Using Both click and dblClick Events

[Gene Wirchenko]

Dear JavaScripters:

Suppose that one wishes to have an action take place when an
element is clicked and a different one when it is doubleclicked. How
does the event processing work?

From my checking under IE9, if I doubleclick, the click event
will fire twice before the dblClick fires. How do I know when the
second click will not be coming and can safely proceed with the click
event action?

Sincerely,

Gene Wirchenko

 

[Denis McMahon]

From my checking under IE9, if I doubleclick, the click event
will fire twice before the dblClick fires. How do I know when the
second click will not be coming and can safely proceed with the click
event action?

One approach that might work (untested):

Create a counter for each element that might be either clicked or double
clicked. Initialise the counter to 0.

When the element is clicked, check the counter. If 0, increment the
counter and call a delayed click event. 200 mSecs should be enough. If
not 0, just increment the counter.

In the delayed click event, if the counter is exactly 1, process it as a
single-click.

At the end of both click and double click event processing, set the
counter back to 0.

The code might look something like:

<script type="text/javascript">

var btn5ClickCount = 0;

function btn5Clicked() {
if (btn5ClickCount++ == 0) setTimeout("btn5DelayedSingleClick()",200);
}

function btn5DblClicked() {
// do stuff
btn5ClickCount = 0;
}

function btn5DelayedSingleClick() {
if (btn5ClickCount == 1){
// do stuff
}
btn5ClickCount = 0;
}

</script>

<input type="button" id="btn5" name="btn5" value="Button 5"
onclick="btn5Clicked()" ondblclick="btn5DblClicked()">

Rgds

Denis McMahon

 

[Tim Streater]

Dear JavaScripters:

Suppose that one wishes to have an action take place when an
element is clicked and a different one when it is doubleclicked. How
does the event processing work?

From my checking under IE9, if I doubleclick, the click event
will fire twice before the dblClick fires. How do I know when the
second click will not be coming and can safely proceed with the click
event action?

As far as I am aware, you don't except by timing it yourself. On the
first click set a timer in the single-click handler. If the second click
occurs within xx msec (I use 250), then in the double-click handler you
cancel the timer and proceed. If the timer goes off then the two clicks
get treated separately. You also need a flag so that, on the second
click within the period, the single-click handler does nothing.

A nuisance if you ask me but unclear how to avoid it. Trouble is it
means all single-click actions are delayed by 250msec.

 

[John G Harris]

Dear JavaScripters:

Suppose that one wishes to have an action take place when an
element is clicked and a different one when it is doubleclicked. How
does the event processing work?

From my checking under IE9, if I doubleclick, the click event
will fire twice before the dblClick fires. How do I know when the
second click will not be coming and can safely proceed with the click
event action?

In Windows the idea is that the first click selects something and the
second click says do some action on the selected thing. Do you really
want to make the first and second clicks so separate that you never want
to do both ?

The trouble with waiting long enough for a possible second click to
happen is that the Control Panel allows the user to make Windows' double
click timeout longer or shorter. If you make your timeout shorter than
windows' worst case then it's a disaster waiting to happen. If, though,
it's long enough then it will take a long time to recognise the first
click. This will drive you mad when you're testing, never mind the
customers.

Something that would work is to do the first click action, then cancel
or undo it if a double click is reported.

John

 

[Gene Wirchenko]

Dear JavaScripters:

Suppose that one wishes to have an action take place when an
element is clicked and a different one when it is doubleclicked. How
does the event processing work?

From my checking under IE9, if I doubleclick, the click event
will fire twice before the dblClick fires. How do I know when the
second click will not be coming and can safely proceed with the click
event action?

Thank you for the responses. I was wondering if I was missing
something on this. I ran into the same issue when I was first
starting out with Visual FoxPro years ago.

I wonder how Windows deals with it internally.

Sincerely,

Gene Wirchenko

 

[Tim Streater]

Thank you for the responses. I was wondering if I was missing
something on this. I ran into the same issue when I was first
starting out with Visual FoxPro years ago.

I wonder how Windows deals with it internally.

Or Mac OS X or presumably Linux too. Same way, I expect. I know that
under OS X if I double-click on something for which a single click is
significant (usually select), it does the single-click action and then
undoes it and does the double-click action.

 

[Gene Wirchenko]

Or Mac OS X or presumably Linux too. Same way, I expect. I know that
under OS X if I double-click on something for which a single click is
significant (usually select), it does the single-click action and then
undoes it and does the double-click action.

I am wondering about which events get revealed. If JavaScript
(or Windows) held onto the click until the time for a doubleclick had
expired before firing click, the problem with doubleclicking would not
occur. Maybe.

Sincerely,

Gene Wirchenko

 

[Tim Streater]

I am wondering about which events get revealed. If JavaScript
(or Windows) held onto the click until the time for a doubleclick had
expired before firing click, the problem with doubleclicking would not
occur. Maybe.

But then there would have to be a noticeable delay before any
single-click action was allowed to proceed. I can't remember the exact
reasoning when developing this aspect for my app, but I know I wanted to
clearly separate single and double-click actions. So in my case I had to
accept that there would be a delay for single-click actions. But there
are plenty of situations where that wouldn't apply so you don't want to
penalise those too.

 

[Gene Wirchenko]

[snip]

I am wondering about which events get revealed. If JavaScript
(or Windows) held onto the click until the time for a doubleclick had
expired before firing click, the problem with doubleclicking would not
occur. Maybe.

But then there would have to be a noticeable delay before any
single-click action was allowed to proceed. I can't remember the exact
reasoning when developing this aspect for my app, but I know I wanted to
clearly separate single and double-click actions. So in my case I had to
accept that there would be a delay for single-click actions. But there
are plenty of situations where that wouldn't apply so you don't want to
penalise those too.

I know. I suspect, now having thought about it a bit more, that
Windows does not ever have anything significant happen with both
events. Clicking on something can give it focus. Big deal. This
does not make a change.

What we do not see -- correct me if you have an example -- of
where both click and doubleclick do something significant. For
example, click executing the object and doubleclick opening it in
NotePad. If this is so, then it is a bit of smoke and mirrors.

Sincerely,

Gene Wirchenko

 

[Tim Streater]

[snip]

I am wondering about which events get revealed. If JavaScript
(or Windows) held onto the click until the time for a doubleclick had
expired before firing click, the problem with doubleclicking would not
occur. Maybe.

But then there would have to be a noticeable delay before any
single-click action was allowed to proceed. I can't remember the exact
reasoning when developing this aspect for my app, but I know I wanted to
clearly separate single and double-click actions. So in my case I had to
accept that there would be a delay for single-click actions. But there
are plenty of situations where that wouldn't apply so you don't want to
penalise those too.

I know. I suspect, now having thought about it a bit more, that
Windows does not ever have anything significant happen with both
events. Clicking on something can give it focus. Big deal. This
does not make a change.

What we do not see -- correct me if you have an example -- of
where both click and doubleclick do something significant. For
example, click executing the object and doubleclick opening it in
NotePad. If this is so, then it is a bit of smoke and mirrors.

I don't use Windows very much, but in the case OS X that may well be
true. In the case of my own app It is definitely *not* the case.

 

[John G Harris]

What we do not see -- correct me if you have an example -- of
where both click and doubleclick do something significant.

<snip>

In Windows File Manager, the first click says you want to use this
picture, not that program that deletes all your files; the second click
says Open it.

Sounds pretty significant to me.

John