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Pixel Conversion(3W)             UNIX System V             Pixel Conversion(3W)


NAME
      PixelConversion - a group of routines which examine the data structures
      that describe the physical dimensions and the pixel resolution of a
      screen

SYNOPSIS
      #include <Xlib.h>
      #include <OpenLook.h>

      Screen *OlDefaultScreen;
      Display *OlDefaultDisplay;

      Axis axis;
      Screen screen;

      OlMMToPixel(axis, millimeters);
      OlMMToPixel(axis, millimeters);

      OlPointToPixel(axis, points);
      OlPointToPixel(axis, points);

      OlScreenMMToPixel(axis, millimeters, screen);
      OlScreenMMToPixel(axis, millimeters, screen);

      OlScreenPointToPixel(axis, points, screen);
      OlScreenPointToPixel(axis, points, screen);

      OlPixelToMM(axis, pixels);
      OlPixelToMM(axis, pixels);

      OlPixelToPoint(axis, pixels);
      OlPixelToPoint(axis, pixels);

      OlScreenPixelToPoint(axis, pixels, screen);
      OlScreenPixelToPoint(axis, pixels, screen);

      OlScreenPixelToMM(axis, pixels, screen);
      OlScreenPixelToMM(axis, pixels, screen);

DESCRIPTION
      All the X-based OPEN LOOK widgets refer to pixels in coordinates and
      dimensions for compatibility with other X Window System widgets.
      However, this puts the burden on the application programmer to convert
      between externally useful measures, such as points or millimeters, and
      pixels as applied to the screen at hand.  These routines examine the data
      structures that describe the physical dimensions and the pixel resolution
      of a screen and convert among millimeters, points, and pixels for that
      screen.

   Which Screen?
      The shorter forms of these routines (the ones without the word Screen in
      their names) work for the default screen.  This is the screen that is


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Pixel Conversion(3W)             UNIX System V             Pixel Conversion(3W)


      active when the X Toolkit Intrinsics are started.  The longer forms of
      these routines take a Screen * type argument that refers to a particular
      screen.

      The macros OlDefaultScreen and OlDefaultDisplay identify the current
      screen and display being used by the Intrinsics.  Although the SYNOPSIS
      above implies these are variables of type Screen * and Display *,
      respectively, they are really macros that produce values of these types.

      Note:  Use After Toolkit Initialization
      These routines make use of data structures that are initialized when the
      Toolkit is initialized (see OlInitialize later in this document).
      Therefore, using them before Toolkit initilization (for example, as an
      initial value to a statically defined variable) will result in a run time
      error.

   Axis Argument
      The first argument of all the routines is the direction in which the
      measurement is made.  This is necessary because not all screens have
      equivalent resolution in the horizontal and vertical axes.  The axis
      argument can take one of the two values:  OLHORIZONTAL or OLVERTICAL.
      These routines are not directly usable in computing a diagonal measure.
      (Find the diagonal with the Pythagorean Theorem:  a2 + b2 = c2)

   Implemented as Macros
      All these routines are implemented as macros, so they can take any
      reasonable type value for the millimeters, points, and pixels.  The
      macros cast the values into the proper type needed for the conversion.
      However, only a single type value can be "returned".  The routines
      without an underscore in their names produce values of type int (the
      values are rounded to the nearest integer).  The routines with an
      underscore in their names produce values of type double (these values
      have not been rounded, leaving it up to the application to round up,
      round down, or truncate as needed).  Given the small size of the units
      involved, the integer returning routines should be sufficient for many
      applications.

      Because these routines are implemented as macros, there are no function
      addresses available.















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