Limit on pixles in a group [ was: Re: Max number of columns in a datagrid?]

Richard Gaskin ambassador at
Tue Nov 27 13:34:51 EST 2018

Alex Tweedly wrote:

 > On 25/11/2018 23:04, Richard Gaskin via use-livecode wrote:
 >> This limitation may have been eliminated, or close to eliminated,
 >> with the field object.  And now that fields have column-independent
 >> alignment, it's rare that there's ever a need to replace that one
 >> object with a thousand-object DataGrid for simple list views.
 >> The DataGrid is bound to a limitation within LC for group contents:
 >> the formattedWidth and formattedHeight of a group cannot exceed 32765
 >> px. Attempting to go beyond that flips the signed bit internally and
 >> objects will be rendered incorrectly.
 >> I suppose it might be nice to see that extended, but in practice do we
 >> really need it?  How big should a group meaningfully be?
 >> 32,765 px is about 30 feet in size.  That's a lot to ask a user to
 >> scroll through, not to mention being a lot to ask LC to buffer so it
 >> can handle the scroll efficiently.
 > Hmmmm - 32765 pixels at 227 dpi is "only" about 12 feet :-)
 > Still too much - except ....

If LC is rendering such high resolution so small, that would be a bug, 
and a clear indicator that resolution independence would need to be 
ported from the mobile engine to the desktop engine if it hasn't been 

 > While it might be too much for horizontal scrolling, it's not so clear
 > for vertical scrolling.  Twelve feet is about 13 pages vertically of
 > A4/letter paper; so if I had a document that (for its own reasons) was
 > in continuous format rather than paginated, I might well want to have
 > it all in a single group. I probably wouldn't want to scroll through
 > it -  but I might want to have some method of (say) going directy to a
 > specified chapter or verse - and then see it in its continuous
 > context.

The existing field object does a fine job buffering for smooth scrolling 
of just about any text of practical length.  Logically, the limit of 
field contents is about 4GB (UINT4), but in practical terms other memory 
needs may not allow quite that much.  FWIW I've loaded the Bible into a 
field and it scroll quite nicely, much more smoothly than Microsoft 
Word's paging scroll.

 > And if we were to consider non-European languages, maybe that would
 > apply horizontally as well ??

What non-European languages have no line wrapping?  How do such 
languages display anything on any electronic or printed surface?

  Richard Gaskin
  Fourth World Systems
  Software Design and Development for the Desktop, Mobile, and the Web
  Ambassador at      

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