In the multi-window implementation, which can be selected in Xic by setting the boolean variable HelpMultiWin with the !set command, a separate window is brought up for each press of a command button or menu item while in help mode. In either case, clicking on a link may or may not produce a new window, depending upon whether button 1 or button 2 was clicked.
Text shown in the viewer that is not part of an image can be selected by dragging with button 1, and can be pasted into other windows in the usual way.
The viewer can be used to display any text file or URL. The name given to the !help command, or to to the Open command in the viewer's File menu, can be
If the given name can be resolved, the resulting text will be displayed in the viewer. Also, the HTML viewer is sensitive as a drop receiver. If a file name or URL is dragged into the viewer and dropped, that file or URL is read into the viewer, after confirmation.
The ability to access general URLs should be convenient for accessing information from the Internet while using Xic. The prefix ``http://'' must be provided with the URL. Thus, for example,
!help http://www.wrcad.comwill bring up the Whiteley Research web page. The links can be followed by clicking in the usual way. Of course, the computer must have Internet access for web pages to be accessible.
The URL given in the Open command or through the !help command is not relative to the current page, however if a `+' is given before the URL, it will be treated as relative. For example, if the viewer is currently displaying http://www.foo.bar, if one enters ``/dir/file.html'', the display will be updated to /dir/file.html on the local machine. If instead one enters ``+/dir/file.html'', the display will be loaded with http://www.foo.bar/dir/file.html.
The HTTP capability imposes some obvious limitations on the string tokens which can be used in the help database. These keywords should not use the `/' character, or begin with a protocol specifier such as ``http:''.
HTML files on a local machine can be loaded by giving the full path name to the file. Relative references will be found. HTML files will also be found if they are located in the help path, however relative references will be found only if the referenced file is also in the help path. If a directory is referenced rather than a file, a formatted list of the files in the directory is shown.
If a filename passed to the viewer has one of the following extensions, the text is shown verbatim. The (case insensitive) extensions for plain-text files are ``.txt'', ``.doc'', ``.log'', ``.scr'', ``.sh'', ``.c'', ``.cc'', and ``.h''.
Holding Shift while clicking on an anchor that points to a URL which specifies a file on a remote system will download the file, as in Netscape. Downloading makes use of the httpget utility program available in the Accessories distribution. Installation of the accessories is required for downloading to be available under Unix/Linux. References to files with extensions ``.rpm'', ``.gz'', and other common binary file suffixes will automatically cause downloading rather than viewing. When downloading, the file selection pop-up will appear, pre-loaded with the file name (or ``http_return'' if the name is not known) in the current directory. One can change the saved name and the directory of the file to be downloaded. Pressing the Download button will start downloading. A pop-up will appear that monitors the transfer, which can be aborted with the Cancel button.