Hi all, I'm reposting this here as I think this is of interest to non-developers as well, and I don't get much response on zope-dev anyway :) When using batching in dtml-in, why is 'previous-sequence' only defined at the first iteration of the current batch? And why is 'next-sequence' only defined at the last iteration of the current batch? This behaviour makes it difficult to display a batch like this: -- begin sample -- Item N Item N+1 Item N+2 (link to previous items) (link to next items) -- end sample -- Because the code would be something like: -- begin sample -- <dtml-in something start=query_start size=3> [do something with sequence-item] <dtml-if sequence-end> <!-- check if last item of batch --> <dtml-if previous-sequence> (link to previous items) </dtml-if> <dtml-if next-sequence> (link to next items) </dtml-if> </dtml-if> </dtml-in> -- end sample -- However, if your batchsize is larger than 1, 'previous-sequence' will always be untrue at the last item (when sequence-item is true). The only solution would be implement a second dtml-in after the first one purely for displaying the previous link. Also, dtml-in would re-execute your "expr" (which it does not very efficiently), so if you want to avoid doing the "expr" twice, you'd have to store it temporarily using dtml-let (or my dtml-set tag ;). The end result would be: -- start sample -- <dtml-let foo="expr"> <dtml-in foo start=start_query size=3> [do something with sequence-item] </dtml-in> <dtml-in foo start=start_query size=3> <!-- code below is safe, as the variables are only true at the resp. top and end, though the truly paranoid could check for sequence-start / -end patch #1 below would break such code! --> <dtml-if sequence-end> <dtml-if previous-sequence> (link to previous items) </dtml-if> <dtml-if next-sequence> (link to next items) </dtml-if> </dtml-if> </dtml-in> </dtml-let> -- end sample -- And at this point I really would start to implement the batching myself in python :) Of course, basically the same applies if you want both the previous/next link at the top of the batch display. (Imagine you want both! :) Either I'm missing something really obvious here, or the patches below make sense. There are two versions: - patch #1: This version fixes the issue above by enabling the values of previous/next-sequence throughout the entire batch (and other related variables as well: X-sequence, X-sequence-start-index, X-sequence-end-index, X-sequence-size) (which may break existing sites), and - patch #2: This version introduces new variablenames, leaving the behaviour of previous/next-sequence. A third alternative would be to only define the variables at the top and bottom of the batch. Both versions fix (I think) a grammatical error. It's up to the DC guys if they feel like incorporating either of these patches in a next release :) patch #1: define variables everywhere in the batch This patch makes sure that the following variables are available through each iteration of dtml-in, for each item. !!!!! This patch may break alot of dtml code !!!!!! next-sequence next-sequence-start-index next-sequence-end-index next-sequence-size previous-sequence previous-sequence-start-index previous-sequence-end-index previous-sequence-size -- patch begins here -- *** Zope-2.3.2-orig/lib/python/DocumentTemplate/DT_In.py Fri Apr 13 21:30:38 2001 --- Zope-2.3.2-src/lib/python/DocumentTemplate/DT_In.py Tue May 29 19:52:36 2001*************** *** 583,611 **** for index in range(first,end): # preset kw['previous-sequence']= 0 ! kw['next-sequence']= 0 # now more often defined then previously # ! if index==first or index==last: ! # provide batching information ! if first > 0: ! pstart,pend,psize=opt(0,first+overlap, ! sz,orphan,sequence) ! if index==first: kw['previous-sequence']=1 ! kw['previous-sequence-start-index']=pstart-1 ! kw['previous-sequence-end-index']=pend-1 ! kw['previous-sequence-size']=pend+1-pstart ! try: ! # The following line is a sneaky way to ! # test whether there are more items, ! # without actually computing a length: ! sequence[end] ! pstart,pend,psize=opt(end+1-overlap,0, ! sz,orphan,sequence) ! if index==last: kw['next-sequence']=1 ! kw['next-sequence-start-index']=pstart-1 ! kw['next-sequence-end-index']=pend-1 ! kw['next-sequence-size']=pend+1-pstart ! except: pass if index==last: kw['sequence-end']=1 --- 583,610 ---- for index in range(first,end): # preset kw['previous-sequence']= 0 ! kw['next-sequence']= 0 # now more often defined than previously # ! # provide batching information ! if first > 0: ! pstart,pend,psize=opt(0,first+overlap, ! sz,orphan,sequence) ! kw['previous-sequence']=1 ! kw['previous-sequence-start-index']=pstart-1 ! kw['previous-sequence-end-index']=pend-1 ! kw['previous-sequence-size']=pend+1-pstart ! try: ! # The following line is a sneaky way to ! # test whether there are more items, ! # without actually computing a length: ! sequence[end] ! pstart,pend,psize=opt(end+1-overlap,0, ! sz,orphan,sequence) ! kw['next-sequence']=1 ! kw['next-sequence-start-index']=pstart-1 ! kw['next-sequence-end-index']=pend-1 ! kw['next-sequence-size']=pend+1-pstart ! except: pass if index==last: kw['sequence-end']=1 -- end -- patch #2: introduce new variables This patch introduces the variables batch-next-sequence batch-next-sequence-start-index batch-next-sequence-end-index batch-next-sequence-size batch-previous-sequence batch-previous-sequence-start-index batch-previous-sequence-end-index batch-previous-sequence-size Which behave exactly the same as the variables withouth 'batch-' in front, but these are available with each iteration/item of dtml-in, not just the first/last. This patch should not break any existing dtml code. -- patch begins here -- *** Zope-2.3.2-orig/lib/python/DocumentTemplate/DT_In.py Fri Apr 13 21:30:38 2001 --- Zope-2.3.2-src/lib/python/DocumentTemplate/DT_In.py Tue May 29 20:23:24 2001 *************** *** 583,589 **** for index in range(first,end): # preset kw['previous-sequence']= 0 ! kw['next-sequence']= 0 # now more often defined then previously # if index==first or index==last: # provide batching information --- 583,609 ---- for index in range(first,end): # preset kw['previous-sequence']= 0 ! kw['next-sequence']= 0 # now more often defined than previously ! # provide batching information ! if first > 0: ! pstart,pend,psize=opt(0,first+overlap, ! sz,orphan,sequence) ! kw['batch-previous-sequence']=1 ! kw['batch-previous-sequence-start-index']=pstart-1 ! kw['batch-previous-sequence-end-index']=pend-1 ! kw['batch-previous-sequence-size']=pend+1-pstart ! try: ! # The following line is a sneaky way to ! # test whether there are more items, ! # without actually computing a length: ! sequence[end] ! pstart,pend,psize=opt(end+1-overlap,0, ! sz,orphan,sequence) ! kw['batch-next-sequence']=1 ! kw['batch-next-sequence-start-index']=pstart-1 ! kw['batch-next-sequence-end-index']=pend-1 ! kw['batch-next-sequence-size']=pend+1-pstart ! except: pass # if index==first or index==last: # provide batching information -- To apply either of them, cd to your SOFTWARE_HOME (i.e. Zope-2.3.2-src) and patch -p1 < /location/of/patch NOTE! It only makes sense to apply one of these patches, not both! Cheers, Ivo -- Drs. I.R. van der Wijk -=- Brouwersgracht 132 Amaze Internet Services V.O.F. 1013 HA Amsterdam -=- Tel: +31-20-4688336 Linux/Web/Zope/SQL Fax: +31-20-4688337 Network Solutions Web: http://www.amaze.nl/ Consultancy Email: ivo@amaze.nl -=-