forms.ps

这是一个同样来自贝尔实验室的和UNIX有着渊源的操作系统, 其简洁的设计和实现易于我们学习和理解

%
% Procedures that let you print any number of pages on each sheet of paper. It's
% far from perfect and won't handle everything (eg. it's not recursive), but should
% be good enough for now. Assumes the default page coordinate system has been set
% up before setupforms is called. lastpage makes certain the last page is printed,
% and should be called immediately after the %%Trailer comment.
%
% Three lines of code needed for page image clipping have been commented out for
% now. It works, but can really slow things down on some versions of PostScript.
% Uncomment them if you want to clip pages.
%

/setupforms {
    /formsperpage exch def

    /currentform 0 def
    /slop 5 def
    /min {2 copy gt {exch} if pop} def

%
% Save the current environment so the real showpage can be restored when we're all
% done. Occasionally helps when a banner page is included with the job.
%

    /saveobj save def

%
% Number of rows and columns we'll need - may exchange them later.
%

    /columns formsperpage sqrt ceiling cvi def
    /rows formsperpage columns div ceiling cvi def

%
% Slop leaves a little room around the edge so page images can be outlined and have
% the borders show up. Distance is in default coordinates, so we need to figure out
% how it maps into user coordinates.
%

    6 array defaultmatrix
    6 array currentmatrix
    6 array invertmatrix
    6 array concatmatrix
    /tempmatrix exch def

    0 slop tempmatrix dtransform dup mul exch dup mul add sqrt
    /slop exch def

%
% Determine how big the image area is, using the clipping path bounding box minus
% a little and leave the coordinates of the lower left corner of the clipping path
% on the stack. Also temporarily set the size of each page (ie. formheight and
% formwidth) from the clipping path - just in case old software uses this stuff.
% Only works for coordinate systems that have been rotated by a multiple of 90
% degrees.
%

    newpath clippath pathbbox
    2 index sub dup /formheight exch def slop 2 mul sub /pageheight exch def
    2 index sub dup /formwidth exch def slop 2 mul sub /pagewidth exch def

%
% New translators all store the size of each page in default coordinates in the
% pagebbox array and it can be different than the size determined by the clipping
% path. If we can find pagebbox use it to set the real dimensions of each page.
% Leaves the coordinates of the lower left corner on the stack, (either from
% pagebbox or clippath) so four numbers are there when we're done.
%

    userdict /gotpagebbox known userdict /pagebbox known and {
	newpath
	pagebbox 0 get pagebbox 1 get tempmatrix transform moveto
	pagebbox 0 get pagebbox 3 get tempmatrix transform lineto
	pagebbox 2 get pagebbox 3 get tempmatrix transform lineto
	pagebbox 2 get pagebbox 1 get tempmatrix transform lineto
	closepath pathbbox
	2 index sub /formheight exch def
	2 index sub /formwidth exch def
    } {2 copy} ifelse

%
% Top two numbers are the displacement from the job's origin to the lower left
% corner of each page image when we finish setting up the new coordinate system.
%

    /ycorner exch def
    /xcorner exch def

%
% The two numbers left on the stack are the coordinates of the lower left corner
% of the clipping path. Go there and then up a bit so page images can be outlined.
%

    translate
    slop slop translate

%
% If the page is wider than high we may be able to do better if we exchange rows
% and columns. Won't make a difference in the current orientation or if rows and
% columns are the same.
%

    pagewidth pageheight gt {
	rows columns /rows exch def /columns exch def
    } if

%
% Find the orientation and scaling that makes things as large as possible. More
% than what's really needed. First calculation essentially finds the minimum of
% 1/rows and 1/columns.
%

    pagewidth formwidth columns mul div pageheight formheight rows mul div min
    pageheight formwidth columns mul div pagewidth formheight rows mul div min

    2 copy lt {
	rotation 1 eq {
	    landscape {
		0 pageheight translate
		-90 rotate
	    }{
		pagewidth 0 translate
		90 rotate
	    } ifelse
	}{
	    landscape {
		pagewidth 0 translate
		90 rotate
	    }{
		0 pageheight translate
		-90 rotate
	    } ifelse
	} ifelse
	pagewidth pageheight /pagewidth exch def /pageheight exch def
	exch
    } if

%
% Second number from the top is the best choice. Scale so everything will fit on
% the current page, go back to the original origin, and then get ready for the
% first page - which goes in the upper left corner.
%

    pop dup dup scale
    xcorner neg ycorner neg translate
    0 rows 1 sub formheight mul translate

%
% Try to center everything on the page - scaling we used is on top of the stack.
%

    dup pagewidth exch div formwidth columns mul sub 2 div
    exch pageheight exch div formheight rows mul sub 2 div translate

%
% Redefine showpage.
%

    /!PreForms~showpage~ /showpage load def		% save current showpage

    /showpage {
	saveobj restore
%	initclip
	formsperpage 1 gt {
	    gsave .1 setlinewidth outlineform stroke grestore
	} if
	formwidth 0 translate
	/currentform currentform 1 add def
	currentform columns mod 0 eq {
	    columns formwidth mul neg formheight neg translate
	} if
	currentform formsperpage mod 0 eq {
	    gsave !PreForms~showpage~ grestore
	    currentform columns mod formwidth mul neg
	    formsperpage columns idiv formheight mul translate
	    /currentform 0 def
	} if
%	outlineform clip newpath
	/saveobj save def
    } bind def

    /outlineform {
	newpath
	xcorner ycorner moveto
	formwidth 0 rlineto
	0 formheight rlineto
	formwidth neg 0 rlineto
	closepath
    } bind def

    /lastpage {
	formsperpage 1 gt {
	    currentform 0 ne {
		/saveobj save def
		0 1 formsperpage currentform sub formsperpage mod {
		    pop showpage
		} for
		saveobj restore
	    } if
	    saveobj restore
	    saveobj restore
	} if
    } def

%
% Clip the first page image and save the environment we just set up, including
% the redefined showpage.
%

%   outlineform clip
    newpath
    /saveobj save def
} def