How to trigger an event onMousewheel? - javascript

I am developing a WebGL application. For example, I have a sphere object that uses orbit controls for Zoom in/out.
Now I want to setup an event for the mousewheel. When zooming on my current WebGL block corresponding map location it can be zoomed in/out (used inline-block) for maps and WebGL. But the problem is that first of all my event is being triggered when I use the mousewheel. I also want to know whether my event logic is correct or not.
root.addEventListener('mousewheel', mousewheel, false);
function mousewheel(event) {
var mX = (event.wheeldetailX/width)* 2 - 1;
var mY = (event.wheeldetailY/height)* 2 + 1;
var WebGLZoom = new THREE.Vector3(mX, mY, 1);
var raycaster = new THREE.Raycaster();
raycaster.setFromCamera(WebGLZoom, camera);
WebGLZoom.sub(camera.position);
var mapzoom = map.getZoom();
if (WebGLZoom.z <= 5 && WebGLZoom.z > 2) {
map.setZoom(17);
} else if (WebGLZoom.z <= 2 && WebGLZoom.z > 0.0) {
map.setZoom(19);
} else {
map.setZoom(14);
}
}

You can use the wheel event like so.
document.addEventListener('wheel', function(event){
console.log(event.deltaY);
}, false);
This will result in a console log every time your mousewheel scrolls over the document. The deltaX and deltaY properties of the MouseWheel event are especially useful to figure out exactly how much the user scrolled and in which direction.

The event to use is wheel. You can find a working example here.

Related

How to make jquery setinterval movement in mobile smoother?

Sorry for bad english.
Here's link to site.
My task is to create site with no scroll. When user clicks to right part of screen car starts to move forward. When it reaches middle of screen - car stops and fixed content-block starts to move in opossite direction. if user moves cursor to left side of screen (while holding mouse button clicked) car should move backward.
Desktop version works as expected. But mobile version is slow. (it's not exactly slow, it's not as smooth as desktop i guess)
What can i do fix this problem?
On touchstart event i get event.pageX value to check what part of screen user touched. (so i would know what direction car should move) and store this value in variable "mousePos". Then i call setInterval with movement function
On touchend event i clear interval to stop car from moving.
On touchmove i will rewrite "mousePos" var with new event.pageX value. For example: user clicked, car starts to move, if user moved cursor to left i will use this var to check direction and turn car back.
In mouseMove function i will check car position and decide what action should be done - either move car or move background and i'll check if it reached start of end points
events:
$(document).on('mousedown touchstart', '.mouse-click', function(event){
clicking = true;
mousePos = event.pageX;
if ( event.target.className == 'helper' ) {
showModal();
} else {
moveStuff = setInterval(mouseMove, 1);
}
});
$(document).on('mouseup touchend', function(){
clicking = false;
carLights.removeClass('blink');
clearInterval(moveStuff);
})
$(document).on('mousemove touchmove', '.mouse-click', function(event){
if(clicking == false) {
return;
} else {
mousePos = event.pageX;
}
});
function:
function mouseMove() {
let offset = parseInt( mainContent.css('left') );
let offsetCar = parseInt( car.css('left') );
if ( mousePos > middleScreen ) {
carLights.removeClass('blink');
if ( offset < - ( contentWidth ) ) {
return;
} else {
rotateWheelsForward();
if ( offsetCar < middleScreen ) {
car.css('left', (offsetCar + mouseSpeed) + 'px');
} else {
mainContent.css('left', (offset - mouseSpeed) + 'px');
}
}
} else if ( mousePos < middleScreen ) {
carLights.addClass('blink');
if ( offset > 0 ) {
carLights.removeClass('blink');
return;
} else {
rotateWheelsBackward();
if ( offsetCar > minCarLeft ) {
car.css('left', (offsetCar - mouseSpeed) + 'px');
} else {
mainContent.css('left', (offset + mouseSpeed) + 'px');
}
}
}
}
So how can i make movement smoother in mobile? (i use iphone 5s safari, but tested in iphone 6, still works bad)
What changes should i implement to this code?
I suggest to use transform rather than position eg: left, top cause thats really affect layer reflow-repaint. Use requestAnimationFrame (wisely) to perform smooth event animation like scroll, mouseup, or any other event.
Then use will-change: transform; to element which will "transformed" on the future. This will creates new layer and prepare for the element changes later.
In my case, relative position impact reflow or green flash on the rendering tool chrome. So I prefer use fixed/absolute position to prevent this.
Here's some great article for you to get Leaner, Meaner, Faster Animations with requestAnimationFrame and how to achieving 60 fps animations with css
Hope this help ;)

How can I add some buffer to a mousemove event so it doesn't disrupt mouseup events

I'm currently building a menu that is also draggable and I'm using the following on each individual tab:
(mousedown)="dragging = false"
(mousemove)="checkMouseMove($event)"
(mouseup)="changeRoute('forms')"
Change Route looks like this:
changeRoute(routeName: string) {
// manual reset for dragging.
if (this.dragging) {
return;
}
Past this is just my routing and switch statement's that correctly will change route and apply styling etc.
Previously inside the mousemove event I just had dragging = true but the problem with this is that even the slightest movement will mean that a click does not occur when it's likely to be intended to.
My first instinct was that I need to add a buffer to the amount of space it will need to move to be called a drag but given the output events I'm not sure how to achieve this.
checkMouseMove(event) {
console.log(event);
}
This event provides me with the following output:
How can I use these events in conjunction with my checkMouseMove / Component to only change dragging after a reasonable amount of movement?
You can save the last mouse position and calculate the distance the cursor moved.
Based on this distance you can filter small and unwanted drags.
var lastEvent;
function checkMouseMove (event){
var dx = 0;
var dy = 0;
if (lastEvent) {
dx = event.clientX - lastEvent.clientX;
dy = event.clientY - lastEvent.clientY;
}
var d = Math.sqrt(Math.pow(dx, 2) + Math.pow(dy, 2));
if (d > 5) { /* handle mouse move here */ }
lastEvent = event;
}
You can also use any other non euclidean heuristics like Manhattan or Chebyshev.

Best way to make marker resizable in leaflet

I am trying to resize my markers every time the map is zoomed in or out.
Currently I am using this approach:
Iterate all markers in zoomend method.
get current icon size
Perform some calculation to get the new marker size according the zoom size.
set the new dimension to the icon object.
map.on('zoomend', function() {
zoomEndLevel = map.getZoom();
var difference = zoomEndLevel - zoomStartLevel;
console.log("difference in zoom " + difference);
markerArray.forEach(function(marker) {
var icon = marker.options.icon;
var oldX = icon.options.iconSize[0];
var oldY = icon.options.iconSize[1];
var newX = getNewIconAxis(oldX, difference);
var newY = getNewIconAxis(oldY, difference);
console.log(newX + " " + newY);
icon.options.iconSize = [ newX, newY ];
marker.setIcon(icon);
});
});
map.on('zoomstart', function() {
zoomStartLevel = map.getZoom();
});
function getNewIconAxis(value, zoomChange) {
if (zoomChange > 0) {
for (var i = zoomChange; i > 0; i--) {
value = value * 2;
}
} else {
for (var i = zoomChange; i < 0; i++) {
value = value / 2;
}
}
return value;
}
Problem :
This code works fine if I zoom in and out 1 level at once. If I scroll in and out my mouse too frequently then this code given strange outputs. Sometimes the marker size becomes too large or too small.
Question :
1) Is this the only way to make the markers resizable on different zoom levels?
2) If yes then what am I missing here or what changes should be made to make it work perfectly.?
Note : Tagging google maps also because it's more of a logical issue with map (either google or leaflet or mapbox) rather than api specific issue.
Looks like there are several previous posts that you guide you:
Mapbox,leaflet: Increase marker size on Zoom
is there a way to resize marker icons depending on zoom level in leaflet?
https://gis.stackexchange.com/questions/171609/resize-divicons-svgs-at-zoom-levels-leaflet
As for your bug, instead of reading the current icon size value at "zoomstart" event, you might better remember the previous zoom value and read it only at "zoomend" event. I am not sure the "zoomstart" event is fired only once when you scroll (to zoom in/out) successively, while the "zoomend" event may be fired only at the very end.

How to implement canvas panning with Fabric.js

I have a Fabric.js canvas and I want to implement the full-canvas panning that software packages usually do with a "hand" tool. It's when you press one of the mouse buttons, then move over the canvas while holding the mouse button and the visible portion of the canvas changes accordingly.
You can see in this video what I want to achieve.
In order to implement this functionality I wrote the following code:
$(canvas.wrapperEl).on('mousemove', function(evt) {
if (evt.button == 2) { // 2 is the right mouse button
canvas.absolutePan({
x: evt.clientX,
y: evt.clientY
});
}
});
But it doesn't work. You can see in this video what happens.
How can I modify my code in order:
For panning to work like in the first video?
For the event handler to consume the event? It should prevent the context menu from appearing when the user presses or releases the right mouse button.
An easy way to pan a Fabric canvas in response to mouse movement is to calculate the cursor displacement between mouse events and pass it to relativePan.
Observe how we can use the screenX and screenY properties of the previous mouse event to calculate the relative position of the current mouse event:
function startPan(event) {
if (event.button != 2) {
return;
}
var x0 = event.screenX,
y0 = event.screenY;
function continuePan(event) {
var x = event.screenX,
y = event.screenY;
fc.relativePan({ x: x - x0, y: y - y0 });
x0 = x;
y0 = y;
}
function stopPan(event) {
$(window).off('mousemove', continuePan);
$(window).off('mouseup', stopPan);
};
$(window).mousemove(continuePan);
$(window).mouseup(stopPan);
$(window).contextmenu(cancelMenu);
};
function cancelMenu() {
$(window).off('contextmenu', cancelMenu);
return false;
}
$(canvasWrapper).mousedown(startPan);
We start panning on mousedown and continue panning on mousemove. On mouseup, we cancel the panning; we also cancel the mouseup-cancelling function itself.
The right-click menu, also known as the context menu, is cancelled by returning false. The menu-cancelling function also cancels itself. Thus, the context menu will work if you subsequently click outside the canvas wrapper.
Here is a page demonstrating this approach:
http://michaellaszlo.com/so/fabric-pan/
You will see three images on a Fabric canvas (it may take a moment or two for the images to load). You'll be able to use the standard Fabric functionality. You can left-click on the images to move them around, stretch them, and rotate them. But when you right-click within the canvas container, you pan the whole Fabric canvas with the mouse.
I have an example on Github using fabric.js Canvas panning: https://sabatinomasala.github.io/fabric-clipping-demo/
The code responsible for the panning behaviour is the following: https://github.com/SabatinoMasala/fabric-clipping-demo/blob/master/src/classes/Panning.js
It's a simple extension on the fabric.Canvas.prototype, which enables you to toggle 'drag mode' on the canvas as follows:
canvas.toggleDragMode(true); // Start panning
canvas.toggleDragMode(false); // Stop panning
Take a look at the following snippet, documentation is available throughout the code.
const STATE_IDLE = 'idle';
const STATE_PANNING = 'panning';
fabric.Canvas.prototype.toggleDragMode = function(dragMode) {
// Remember the previous X and Y coordinates for delta calculations
let lastClientX;
let lastClientY;
// Keep track of the state
let state = STATE_IDLE;
// We're entering dragmode
if (dragMode) {
// Discard any active object
this.discardActiveObject();
// Set the cursor to 'move'
this.defaultCursor = 'move';
// Loop over all objects and disable events / selectable. We remember its value in a temp variable stored on each object
this.forEachObject(function(object) {
object.prevEvented = object.evented;
object.prevSelectable = object.selectable;
object.evented = false;
object.selectable = false;
});
// Remove selection ability on the canvas
this.selection = false;
// When MouseUp fires, we set the state to idle
this.on('mouse:up', function(e) {
state = STATE_IDLE;
});
// When MouseDown fires, we set the state to panning
this.on('mouse:down', (e) => {
state = STATE_PANNING;
lastClientX = e.e.clientX;
lastClientY = e.e.clientY;
});
// When the mouse moves, and we're panning (mouse down), we continue
this.on('mouse:move', (e) => {
if (state === STATE_PANNING && e && e.e) {
// let delta = new fabric.Point(e.e.movementX, e.e.movementY); // No Safari support for movementX and movementY
// For cross-browser compatibility, I had to manually keep track of the delta
// Calculate deltas
let deltaX = 0;
let deltaY = 0;
if (lastClientX) {
deltaX = e.e.clientX - lastClientX;
}
if (lastClientY) {
deltaY = e.e.clientY - lastClientY;
}
// Update the last X and Y values
lastClientX = e.e.clientX;
lastClientY = e.e.clientY;
let delta = new fabric.Point(deltaX, deltaY);
this.relativePan(delta);
this.trigger('moved');
}
});
} else {
// When we exit dragmode, we restore the previous values on all objects
this.forEachObject(function(object) {
object.evented = (object.prevEvented !== undefined) ? object.prevEvented : object.evented;
object.selectable = (object.prevSelectable !== undefined) ? object.prevSelectable : object.selectable;
});
// Reset the cursor
this.defaultCursor = 'default';
// Remove the event listeners
this.off('mouse:up');
this.off('mouse:down');
this.off('mouse:move');
// Restore selection ability on the canvas
this.selection = true;
}
};
// Create the canvas
let canvas = new fabric.Canvas('fabric')
canvas.backgroundColor = '#f1f1f1';
// Add a couple of rects
let rect = new fabric.Rect({
width: 100,
height: 100,
fill: '#f00'
});
canvas.add(rect)
rect = new fabric.Rect({
width: 200,
height: 200,
top: 200,
left: 200,
fill: '#f00'
});
canvas.add(rect)
// Handle dragmode change
let dragMode = false;
$('#dragmode').change(_ => {
dragMode = !dragMode;
canvas.toggleDragMode(dragMode);
});
<div>
<label for="dragmode">
Enable panning
<input type="checkbox" id="dragmode" name="dragmode" />
</label>
</div>
<canvas width="300" height="300" id="fabric"></canvas>
<script src="https://ajax.googleapis.com/ajax/libs/jquery/2.1.1/jquery.min.js"></script>
<script src="https://cdnjs.cloudflare.com/ajax/libs/fabric.js/1.7.15/fabric.min.js"></script>
Not sure about FabricJS, but it could be in such a way:
for it to work like in the first video:
By making use of CSS cursor property, toggling it on mousedown and mouseup events using javascript.
the event handler consume the event (prevent the context menu from appearing, when the user releases the right mouse button):
Using javascript we return false on contextmenu event
CODE: with a little problem ( * )
using jQuery JS Fiddle 1
$('#test').on('mousedown', function(e){
if (e.button == 2) {
// if right-click, set cursor shape to grabbing
$(this).css({'cursor':'grabbing'});
}
}).on('mouseup', function(){
// set cursor shape to default
$(this).css({'cursor':'default'});
}).on('contextmenu', function(){
//disable context menu on right click
return false;
});
Using raw javascript JS Fiddle 2
var test = document.getElementById('test');
test.addEventListener('mousedown', function(e){
if (e.button == 2) {
// if right-click, set cursor shape to grabbing
this.style.cursor = 'grabbing';
}
});
test.addEventListener('mouseup', function(){
// set cursor shape to default
this.style.cursor = 'default';
});
test.oncontextmenu = function(){
//disable context menu on right click
return false;
}
( * ) Problem:
The above snippets works as it should but there's a cross-browser issue, if you check the above fiddles in Firefox - or Opera -you'll see the correct behavior, when checked in Chrome and IE11 - didn't checked it with Edge or Safari - I found that Chrome and IE don't support the grabbing cursor shape, so in the above code snippets, change the cursor lines into this:
jQuery: $(this).css({'cursor':'move'}); JS Fiddle 3
Raw javascript: this.style.cursor = 'move'; JS Fiddle 4
Now we have a working code but without the hand cursor. but there is the following solution:-
SOLUTIONS:
Chrome and Safari support grab and grabbing with the -webkit- prefix like:
$(this).css({'cursor': '-webkit-grabbing'});
but you need to make browser sniffing first, if Firefox then the default and standard code, if Chrome and Safari then with the -webkit- prefix, and this still makes IE out of the game.
Have a look at this example, test it with Chrome, Safari, Firefox, Opera and IE you can see that cursor: url(foo.bar) works and supported in ALL browsers.
Chrome, Safari, Firefox and Opera shows the yellow smile image smiley.gif, but IE shows the red ball cursor url(myBall.cur).
So I think you can make use of this, and a grabbing hand image like this
Or this:
You can use an image like the above, a png or gif format with all browsers except IE which supports .cur, so you need to find a way to convert it into a .cur. Google search shows many result of convert image to cur
Note that, although this cursor:url(smiley.gif),url(myBall.cur),auto; - with fallback support separated by comma, works well in the W3Schools example shown above, I couldn't get it to work the same way in javascript, I tried $(this).css({'cursor': 'grabbing, move'}); but it didn't work.
I also tried doing it as CSS class
.myCursor{ cursor: grabbing, -webkit-grabbing, move; }
Then with jQuery $(this).addClass('myCursor'); but no avail either.
So you still need to make browser sniffing whether you are going the second solution or a hybrid fix of the both solutions, this is my code which I've used couple times to detect browser and it worked well at the time of this post but you porbabely won't need the "Mobile" and "Kindle" parts.
// Detecting browsers
$UA = navigator.userAgent;
if ($UA.match(/firefox/i)) {
$browser = 'Firefox';
} else if ($UA.indexOf('Trident') != -1 && $UA.indexOf('MSIE') == -1) {
$browser = 'MSIE';
} else if ($UA.indexOf('MSIE') != -1) {
$browser = 'MSIE';
} else if ($UA.indexOf('OPR/') != -1) {
$browser = 'Opera';
} else if ($UA.indexOf("Chrome") != -1) {
$browser = 'Chrome';
} else if ($UA.indexOf("Safari")!=-1) {
$browser = 'Safari';
}
if($UA.match(/Android|webOS|iPhone|iPad|iPod|BlackBerry|IEMobile|Nokia|Mobile|Opera Mini/i)) {
$browser = 'Mobile';
}else if($UA.match(/KFAPWI/i)){
$browser = 'Kindle';
}
console.log($browser);
Resources:
https://developer.mozilla.org/en-US/docs/Web/CSS/cursor
http://www.w3schools.com/cssref/pr_class_cursor.asp
https://css-tricks.com/almanac/properties/c/cursor/
Google images search of grabbing hand cursor
i have made an example on jsfiddle , that we can actually drag the whole canvas with all its objects, into a parent div, like the picture,and i will try to explain it step by step.
First of all i download the drag library jquery.dradscroll.js, you can find it on the net. This is a small js file that with little changes it can helps us complete the task.
download link: http://www.java2s.com/Open-Source/Javascript_Free_Code/jQuery_Scroll/Download_jquery_dragscroll_Free_Java_Code.htm
create the container that holds our canvas.
<div class="content">
<canvas id="c" width="600" height="700" ></canvas>
</div>
little css
.content{
overflow:auto;
width:400px;
height:400px;
}
javascript:
a. create the canvas.
b. make default cursor , when it is over canvas , open hand
canvas.defaultCursor = 'url(" http://maps.gstatic.com/intl/en_us/mapfiles/openhand_8_8.cur") 15 15, crosshair';
c. override the __onMouseDown function , for change to the closedhand cursor( at end).
fabric.Canvas.prototype.__onMouseDown = function(e){
// accept only left clicks
var isLeftClick = 'which' in e ? e.which === 1 : e.button === 1;
if (!isLeftClick && !fabric.isTouchSupported) {
return;
}
if (this.isDrawingMode) {
this._onMouseDownInDrawingMode(e);
return;
}
// ignore if some object is being transformed at this moment
if (this._currentTransform) {
return;
}
var target = this.findTarget(e),
pointer = this.getPointer(e, true);
// save pointer for check in __onMouseUp event
this._previousPointer = pointer;
var shouldRender = this._shouldRender(target, pointer),
shouldGroup = this._shouldGroup(e, target);
if (this._shouldClearSelection(e, target)) {
this._clearSelection(e, target, pointer);
}
else if (shouldGroup) {
this._handleGrouping(e, target);
target = this.getActiveGroup();
}
if (target && target.selectable && !shouldGroup) {
this._beforeTransform(e, target);
this._setupCurrentTransform(e, target);
}
// we must renderAll so that active image is placed on the top canvas
shouldRender && this.renderAll();
this.fire('mouse:down', { target: target, e: e });
target && target.fire('mousedown', { e: e });
if(!canvas.getActiveObject() || !canvas.getActiveGroup()){
flag=true;
//change cursor to closedhand.cur
canvas.defaultCursor = 'url("http://maps.gstatic.com/intl/en_us/mapfiles/closedhand_8_8.cur") 15 15, crosshair';
}//end if
override the __onMouseUp event ,to change back the cursor to openhand.
fabric.Canvas.prototype.__onMouseUp = function(e){
if(flag){
canvas.defaultCursor = 'url(" http://maps.gstatic.com/intl/en_us/mapfiles/openhand_8_8.cur") 15 15, crosshair';
flag=false;
}
};
You initialize the dragScroll() to work on the content that hosts the canvas:
$('.content').dragScroll({});
Some small changes on the jquery.dragScroll.js file, so as to understand when to drag the canvas and when not. On mousedown() event we add an if statement to check whether we have an active object or group.If true ,no canvas drag.
$($scrollArea).mousedown(function (e) {
if (canvas.getActiveObject() || canvas.getActiveGroup()) {
console.log('no drag');return;
} else {
console.log($('body'));
if (typeof options.limitTo == "object") {
for (var i = 0; i < options.limitTo.length; i++) {
if ($(e.target).hasClass(options.limitTo[i])) {
doMousedown(e);
}
}
} else {
doMousedown(e);
}
}
});
on mousedown event we grab the DOM element (.content) and get the top & left position
function doMousedown(e) {
e.preventDefault();
down = true;
x = e.pageX;
y = e.pageY;
top = e.target.parentElement.parentElement.scrollTop; // .content
left = e.target.parentElement.parentElement.scrollLeft;// .content
}
If we dont want to have the scrollbars visible:
.content{
overflow:hidden;
width:400px;
height:400px;
}
There is a small problem though,jsfiddle, accepts only https libraries ,so it blocks fabricjs, except if you add it from 'https://rawgit.com/kangax/fabric.js/master/dist/fabric.js', but again it still blocks it some times (at least on my chrome and mozilla).
jsfiddle example : https://jsfiddle.net/tornado1979/up48rxLs/
you may have better luck ,than me, on your browser , but it would definitelly work on your live app.
Anyway,
i hope helps ,good luck.
I know this has already been answered, but I redid the pen created in this answer using the new version of fabricjs (4.5.0)
Pen: https://codepen.io/201flaviosilva/pen/GROLbQa
In this case, I used the middle button in the mouse to pan :)
// Enable mouse middle button
canvas.fireMiddleClick = true;
// Mouse Up Event
if (e.button === 2) currentState = STATE_IDLE;
// Mouse Down Event
if (e.button === 2) currentState = STATE_PANNING;
:)

Preventing the default action only for a left swipe/right swipe event

I am using event.preventDefault but after some checks, I want the event to continue.
For eg, For the
touchmove
event I am using event.preventDefault() as I don't want the browser to scroll horizontally, but after determining the direction of swipe, if the direction turns out to be up/down, whatever event i have prevented, i want to nullify the effect. Is that possible?
My scenario
This is my html
<div id="teazer" class="globalTeaser" ontouchcancel="touchCancel(event);" ontouchmove="touchMove(event);" ontouchend="touchEnd(event,'gTeaser');" ontouchstart="touchStart(event,'teazer');">
This is my js after removing the irrelevant part
function touchMove(event) {
if(fingerCount==1){
event.preventDefault();
if ( event.touches.length == 1 ) {
curX = event.touches[0].pageX;
curY = event.touches[0].pageY;
}
else {
touchCancel(event);
}
}else {
touchCancel(event);
alert("hi");
}
}
function touchEnd(event,eventType) {
//I get the swipe direction here,after some calculations
//I get the directions fine,now
//if the swipe direction is up/down whatever event i have prevented in touch move I need to nullify
}
Please note, if anyone is gonna suggest window.scrollBy, for some reason its not working for me. Any other solutions I am happy to try.
I don't know how your code behaves exactly, but this is the general principle:
// Keep a reference for last point both events can access
var start;
$( 'body' ).on( {
// On start, assign the event data to start
touchstart : function touchStart( touchstartEvent ){
start = touchstartEvent.touches[ 0 ];
},
touchmove : function touchMove( touchmoveEvent ){
// The difference between both events positions
var delta = {};
// The end event's position
var end = touchmoveEvent.touches[ 0 ];
// Calculate the offset compared to start for this move event
delata.pageX = start.pageX - end.pageX;
delata.pageY = start.pageY - end.pageY;
// If pageX is less than or greater than 0, it means there has been horizontal movement,
// and this if condition will pass
if( delta.pageX ){
touchmoveEvent.preventDefault();
}
}
} );
This isn't perfect, because in practice it's very difficult to create a perfect downward or upward swipe — my finger might move a couple of pixels left or right even if the main movement is downwards. But then you have the problem of preventing horizontal motion but not vertical! In any case, the general principal for testing different properties of a touch event and only preventing default in certain conditions is illustrated.
My touchMove() function has been rewritten as follows
function touchMove(event) {
if (event.touches.length == 1) {
curX = event.touches[0].pageX;
curY = event.touches[0].pageY;
if (Math.abs((curX - startX)) > 10) {
//default acion is prevented only if the
//finger count is one and change in
//x coordinatesis greater than 10 px
event.preventDefault();
}
}
else {
touchCancel(event);
}
}
This code will make sure of two things
1)Pinch to zoom is not affected
2)default action for vertical swipe is not affected

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