Ethereal-dev: Re: [Ethereal-dev] Deactivate "Apply" button if the display filte ris not valid?
On Feb 10, 2004, at 9:51 AM, Ulf Lamping wrote:
Ok, no problem if you tend to "ignore" whitespace changes. I just
don't know how to implement this in the filter engine.
Ignoring whitespace changes in arbitrary filters is more work than
ignoring filters that contain only white space; I think Olivier was
talking about the latter.
You can tell whether a filter was empty by checking whether
"dfilter_compile()" supplied a non-null "dfilter_t" pointer - if the
pointer it supplied was null, the filter was empty.
Note that "filter_packets()" will, if the filter is empty, set
"cf->dfilter" to null - even if it's "empty" because it's a non-null
string that contains nothing but white space, so the "Clear" button
should be turned off if "cf->dfilter" is null.
That would implement "deactivate the clear button if the string is
already empty", and would consider, for example, a single space as an
empty string.
Note that you can't type a tab into the "Filter:" text box, as Tab
means "go to the next control that can have the input focus". (You can
get a tab into that box by manually putting tabs into filter
expressions in your dfilter file - but the tabs display strangely, e.g.
as a square box, and editing the field doesn't seem to work very well.)
You can type spaces in there - but you can't always tell the spaces are
there, especially if they're at the end of the string, or if the string
is *all* spaces.
As such, I don't see the user being bothered by us treating all
white-space-only filters as empty - they'd probably be more surprised
by a filter with a space in it being treated *differently* from a
filter with nothing in it, as you can't easily tell the difference
between them (you can't tell by looking at the field unless you notice
that the typing cursor isn't at the left-hand edge of the field).
