MetaFun - Pragma ADE

fill shape ; draw shape ; filldraw shape ; drawfill shape ;
currentpicture := finalpicture ;
Here we introduce a macro definition, shape. In METAPOST, the start of a macro definition is indicated
with the keyword def. Thereafter, you can insert other variables and commands, even
other macro definitions. The keyword enddef signals the end of the macro definition. The result
is shown in figure 2.1; watch the bounding boxes. Close reading of the macro will reveal that the
fill, draw, filldraw and drawfill macros are applied to the first unitsquare path in the macro.
Figure 2.1 A fill, draw, filldraw and
drawfill applied to the same square.
In this macro, bbox calls a macro that returns the enlarged bounding box of a path. By setting
bboxmargin we can influence how much the bounding box is enlarged. Since this is an existing
variable, we don't have to allocate it, like we do with numeric n. Unless you take special precautions,
variables are global by nature and persistent outside macros.
picture finalpicture ; finalpicture := nullpicture ;
Just as numeric allocates an integer variable, the picture primitive allocates a picture data structure.
We explicitly have to set this picture to nothing using the built--in primitive nullpicture.
Later on, we will add the drawn paths as accumulated in currentpicture to this finalpicture
in the following manner.
addto finalpicture also currentpicture shifted(n*3cm,0) ;
Since we want to add a few more and don't want them to overlap, we shift them. Therefore we
have to erase the current picture as well as increment the shift counter.
currentpicture := nullpicture ; n := n+1 ;
The drawfill macro is one of the METAFUN macros. Another handy macro is boundingbox. When
used instead of bbox, you don't have to set the margin to zero.
Figure 2.2 The influence of pens on fill.
Bounding boxes A few more details
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