gv 3.5, June 1997: Comments about the user interface

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## 6. Comments about the user interface

Scales

  The "Scale" menu which allows to view the document at different sizes is divided into two parts. The first part shows a list of available scale bases, the second part, separated by a line, lists the relative scales which are applied with respect to the selected scale base.

  By default two scales bases are available, the "Natural size" and the "Pixel based" base. When choosing the "Pixel based" scale base a relative scale of 1.0 causes one postscript point to correspond to one pixel on the screen.

  When viewing a document at a relative scale of 1.0 using the "Natural size" base the page should appear in its real size, as if printed on paper. For the "Natural size" base to work properly gv has to know the correct size of the root window. Automatic detection of this size unfortunately only provides approximate results, therefore it is best if it is provided by the user. To do so the resource

         GV.screenSize:  <width> x <height>

  should be added to the "SCREEN_RESOURCES" property of the screen the document is viewed on, with <width> and <height> describing the width and height of the root window in units of millimeters. For instance by using the command

         echo "GV.screenSize: 396 x 291" | xrdb -override -screen

  a width of 346 mm and a height of 291 mm will be used for the "Natural size" scale base. Alternatively the resource

         GV.screenSize_<machine>_<disp>_<scr>:  <width> x <height>

  may be added to a resource file read by gv. Here <machine> ,<disp> and ANGLED) describe the display on which gv displays the document. For instance, if the display is set to "tic.tac.toe.wo:0.1" the resource should be specified as

         GV.screenSize_tic_0_1: 396 x 291

  Note that this method doesn't work on VMS. As a last alternative the resource

         GV.screenSize:  <width> x <height>

  may be added to one of the resource files. However, for obvious reasons this method should be used only on single user machines.
Scrolling

  It is probably a de facto standard for user interfaces that windows are supposed to be scrolled by means of scrollbars attached to their sides. However, for various reasons the use of scrollbars has been minimized in gv.

  Instead, in all windows with obscured data, scrolling may be performed by

  > pressing button1, moving the mouse, then releasing button1

  directly in the window. This includes the displayed page, zoom popups, the table of contents and the file and directory lists displayed in the file selection popup.
Displaying new versions of a document

  During document creation it is usually desirable to always display the newest version of the document in work.

  Instead of explicitly loading it via the file selection popup the most recent version can be displayed by pressing the "Redisplay" button in the main window (VMS users should use the "Update File" entry in the "File" menu). Choosing the "Redisplay" entry in the menu that pops up when clicking with the third mouse button anywhere on the displayed page certainly has the same effect.

  More comfortable is the "Watch File" feature which may be switched on by selecting the corresponding entry in the "State" menu. If activated gv will check every now and then if a new version of the displayed file exists. If so it will be displayed automatically. By default the file is checked about once every second.

  Finally it may also be left to the document creating program to trigger gv to update its display. To do so the program should send the SIGHUP signal to gv. For instance at the end of a shell script generating a postscript file from latex sources the line

         kill -SIGHUP <gv_pid>

  may be added (here `<gv_pid>` is the process id of gv). Executing the script and thereby creating a new version of the document will then also cause the result to be displayed instantaneously. Please note that this feature is available only on X11 R6 based systems.

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