XScreenSaver

            a screen saver and locker for the X window system
                            by Jamie Zawinski

                              version 5.42
                               28-Dec-2018

                     https://www.jwz.org/xscreensaver/

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This directory contains XML files that describe each of the screenhacks;
the per-hack user interface is constructed based on the things in these
files.  The files are loaded at run-time by xscreensaver-demo (also
known as "the Control Center screensaver properties capplet".)

The tags and parameters used here are:

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  <screensaver name="PROGRAM-NAME" _label="PRETTY NAME">
     ...
  </screensaver>

        This encloses the whole file: all of the tags described below
        are inside this one.

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  <command arg="-SWITCH"/>

        specifies that "-SWITCH" always appears on the command line.
        You'll most often see this with "-root".

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  <boolean id="SYMBOLIC NAME"
           _label="USER VISIBLE STRING"
            arg-set="-SWITCH-A"
            arg-unset="-SWITCH-B"
           />

        This creates a checkbox.

        "id" is currently unused, but may eventually be used for
        letting other widgets refer to this one.

        "_label" is the string printed next to the checkbox.

        "arg-set" is what to insert into the command line if the
        box is checked.

        "arg-unset" is what to insert into the command line if the
        box is unchecked.

        You will probably never specify both "arg-set" and "arg-unset",
        because the setting that is the default should insert nothing
        into the command line (that's what makes it the default.)
        For example:

           <boolean _label="foo" arg-set="-foo" />

        or if "foo" is the default, and must be explicity turned off,

           <boolean _label="foo" arg-unset="-no-foo" />

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  <number id="SYMBOLIC NAME"
          type="slider"
          arg="-SWITCH %"
          _label="HEADING LABEL"
          _low-label="LEFT LABEL"
          _high-label="RIGHT LABEL"
          low="MIN VALUE"
          high="MAX VALUE"
          default="DEFAULT VALUE"
          [ convert="invert" ]
          />

        This creates a slider.

        The _label is printed above the slider.  The _low-label and
        _high-label are printed to the left and right, respectively.

        If any of the numbers you type has a decimal point, then
        the range is assumed to be a floating-point value; otherwise,
        only integral values will be used.  So be careful about "1"
        versus "1.0".

        If convert="invert" is specified, then the value that the
        user tweaks goes the other way from the value the command
        line expects: e.g., if the slider goes from 10-20 and the
        user picks 13, the converted value goes from 20-10 (and
        would be 17.)  This is useful for converting between the
        concepts of "delay" and "speed".

        In the "arg" string, the first occurence of "%" is replaced
        with the numeric value, when creating the command line.

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  <number id="SYMBOLIC NAME"
          type="spinbutton"
          arg="-SWITCH %"
          _label="HEADING LABEL"
          low="MIN VALUE"
          high="MAX VALUE"
          default="DEFAULT VALUE"
          [ convert="invert" ]
          />

        This creates a spinbox (a text field with a number in it,
        and up/down arrows next to it.)

        Arguments are exactly like type="slider", except that
        _low-label and _high-label are not used.  Also, _label
        appears to the left of the box, instead of above it.

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  <select id="SYMBOLIC NAME">
    <option id="SYMBOLIC NAME"
            _label="USER VISIBLE STRING"
            arg-set="-SWITCH"
            />
    [ ... more <options> ... ]
  </select>

        This creates a selection popup menu.

        Options should have arg-set (arg-unset is not used here.)

        One of the menu items (the default) should have no arg-set.

        Each arg-set should begin with the same switch: that is,
        all the args in a given menu should look like:

           -mode one
           -mode two
           -mode three

        and not

           -this
           -that
           -the other

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  <string id="SYMBOLIC NAME"
           _label="USER VISIBLE STRING"
           arg="-SWITCH %"
           />

        This creates a text entry field.

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  <file id="SYMBOLIC NAME"
        _label="USER VISIBLE STRING"
        arg="-SWITCH %"
        />

        This creates a file entry field (a text field with a "Browse"
        button next to it.)

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  <xscreensaver-text />

        This indicates that this screen saver displays text via the
        "xscreensaver-text" program.  

        In the X11 version, this tag does nothing: the text-related
        preferences are in the main Screen Saver Preferences window,
        not in the per-display-mode preferences.

        In the MacOS version, the text-related preferences appear
        in this pane, and this tag emits those several controls.

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  <xscreensaver-image />

        This indicates that this screen saver displays images via the
        "xscreensaver-getimage" program.  

        In the X11 version, this tag does nothing: the image-loading
        and screen-grabbing-related preferences are in the main
        Screen Saver Preferences window, not in the per-display-mode
        preferences.

        In the MacOS version, the image-related preferences appear
        in this pane, and this tag emits those several controls.

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  <xscreensaver-updater />

        Where to position the "Check for Updates" options.
        This is used on MacOS and ignored on X11.

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  <video href="URL" />

        A link to a Youtube preview of this screen saver.

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  <hgroup>
    [ ... <boolean>s ... ]
    [ ... <number>s ... ]
    [ ... <select>s ... ]
    [ ... <string>s ... ]
    [ ... <file>s ... ]
    [ ... <vgroup>s ... ]
  </hgroup>

        A horizontal group of widgets/groups.  No more than 4 widgets 
        or groups should be used in a row.

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  <vgroup>
    [ ... <boolean>s ... ]
    [ ... <number>s ... ]
    [ ... <select>s ... ]
    [ ... <string>s ... ]
    [ ... <file>s ... ]
    [ ... <hgroup>s ... ]
  </vgroup>

        A vertical group of widgets/groups.  No more than 10 widgets 
        or groups should be used in a column.
        
        Since the default alignment of widgets is a column, the 
        <vgroup> element is only of use inside an <hgroup> element.

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  <_description>
        FREE TEXT
  </_description>

        This is the description of the hack that appears in the right
        part of the window.  Lines are wrapped; paragraphs are separated
        by blank lines.  Lines that begin with whitespace will not be
        wrapped (see "munch.xml" for an example of why.)

        Make sure you use "&lt;" instead of "<", etc.  Character
        entities are allowed; HTML (and other markup) is not.

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If you are DTD-minded, you may also find the included files "xss.dtd"
and "xss.xsd" useful.

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