[reportlab-users] question about keepWithNext and multibuild

[adam hyde]

goodness...it appears to work :)

I patched reportlab 2.1 and it looks good. I will run some more tests
today and tomorrow and let confirm the situation, but from what I see
now it is holding the keepWithNext while building the TOC. Fantastic!
Many thanks for all your help!

adam



On Tue, 2008-09-23 at 18:03 +0100, Robin Becker wrote:

> adam hyde wrote:

> >........

> > So we are really needing to build a TOC without multipass. We just pick

> > up on h1 headings using Pisa as this is the only depth required in a

> > book TOC for our purposes. If anyone has a nice snippet for producing a

> > TOC without multipass we would very much appreciate it.

> > 

> > adam

> .........

> 

> At the moment the keepTogether style is handled thusly;

> 

> in the main loop of the doctemplate build process at the start of the flowable 

> handling the head of the list is examined for flowables with keepWithNext style. 

> If any are found these are bundled together and replaced by a single 

> KeepTogether flowable; to avoid doing this recursively we force the keepWithNext 

> value for each flowable to be zero.

> 

> KeepTogether has just enough intelligence to try and ensure its contents stay on 

> a single page and when wrapped it always fails first time inorder to allow the 

> split method a chance to force a frame throw.

> 

> Even though we've messed about with the current passed story quite a bit the 

> main problem is that we changed the keepWithNext attribute on each flowable we 

> bundled together. The multiBuild method is careful to keep the original story 

> list intact, but we have forgotten that flowables are mutable (in this case a 

> structural property of the flowable was changed).

> 

> It should be possible to just remember the flowables which have been modified by 

> the handle_keepWithNext method and restore them at the end of the loop. After 

> checking I see that we are already attempting to eliminate some side effects of 

> the main loop.

> 

> 

> I have run all tests with this patch in place. It attempts to fix the 

> keepWithNext values back to their original state. Can you give it a whirl? It is 

> against current head, but the coding is not that hard so should apply to recent 

> sources.

> 

> C:\code\reportlab\platypus>svn diff doctemplate.py

> Index: doctemplate.py

> ===================================================================

> --- doctemplate.py      (revision 3298)

> +++ doctemplate.py      (working copy)

> @@ -600,8 +600,17 @@

>           if i:

>               if i<n and not getattr(flowables[i],'locChanger',None): i += 1

>               K = KeepTogether(flowables[:i])

> -            for f in K._content[:-1]:

> -                f.__dict__['keepWithNext'] = 0

> +            mbe = getattr(self,'_multiBuildEdits',None)

> +            if mbe:

> +                for f in K._content[:-1]:

> +                    if hasattr(f,'keepWithNext'):

> +                        mbe((setattr,f,'keepWithNext',f.keepWithNext))

> +                    else:

> +                        mbe((delattr,f,'keepWithNext')) #must get it from a style

> +                    f.__dict__['keepWithNext'] = 0

> +            else:

> +                for f in K._content[:-1]:

> +                    f.__dict__['keepWithNext'] = 0

>               del flowables[:i]

>               flowables.insert(0,K)

> 

> @@ -818,6 +827,8 @@

>           #better fix for filename is a 'file' problem

>           self._doSave = 0

>           passes = 0

> +        mbe = []

> +        self._multiBuildEdits = mbe.append

>           while 1:

>               passes += 1

>               if self._onProgress:

> @@ -832,12 +843,6 @@

>               self.build(tempStory, filename, canvasmaker)

>               #self.notify('debug',None)

> 

> -            #clean up so multi-build does not go wrong - the frame

> -            #packer might have tacked an attribute onto some flowables

> -            for elem in story:

> -                if hasattr(elem, '_postponed'):

> -                    del elem._postponed

> -

>               for fl in self._indexingFlowables:

>                   fl.afterBuild()

> 

> @@ -850,6 +855,18 @@

>               if passes > maxPasses:

>                   raise IndexError, "Index entries not resolved after %d passes" 

> % maxPasses

> 

> +            #clean up so multi-build does not go wrong - the frame

> +            #packer might have tacked an attribute onto some flowables

> +            for elem in story:

> +                if hasattr(elem, '_postponed'):

> +                    del elem._postponed

> +

> +            #work through any edits

> +            while mbe:

> +                e = mbe.pop(0)

> +                e[0](*e[1:])

> +

> +        del self._multiBuildEdits

>           if verbose: print 'saved'

> 

>       #these are pure virtuals override in derived classes

> 

> plain text document attachment (mbe.patch)

> Index: doctemplate.py

> ===================================================================

> --- doctemplate.py	(revision 3298)

> +++ doctemplate.py	(working copy)

> @@ -600,8 +600,17 @@

>          if i:

>              if i<n and not getattr(flowables[i],'locChanger',None): i += 1

>              K = KeepTogether(flowables[:i])

> -            for f in K._content[:-1]:

> -                f.__dict__['keepWithNext'] = 0

> +            mbe = getattr(self,'_multiBuildEdits',None)

> +            if mbe:

> +                for f in K._content[:-1]:

> +                    if hasattr(f,'keepWithNext'):

> +                        mbe((setattr,f,'keepWithNext',f.keepWithNext))

> +                    else:

> +                        mbe((delattr,f,'keepWithNext')) #must get it from a style

> +                    f.__dict__['keepWithNext'] = 0

> +            else:

> +                for f in K._content[:-1]:

> +                    f.__dict__['keepWithNext'] = 0

>              del flowables[:i]

>              flowables.insert(0,K)

>  

> @@ -818,6 +827,8 @@

>          #better fix for filename is a 'file' problem

>          self._doSave = 0

>          passes = 0

> +        mbe = []

> +        self._multiBuildEdits = mbe.append

>          while 1:

>              passes += 1

>              if self._onProgress:

> @@ -832,12 +843,6 @@

>              self.build(tempStory, filename, canvasmaker)

>              #self.notify('debug',None)

>  

> -            #clean up so multi-build does not go wrong - the frame

> -            #packer might have tacked an attribute onto some flowables

> -            for elem in story:

> -                if hasattr(elem, '_postponed'):

> -                    del elem._postponed

> -

>              for fl in self._indexingFlowables:

>                  fl.afterBuild()

>  

> @@ -850,6 +855,18 @@

>              if passes > maxPasses:

>                  raise IndexError, "Index entries not resolved after %d passes" % maxPasses

>  

> +            #clean up so multi-build does not go wrong - the frame

> +            #packer might have tacked an attribute onto some flowables

> +            for elem in story:

> +                if hasattr(elem, '_postponed'):

> +                    del elem._postponed

> +

> +            #work through any edits

> +            while mbe:

> +                e = mbe.pop(0)

> +                e[0](*e[1:])

> +

> +        del self._multiBuildEdits

>          if verbose: print 'saved'

>  

>      #these are pure virtuals override in derived classes

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-- 
Adam Hyde
Founder FLOSS Manuals
http://www.flossmanuals.net