Michael,
On Thu, Jul 26, 2018 at 6:32 AM mferguson--- via 4D_Tech <
[email protected]> wrote:
> We have a memory leak in our v15.6 Windows database and have narrowed it
> down to a listbox where the columns are dynamically added using LISTBOX
> INSERT COLUMN.
> The header and footer variables are nil pointers, in accordance with the
> documentation.
> And to reference these variables for the assignment of properties, per the
> documentation:
>
> $FtrVar_P:=OBJECT Get pointer(Object named;FTR_Names_aT{$Ndx})
> $HdrVar_P:=OBJECT Get pointer(Object named;HDR_Names_aT{$Ndx})
>
> However, the get object pointer above returns nil pointers, so we can’t
> assign properties.
>
I was just writing about using Listbox get arrays for this purpose when I
saw Olivier's post. I suggest this approach as well.
> So, we set up our own variable manager that declares and reuses header and
> footer variables for the listbox, using execute formula. The variable
> manager has been tested and the number of variables for the form does not
> grow. However, the apparent search speed preceding the display gets slower
> and slower. The queries themselves are fast, but the re-display seems to be
> the culprit eating up memory.
>
Using EXECUTE ... is probably not the best solution for what you are
attempting to do. 4D is pretty good at managing these variables. It sounds
like you're working with 4D interpreted. There are a lot of tricks you can
get away with using Execute in an interpreted db that fail if you plan on
compiling it later.
A few weeks ago another developer was having speed issues with listboxes as
well. In that case he was rebuilding the listboxes every time there was a
change and found the LISTBOX INSERT ARRAY command was slow. When I build
listboxes dynamically I handle the chores of configuring the listbox (that
is, inserting the columns, headers and footers) and populating them
independently. Changes in the data may require a REDRAW command but usually
not re-configuring the whole listbox. The point is once he changed his
approach he found the speed issue disappeared and overall management was
easier.
--
Kirk Brooks
San Francisco, CA
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