diff options
Diffstat (limited to 'doc')
| -rw-r--r-- | doc/refman.tex | 28 |
1 files changed, 26 insertions, 2 deletions
diff --git a/doc/refman.tex b/doc/refman.tex index bf41c05..026139a 100644 --- a/doc/refman.tex +++ b/doc/refman.tex @@ -446,8 +446,17 @@ of the \ident{canvas} command set. search specification. If the tag is already present on some item, nothing is done for that item. The command has no effect if no item satisfy the given criteria. The command returns an empty - string. The search specification and the associated arguments can + string. + + Many commands take a group as a starting point for the search. If no + group is given, the top group is assumed. In any cases, the starting + group will not be reported in the search result. This means that the + top group will never be reported in a search and that tags cannot be + attached to it except in specifying its id. + + The search specification and the associated arguments can take the following forms: + \begin{description} \item{\tt above tagOrId ?inGroup? ?recursive?} \\ Selects the item just above the one given by {\tt tagOrId}. If @@ -497,11 +506,17 @@ of the \ident{canvas} command set. must be no greater than {\tt xo} and {\tt yo} must be no greater than {\tt yc}. All coordinates must be integers. + It may be necessary to update the zinc internal geometry with a call + to {\tt update} if the current state is not stable (i.e before calling + the main loop or in a callback after modifying the transform or doing + something else affecting the geometry of items). + \item{\tt overlapping xo yo xc yc} \\ Selects all the items that overlaps or are enclosed in the rectangle whose origin is at {\tt xo - yo} and corner at {\tt xc - yc}. {\tt xc} must be no greater than {\tt xo} and {\tt yo} must be no greater than - {\tt yc}. All coordinates must be integers. + {\tt yc}. All coordinates must be integers. See also the {\tt enclosed} + variant above for a discussion on updating the geometry. \item{\tt withtag tagOrId ?inGroup? ?recursive?} \\ Selects all the items given by {\tt tagOrId}. The inGroup and @@ -667,6 +682,15 @@ of the \ident{canvas} command set. An error in generated if the items are not of a correct type or if the coordinate list is malformed. + + The order of the contours generated by the command is not easily + predictable, as a result, it is not easy to use the coords command + to edit those contours. Another side effect is the reordering of + the contours vertices depending whether the contour is classified + as an internal hole or as an external contour (externals are clockwise + while holes are counter-clockwise). This is usually not + a problem if the curve item is used to describe polygonal areas but + can lead to unpredicted effects on real unclosed curves. \emph{NOTE: This command is available only when GPC support has been built in Zinc.} |