Prevent left click on HTML canvas and enable right click to pass through with pointer-events

Question

Prevent left click on HTML canvas and enable right click to pass through with pointer-events

In my scenario, I have an HTML canvas positioned above various other HTML elements that detect right-click mouse events. The goal is to be able to draw on the canvas with the left mouse button while simultaneously interacting with the underlying HTML elements using the right mouse button.

I understand that setting the CSS property "pointer-events" to "none" allows all mouse events to pass through the canvas. However, I specifically want only right-click events to pass through.

One possible solution could involve listening for right-click events on the canvas, then in the callback, setting "pointer-events" to "none", manually triggering a right-click event, and then reverting "pointer-events" back to "auto".

For context, I'm utilizing KineticJS, and I am unsure of how to manually trigger mouse events using this library.

If anyone has any suggestions or insights on accomplishing this task, they would be greatly appreciated.

javascript html5-canvas mouseevent kineticjs

Answer 1

Answer №1

Engaging topic that captured my interest. It was enjoyable to devise a solution for it using this jQuery technique among others. Although I am not acquainted with KineticsJS, this method utilizes plain JavaScript.

In summary, you can simulate a pointer-events:none specifically for right-click by leveraging the object's dimensions and positioning along with onmousedown's event.which to identify if a right-click occurred on the background elements. The code snippet below demonstrates this approach, with explanatory comments included.

// Retrieve all overlaying canvases
var canvas = document.getElementsByTagName("canvas"); 
// Fetch all elements where the click should register
var background = document.getElementsByClassName("background"); 

// Employ mouse location and element details to allow clicks to pass through
function passThrough(e) { 
    // Permit only right-click events to pass through
    if (e.which == 2 || e.which == 3) { 
        // Iterate through all background elements
        for (var i = 0; i < background.length; i++) { 
            // Check if clicked point (obtained from event) is within the element
            var mouseX = e.pageX;
            var mouseY = e.pageY;
            var obj = background[i];
            var width = obj.clientWidth;
            var height = obj.clientHeight;

            if (mouseX > obj.offsetLeft && mouseX < obj.offsetLeft + width 
                && mouseY > obj.offsetTop && mouseY < obj.offsetTop + height) {
                // Trigger click event if within boundaries
                background[i].onclick(); 
            }
        }
    }
}

for (var i = 0; i < canvas.length; i++) {
    // Invoke our function upon click
    canvas[i].onmousedown = passThrough; 
    // Prevent context menu from appearing
    canvas[i].oncontextmenu = function(event) { event.returnDefault; return false; } 
}
for (var i = 0; i < background.length; i++) {
    // Toggle background color upon click (to demonstrate functionality)
    background[i].onclick = function() { 
        if (this.style.background == "black") {
            this.style.background = "red";
        }
        else {
            this.style.background = "black";
        }
    }
}

http://jsfiddle.net/z7TUX/3/

I trust this meets your requirements!

Answer 2

Engaging topic that captured my interest. It was enjoyable to devise a solution for it using this jQuery technique among others. Although I am not acquainted with KineticsJS, this method utilizes plain JavaScript.

In summary, you can simulate a pointer-events:none specifically for right-click by leveraging the object's dimensions and positioning along with onmousedown's event.which to identify if a right-click occurred on the background elements. The code snippet below demonstrates this approach, with explanatory comments included.

// Retrieve all overlaying canvases
var canvas = document.getElementsByTagName("canvas"); 
// Fetch all elements where the click should register
var background = document.getElementsByClassName("background"); 

// Employ mouse location and element details to allow clicks to pass through
function passThrough(e) { 
    // Permit only right-click events to pass through
    if (e.which == 2 || e.which == 3) { 
        // Iterate through all background elements
        for (var i = 0; i < background.length; i++) { 
            // Check if clicked point (obtained from event) is within the element
            var mouseX = e.pageX;
            var mouseY = e.pageY;
            var obj = background[i];
            var width = obj.clientWidth;
            var height = obj.clientHeight;

            if (mouseX > obj.offsetLeft && mouseX < obj.offsetLeft + width 
                && mouseY > obj.offsetTop && mouseY < obj.offsetTop + height) {
                // Trigger click event if within boundaries
                background[i].onclick(); 
            }
        }
    }
}

for (var i = 0; i < canvas.length; i++) {
    // Invoke our function upon click
    canvas[i].onmousedown = passThrough; 
    // Prevent context menu from appearing
    canvas[i].oncontextmenu = function(event) { event.returnDefault; return false; } 
}
for (var i = 0; i < background.length; i++) {
    // Toggle background color upon click (to demonstrate functionality)
    background[i].onclick = function() { 
        if (this.style.background == "black") {
            this.style.background = "red";
        }
        else {
            this.style.background = "black";
        }
    }
}

http://jsfiddle.net/z7TUX/3/

I trust this meets your requirements!

Prevent left click on HTML canvas and enable right click to pass through with pointer-events

Answer №1

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