I'm extending Leaflet's GridLayer to show canvas tiles on which I draw some data points - the problem is that after zooming in and out the other zoom layers are still visible, or are partially chopped off in random ways.
E.g. on the left is zoom level 13, on the right is after zooming out to 11 and back to 13 -
How can I show only the current zoom level, and prevent the canvas tiles from getting chopped off?
This is how I ended up fixing it, though there might be better ways...
Here's my GridCanvas class -
L.GridLayer.GridCanvas = L.GridLayer.extend({
onAdd: function (map) {
L.GridLayer.prototype.onAdd.call(this, map);
map.on('zoomend', e => this.onZoomEnd(e.target._zoom));
},
// on zoom end, want to hide all the tiles that are not on this zoom level,
// and show all the ones that are
onZoomEnd: function (zoom) {
Object.values(this._levels).forEach(level => {
level.el.style.display = (level.zoom === zoom) ? 'block' : 'none';
});
},
createTile,
});
The visibility of the tiles also gets set in seemingly random ways - this seemed to fix the problem - adding a class to the canvas elements and setting them to always be visible -
function createTile(coords, done) {
const canvas = L.DomUtil.create('canvas', 'grid-canvas-tile');
...
}
with styles.css:
.grid-canvas-tile {
visibility: visible !important;
}
I'm using a some code from https://github.com/dimxasnewfrozen/Panning-Zooming-Canvas-Demos/blob/master/demo12/main.js (demo at http://dayobject.me/canvas/demo12/) to zoom in on an image using the Canvas element.
However, when zooming the jump between one zoom level and the next is too large, so I need to add a scale parameter.
How would I got about doing this?
In your main.js, you can change your zoomLevel here,
mouseWheel: function (e) {
e.preventDefault() // Please add this, coz the scroll event bubbles up to document.
var zoomLevel = 2;
...
if (delta > 0)
{
// ZOOMING IN
var zoomedX = canvasPos.deltaX - (canvasZoomX - canvasPos.deltaX);
var zoomedY = canvasPos.deltaY - (canvasZoomY - canvasPos.deltaY);
// scale the image up by 2
initialImageWidth = initialImageWidth * zoomLevel;
}
else
{
// ZOOMING OUT
var zoomedX = (canvasPos.deltaX + canvasZoomX);
var zoomedY = (canvasPos.deltaY + canvasZoomY);
// scale the image down by 2
initialImageWidth = initialImageWidth / zoomLevel;
}
}
Disclaimer: this ruins the zoomedX and zoomedY values. You gotta fix them :)
It seams to me as if the algorithm always takes half of the dimension befor the zoom. At the end of you code you see it in main.js the mouseWheel function:
initialImageWidth = initialImageWidth * 2;
the width is divided by 2 so just change the used value.
You said the step used to zoom in and out is too big.
So I suggest that you generate the new value by using the dimensions of the image you want to zoom. For example you take a percentage of the biggest dimension of the current image.
That's how you can implement a zoom function that zooms according to the dimensions of the image
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.
Right now what I'm trying to do is zoom the map in and out based on screen size, so that you can always see basically every piece of land in the world. I'm not worried about the repeating world, but I ideally want to keep it centered basically on the west coast of Africa, like a typical map.
I have something that looks as follows:
function fitMap() {
if ($) {
var height = $(window).height();
var width = $(window).width();
//Put map into full screen
$('#map').css({position: "absolute", top: "0", left: "0", right: "0", bottom:"0"});
if ((height < 586 && width < 1095) || height < 325 || (width < 700 && height > 586)) {
map.setZoom(1);
}
else if (width >= 1500 && height > 900) {
map.setZoom(3);
}
else {
map.setZoom(2);
}
}
};
//Fit the map more appropriately to screen sizes.
window.onload = fitMap;
window.onresize = fitMap;
I find this to be really hacky and it works if I were to try and put this on a 1920x1080 all the way down to a small 1024x768 but I didn't see anything in Leaflet that would allow me to do this. One idea I had was to create an invisible feature group that basically creates a perimeter from dateline to dateline and use .getBounds() like this: Centering Leaflet map with getbounds and related issues
Does anyone have a better solution?
Leaflet offers a fitWorld() method to do just this.
You would use this by calling map.fitWorld();, and here's a full example.
Please note, that fitWorld takes zoomSnap into account, so if you are using the default value of 1 and call fitZoom on resize, the map doesn't really fit well in a lot of situations. Decrease zoomSnap to a value that's okay for you.
I also recommend setting animate to false with this approach:
map.on( 'resize', () => {
map.fitWorld( { animate: false } );
} );
Is it possible to detect, using JavaScript, when the user changes the zoom in a page?
I simply want to catch a "zoom" event and respond to it (similar to window.onresize event).
Thanks.
There's no way to actively detect if there's a zoom. I found a good entry here on how you can attempt to implement it.
I’ve found two ways of detecting the
zoom level. One way to detect zoom
level changes relies on the fact that
percentage values are not zoomed. A
percentage value is relative to the
viewport width, and thus unaffected by
page zoom. If you insert two elements,
one with a position in percentages,
and one with the same position in
pixels, they’ll move apart when the
page is zoomed. Find the ratio between
the positions of both elements and
you’ve got the zoom level. See test
case.
http://web.archive.org/web/20080723161031/http://novemberborn.net/javascript/page-zoom-ff3
You could also do it using the tools of the above post. The problem is you're more or less making educated guesses on whether or not the page has zoomed. This will work better in some browsers than other.
There's no way to tell if the page is zoomed if they load your page while zoomed.
Lets define px_ratio as below:
px ratio = ratio of physical pixel to css px.
if any one zoom The Page, the viewport pxes (px is different from pixel ) reduces and should be fit to The screen so the ratio (physical pixel / CSS_px ) must get bigger.
but in window Resizing, screen size reduces as well as pxes. so the ratio will maintain.
zooming: trigger windows.resize event --> and change px_ratio
but
resizing: trigger windows.resize event --> doesn’t change px_ratio
//for zoom detection
px_ratio = window.devicePixelRatio || window.screen.availWidth / document.documentElement.clientWidth;
$(window).resize(function(){isZooming();});
function isZooming(){
var newPx_ratio = window.devicePixelRatio || window.screen.availWidth / document.documentElement.clientWidth;
if(newPx_ratio != px_ratio){
px_ratio = newPx_ratio;
console.log("zooming");
return true;
}else{
console.log("just resizing");
return false;
}
}
The key point is difference between CSS PX and Physical Pixel.
https://gist.github.com/abilogos/66aba96bb0fb27ab3ed4a13245817d1e
Good news everyone some people! Newer browsers will trigger a window resize event when the zoom is changed.
I'm using this piece of JavaScript to react to Zoom "events".
It polls the window width.
(As somewhat suggested on this page (which Ian Elliott linked to): http://novemberborn.net/javascript/page-zoom-ff3 [archive])
Tested with Chrome, Firefox 3.6 and Opera, not IE.
Regards, Magnus
var zoomListeners = [];
(function(){
// Poll the pixel width of the window; invoke zoom listeners
// if the width has been changed.
var lastWidth = 0;
function pollZoomFireEvent() {
var widthNow = jQuery(window).width();
if (lastWidth == widthNow) return;
lastWidth = widthNow;
// Length changed, user must have zoomed, invoke listeners.
for (i = zoomListeners.length - 1; i >= 0; --i) {
zoomListeners[i]();
}
}
setInterval(pollZoomFireEvent, 100);
})();
This works for me:
var deviceXDPI = screen.deviceXDPI;
setInterval(function(){
if(screen.deviceXDPI != deviceXDPI){
deviceXDPI = screen.deviceXDPI;
... there was a resize ...
}
}, 500);
It's only needed on IE8. All the other browsers naturally generate a resize event.
There is a nifty plugin built from yonran that can do the detection. Here is his previously answered question on StackOverflow. It works for most of the browsers. Application is as simple as this:
window.onresize = function onresize() {
var r = DetectZoom.ratios();
zoomLevel.innerHTML =
"Zoom level: " + r.zoom +
(r.zoom !== r.devicePxPerCssPx
? "; device to CSS pixel ratio: " + r.devicePxPerCssPx
: "");
}
Demo
Although this is a 9 yr old question, the problem persists!
I have been detecting resize while excluding zoom in a project, so I edited my code to make it work to detect both resize and zoom exclusive from one another. It works most of the time, so if most is good enough for your project, then this should be helpful! It detects zooming 100% of the time in what I've tested so far. The only issue is that if the user gets crazy (ie. spastically resizing the window) or the window lags it may fire as a zoom instead of a window resize.
It works by detecting a change in window.outerWidth or window.outerHeight as window resizing while detecting a change in window.innerWidth or window.innerHeight independent from window resizing as a zoom.
//init object to store window properties
var windowSize = {
w: window.outerWidth,
h: window.outerHeight,
iw: window.innerWidth,
ih: window.innerHeight
};
window.addEventListener("resize", function() {
//if window resizes
if (window.outerWidth !== windowSize.w || window.outerHeight !== windowSize.h) {
windowSize.w = window.outerWidth; // update object with current window properties
windowSize.h = window.outerHeight;
windowSize.iw = window.innerWidth;
windowSize.ih = window.innerHeight;
console.log("you're resizing"); //output
}
//if the window doesn't resize but the content inside does by + or - 5%
else if (window.innerWidth + window.innerWidth * .05 < windowSize.iw ||
window.innerWidth - window.innerWidth * .05 > windowSize.iw) {
console.log("you're zooming")
windowSize.iw = window.innerWidth;
}
}, false);
Note: My solution is like KajMagnus's, but this has worked better for me.
⬤ The resize event works on modern browsers by attaching the event on window, and then reading values of thebody, or other element with for example (.getBoundingClientRect()).
In some earlier browsers it was possible to register resize event
handlers on any HTML element. It is still possible to set onresize
attributes or use addEventListener() to set a handler on any element.
However, resize events are only fired on the window object (i.e.
returned by document.defaultView). Only handlers registered on the
window object will receive resize events.
⚠️ Do resize your tab, or zoom, to trigger this snippet:
window.addEventListener("resize", getSizes, false)
function getSizes(){
let body = document.body
body.width = window.innerWidth
body.height = window.innerHeight
console.log(body.width +"px x "+ body.height + "px")
}
getSizes()
⬤ An other modern alternative: the ResizeObserver API
Depending your layout, you can watch for resizing on a particular element.
This works well on «responsive» layouts, because the container box get resized when zooming.
function watchBoxchange(e){
info.textContent = e[0].contentBoxSize[0].inlineSize+" x "+e[0].contentBoxSize[0].blockSize + "px"
}
new ResizeObserver(watchBoxchange).observe(fluid)
#fluid {
width: 200px;
height:100px;
overflow: auto;
resize: both;
border: 3px black solid;
display: flex;
flex-direction: column;
justify-content: center;
align-items: center;
font-size: 8vh
}
<div id="fluid">
<info id="info"></info>
</div>
💡 Be careful to not overload javascript tasks from user gestures events. Use requestAnimationFrame whenever you needs redraws.
I'd like to suggest an improvement to previous solution with tracking changes to window width. Instead of keeping your own array of event listeners you can use existing javascript event system and trigger your own event upon width change, and bind event handlers to it.
$(window).bind('myZoomEvent', function() { ... });
function pollZoomFireEvent()
{
if ( ... width changed ... ) {
$(window).trigger('myZoomEvent');
}
}
Throttle/debounce can help with reducing the rate of calls of your handler.
According to MDN, "matchMedia" is the proper way to do this https://developer.mozilla.org/en-US/docs/Web/API/Window/devicePixelRatio#Monitoring_screen_resolution_or_zoom_level_changes
it's a bit finicky because each instance can only watch one MQ at a time, so if you're interested in any zoom level change you need to make a bunch of matchers.. but since the browser is in charge to emitting the events it's probably still more performant than polling, and you could throttle or debounce the callback or pin it to an animation frame or something - here's an implementation that seems pretty snappy, feel free to swap in _throttle or whatever if you're already depending on that.
Run the code snippet and zoom in and out in your browser, note the updated value in the markup - I only tested this in Firefox! lemme know if you see any issues.
const el = document.querySelector('#dppx')
if ('matchMedia' in window) {
function observeZoom(cb, opts) {
opts = {
// first pass for defaults - range and granularity to capture all the zoom levels in desktop firefox
ceiling: 3,
floor: 0.3,
granularity: 0.05,
...opts
}
const precision = `${opts.granularity}`.split('.')[1].length
let val = opts.floor
const vals = []
while (val <= opts.ceiling) {
vals.push(val)
val = parseFloat((val + opts.granularity).toFixed(precision))
}
// construct a number of mediamatchers and assign CB to all of them
const mqls = vals.map(v => matchMedia(`(min-resolution: ${v}dppx)`))
// poor person's throttle
const throttle = 3
let last = performance.now()
mqls.forEach(mql => mql.addListener(function() {
console.debug(this, arguments)
const now = performance.now()
if (now - last > throttle) {
cb()
last = now
}
}))
}
observeZoom(function() {
el.innerText = window.devicePixelRatio
})
} else {
el.innerText = 'unable to observe zoom level changes, matchMedia is not supported'
}
<div id='dppx'>--</div>
You can also get the text resize events, and the zoom factor by injecting a div containing at least a non-breakable space (possibly, hidden), and regularly checking its height. If the height changes, the text size has changed, (and you know how much - this also fires, incidentally, if the window gets zoomed in full-page mode, and you still will get the correct zoom factor, with the same height / height ratio).
<script>
var zoomv = function() {
if(topRightqs.style.width=='200px){
alert ("zoom");
}
};
zoomv();
</script>
On iOS 10 it is possible to add an event listener to the touchmove event and to detect, if the page is zoomed with the current event.
var prevZoomFactorX;
var prevZoomFactorY;
element.addEventListener("touchmove", (ev) => {
let zoomFactorX = document.documentElement.clientWidth / window.innerWidth;
let zoomFactorY = document.documentElement.clientHeight / window.innerHeight;
let pageHasZoom = !(zoomFactorX === 1 && zoomFactorY === 1);
if(pageHasZoom) {
// page is zoomed
if(zoomFactorX !== prevZoomFactorX || zoomFactorY !== prevZoomFactorY) {
// page is zoomed with this event
}
}
prevZoomFactorX = zoomFactorX;
prevZoomFactorY = zoomFactorY;
});
Here is a clean solution:
// polyfill window.devicePixelRatio for IE
if(!window.devicePixelRatio){
Object.defineProperty(window,'devicePixelRatio',{
enumerable: true,
configurable: true,
get:function(){
return screen.deviceXDPI/screen.logicalXDPI;
}
});
}
var oldValue=window.devicePixelRatio;
window.addEventListener('resize',function(e){
var newValue=window.devicePixelRatio;
if(newValue!==oldValue){
// TODO polyfill CustomEvent for IE
var event=new CustomEvent('devicepixelratiochange');
event.oldValue=oldValue;
event.newValue=newValue;
oldValue=newValue;
window.dispatchEvent(event);
}
});
window.addEventListener('devicepixelratiochange',function(e){
console.log('devicePixelRatio changed from '+e.oldValue+' to '+e.newValue);
});
Here is a native way (major frameworks cannot zoom in Chrome, because they dont supports passive event behaviour)
//For Google Chrome
document.addEventListener("mousewheel", event => {
console.log(`wheel`);
if(event.ctrlKey == true)
{
event.preventDefault();
if(event.deltaY > 0) {
console.log('Down');
}else {
console.log('Up');
}
}
}, { passive: false });
// For Mozilla Firefox
document.addEventListener("DOMMouseScroll", event => {
console.log(`wheel`);
if(event.ctrlKey == true)
{
event.preventDefault();
if(event.detail > 0) {
console.log('Down');
}else {
console.log('Up');
}
}
}, { passive: false });
I'am replying to a 3 year old link but I guess here's a more acceptable answer,
Create .css file as,
#media screen and (max-width: 1000px)
{
// things you want to trigger when the screen is zoomed
}
EG:-
#media screen and (max-width: 1000px)
{
.classname
{
font-size:10px;
}
}
The above code makes the size of the font '10px' when the screen is zoomed to approximately 125%. You can check for different zoom level by changing the value of '1000px'.