SysListview32 slow population means search-by-keyboard doesn't work anymore. How to solve ?

[R.Wieser]

Hello all,

I've got a listview in ownerdata mode, in which the generation of that
ownerdata (thumbnails) is rather slow. As a result the listviews own
searching for a (thumbnails) name doesn't work anymore, as the end-of-word
delay times out before the (re)population is finished.

That means that when I try to search for "abc" the slow repopulation kicks
in after I've pressed the "b" key, doesn't recognise more characters being
typed because of the slow population, sees a long delay between "b" and "c"
being recognised which exeedes its "word restart timeout", and than happily
restarts the search starting with "c".

My question: How do I change, for that one listview, the "word restart
timeout" value. Although I've tried several keywords and combinations
thereof I've not been able to find anything. :-(

Regards,
Rudy Wieser

[JJ]

Post by R.Wieser
Hello all,
I've got a listview in ownerdata mode, in which the generation of that
ownerdata (thumbnails) is rather slow. As a result the listviews own
searching for a (thumbnails) name doesn't work anymore, as the end-of-word
delay times out before the (re)population is finished.
That means that when I try to search for "abc" the slow repopulation kicks
in after I've pressed the "b" key, doesn't recognise more characters being
typed because of the slow population, sees a long delay between "b" and "c"
being recognised which exeedes its "word restart timeout", and than happily
restarts the search starting with "c".
My question: How do I change, for that one listview, the "word restart
timeout" value. Although I've tried several keywords and combinations
thereof I've not been able to find anything. :-(
Regards,
Rudy Wieser

The LVN_GETDISPINFO notification needs to be handled to provide the item
text. There are also other notifications which should be handled for virtual
ListView.

[R.Wieser]

JJ,

Post by JJ
The LVN_GETDISPINFO notification needs to be handled to provide the
item text.

I see I did not make myself completely clear.

The problem occurs *after* the listview has been initially populated (that
part works) and I try to type the name of one of the thumbnails to
find-and-select it.

Post by JJ
There are also other notifications which should be handled
for virtual ListView.

If you could point out which one/ones has/have something to do with the
search-by-keyboard problem I would appreciate it.

Regards,
Rudy Wieser

[JJ]

Post by R.Wieser
If you could point out which one/ones has/have something to do with the
search-by-keyboard problem I would appreciate it.

All of the requirements for the virtual list functionalities needs to be
fullfilled first. Otherwise the list view won't know what text an item has,
in order to be looked up on using keyboard.

https://learn.microsoft.com/en-us/windows/win32/controls/use-virtual-list-view-controls

[R.Wieser]

JJ,

Post by JJ
All of the requirements for the virtual list functionalities needs
to be fullfilled first. Otherwise the list view won't know what text
an item has, in order to be looked up on using keyboard.

You're concentrating on the wrong things I'm afraid.

As I wrote, the problem is not the searching itself, but that it decides
that, due to a timeout, I'm starting a new search when I'm not.

Or, to put it differently : I *can* do a search when I use a small dialog
showing just a few thumbnails (read: the repopulation is finished quickly),
but I *can't* when I go fullscreen, showing 28 of them (read: the
repopulation takes a while).

Regards,
Rudy Wieser

[JJ]

Post by R.Wieser
You're concentrating on the wrong things I'm afraid.
As I wrote, the problem is not the searching itself, but that it decides
that, due to a timeout, I'm starting a new search when I'm not.
Or, to put it differently : I *can* do a search when I use a small dialog
showing just a few thumbnails (read: the repopulation is finished quickly),
but I *can't* when I go fullscreen, showing 28 of them (read: the
repopulation takes a while).
Regards,
Rudy Wieser

The rendered images should be cached and be stored as part of the items'
data for quick retrieval.

If you want a more responsive UI, render the item's image in a background
thread instead of the window handler's thread. When done, notify the window
handler's thread to update the list item's display.

When the item dimension is changed, e.g. if the list view is for displaying
image thumbnails and the thumbnail size is changed, rerender the item
images.

[R.Wieser]

JJ,

Post by JJ
The rendered images should be cached and be stored as part of the
items' data for quick retrieval.

Whould you mind it very much to first try to help me find an answer to my
question to how to influence the keyboard timeout for the listviews search
function ?

You see, that one would probably solve al my problems in a way that has
likely the least ammount of side effects (as always, I do not mind to be
shown to be incorrect here).

What I mean ? Your "caching" solution just moves the delay to the start of
the program, causing a "go brew some coffee and drink it" delay there. If
you mean I should pre-generate them than you introduce a "how do I keep them
in sync" problem.

Both solutions either need a lot of memory (caching using an imagelist) or
quite a file (caching them in a "database" of sorts).

If yoiu are thinking of storing the thumbnails back into the image files
they came from than that has its own problem : not all image formats allow
it.


My own idea for I can't get a hold on that keyboard timeout I will probably
just generate-and-load the first matching thumbnail, and only (lazy) load
the other thumbnails after a keystoke timeout (which I wil try to set a bit
longer than the "end of search word" timeout - watever it is).


IOW, I've been thinking about how to solve the problem myself before even
considering posting here. And for some odd reason I would like to try to go
thru them starting with the simpelest, easiest and least side-effects one
first - and than, if needed, work my way up. :-)

Regards,
Rudy Wieser

[JJ]

Post by R.Wieser
Whould you mind it very much to first try to help me find an answer to my
question to how to influence the keyboard timeout for the listviews search
function ?

The timeout is defined and handled by the ListView's built in handler, which
is not exposed as API. What you want is thinkering with (undocumented)
software internals which may vary between software versions.

Post by R.Wieser
What I mean ? Your "caching" solution just moves the delay to the start of
the program, causing a "go brew some coffee and drink it" delay there.

I did mentioned to generate the rendered image in a background thread. Only
the images. Not including the item's text. The image generation would not
block or interfere the window handler's thread, since it's run in other
thread. Even if it's run on a single core CPU, the background thread can be
set to use a lower priority.

Post by R.Wieser
Both solutions either need a lot of memory (caching using an imagelist) or
quite a file (caching them in a "database" of sorts).

Is the displayed image for each ListView item really THAT big? Like... half
of a screen?

Post by R.Wieser
If yoiu are thinking of storing the thumbnails back into the image files
they came from than that has its own problem : not all image formats allow
it.

I never suggested that, considering that file system storage is slower than
RAM. Performance, and memory usage usually don't agree with each other.

[R.Wieser]

JJ,

The timeout ... is not exposed as API.

That is what I needed to hear. I would have /liked/ to hear that I
overlooked something and how to do it, but the above is second best.

It means that I can stop thinking about & search for it, and focus on other
possible (but more complex) methods.

I did mentioned to generate the rendered image in a background thread.

I just took a peek at your past messages (I could have missed it as I was
focussed on getting the timeout question answered), but I do not see it.

But yes, thats something I did not even think about. I'm not at all sure
about how I would/should manage aborts of such retrievals though (when the
listviews contents change while its still filling images in).

Post by R.Wieser
Both solutions either need a lot of memory (caching using an imagelist) or
quite a file (caching them in a "database" of sorts).

Is the displayed image for each ListView item really THAT big? Like...
half of a screen?

No, they are small(ish) (placed 7 wide, 4 high when at fullscreen). But as
they are many it ofcourse adds up.

Post by R.Wieser
If yoiu are thinking of storing the thumbnails back into the image files
they came from than that has its own problem : not all image formats allow
it.

I never suggested that,

No, you didn't. I provided it as something that went thru my mind as one of
the possibilities to store thumbnails (in a way which needs the least
ammount of bookkeeping).

Thanks for telling me that I can't do anything with the timeout (I really
needed that).

Regards,
Rudy Wieser