Develop Reference

how do I recreate the sencha style gesture scroll for lists and content?

So... I am working on an interaction design project and I want to create a sencha-style gesture scroll for content areas. The way I've done it so far, is to attach touchmove/start/end events to the content area, and it translateY's the contents. It works in on desktop with mousemove/up/down events, but it jumps around like crazy with touch. I'm not sure whats wrong.. here is a link to a prototype.
**requires webkit.
http://apps.omorphos.com/gesture-scroll
I think it is an issue with the event response, but I tried and haven't been able to nail it down. Any help is greatly appreciated!

So, I figured this out.
What I was doing was attaching the touch event to the list tag itself.. and, that works fine on desktop with mouse events; however, with touch, the target changes and touchend doesn't fire properly.
So, what I did, and what I believe sencha does, ... and I had originally implemented but went in a different direction... is have an absolutely positioned element with a transparent background color floating above the element that will be manipulated. All of the touch events will be captured by that DIV and then the elements below can be manipulated without losing the event data.
In the new version I used HammerJs ... more info: http://eightmedia.github.io/hammer.js/
but i'm pretty sure you could just use standard events; but the good thing about hammer js, is that it will translate touch events to mouse events for testing in the browser, this also means making the coordinates for touch the same as mouse, so you can access mouse event coords via
e.gesture.touches[0].pageX
e.gesture.touches[0].pageY
which let's you write less code.
Part 2:
Additionally... part of the issue is... how do you click on the content/components(e.g. links) below the screen.
How you do this... is you take the coords from the event handler and pass them through this native Javascript function...
var a = document.elementFromPoint(x, y);
this will return the dom element. and all you have to do is trigger the click/tap event.
Which would be great, except it will pick the element with the highest z-index.. so that is your screen obj(the one that is capturing all of the touch events). So, what you need to do, is hide the screen after a tap is registered, and then execute this function 200ms later, and then bring back the screen to capture whatever events.
You can do this with this function...
$(theScreen).on('tap', function(e){
screen.hide();
var hit = document.elementFromPoint(e.gesture.touches[0].pageX, e.gesture.touches[0].pageY);
$(hit)[0].tagName !=="A" || $(hit).trigger('click');
setTimeout(function(){screen.show()},300);
});
And, that is how I solved it!
My code is not super annotated, but you can find it at the link below:
Updated example:
http://apps.omorphos.com/gesture-scroll/v2/

Detect if mousedown is for a selection drag

I am tracking the mousedown state and not only does Secondary mouse button click trigger the mousedown event while failing to deliver on a mouseup event, so does the situation of dragging on something selected (note this is different from dragging to select).
I am currently experiencing this on Safari 6 on a Mac and I'll report back if I see it on other platforms/systems.
Is there a way to intercept this so that my JS program can be not confused about what's going on? For the secondary button situation I simply check event.which === 3 in my handler and just don't mark my button as down, and that takes care of that, but I am using the left button to initiate drag on a selected bit of text as well..

I am not sure I understand what you want to do, but checking which button has been pressed may involve a bit more work other that checking the which property.
Have a look this quirksmode page. The rightclick section contains some code that may help you.
A very thorough explanation on mouse events is also available here. It can really help you deal with browser quirks.

The specific issue here is that mousedown is not triggered when dragging a selection.
The solution is to simply prevent selection where it may become problematic.

JavaScript pass mouseenter event to element that is underneath another element

I'm trying to build a little calendar app sort of like Google Calendar. I'm trying to create events with a click and drag functionality so that the events align to a grid. I'm trying to
tie the dragging to TD elements below the event DIV element, which works when moving downwards (lengthening the event), but it doesn't work moving upwards (shrinking the event).
What occurs is that the mouseenter event is fired for the event DIV element, but it is never fired for the underlying TD. If you try to resize the DIV by moving upwards on the side, it works because the TDs actually receive the mouseenter event.
Google Calendar and jQuery Week Calendar use the mousemove event, but the mousemove event is fired for every pixel, which seems a waste. Is there a way to write this without using the mousemove event?
Is it possible to put the DIV element behind the table and the TDs? If the table is somewhat transparent, the user would still be able to see the DIV, but would actually be firing events on the TDs. I tried to do this with z-index, but it didn't seem to actually work.
jsFiddle example code: http://jsfiddle.net/rockymeza/8SHpA/

It sounds like you're having a similar kind of issue that I had:
you want to fire event behind an element? The answer is CSS. Set pointer-events:none; to the parent.
I had made a test where I tried to (unsuccessfully) implement the same behavior on touch devices. You can check that at: http://www.hakoniemi.net/misc/pointer-events.html if it'd help you with your issue.

javascript mouseover while dragging

I'm trying to implement a drag and drop script and have hit the wall with one problem. When you take an item and start dragging it - the item is directly below your cursor and onmouseover event is very rarely fired on the items below. But i want other items to highlight when i drag something over them. One of the solutions would be not to drag anything at all - that way the mouse events would work, but that would look ugly. Has anyone ever done something like this and know how to overcome this problem?
If you're thinking about suggesting some JQuery plugin or something like that - please don't. I don't need a completed solution, this is educational.

IMO, in order to have the mouseover event to be fired up frequently would be binding the mouseover event to the parent element of all the affected elements, or perhaps to the document itself, since events get bubbled up, they are probably the only elements that can fire the mouseover events.
Then further, write a hit method in your mouseover event and actively check the position of your mouse cursor, see whether it's going under the target element's boundary. Tradeoff in usability and performance. You choose.
My 2cents.
Or perhaps, you can reverse engineer jQuery UI to see how they implement the drag element. Haven't check thou, but I think there should be a wiser way.

Simple JavaScript drag and drop witout the help of a library

I am simply looking for a way of using drag and drop without jquery or any other library. If a dragged object is dropped on another element the later element should start an event (in FF - better would be browser independent).
I know that drag and drop for JavaScript was discussed sometimes before but the previous postings didn't help me.
Although I found some examples it is not clear to me if there is a "drop" or "dragdrop" events exist but these things don't work:
<p ondrop='alert("It worked");'>Text</p>
<p ondragdrop='alert("It worked");'>Text</p>
How could this be done?
Many thanks in advance.

I agree with the other answers. A library will save you a lot of time and headache. This is coming from someone who just recently created a drag-and-drop control from scratch.
If you insist though this is what you'll need to do:
Bind a onmousedown event to the div you want to drag (div.onmousedown).
Change the div's position style to absolute (div.style.position = 'absolute')
Begin capturing mouse movement (document.onmousemove).
On mouse move update the div's position (div.style.top|left = '[location]px')
On the div's onmouseup event (or the document's) unbind all the handlers and do any other cleanup (null out position changes, etc).
Some problems a library will probably solve:
While dragging you will select text on the page (looks ugly).
Binding to events is different between browsers.
You have to calculate the size of the element being dragged if you want to show placeholders and to make it not "pop" when you begin dragging the control (since changing to absolute positioning will remove the element from flow).
You will probably want your dragged element to move fluidly so you will have to store some mouse offset when selecting the element or automatically center the element to the mouse.
If you want to drag an item in a list you'll have to write a ton more custom code for that list to accept the dragged item.
You'll have to take into consideration dragging when the window is scrolled and possibly dragging inside other elements that are positioned strangely.

I am simply looking for a way of using drag and drop without jquery or any other library.
I'm sorry, but there are no such thing as simply drag and drop without any library. You can write it all yourself, but that will be a lot of JS to make it work in all browsers.

Hmm. It's probably not that simple that you'd want to do it yourself, but I would look at Peter Michaux's FORK Javascript drag and drop library -- unlike JQuery or all those big libraries, FORK's modules are decoupled from each other, and are simple enough that you could probably look at Peter's source code and figure out the bits you need. (edit: I'd just use FORK.Drag as it's really small: 7.6KB total minified)

While I agree that library is the way to go, the answer you want is onmousedown, onmousemove, onmouseup. You have to handle those three events.
In onmousedown you'd find the target (event.target or similar in different browsers) and set draggedObject = event.target. You'd also start handling the onmousemove event.
Whenever the onmousemove event fired, you'd move the dragged element based on the difference in position since last time the onmousemove event fired.
In the onmouseup event, you'd clear your draggedObject variable and stop handling onmousemove.
It's not very crossbrowser, but it's the core of what you'd need to do for dragging and dropping.