Here's a working virtual listview script

[martin]

I'm sure somebody can use this someday....
You can 'load' millions of items within a second into the listview. The listview shows in fact only the records that should be visible. Instead of an array you can also use a database (FILE_GETR command for example). The 4th listview column in this example is a hidden column with the record numbers.

Key handling (up/down/home/end/pgup/pgdn) is done by the script
Horizontal and vertical scrollbars are virtual

Although I am pretty proud of it, I couldn't make this without the help of our master Eros, who solved some problems for me.

[Petr Schreiber]

:eusaclap:

Martin, this is very elegant solution,
thanks a lot for sharing!

[ErosOlmi]

Thank you very much martin.

I think it can be a great teaching example of anyone in need of a method to manage a lot of data.

Ciao
Eros

PS: I attached the script as file + added an image. Better for those willing to test it or get source.
To run the script, you need to have thinBasic at least version 1.7.9.0 beta or above

[martin]

Hi Eros,

First of all, thanks for your hard work on the new ThinAir version. Unfortunately a lot of things aren't working yet, but I am very happy that the Undo problem has been solved!! :eusaclap:

Now my problem for today :lol:

I discovered a problem with the script I posted in this topic.
I have add small code to callback function cbSlave():


CASE %LVN_COLUMNCLICK 'sort the listview
do while not Terminate
'some commands here
doevents
loop


In the dialog callback function WindowMainProc() I set the global viariable Terminate to %TRUE when the dialog is closed


CASE %WM_CLOSE
terminate=%true
STOP


You can find complete code in attachment....

If execute this script and then close the dialog by clicking the red closing-button (X) at the right top, the program crash. Is there a way to solve this? I tried the same code in another listview script and then everything works fine, I am pretty sure that this has something to do with the cbSlave callback function (i know....you already warned me that using this could be tricky :roll:)

Thanks in advance for your reply!

Martin

[martin]

Oh, I forgot to tell that you must first click on a (grey) listview column and then close the dialog! Only then the program will crash

[martin]

problem "solved" by removing doevents instruction

[lydia_sp]

martin, how to use your script ?

some minutes before I wanted to write you, that your script causes at my pc more than one gpf`s. you are faster, good guy! I will test your script again :) thanks!

bye, lydia

[martin]

martin, how to use your script ?

some minutes before I wanted to write you, that your script causes at my pc more than one gpf`s. you are faster, good guy! I will test your script again :) thanks!

bye, lydia


Lydia, as fas as I know my script should work fine, but please download the one at the top of this topic http://community.thinbasic.com/index.php?action=dlattach;topic=2895.0;attach=5692

Please let me know if there's something wrong, i hate errors :grrrr:

[lydia_sp]

works fine ! have downloaded another script of this morning :)

saludos, lydia

[lydia_sp]

hello martin.

my instincts are correct ;)

your last script has the problem I have noticed yesterday morning. your first script (first post) is ok.

the last script: may be a problem in line 32 (please use debug modus!) with F8 you will come into a loop and cannot check whole script.
if I push grey column then any line below, close the window the gpf will come.

lydia

[martin]

Hi Lydia,

Please ignore the last script, it was just an example for Eros to show him a problem. I don't know why ThinDebug doesn't come out that FOR-NEXT loop, maybe Eros can tell....it's strange indeed because this problem does not seems to happen when you run the script in normal mode (without ThinDebug).

Have a nice day,

Martin

[Jordi Vallès]

Do you know this note?
" Background color to set or the CLR_NONE value for no background color. List-view controls with background colors redraw themselves significantly faster than those without background colors."
on http://msdn.microsoft.com/en-us/library/bb761153%28VS.85%29.aspx

I verified this and is true.

Also in http://www.powerbasic.com/support/forums/Forum7/HTML/002913.html

[Petr Schreiber]

Hi Jordi,

thanks for the tip, I didn't know this trick!