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PIXEL CONVERSION ROM
UI
TI
SC
N.
ES(
R3
EF
W)
ERENCE MA
PI
NU
XA
EL C
PA
OG
NE
VE
SRSION ROUTINES(3W)



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 coordi-
     nates  and  dimensions for compatibility with other X Window
     System widgets.  However, this puts the burden on the appli-
     cation programmer to convert between externally useful meas-
     ures, 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  active  when  the
     X Toolkit Intrinsics are started.  The longer forms of these
     routines take a Screen * type argument that refers to a par-
     ticular  screen.   The macros OlDefaultScreen and OlDefault-
     Display identify the current screen and display  being  used
     by  the  Intrinsics.   Although  the  SYNOPSIS above implies
     these are variables of type Screen * and Display *,  respec-
     tively,  they are really macros that produce values of these
     types.

     Note:  Use After Toolkit Initialization
     These routines make use of data structures that are initial-
     ized  when  the  Toolkit is initialized (see OlInitialize in
     "Mandatory Routines" earlier in this document).   Therefore,
     using  them before Toolkit initilization (for example, as an



Amiga Unix                Last change:                          1

PIXEL CONVERSION ROM
UI
TI
SC
N.
ES(
R3
EF
W)
ERENCE MA
PI
NU
XA
EL C
PA
OG
NE
VE
SRSION ROUTINES(3W)



     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 neces-
     sary 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 diago-
     nal  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.





























Amiga Unix                Last change:                          2