List box scroll speed

Question

5.00/5 (1 vote)

See more:

Hi All,

I have built a control in the style of Excels grid in which a collection of cells is presented to the user to scroll and select etc.

When i key up or down the current row moves up and down similar to a list box, if i hold the down key the control performs the action of scrolling through the items quickly.

The speed of this however appears fixed. I was wondering what is restricting this as there is no flickering or anything indicating that the PC is struggling to render the table.

Is it the amount of processing being carried out or a standard in .Net fixing the speed of event firing when holding down a key etc?

Thanks George

Posted 4-Jan-11 22:29pm

grwithey

Updated 4-Jan-11 22:32pm

Nuri Ismail

v2

Add a Solution

Comments

Nuri Ismail 5-Jan-11 4:33am

Removed bold.

2 solutions

Solution 2

My guess is that you are repainting to often.

OriginalGriffs idea "What you may need to do is work from the keydown and keyup events with a timer and scroll in larger increments the longer the key is kept down - and ignore the keypress event while you are doing it!" is a good one.

If you just invalidate the area that needs repainting in your input handling you will probably see an improvement.

Regards
Espen Harlinn

Posted 4-Jan-11 22:54pm

Espen Harlinn

Comments

grwithey 5-Jan-11 5:09am

It currently only calls a refresh once during the key press and only draws the items that are visible area of the control.

I have tested the control to 1 million entries and it scrolls the same speed so i think OriginalGiffs suggestion is a good idea.

Thanks George

Add a Solution

Add your solution here

Treat my content as plain text, not as HTML

Preview 0

…

Existing Members

Sign in to your account

...or Join us

Download, Vote, Comment, Publish.

Your Email
Password
Forgot your password?

Your Email
This email is in use. Do you need your password?
Optional Password

I have read and agree to the Terms of Service and Privacy Policy
Please subscribe me to the CodeProject newsletters

When answering a question please:

Read the question carefully.
Understand that English isn't everyone's first language so be lenient of bad spelling and grammar.
If a question is poorly phrased then either ask for clarification, ignore it, or edit the question and fix the problem. Insults are not welcome.
Don't tell someone to read the manual. Chances are they have and don't get it. Provide an answer or move on to the next question.

Let's work to help developers, not make them feel stupid.

This content, along with any associated source code and files, is licensed under The Code Project Open License (CPOL)

OriginalGriff · Accepted Answer · 2011-01-04T22:41:00

Solution 1

Does it stop immediately when you release the key?
If not, then it is processing.
If so, then it may be you key repeat speed - a windows feature you cna change in control panel!

What you may need to do is work from the keydown and keyup events with a timer and scroll in larger increments the longer the key is kept down - and ignore the keypress event while you are doing it!

Posted 4-Jan-11 22:41pm

OriginalGriff

Comments

grwithey 5-Jan-11 4:48am

Ah that makes sense, it does stop immediately when released which would indicate it is the repeat speed.

That sounds like a good way of overcoming this thanks for the help.

Espen Harlinn 5-Jan-11 4:55am

5+ Good idea about the keyboard handling

JF2015 5-Jan-11 4:56am

Good. Have my 5.

JOAT-MON 5-Jan-11 4:58am

Nice test, nice solution. +5

Nuri Ismail 5-Jan-11 5:05am

Good call.