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HTML

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CSS

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JavaScript

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Babel includes JSX processing.

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HTML 

              
                <body bgcolor="#D0D0D0">
  <div id="canvasContainer" align="center">
    <select id="mouseBehavior">
      <option value="1">Compute position by intersection of canvas edge</option>
      <option value="2">Lock mouse cursor inside canvas</option>
      <option value="3">Use last position inside canvas</option>
    </select><br><br>
    <canvas id="canvas" width="300" height="300" style="background-color: #ffffff">
      Your browser doesn't support canvas object!
    </canvas>
  </div>
</body>
!

CSS 

              
                body {
    margin: 0px;
    padding: 0px;    
    overflow:hidden;    
}
!

JS 

              
                var canvas;
var ctx;
var mouse = [];

mouse.INTERSECTION = 1;
// compute intersection between line mouseDown - mouseUp and edge of canvas
mouse.LOCK_INSIDE = 2;
// lock mouse cursor inside
mouse.MOUSEOUT_POS = 3;
// use position where mouse left canvas

mouse.mode = mouse.INTERSECTION;

///////////////////////////////

function circle(x, y, r) {
    ctx.beginPath();
    ctx.arc(x, y, r, 0, Math.PI * 2, true);
    ctx.fill();
    ctx.closePath();
}

function mouseDraggedOut(x1, y1, x2, y2, lineStyle, lineWeight) {
    // x1,y1 = mouseDown;  x2,y2 = mouseUp

    var x3, y3, x4, y4, thisX, thisY;

    if (x2 < 0) {// left edge
        x3 = 0;
        y3 = 0;
        x4 = 0;
        y4 = canvas.height;
        thisX = Math.round(x1 + (((x4 - x3) * (y1 - y3) - (y4 - y3) * (x1 - x3)) / ((y4 - y3) * (x2 - x1) - (x4 - x3) * (y2 - y1))) * (x2 - x1));
        thisY = Math.round(y1 + (((x4 - x3) * (y1 - y3) - (y4 - y3) * (x1 - x3)) / ((y4 - y3) * (x2 - x1) - (x4 - x3) * (y2 - y1))) * (y2 - y1));

        // I must do this for other checks, else corners (when two conditions are true) couldn't be handled
        // So I'll handle it one after another
        x2 = thisX;
        y2 = thisY;

    }

    if (x2 > canvas.width) {// right edge
        x3 = canvas.width;
        y3 = 0;
        x4 = canvas.width;
        y4 = canvas.height;
        thisX = Math.round(x1 + (((x4 - x3) * (y1 - y3) - (y4 - y3) * (x1 - x3)) / ((y4 - y3) * (x2 - x1) - (x4 - x3) * (y2 - y1))) * (x2 - x1));
        thisY = Math.round(y1 + (((x4 - x3) * (y1 - y3) - (y4 - y3) * (x1 - x3)) / ((y4 - y3) * (x2 - x1) - (x4 - x3) * (y2 - y1))) * (y2 - y1));
        x2 = thisX;
        y2 = thisY;
    }

    if (y2 < 0) {// top edge
        x3 = 0;
        y3 = 0;
        x4 = canvas.width;
        y4 = 0;
        thisX = Math.round(x1 + (((x4 - x3) * (y1 - y3) - (y4 - y3) * (x1 - x3)) / ((y4 - y3) * (x2 - x1) - (x4 - x3) * (y2 - y1))) * (x2 - x1));
        thisY = Math.round(y1 + (((x4 - x3) * (y1 - y3) - (y4 - y3) * (x1 - x3)) / ((y4 - y3) * (x2 - x1) - (x4 - x3) * (y2 - y1))) * (y2 - y1));
        x2 = thisX;
        y2 = thisY;
    }

    if (y2 > canvas.height) {// bottom edge
        x3 = 0;
        y3 = canvas.height;
        x4 = canvas.width;
        y4 = canvas.height;
        thisX = Math.round(x1 + (((x4 - x3) * (y1 - y3) - (y4 - y3) * (x1 - x3)) / ((y4 - y3) * (x2 - x1) - (x4 - x3) * (y2 - y1))) * (x2 - x1));
        thisY = Math.round(y1 + (((x4 - x3) * (y1 - y3) - (y4 - y3) * (x1 - x3)) / ((y4 - y3) * (x2 - x1) - (x4 - x3) * (y2 - y1))) * (y2 - y1));
    }

    if ((lineStyle != undefined) || (lineWeight != undefined)) {
        ctx.save();
        if (lineStyle != undefined) {
            ctx.strokeStyle = lineStyle;
        }
        if (lineWeight != undefined) {
            ctx.lineWidth = lineWeight;
        }
        line(x3, y3, x4, y4);
        ctx.restore();

    } else {
        line(x3, y3, x4, y4);
    }

    return {
        'x' : thisX,
        'y' : thisY
    };

}

function line(x1, y1, x2, y2) {
    ctx.beginPath();
    ctx.moveTo(x1, y1);
    ctx.lineTo(x2, y2);
    ctx.stroke();
    ctx.closePath();

}

/////////////////////////////////////////
// Mouse events

function onMouseMove(e) {
    if (mouse.isMouseOver) {
        canvas.style.cursor = "none";
    } else {
        canvas.style.cursor = "";
    }

    mouse.x = e.clientX - canvas.getBoundingClientRect().left;
    mouse.y = e.clientY - canvas.getBoundingClientRect().top;
//console.log((e.clientX-canvas.getBoundingClientRect().left)+", "+(e.clientY-canvas.getBoundingClientRect().top)+"    ->    "+(e.pageX-canvas.getBoundingClientRect().left)+", "+(e.pageY-canvas.getBoundingClientRect().top)+"    ->    "+(e.screenX-canvas.getBoundingClientRect().left)+", "+(e.screenY-canvas.getBoundingClientRect().top));

    if (!mouse.isMouseOver) {
        if (mouse.mode == mouse.LOCK_INSIDE) {

            if (mouse.isMouseDragged) {
                var edgeIntersect = mouseDraggedOut(mouse.xDown, mouse.yDown, mouse.x, mouse.y, "rgba(255, 0, 0, 0.2)", 2);
            } else {
                ctx.save();
                ctx.strokeStyle = "rgba(100,100,100,0.07)";
                ctx.lineWidth = 15;
                var edgeIntersect = mouseDraggedOut(canvas.width / 2, canvas.height / 2, mouse.x, mouse.y, "rgba(255, 0, 0, 0.2)", 2);
                ctx.lineCap = "round";
                line(canvas.width / 2, canvas.height / 2, edgeIntersect.x, edgeIntersect.y);
            }
            mouse.x = edgeIntersect.x;
            mouse.y = edgeIntersect.y;

            mouse.xOut = undefined;
            mouse.yOut = undefined;
            //mouse.isMouseOver = true;
        }
    }
}

function onMouseDown(e) {
    mouse.xDown = e.clientX - canvas.getBoundingClientRect().left;
    mouse.yDown = e.clientY - canvas.getBoundingClientRect().top;
    mouse.isMouseDragged = true;
}

function onMouseUp(e) {
    if (mouse.isMouseDragged) {
        mouse.xUp = e.clientX - canvas.getBoundingClientRect().left;
        mouse.yUp = e.clientY - canvas.getBoundingClientRect().top;

        // FIRST OPTION
        if (mouse.mode == mouse.INTERSECTION) {
            if (!mouse.isMouseOver) {

                //ctx.save();
                //ctx.strokeStyle = "rgba(255,0,0,1)";
                //ctx.lineWidth = 10;
                var edgeIntersect = mouseDraggedOut(mouse.xDown, mouse.yDown, mouse.xUp, mouse.yUp, "rgba(255,0,0,1)", 10);
                //ctx.restore();

                mouse.xUp = edgeIntersect.x;
                mouse.yUp = edgeIntersect.y;
            }
        }
        // SECOND OPTION
        if (mouse.mode == mouse.LOCK_INSIDE) {
            mouse.xUp = mouse.x;
            mouse.yUp = mouse.y;
        }
        mouse.isMouseDragged = false;
    }
}

function onMouseOut(e) {
    mouse.xOut = e.clientX - canvas.getBoundingClientRect().left;
    mouse.yOut = e.clientY - canvas.getBoundingClientRect().top;
    mouse.isMouseOver = false;

    // fix after swift move with mouse, when position is beyond canvas (put it on edge of canvas)
    if (mouse.xOut < 0)
        mouse.xOut = 0;
    if (mouse.xOut > canvas.width)
        mouse.xOut = canvas.width;
    if (mouse.yOut < 0)
        mouse.yOut = 0;
    if (mouse.yOut > canvas.height)
        mouse.yOut = canvas.height;

    // THIRD OPTION
    if (mouse.isMouseDragged) {
        if (mouse.mode == mouse.MOUSEOUT_POS) {
            mouse.xUp = mouse.xOut;
            mouse.yUp = mouse.yOut;
            mouse.isMouseDragged = false;
        }
    }

    //console.log("MouseOut : " + mouse.xOut + "," + mouse.yOut);
}

function onMouseOver(e) {
    mouse.xOver = e.clientX - canvas.getBoundingClientRect().left;
    mouse.yOver = e.clientY - canvas.getBoundingClientRect().top;
    mouse.isMouseOver = true;
}

//////////////////////////

///////+++      M  A  I  N      F   U   N   C   T   I  O   N   S

/////////////////////////////////////////////////////////////////
// Compatibility animation loop
window.requestAnimFrame = (function(callback) {
    return window.requestAnimationFrame || window.webkitRequestAnimationFrame || window.mozRequestAnimationFrame || window.oRequestAnimationFrame || window.msRequestAnimationFrame ||
    function(callback) {
        window.setTimeout(callback, 1000 / 60);
    };
})();
/////////////////////////////////////////////////////////////////

//+++ L O O P ///////////////////////////////////////////////////////////////
function loop() {
    update();
    draw();
    requestAnimFrame(loop);
}

//+++ L O O P ///////////////////////////////////////////////////////////////

//+++ I N I T ///////////////////////////////////////////////////////////////
function init() {
    canvas = document.getElementById('canvas');
    ctx = canvas.getContext('2d');

    canvas.addEventListener('contextmenu', function(e) {
        //Don't show context menu by pressing right mouse button
        if (e.button == 2) {
            //!!!needs to fix number, that varies by browser!!!
            e.preventDefault();
            return false;
        }
    }, false);

    window.addEventListener("mousemove", onMouseMove, false);

    canvas.addEventListener("mousedown", onMouseDown, false);
    window.addEventListener("mouseup", onMouseUp, false);

    canvas.addEventListener("mouseover", onMouseOver, false);
    canvas.addEventListener("mouseout", onMouseOut, false);

    loop();

    document.onselectstart = function() {
        if (mouse.isMouseDragged) {
            // do not select text outside if animation in canvas is active
            return false;
        }
    };
}

//--- I N I T ///////////////////////////////////////////////////////////////

//+++ U P D A T E ///////////////////////////////////////////////////////////////
function update() {
    mouse.mode = mouseBehavior.options[mouseBehavior.selectedIndex].value;
}

//--- U P D A T E ///////////////////////////////////////////////////////////////

//+++ D R A W ///////////////////////////////////////////////////////////////
function draw() {
    //ctx.clearRect(0,0,canvas.width, canvas.height);
    ctx.fillStyle = "rgba(255,255,255,0.1)";
    ctx.fillRect(0, 0, canvas.width, canvas.height);

    ctx.fillStyle = "rgba(0,255,255,0.8)";
    ctx.fillRect(mouse.xOut - 20, mouse.yOut - 20, 40, 40);
    ctx.fillStyle = "rgb(0,0,0)";
    ctx.fillRect(mouse.xOut - 2, mouse.yOut - 2, 4, 4);

    ctx.fillStyle = "rgba(255,255,0,0.8)";
    ctx.fillRect(mouse.xOver - 20, mouse.yOver - 20, 40, 40);
    ctx.fillStyle = "rgb(0,0,0)";
    ctx.fillRect(mouse.xOver - 2, mouse.yOver - 2, 4, 4);

    ctx.fillStyle = "rgb(255,0,0)";
    ctx.fillRect(mouse.xDown - 15, mouse.yDown - 15, 30, 30);
    ctx.fillStyle = "rgb(0,0,0)";
    ctx.fillRect(mouse.xDown - 2, mouse.yDown - 2, 4, 4);

    ctx.fillStyle = "rgba(0,0,255,0.8)";
    ctx.fillRect(mouse.xUp - 15, mouse.yUp - 15, 30, 30);
    ctx.fillStyle = "rgb(0,0,0)";
    ctx.fillRect(mouse.xUp - 2, mouse.yUp - 2, 4, 4);

    /// actual cursor
    ctx.fillStyle = "rgb(100,100,255)";
    ctx.strokeStyle = "rgb(0,0,100)";
    circle(mouse.x, mouse.y, 10);
    ctx.stroke();

    ctx.strokeStyle = "rgba(0, 0, 0, 0.25)";
    ctx.lineWidth = 1;

    if (mouse.isMouseDragged) {
        ctx.save();
        ctx.strokeStyle = "rgba(100,100,100,0.07)";
        ctx.fillStyle = ctx.strokeStyle;
        ctx.lineWidth = 15;
        ctx.lineCap = "round";

        var edgeIntersect = mouseDraggedOut(mouse.xDown, mouse.yDown, mouse.x, mouse.y, "rgba(0, 0, 255, 1)", 2);
        if (edgeIntersect.x === undefined || edgeIntersect.y === undefined) {
            edgeIntersect.x = mouse.x;
            edgeIntersect.y = mouse.y;
        }
        line(mouse.xDown, mouse.yDown, edgeIntersect.x, edgeIntersect.y);
        ctx.strokeStyle = "rgba(0,0,0,0.07)";
        circle(mouse.xDown, mouse.yDown, 20);
        circle(edgeIntersect.x, edgeIntersect.y, 20);
        ctx.lineWidth = 1;
        ctx.stroke();

        ctx.restore();
    } else {
        ctx.save();
        ctx.strokeStyle = "rgba(0,0,0,1)";
        ctx.lineWidth = 1;
        line(mouse.xDown, mouse.yDown, mouse.xUp, mouse.yUp);
        ctx.restore();
    }
}

//--- D R A W ///////////////////////////////////////////////////////////////

///////---      M  A  I  N      F   U   N   C   T   I  O   N   S

init();
!
999px

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