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diff --git a/doc/context/sources/general/manuals/metafun/metafun-backgrounds.tex b/doc/context/sources/general/manuals/metafun/metafun-backgrounds.tex new file mode 100644 index 000000000..200620cae --- /dev/null +++ b/doc/context/sources/general/manuals/metafun/metafun-backgrounds.tex @@ -0,0 +1,878 @@ +% language=uk +% +% copyright=pragma-ade readme=readme.pdf licence=cc-by-nc-sa + +\startcomponent metafun-backgrounds + +\environment metafun-environment + +\startchapter[reference=sec:page,title={Page backgrounds}] + +\startintro + +Especially in interactive documents, adding backgrounds to the page and text +areas not only enhances readability, but also makes it more convenient to +identify header, footers and navigational areas. In this chapter we will +demonstrate that with \METAPOST\ we can go beyond the \TEX\ based features +present in \CONTEXT. One section is dedicated to graphics and printing, +especially bleeding. + +\stopintro + +\startsection[title={The basic layout}] + +\index {layout} + +In the \CONTEXT\ manual you can find many details on the composition of the page. +When \TEX\ typesets text, crossing the page boundary triggers \TEX's output +routine. This routine is responsible for pasting the body text that goes onto a +page in the correct area. A simple representation of such a page is: + +\startbuffer[a] +\startuseMPgraphic{layout 1} + pickup pencircle scaled 1mm ; + fill unitsquare xyscaled (7cm,8cm) + withcolor .85white ; + fill unitsquare xyscaled (5cm,5cm) shifted (1cm,1.5cm) + withcolor .625yellow ; + fill unitsquare xyscaled (5cm,1cm) shifted (1cm,.5cm) + withcolor .625red ; + fill unitsquare xyscaled (5cm,1cm) shifted (1cm,6.5cm) + withcolor .625red ; + draw unitsquare xyscaled (5cm,7cm) shifted (1cm,.5cm) + withcolor .25white ; + drawarrow (2cm,8cm) -- top (2cm,7.5cm) ; + drawarrow (0cm,7cm) -- lft (1cm,7cm) ; + clip currentpicture to unitsquare xyscaled (7cm,8cm) ; +\stopuseMPgraphic +\stopbuffer + +\startbuffer[b] +\startuseMPgraphic{layout 2} + \includeMPgraphic{layout 1} + clip currentpicture to unitsquare scaled 3cm shifted (0,5cm) ; + currentpicture := currentpicture scaled 2 shifted (0,-8cm) ; + setbounds currentpicture to unitsquare xyscaled (6cm,8cm) ; +\stopuseMPgraphic +\stopbuffer + +\getbuffer[a,b] + +\startbuffer[c] +\startlinecorrection[blank] +\hbox + {\useMPgraphic{layout 1}\hskip1cm + \useMPgraphic{layout 2}} +\stoplinecorrection +\stopbuffer + +\getbuffer[c] + +The red areas are the header and footer, while the yellow areas contains the text +flow. We can turn headers on and off and|/|or hide them. For this reason, the +header, text and footer areas together make up the height of the text. + +A close look at the left picture will reveal that the two arrows point to the +center of the lines. This is achieved by the \type {top} and \type {lft} +directives. If we would not have clipped the picture, the arrow would have stuck +half a line width outside the gray area that represents the page. When +constructing such pictures, one should really pay attention to such details, +since it pays off in the overall look and feel of the document. + +The vertical arrow represents the top space, while the horizontal arrow denotes +the distance to the back of the cover (back space). By changing their values, you +can shift the main body text on the page. In a double sided layout scheme, the +back space is automatically mirrored on even pages. + +An advanced \METAPOST\ user may wonder why we hard code the dimensions, and avoid +\METAPOST's powerful mechanisms for defining relations. Our experience has taught +us that in pictures like this, providing a general solution seldom pays large +dividents or savings in time. + +\typebuffer[a] + +As you can see, the left graphic is defined as a series of rectangles. The \type +{xyscaled} macro is part of the \CONTEXT\ files, and saves some typing and space. +It is defined as a primary, requiring both left and right operands. + +\starttyping +primarydef p xyscaled q = + p xscaled (xpart q) yscaled (ypart q) +enddef ; +\stoptyping + +Zooming in on the top left corner only takes a few lines. First we clip the +correct part, next we scale it up, and finally we let the bounding box suit the +left picture. + +\typebuffer[b] + +This code demonstrates how you can reuse a graphic inside another one. This +strategy can easily be used to stepwise build (or extend) graphics. The two +graphics were put side by side with the following command. Watch the use of line +correction commands. They optimize the white space around the graphic. + +\typebuffer[c] + +As soon as you want to make an electronic document, you will want to use +different areas of the screen for different purposes: text, menus, buttons, etc. +For this reason, \CONTEXT\ provides not only left and right margins, but also +additional left and right edge areas and top and bottom margins. These areas are +shown in the figure on the next page. + +\startbuffer[aa] +pickup pencircle scaled 2pt ; + +numeric w[], h[], x[], y[], u ; u := .5cm ; + +numeric width ; width := \the\textwidth ; +numeric height ; height := \the\textheight ; +\stopbuffer + +\startbuffer[bb] +w[1] = 2u ; w[2] = 3u ; w[4] = 3u ; w[5] = 2u ; +h[1] = 1u ; h[2] = 1u ; h[4] = 1u ; h[5] = 1u ; + +w[1]+w[2]+w[3]+w[4]+w[5]+4u = width ; +h[1]+h[2]+h[3]+h[4]+h[5]+4u = height ; + +x[1] = 1u ; y[1] = 1u ; +x[2] = x[1] + w[1] + .5u ; y[2] = y[1] + h[1] + .5u ; +x[3] = x[2] + w[2] + .5u ; y[3] = y[2] + h[2] + .5u ; +x[4] = x[3] + w[3] + .5u ; y[4] = y[3] + h[3] + .5u ; +x[5] = x[4] + w[4] + .5u ; y[5] = y[4] + h[4] + .5u ; +\stopbuffer + +\startbuffer[cc] +def do_it (expr xx, yy, cc) = + draw unitsquare + xyscaled (w[xx],h[yy]) shifted (x[xx],y[yy]) + withcolor if cc : .625red else : .625yellow fi ; +enddef ; + +fill unitsquare xyscaled (width,height) withcolor .85white; + +do_it (1,1,false) ; do_it (5,1,false) ; +do_it (2,1,false) ; do_it (3,1,false) ; do_it (4,1,false) ; + +do_it (1,2,false) ; do_it (5,2,false) ; +do_it (2,2,true ) ; do_it (3,2,true ) ; do_it (4,2,true ) ; + +do_it (1,3,false) ; do_it (5,3,false) ; +do_it (2,3,true ) ; do_it (3,3,true ) ; do_it (4,3,true ) ; + +do_it (1,4,false) ; do_it (5,4,false) ; +do_it (2,4,true ) ; do_it (3,4,true ) ; do_it (4,4,true ) ; + +do_it (1,5,false) ; do_it (5,5,false) ; +do_it (2,5,false) ; do_it (3,5,false) ; do_it (4,5,false) ; +\stopbuffer + +\startbuffer[dd] +def do_it (expr yy, tt) = + path p ; + p := unitsquare xyscaled (w[1],h[yy]) shifted (x[1],y[yy]) ; + label.lft(tt, center p shifted (-w[1]/2-u-.25cm,0)) ; +enddef ; + +do_it (1,btex bottom etex) ; +do_it (2,btex footer etex) ; +do_it (3,btex text etex) ; +do_it (4,btex header etex) ; +do_it (5,btex top etex) ; +\stopbuffer + +\startbuffer[ee] +def do_it (expr xx, tt) = + path p ; + p := unitsquare xyscaled (w[xx],h[1]) shifted (x[xx],y[1]) ; + label(tt, center p shifted (0,height-h[1]/2)) ; +enddef ; + +do_it (1,btex edge etex) ; +do_it (2,btex margin etex) ; +do_it (3,btex text etex) ; +do_it (4,btex margin etex) ; +do_it (5,btex edge etex) ; +\stopbuffer + +\startbuffer[ff] +setbounds currentpicture to + unitsquare xyscaled (width,height) ; +\stopbuffer + +% We use two chars for buffer names, otherwise we can get +% get in conflict with the next buffers with similar names. + +\startpostponing +\centerbox{\processMPbuffer[aa,bb,cc,dd,ee,ff]} +\stoppostponing + +When defining this graphic, all areas have related dimensions. Here it makes +sense to let \METAPOST\ calculate these dimensions as much as possible. First we +define the five by five matrix of areas. We pass the width and height of the main +text area. Because they are stored in \TEX\ dimension registers, we have to +prefix them by \type {\the}. + +\typebuffer[aa] + +We now specify the lower left corners using \type {=} instead of the \type {:=}, +which means that \METAPOST\ will calculate \type {w[3]} and \type {h[3]} for us. + +\typebuffer[bb] + +Because we are going to repeat ourselves, we draw the areas using a macro. +Depending on its importance, we color it red or yellow. + +\typebuffer[cc] + +This picture in itself is not yet explanatory, so we add some labels. Again, we +use a macro, which we feed with a picture generated by \TEX. Since these pictures +are filtered from the source and pre||processed, we cannot embed the \type +{btex}||\type {etex} in the macro \type {do_it} and pass a string. It has to be +done this way. \footnote {This is true only in a regular \METAPOST\ run. In +\CONTEXT\ \MKIV\ we follow a different route.} + +\typebuffer[dd] + +In the horizontal direction we have edges, margins and text. There are left and +right edges and margins, which are swapped on even pages when you typeset a +double sided document. + +\typebuffer[ee] + +Since we want the graphic to match the dimensions of the text area of the current +page, we have to make sure that the bounding box is adapted accordingly. By this +action, the labels will fall outside the bounding box. When we directly embed a +graphic, this works ok, but when we start scaling and reusing, due to the object +reuse mechanism the graphic will be clipped to the bounding box. + +\typebuffer[ff] + +In the following sections we will demonstrate how you can put graphics behind +these 25~areas, as well as behind the (left and right) page. + +\stopsection + +\startsection[title={Setting up backgrounds}] + +\index {overlays} +\index {backgrounds} + +One way of protecting a document for unwanted usage is to put an annoying word in +the background. If you like this, you may try the following. The macro \type +{ysized} is part of the macros that come with \CONTEXT\ and scales a picture to a +specific size. + +\startbuffer[a] +\startuniqueMPgraphic{concept} + draw btex \colored[s=.8]{\bf CONCEPT} etex rotated 60 ; + currentpicture := currentpicture + ysized (\overlayheight-.5cm) ; +\stopuniqueMPgraphic + +\defineoverlay[concept][\uniqueMPgraphic{concept}] +\stopbuffer + +\typebuffer[a] + +You can now put this graphic in the page background by +saying: + +\starttyping +\setupbackgrounds[page][background=concept] +\stoptyping + +You may consider the next alternative a bit better, but still it renders the text +unreadable. Like \type {xysized}, the macro \type {enlarged} is not part of +standard \METAPOST, but comes with \CONTEXT. + +\startbuffer[b] +\startuniqueMPgraphic{copyright} + picture p ; p := btex \colored[s=.8]{COPYRIGHT} etex + rotated 90 ; + setbounds p to boundingbox p enlarged 1pt ; + draw p ; + currentpicture := currentpicture + xysized (\overlaywidth,\overlayheight) ; +\stopuniqueMPgraphic + +\defineoverlay[copyright][\uniqueMPgraphic{copyright}] +\stopbuffer + +\typebuffer[b] + +Again, we put this graphic in the background. By using a unique graphic, we make +sure that it's rendered only once and reused when possible. + +\startbuffer[c] +\setupbackgrounds[text][rightmargin][background=copyright] +\stopbuffer + +\typebuffer[c] + +\doifnotmode{screen}{\getbuffer[b,c]} + +In both cases, we slightly scale down the graphic. We do so because otherwise a +small portion of the text is clipped off. This is unrelated to \TEX\ or +\METAPOST, but a characteristic of the font. Compare the following Pagella, Latin +Modern and Termes gi's (the Pagella is the body font of this text). + +\startbuffer +\hbox \bgroup + \hbox{\definedfont[file:texgyrepagella-regular at 6cm]gi}% + \hbox{\definedfont[file:lmroman10-regular at 6cm]gi}% + \hbox{\definedfont[file:texgyretermes-regular at 6cm]gi}% +\egroup +\stopbuffer + +\typebuffer + +\startlinecorrection[blank] +{\showboxes \getbuffer} +\stoplinecorrection + +Watch how the bounding boxes differ and sometimes cross the shape. So, in order +not to loose part of a glyph when clipping, you need to add a bit of space. \in +{Figure} [fig:annoying] shows the two backgrounds in action. + +\startbuffer +\getbuffer[a,b] +\def\ShowPage#1% % (yet) no image as background to image + {\framed % possible due to nested file problems + [background=#1,offset=overlay] + {\typesetfile[mfun-900.tex][page=1,width=.4\textwidth]}} +\startcombination + {\ShowPage{concept}} {concept} + {\ShowPage{copyright}} {copyright} +\stopcombination +\stopbuffer + +\placefigure + [here][fig:annoying] + {Two examples of annoying backgrounds.} + {\getbuffer} + +If you really want to add such texts to a document, in \CONTEXT\ we don't have to +use the page background, but can use one of the layout areas instead (like \type +{[text][text]} or \type {[text][leftmargin]}) + +\typebuffer[d] + +There is one drawback: when your left and right margin have different dimensions, +the text will be scaled differently on odd and even pages. Normally this is no +problem for a draft. + +As an alternative you can use the \type {\setuptexts} command and wrap the +graphic in a box with the right dimensions, using code like: + +\starttyping +\startuniqueMPgraphic{copyright} + picture p ; p := btex COPYRIGHT etex rotated 90 ; + setbounds p to boundingbox p enlarged 1pt ; + draw p withcolor .8white ; + xyscale_currentpicture(\the\leftmarginwidth,\the\textheight) ; +\stopuniqueMPgraphic + +\setuptexttexts [margin] [] [\uniqueMPgraphic{copyright}] +\stoptyping + +The graphic goes into the outer margin. The second argument can be used to put +something in the inner margin. + +\stopsection + +\startsection[title={Multiple overlays}] + +\index{overlays+stack} + +\setupbackgrounds[text][rightmargin][background=] + +You can stack overlays. Consider the next case, where we assume that you have +enabled interaction support using \type {\setupinteraction[state=start]}: + +\starttyping +\setupbackgrounds + [page] + [background={color,nextpage}, + backgroundcolor=darkyellow] +\stoptyping + +Here, the page gets a colored background and a hyperlink to the next page, +previously defined by: + +\starttyping +\defineoverlay[nextpage][\overlaybutton{nextpage}] +\stoptyping + +An \type {\overlaybutton} is just a button, with all attributes (color, frame, +etc) set to nothing, having the dimensions of the overlay. The argument is one of +the permitted destinations, like \type {nextpage}, \type {firstpage}, \type +{SearchDocument} and alike. + +For efficiency reasons, the background areas (like \type {[text][text]}) are +calculated only when their definition has changed. When a background changes per +page, we have to recalculate it on each page. In the next example, the macro +\type {\overlaybutton} generates a different button on each page. But, since we +don't explicitly set the background at each page, there is no way the background +drawing mechanism can know that this button has changed. Therefore, we must force +recalculation with: + +\starttyping +\setupbackgrounds[state=repeat] +\stoptyping + +You can test this concept yourself with the following code. Here we assume that +you have a file called \type {tufte.tex} on your system, which is the case if you +have \CONTEXT\ installed. However, you can just as easily use any file having a +paragraph of two of text. + +\starttyping +\starttext +\setupinteraction[state=start] +\setupbackgrounds[state=repeat] +\defineoverlay[nextpage][\overlaybutton{nextpage}] +\setupbackgrounds[text][text][background=nextpage] +\dorecurse{20}{\input tufte \par} +\stoptext +\stoptyping + +Note that you can move forward from page to page in the resulting \PDF\ file by +clicking on each page with the mouse. Now compile this file without setting the +background state to \type {repeat} and note the difference as you click pages +with the mouse. + +Setting the state was not needed when we used the page background: + +\starttyping +\setupbackgrounds[page][background=nextpage] +\stoptyping + +The \type {\dorecurse} macro is handy for testing since it saves us typing. One +can nest this macro as in: + +\starttyping +\dorecurse{20}{\dorecurse{10}{Hello World! }\par} +\stoptyping + +The current step is available in \type {\recurselevel} and the depth (nesting +level) in \type {\recursedepth}. + +\stopsection + +\startsection[title={Crossing borders}] + +\index{backgrounds} + +In many cases, the previously mentioned background areas will suffice, but in the +case of more complicated backgrounds, you may wish to use \METAPOST\ to draw +graphics that combine or span these areas. + +At runtime \CONTEXT\ saves information on the layout that can be picked up by +\METAPOST. The framework for a page graphic is: + +\starttyping +StartPage; + % all kind of commands +StopPage ; +\stoptyping + +Between the \type {StartPage} and \type {StopPage} command you have access to a +wide range of variables: + +\starttabulate[|l|Tp|] +\HL +\NC page \NC PaperHeight PaperWidth \NC \NR +\NC \NC PrintPaperHeight PrintPaperWidth \NC \NR +\NC \NC PageOffset PageDepth \NC \NR +\NC margins \NC TopSpace BackSpace \NC \NR +\NC text \NC MakeupHeight MakeupWidth \NC \NR +\NC vertical \NC TopHeight TopDistance \NC \NR +\NC \NC HeaderHeight HeaderDistance \NC \NR +\NC \NC TextHeight \NC \NR +\NC \NC FooterDistance FooterHeight \NC \NR +\NC \NC BottomDistance BottomHeight \NC \NR +\NC horizontal \NC LeftEdgeWidth LeftEdgeDistance \NC \NR +\NC \NC LeftMarginWidth LeftMarginDistance \NC \NR +\NC \NC TextWidth \NC \NR +\NC \NC RightMarginDistance RightMarginWidth \NC \NR +\NC \NC RightEdgeDistance RightEdgeWidth \NC \NR +\HL +\stoptabulate + +Since using these variables to construct paths is not that handy because the +areas are available as predefined paths, which we will demonstrate here. + +\placefigure + [here][fig:back 1] + {A background with combined areas.} + {\startcombination + {\typesetfile[mfun-900.tex][page=2,width=.4\textwidth]}{even} + {\typesetfile[mfun-900.tex][page=3,width=.4\textwidth]}{odd} + \stopcombination} + +In \in {figure} [fig:back 1] you see two pages (odd and even) with a background +spanning the outer margin and the text area. You can access an area in two ways. +The area itself is available as \type {Area}. + +\starttyping +StartPage ; + fill Area[Text][Text] withcolor .85white ; +StopPage ; +\stoptyping + +If you use an area this way, you will notice that it is not positioned at the +right place. An \type {Area} is just a rectangle. If you want a positioned area, +you should use the \type {Field} array: + +\starttyping +StartPage ; + fill Field[Text][Text] withcolor .85white ; +StopPage ; +\stoptyping + +The location of an area is available in \type {Location}, so the previous +definition is the same as: + +\starttyping +StartPage ; + fill Area[Text][Text] shifted Location[Text][Text] + withcolor .85white ; +StopPage ; +\stoptyping + +The following definition fills and draws the margin and text areas. + +\typebuffer[back-2] + +This background is assigned to the page layer by saying: + +\typebuffer[back-0] + +As you can see in \in {figure} [fig:back 2], the text is typeset rather tightly +between the left and right margins. + +\placefigure + [here][fig:back 2] + {A background with split areas.} + {\startcombination + {\typesetfile[mfun-900.tex][page=4,width=.4\textwidth]}{even} + {\typesetfile[mfun-900.tex][page=5,width=.4\textwidth]}{odd} + \stopcombination} + +This can easily be solved by enlarging the areas a bit. The next example +demonstrates this on the text area, which is shown in \in {figure} [fig:back 3]. + +\typebuffer[back-3] + +\placefigure + [here][fig:back 3] + {A background with enlarged text area.} + {\startcombination + {\typesetfile[mfun-900.tex][page=6,width=.4\textwidth]}{even} + {\typesetfile[mfun-900.tex][page=7,width=.4\textwidth]}{odd} + \stopcombination} + +The \type {enlarged} macro can be used like \type {shifted} and accepts either a +numeric or a pair. + +How do we define a background as in \in {figure} [fig:back 1]? Because \type +{Field} provides us the positioned areas, we can use the corners of those. + +\typebuffer[back-1] + +In this definition we calculate a different path for odd and even pages. When +done, we enlarge the path a bit. If you want to use different offsets in all +directions, you can use moved corner points. + +\typebuffer[back-4] + +Here we displace the corners randomly which leads to backgrounds like \in +{figure} [fig:back 4]. The following definition would have worked as well: + +\typebuffer[back-4x] + +\placefigure + [here][fig:back 4] + {A random text area.} + {\startcombination + {\typesetfile[mfun-900.tex][page=8,width=.4\textwidth]}{even} + {\typesetfile[mfun-900.tex][page=9,width=.4\textwidth]}{odd} + \stopcombination} + +The previous graphics are defined as usable ones, which means that they will be +recalculated each page. This is rather inefficient when the shapes don't change. +But, using a reusable graphic instead, would result in only one graphic for both +pages. Since the layout for the left and right page differs, another method is +needed. + +Instead of putting the same graphic on the page layer, we put two different ones +on the left and right page layer. + +\starttyping +\defineoverlay[left page] [\useMPgraphic{left page}] +\defineoverlay[right page][\useMPgraphic{right page}] + +\setupbackgrounds[leftpage] [background=left page] +\setupbackgrounds[rightpage][background=right page] +\stoptyping + +Now we only have to split the previously defined graphic into two parts. In order +to force consistency, we isolate the code that fills and draws. The left page +code looks like: + +\starttyping +\startreusableMPgraphic{left page} + StartPage ; + path Main ; Main := + llcorner Field[OuterMargin][Text] -- + lrcorner Field[Text] [Text] -- + urcorner Field[Text] [Text] -- + ulcorner Field[OuterMargin][Text] -- cycle ; + \includeMPgraphic{draw page} + StopPage ; +\stopreusableMPgraphic +\stoptyping + +The right page text looks similar: + +\starttyping +\startreusableMPgraphic{right page} + StartPage ; + path Main ; Main := + lrcorner Field[OuterMargin][Text] -- + llcorner Field[Text] [Text] -- + ulcorner Field[Text] [Text] -- + urcorner Field[OuterMargin][Text] -- cycle ; + \includeMPgraphic{draw page} + StopPage ; +\stopreusableMPgraphic +\stoptyping + +Watch how we used a reusable graphic first and a simple usable one next. +Actually, the next graphic is not a stand alone graphic. + +\starttyping +\startuseMPgraphic{draw page} + Main := Main enlarged 6pt ; + pickup pencircle scaled 2pt ; + fill Page withcolor .625white ; + fill Main withcolor .850white ; + draw Main withcolor .625red ; +\stopuseMPgraphic +\stoptyping + +We have seen some predefined paths and locations. Apart from the \type {Page} +path, they take two arguments that specify their position on the layout grid. + +\starttabulate[|lT|l|] +\HL +\NC path Area [][] \NC an area similar to a \CONTEXT\ one \NC \NR +\NC pair Location [][] \NC the position of this area \NC \NR +\NC path Field [][] \NC the area positioned at the right place \NC \NR +\NC path Page \NC the page itself \NC \NR +\HL +\stoptabulate + +Some less used and more obscure variables are the following. + +\starttabulate[|lT|l|] +\HL +\NC numeric Hstep [] \NC the horizontal distance to the previous area \NC \NR +\NC numeric Vstep [] \NC the vertical distance to the previous area \NC \NR +\NC numeric Hsize [] \NC the width of an area \NC \NR +\NC numeric Vsize [] \NC the height of an area \NC \NR +\HL +\stoptabulate + +The array variables are accessed by using constants: + +\starttabulate[|l|l|] +\HL +\NC horizontal \NC vertical \NC \NR +\HL +\NC LeftEdge \NC Top \NC \NR +\NC LeftEdgeSeparator \NC TopSeparator \NC \NR +\NC LeftMargin \NC Header \NC \NR +\NC LeftMarginSeparator \NC HeaderSeparator \NC \NR +\NC Text \NC Text \NC \NR +\NC RightMarginSeparator \NC FooterSeparator \NC \NR +\NC RightMargin \NC Footer \NC \NR +\NC RightEdgeSeparator \NC BottomSeparator \NC \NR +\NC RightEdge \NC Bottom \NC \NR +\HL +\stoptabulate + +In addition to these, there are \type {Margin}, \type {InnerMargin} and \type +{OuterMargin} which adapt themselves to the current odd or even page. The same is +true for \type {Edge}, \type {InnerEdge} and \type {OuterEdge}, although these +will seldom be used, since interactive documents are always single sided. + +We started this chapter with spending a lot of code to simulate the page areas. +It will be clear now that in practice this is much easier using the mechanism +described here. + +\placefigure + [here][fig:back 5] + {A quick way to draw all used areas.} + {\setupexternalfigures[background=color,backgroundcolor=white]% + \startcombination + {\typesetfile[mfun-900.tex][page=10,width=.4\textwidth]}{even} + {\typesetfile[mfun-900.tex][page=11,width=.4\textwidth]}{odd} + \stopcombination} + +In \in {figure} [fig:back 5] we see all used areas. Areas that are not used are +not drawn (which saves some testing). This background was defined as: + +\typebuffer[back-5] + +We use two nested \type {for} loops to step over the areas. A \type {for} loop +with a step of~1 will fail, because the indices are defined in a rather special +way. On the other hand, the mechanism is rather tolerant, in the sense that \type +{[i][j]} and \type {[j][i]} are both accepted. + +\stopsection + +\startsection[title={Bleeding}] + +\index {bleeding} + +If you want to share your document all over the world, it makes sense to use a +paper format like {\em letter} or {\em A4}. In that case, the layout often +matches the paper size. + +\startlinecorrection[blank] +\startMPcode + path p ; p := fullcircle xyscaled (21mm,29.7mm) ; + path q ; q := boundingbox p ; + fill q withcolor .625white ; + fill p withcolor .625yellow ; + currentpicture := currentpicture shifted (-31mm,0) ; + fill q withcolor .625white ; + fill p xsized (bbwidth(p)-2mm) withcolor .625yellow ; + currentpicture := currentpicture shifted (-31mm,0) ; + fill q withcolor .625white ; + fill p withcolor .625yellow ; + draw q enlarged -1mm withpen pencircle scaled 2mm withcolor .625white ; +\stopMPcode +\stoplinecorrection + +The left picture demonstrates what happens when you have a printer that is +capable of printing from edge to edge. If you have such a printer, you're lucky. +The middle picture demonstrates what happens if you have a properly set up +printing program and|/|or printer: the page is scaled down so that the content +fits into the non printable area of the printer. One reason why printers don't +print from edge to edge is that the engine is not that happy when toner or ink +ends up next to the page. The third picture shows what happens when a printer +simply ignores content that runs over the non printable area. In many cases it's +best to make sure that the content leaves a margin of 5mm from the edges. + +Books and magazines seldom use the popular desk||top paper sizes. Here the +designer determined the paper size and layout more or less independent from the +size of the sheet on which the result is printed. Instead of one page per sheet, +arrangements of 2 upto 32 or more pages per sheet are made. The process of +arranging pages in such a way that these sheets can be folded and combined into +books is called page imposition. \CONTEXT\ supports a wide range of page +imposition schemes. More information on this can be found in the \CONTEXT\ +manuals. + +The fact that the sheet on which a page is printed is larger than the page itself +opens the possibility to use the full page for content. In that case, especially +when you use background graphics, you need to make sure that indeed the page is +covered completely. Where in desk top printing you can get away with imperfection +simply because the printing engines have their limitations, in professional +output you need to be more considerate. + +\startlinecorrection[blank] +\startMPcode + path p ; p := fullsquare xyscaled (4cm,5cm) ; + path q ; q := fullsquare xyscaled (3cm,4cm) ; + path r ; r := fullsquare xyscaled (2cm,3cm) shifted (-.5cm,.5cm) ; + fill p withcolor .625white ; + fill q withcolor .850white ; + currentpicture := currentpicture shifted (-45mm,0) ; + fill p withcolor .625white ; + fill q withcolor .850white ; + fill r withcolor transparent(1,.5,.625yellow) ; + currentpicture := currentpicture shifted (-45mm,0) ; + fill p withcolor .625white ; + fill q withcolor .850white ; + r := r topenlarged 2mm leftenlarged 2mm ; + fill r withcolor transparent(1,.5,.625yellow) ; +\stopMPcode +\stoplinecorrection + +Slightly enlarging a graphic so that it exceeds the natural page limits is called +bleeding. Because quite often layout elements have a rectangular nature, +\METAFUN\ provides a couple of operations that can save you some work in defining +bleeding boxes. + +\startbuffer +path p, q ; +def ShowPath = + fill p withcolor transparent(1,.5,.625yellow) ; + fill q withcolor transparent(1,.5,.625yellow) ; + currentpicture := currentpicture shifted (-25mm,0) ; +enddef ; +p := q := fullsquare xyscaled (2cm,3cm) ; ShowPath ; +p := p leftenlarged 2mm ; ShowPath ; +p := p topenlarged 2mm ; ShowPath ; +p := p rightenlarged 2mm ; ShowPath ; +p := p bottomenlarged 2mm ; ShowPath ; +\stopbuffer + +\startlinecorrection[blank] +\processMPbuffer +\stoplinecorrection + +This graphic is generated as follows: + +\typebuffer + +The trick is in the last couple of lines. In addition to the general \type +{enlarged} operator, we have 4~operators that enlarge a rectangle in a certain +direction. This means that we can define the original path using dimensions +related to the layout, and add bleed strips independently. + +\startbuffer +path p ; p := fullsquare xyscaled (4cm,1cm) ; +path q ; q := p leftenlarged 2mm topenlarged 2mm ; +fill p withcolor transparent(1,.5,.625yellow) ; +fill q withcolor transparent(1,.5,.625yellow) ; +draw boundingbox currentpicture withcolor .625red ; +\stopbuffer + +\typebuffer + +\startlinecorrection[blank] +\processMPbuffer +\stoplinecorrection + +This example demonstrates that when we enlarge a graphic, the bounding box also +gets larger. Because this can interfere with the placement of such a graphic, we +need to make sure that the bleeding is there but not seen. + +\startbuffer +path p ; p := fullsquare xyscaled (4cm,1cm) ; +path q ; q := p leftenlarged 2mm topenlarged 2mm ; +fill p withcolor transparent(1,.5,.625yellow) ; +fill q withcolor transparent(1,.5,.625yellow) ; +setbounds currentpicture to p ; +draw boundingbox currentpicture withcolor .625red ; +\stopbuffer + +\typebuffer + +\startlinecorrection[blank] +\processMPbuffer +\stoplinecorrection + +There are two more operators: \type {innerenlarged} and \type {outerenlarged}. +These expand to either \type {leftenlarged} or \type {rightenlarged}, depending +on the page being left or right hand. + +\stopsection + +\stopchapter + +\stopcomponent |