Javascript "dragging" an image across a canvas - javascript

There's quite a few questions about this where the solution provided is to just set the top left and top down values of the image to the position of the mouse/touch, however what I want to do is to have an actual dragging movement. Regardless as to where on the canvas I press, if I drag my finger to the right x pixels, I want the image to move to the right x pixels. Same goes with left, up, and down.
I'm at a complete loss as to where to even start with this. I will be handling mobile touch events, so I feel like using canvas.addEventListener('touchmove') would be the best option, but I'm not sure.
I already have the canvas repainting and everything handled, just really need help with the logic for dragging the image in real time, instead of just snapping it into position.

Get the point where the interaction starts (touchstart) and use it to calculate how much the finger moved on the screen (in the touchmove callback) and add it to the image position (also in touchmove).
PS: Also I recommend using something like PIXI JS for canvas/WebGL stuff ... unless you need a custom solution.

Related

Get position of rotated div

I'm working on a drag and drop div project. In my editor it is possible to resize, position and rotate a selected div. It all works fine as long as the rotation is 0, but once I have set a different rotation, it starts behaving different. I'm not sure exactly what I need to do, but there must be some sort of offset that I need to take into account.
Best example I can provide is: http://recordit.co/0Pskwtrvh0
Notice in the video that without rotation I can move the div around without any problems, but after setting a rotation, everytime I click the div "skips".
Hope someone understands the problem and can push me in the right direction.

How to change position of the cursor using Javascript? [duplicate]

I'm building a HTML5 game and I am trying to put the mouse cursor over a certain control on a specific event so that moving in a specific direction always has the same result. Is this possible?
You cannot move the mousepointer with javascript.
Just think about the implications for a second, if you could ;)
User thinks: "hey I'd like to click this link"
Javascript moves mousecursor to another link
User clicks wrong link and inadvertently downloads malware that formats his c-drive and eats his candy
Run a small web server on the client machine. Can be a small 100kb thing. A Python / Perl script, etc.
Include a small, pre-compiled C executable that can move the mouse.
Run it as a CGI-script via a simple http call, AJAX, whatever - with the coordinates you want to move the mouse to, eg:
http://localhost:9876/cgi/mousemover?x=200&y=450
PS: For any problem, there are hundreds of excuses as to why, and how - it can't, and shouldn't - be done.. But in this infinite universe, it's really just a matter of determination - as to whether YOU will make it happen.
I would imagine you could accomplish placing the mouse cursor to a given area of the screen if you didn't use the real (system) mouse cursor.
For instance, you could create an image to act in place of your cursor, handle an event which upon detecting mouseenter into your scene, set the style on the system cursor to 'none' (sceneElement.style.cursor = 'none'), then would bring up a hidden image element acting as a cursor to be anywhere you like with in the scene based on a predefined axis/bounding box translation.
This way no matter how you moved the real cursor your translation method would keep your image cursor wherever you needed it.
edit: an example in jsFiddle using an image representation and forced mouse movement
Great question. This is really something missing from the Javascript browser API. I'm also working on a WebGL game with my team, and we need this feature. I opened an issue on Firefox's bugzilla so that we can start talking about the possibility of having an API to allow for mouse locking. This is going to be useful for all HTML5/WebGL game developers out there.
If you like, come over and leave a comment with your feedback, and upvote the issue:
https://bugzilla.mozilla.org/show_bug.cgi?id=630979
Thanks!
You could detect position of the mouse pointer and then move the web page (with body position relative) so they hover over what you want them to click.
For an example you can paste this code on the current page in your browser console (and refresh afterwards)
var upvote_position = $('#answer-12878316').position();
$('body').mousemove(function (event) {
$(this).css({
position: 'relative',
left: (event.pageX - upvote_position.left - 22) + 'px',
top: (event.pageY - upvote_position.top - 35) + 'px'
});
});
So, I know this is an old topic, but I'll first say it isn't possible. The closest thing currently is locking the mouse to a single position, and tracking change in its x and y. This concept has been adopted by - it looks like - Chrome and Firefox. It's managed by what's called Mouse Lock, and hitting escape will break it. From my brief read-up, I think the idea is that it locks the mouse to one location, and reports motion events similar to click-and-drag events.
Here's the release documentation:FireFox: https://developer.mozilla.org/en-US/docs/Web/API/Pointer_Lock_APIChrome: http://www.chromium.org/developers/design-documents/mouse-lock
And here's a pretty neat demonstration: http://media.tojicode.com/q3bsp/
You can't move a mouse but can lock it.
Note: that you must call requestPointerLock in click event.
Small Example:
var canvas = document.getElementById('mycanvas');
canvas.requestPointerLock = canvas.requestPointerLock || canvas.mozRequestPointerLock || canvas.webkitRequestPointerLock;
canvas.requestPointerLock();
Documentation and full code example:
https://developer.mozilla.org/en-US/docs/Web/API/Pointer_Lock_API
Interesting. This isn't directly possible for the reasons called out earlier (spam clicks and malware injection), but consider this hack, which creates an impression of the same:
Step 1: Hide the cursor
Let's say you've a div, you can use this css property to hide the real cursor:
.your_div {
cursor: none
}
Step 2: Introduce a pseudo cursor
Simply create an image, a cursor look-alike,and place it within your webpage, with position:absolute.
Step 3: Track actual mouse movement
This is easy. Check internet on how to get real mouse location (X & Y coordinates).
Step 4: Move the pseudo cursor
As the actual cursor move, move your pseudo cursor by same X & Y difference. Similarly, you can always generate a click event at any location on your webpage with javascript magic (just search the internet on how-to).
Now at this point, you can control the pesudo cursor the way you want, and your user will get the impression that the real cursor is moving.
Fair Warning: Do not do it. No one wants their cursor or computer controlled this way, unless if you've some specific use-case, or if you are determined to flee your users away.
You can't move the mouse pointer using javascript, and thus for obvious security reasons. The best way to achieve this effect would be to actually place the control under the mouse pointer.
Couldn't this simply be done by getting actual position of the mouse pointer then calculating and compensating sprite/scene mouse actions based off this compensation?
For instance you need the mouse pointer to be bottom center, but it sits top left; hide the cursor, use a shifted cursor image. Shift the cursor movement and map mouse input to match re-positioned cursor sprite (or 'control') clicks When/if bounds are hit, recalculate. If/when the cursor actually hits the point you want it to be, remove compensation.
Disclaimer, not a game developer.

Zooming image to mouse cursor with Javascript and returning to the images original position

Part of my app requires the user to be able to use the mousewheel to zoom in on an image which is already centered inside a larger container element.
I am using jQueryUI to provide a slider with which the zoom is controlled manually.
When zooming withe mousewheel, the viewport adjusts so that the user is always zooming towards to mouse cursor providing exactly the same behaviour as google maps in terms of zoom functionality.
Also, in order to provide a better experience than using css transitions I have written a momentum based smooth scroll algorithm to make the zooming as smooth as possible.
Everything works perfectly with one exception.
To replicate the problem please follow these steps on the provided jsFiddle:
move mouse cursor to the center of the image.
Very gently move the mousewheel one notch so that the smoothwheel takes over an zooms you in a little.
Then move the mouse cursor to another point of the already slightly zoomed image
Zoom in again, as far as you want this time
Finally zoom all the way out
You will see that the zoomed out image is now misplaced (as the translates have not been removed).
The behaviour I want is for the zoomed out image to return to its original position once the scale is set back to 1.
If you remove the css translate from the image in Firebug you will see that the image returns to the correct location.
Therefore this could easily be achieved with a simple conditional like so:
if(scale == 1){
//remove transforms completely
}
However doing this would provide a jumpy experience and I would like the image to gradually zoom back out to the original position as the user zooms out.
It is worth mentioning that if you zoom all the way in without moving the mouse you will find that everything is correct when you zoom back out. This is simple because no translate gets added to the elements transform, simply a scale and transform-origin. In my code the translate only gets added when you change zoom position with the mouse mid zoom.
Unfortunately I cant seem to get my head around the best way of going about this.
Here is a working jsFiddle:
http://jsfiddle.net/3k332/15/
Thanks in advance for any help.
NOTE: I am well aware that there is some redundant code in my fiddle and that its not particularly elegant but this is merely a quick mock up to help you understand the problem.

In XUL or JavaScript, is there a way to move the mouse cursor to specified position?

In XUL or JavaScript, is there a way to move the mouse cursor to specified position?
The only time that Gecko moves the mouse is on Windows for the snap-to-default-button effect. This is used by XUL dialogs and wizards. The backend code doesn't actually check that you're giving it a button; any XUL control works. The mouse is moved to the centre of the element, if that point is on-screen, and the window is active. Normally the code checks that the system cursor snapping is enabled, but there is a preference that overrides that.
No. you cannot move a mouse cursor using javascript.
But you can do this.
Hide the cursor. Load an image shaped like cursor. Animate the image.
You can use nsIDOMWindowUtils.sendNativeMouseEvent(x, y, 0, 0, null) to reposition the mouse cursor. Perhaps combined with window.screenX/Y to work out where you should move the cursor to, since sendNativeMouseEvent seems to treat the (x,y) as absolute screen coordinates.
I haven't tested this method very thoroughly, so there could be caveats. I can't think of any myself.
I know this is an old question, but I have not seen this solution suggested anywhere before, and it's not exactly obvious.
I've only tested with Firefox v48 on Windows 7. Here, sendNativeMouseEvent calls SetCursorPos to perform the actual repositioning.

Move the mouse pointer to a specific position?

I'm building a HTML5 game and I am trying to put the mouse cursor over a certain control on a specific event so that moving in a specific direction always has the same result. Is this possible?
You cannot move the mousepointer with javascript.
Just think about the implications for a second, if you could ;)
User thinks: "hey I'd like to click this link"
Javascript moves mousecursor to another link
User clicks wrong link and inadvertently downloads malware that formats his c-drive and eats his candy
Run a small web server on the client machine. Can be a small 100kb thing. A Python / Perl script, etc.
Include a small, pre-compiled C executable that can move the mouse.
Run it as a CGI-script via a simple http call, AJAX, whatever - with the coordinates you want to move the mouse to, eg:
http://localhost:9876/cgi/mousemover?x=200&y=450
PS: For any problem, there are hundreds of excuses as to why, and how - it can't, and shouldn't - be done.. But in this infinite universe, it's really just a matter of determination - as to whether YOU will make it happen.
I would imagine you could accomplish placing the mouse cursor to a given area of the screen if you didn't use the real (system) mouse cursor.
For instance, you could create an image to act in place of your cursor, handle an event which upon detecting mouseenter into your scene, set the style on the system cursor to 'none' (sceneElement.style.cursor = 'none'), then would bring up a hidden image element acting as a cursor to be anywhere you like with in the scene based on a predefined axis/bounding box translation.
This way no matter how you moved the real cursor your translation method would keep your image cursor wherever you needed it.
edit: an example in jsFiddle using an image representation and forced mouse movement
Great question. This is really something missing from the Javascript browser API. I'm also working on a WebGL game with my team, and we need this feature. I opened an issue on Firefox's bugzilla so that we can start talking about the possibility of having an API to allow for mouse locking. This is going to be useful for all HTML5/WebGL game developers out there.
If you like, come over and leave a comment with your feedback, and upvote the issue:
https://bugzilla.mozilla.org/show_bug.cgi?id=630979
Thanks!
You could detect position of the mouse pointer and then move the web page (with body position relative) so they hover over what you want them to click.
For an example you can paste this code on the current page in your browser console (and refresh afterwards)
var upvote_position = $('#answer-12878316').position();
$('body').mousemove(function (event) {
$(this).css({
position: 'relative',
left: (event.pageX - upvote_position.left - 22) + 'px',
top: (event.pageY - upvote_position.top - 35) + 'px'
});
});
So, I know this is an old topic, but I'll first say it isn't possible. The closest thing currently is locking the mouse to a single position, and tracking change in its x and y. This concept has been adopted by - it looks like - Chrome and Firefox. It's managed by what's called Mouse Lock, and hitting escape will break it. From my brief read-up, I think the idea is that it locks the mouse to one location, and reports motion events similar to click-and-drag events.
Here's the release documentation:FireFox: https://developer.mozilla.org/en-US/docs/Web/API/Pointer_Lock_APIChrome: http://www.chromium.org/developers/design-documents/mouse-lock
And here's a pretty neat demonstration: http://media.tojicode.com/q3bsp/
You can't move a mouse but can lock it.
Note: that you must call requestPointerLock in click event.
Small Example:
var canvas = document.getElementById('mycanvas');
canvas.requestPointerLock = canvas.requestPointerLock || canvas.mozRequestPointerLock || canvas.webkitRequestPointerLock;
canvas.requestPointerLock();
Documentation and full code example:
https://developer.mozilla.org/en-US/docs/Web/API/Pointer_Lock_API
Interesting. This isn't directly possible for the reasons called out earlier (spam clicks and malware injection), but consider this hack, which creates an impression of the same:
Step 1: Hide the cursor
Let's say you've a div, you can use this css property to hide the real cursor:
.your_div {
cursor: none
}
Step 2: Introduce a pseudo cursor
Simply create an image, a cursor look-alike,and place it within your webpage, with position:absolute.
Step 3: Track actual mouse movement
This is easy. Check internet on how to get real mouse location (X & Y coordinates).
Step 4: Move the pseudo cursor
As the actual cursor move, move your pseudo cursor by same X & Y difference. Similarly, you can always generate a click event at any location on your webpage with javascript magic (just search the internet on how-to).
Now at this point, you can control the pesudo cursor the way you want, and your user will get the impression that the real cursor is moving.
Fair Warning: Do not do it. No one wants their cursor or computer controlled this way, unless if you've some specific use-case, or if you are determined to flee your users away.
You can't move the mouse pointer using javascript, and thus for obvious security reasons. The best way to achieve this effect would be to actually place the control under the mouse pointer.
Couldn't this simply be done by getting actual position of the mouse pointer then calculating and compensating sprite/scene mouse actions based off this compensation?
For instance you need the mouse pointer to be bottom center, but it sits top left; hide the cursor, use a shifted cursor image. Shift the cursor movement and map mouse input to match re-positioned cursor sprite (or 'control') clicks When/if bounds are hit, recalculate. If/when the cursor actually hits the point you want it to be, remove compensation.
Disclaimer, not a game developer.

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