javascript - 如何使用光标类型拖动和调整 Canvas 矩形的大小

Question

在 Canvas 中，我绘制了一个矩形并完成了拖动和调整大小功能。绘制圆圈以表示调整矩形大小的 handle 。但现在我想使用光标类型进行拖动。

我使用的游标类型如下:

$("#canvas").css({'cursor':'ne-resize'});

这是 jsfiddle 链接。 http://jsfiddle.net/BaliBalo/9HXMG/

var canvas = document.getElementById('canvas'),
    ctx = canvas.getContext('2d'),
    rect = {
        x: 150,
        y: 100,
        w: 123,
        h: 58
    },
    handlesSize = 8,
    currentHandle = false,
    drag = false;

function init() {
    canvas.addEventListener('mousedown', mouseDown, false);
    canvas.addEventListener('mouseup', mouseUp, false);
    canvas.addEventListener('mousemove', mouseMove, false);
}

function point(x, y) {
    return {
        x: x,
        y: y
    };
}

function dist(p1, p2) {
    return Math.sqrt((p2.x - p1.x) * (p2.x - p1.x) + (p2.y - p1.y) * (p2.y - p1.y));
}

function getHandle(mouse) {
    if (dist(mouse, point(rect.x, rect.y)) <= handlesSize) return 'topleft';
    if (dist(mouse, point(rect.x + rect.w, rect.y)) <= handlesSize) return 'topright';
    if (dist(mouse, point(rect.x, rect.y + rect.h)) <= handlesSize) return 'bottomleft';
    if (dist(mouse, point(rect.x + rect.w, rect.y + rect.h)) <= handlesSize) return 'bottomright';
    if (dist(mouse, point(rect.x + rect.w / 2, rect.y)) <= handlesSize) return 'top';
    if (dist(mouse, point(rect.x, rect.y + rect.h / 2)) <= handlesSize) return 'left';
    if (dist(mouse, point(rect.x + rect.w / 2, rect.y + rect.h)) <= handlesSize) return 'bottom';
    if (dist(mouse, point(rect.x + rect.w, rect.y + rect.h / 2)) <= handlesSize) return 'right';
    return false;
}

function mouseDown(e) {
    if (currentHandle) drag = true;
    draw();
}

function mouseUp() {
    drag = false;
    currentHandle = false;
    draw();
}

function mouseMove(e) {
    var previousHandle = currentHandle;
    if (!drag) currentHandle = getHandle(point(e.pageX - this.offsetLeft, e.pageY - this.offsetTop));
    if (currentHandle && drag) {
        var mousePos = point(e.pageX - this.offsetLeft, e.pageY - this.offsetTop);
        switch (currentHandle) {
            case 'topleft':
                rect.w += rect.x - mousePos.x;
                rect.h += rect.y - mousePos.y;
                rect.x = mousePos.x;
                rect.y = mousePos.y;
                break;
            case 'topright':
                rect.w = mousePos.x - rect.x;
                rect.h += rect.y - mousePos.y;
                rect.y = mousePos.y;
                break;
            case 'bottomleft':
                rect.w += rect.x - mousePos.x;
                rect.x = mousePos.x;
                rect.h = mousePos.y - rect.y;
                break;
            case 'bottomright':
                rect.w = mousePos.x - rect.x;
                rect.h = mousePos.y - rect.y;
                break;

            case 'top':
                rect.h += rect.y - mousePos.y;
                rect.y = mousePos.y;
                break;

            case 'left':
                rect.w += rect.x - mousePos.x;
                rect.x = mousePos.x;
                break;

            case 'bottom':
                rect.h = mousePos.y - rect.y;
                break;

            case 'right':
                rect.w = mousePos.x - rect.x;
                break;
        }
    }
    if (drag || currentHandle != previousHandle) draw();
}

function draw() {
    ctx.clearRect(0, 0, canvas.width, canvas.height);
    ctx.fillStyle = 'black';
    ctx.fillRect(rect.x, rect.y, rect.w, rect.h);
    if (currentHandle) {
        var posHandle = point(0, 0);
        switch (currentHandle) {
            case 'topleft':
                posHandle.x = rect.x;
                posHandle.y = rect.y;
                break;
            case 'topright':
                posHandle.x = rect.x + rect.w;
                posHandle.y = rect.y;
                break;
            case 'bottomleft':
                posHandle.x = rect.x;
                posHandle.y = rect.y + rect.h;
                break;
            case 'bottomright':
                posHandle.x = rect.x + rect.w;
                posHandle.y = rect.y + rect.h;
                break;
            case 'top':
                posHandle.x = rect.x + rect.w / 2;
                posHandle.y = rect.y;
                break;
            case 'left':
                posHandle.x = rect.x;
                posHandle.y = rect.y + rect.h / 2;
                break;
            case 'bottom':
                posHandle.x = rect.x + rect.w / 2;
                posHandle.y = rect.y + rect.h;
                break;
            case 'right':
                posHandle.x = rect.x + rect.w;
                posHandle.y = rect.y + rect.h / 2;
                break;
        }
        ctx.globalCompositeOperation = 'xor';
        ctx.beginPath();
        ctx.arc(posHandle.x, posHandle.y, handlesSize, 0, 2 * Math.PI);
        ctx.fill();
        ctx.globalCompositeOperation = 'source-over';
    }
}

init();
draw();

<canvas id="canvas" width="500" height="500"></canvas>

Answer 1

在 draw 函数的 swicth 语句中添加所需的光标类型:

var canvas = document.getElementById('canvas'),
    ctx = canvas.getContext('2d'),
    rect = {
        x: 150,
        y: 100,
        w: 123,
        h: 58
    },
    handlesSize = 8,
    currentHandle = false,
    drag = false;

function init() {
    canvas.addEventListener('mousedown', mouseDown, false);
    canvas.addEventListener('mouseup', mouseUp, false);
    canvas.addEventListener('mousemove', mouseMove, false);
}

function point(x, y) {
    return {
        x: x,
        y: y
    };
}

function dist(p1, p2) {
    return Math.sqrt((p2.x - p1.x) * (p2.x - p1.x) + (p2.y - p1.y) * (p2.y - p1.y));
}

function getHandle(mouse) {
    if (dist(mouse, point(rect.x, rect.y)) <= handlesSize) return 'topleft';
    if (dist(mouse, point(rect.x + rect.w, rect.y)) <= handlesSize) return 'topright';
    if (dist(mouse, point(rect.x, rect.y + rect.h)) <= handlesSize) return 'bottomleft';
    if (dist(mouse, point(rect.x + rect.w, rect.y + rect.h)) <= handlesSize) return 'bottomright';
    if (dist(mouse, point(rect.x + rect.w / 2, rect.y)) <= handlesSize) return 'top';
    if (dist(mouse, point(rect.x, rect.y + rect.h / 2)) <= handlesSize) return 'left';
    if (dist(mouse, point(rect.x + rect.w / 2, rect.y + rect.h)) <= handlesSize) return 'bottom';
    if (dist(mouse, point(rect.x + rect.w, rect.y + rect.h / 2)) <= handlesSize) return 'right';
    return false;
}

function mouseDown(e) {
    if (currentHandle) drag = true;
    draw();
}

function mouseUp() {
    drag = false;
    currentHandle = false;
    draw();
}

function mouseMove(e) {
    var previousHandle = currentHandle;
    if (!drag) currentHandle = getHandle(point(e.pageX - this.offsetLeft, e.pageY - this.offsetTop));
    if (currentHandle && drag) {
        var mousePos = point(e.pageX - this.offsetLeft, e.pageY - this.offsetTop);
        switch (currentHandle) {
            case 'topleft':
                rect.w += rect.x - mousePos.x;
                rect.h += rect.y - mousePos.y;
                rect.x = mousePos.x;
                rect.y = mousePos.y;
                break;
            case 'topright':
                rect.w = mousePos.x - rect.x;
                rect.h += rect.y - mousePos.y;
                rect.y = mousePos.y;
                break;
            case 'bottomleft':
                rect.w += rect.x - mousePos.x;
                rect.x = mousePos.x;
                rect.h = mousePos.y - rect.y;
                break;
            case 'bottomright':
                rect.w = mousePos.x - rect.x;
                rect.h = mousePos.y - rect.y;
                break;

            case 'top':
                rect.h += rect.y - mousePos.y;
                rect.y = mousePos.y;
                break;

            case 'left':
                rect.w += rect.x - mousePos.x;
                rect.x = mousePos.x;
                break;

            case 'bottom':
                rect.h = mousePos.y - rect.y;
                break;

            case 'right':
                rect.w = mousePos.x - rect.x;
                break;
        }
    }
    if (drag || currentHandle != previousHandle) draw();


}

function draw() {
    ctx.clearRect(0, 0, canvas.width, canvas.height);
    ctx.fillStyle = 'black';
    ctx.fillRect(rect.x, rect.y, rect.w, rect.h);
    if (currentHandle) {
        var posHandle = point(0, 0);
        var dir;
        switch (currentHandle) {
            case 'topleft':
                dir={x:rect.w>0?'w':'e',y:rect.h>0?'n':'s'};
                canvas.style.cursor= dir.y+dir.x+'-resize';
                break;
            case 'topright':
                dir={x:rect.w>0?'e':'w',y:rect.h>0?'n':'s'};
                canvas.style.cursor= dir.y+dir.x+'-resize';
                break;
            case 'bottomleft':
                dir={x:rect.w>0?'w':'e',y:rect.h>0?'s':'n'};
                canvas.style.cursor= dir.y+dir.x+'-resize';
                break;
            case 'bottomright':
                dir={x:rect.w>0?'e':'w',y:rect.h>0?'s':'n'};
                canvas.style.cursor= dir.y+dir.x+'-resize';
                break;
            case 'top':
                canvas.style.cursor= (rect.h>0?'n':'s')+'-resize';
                break;
            case 'left':
                canvas.style.cursor= (rect.w>0?'w':'e')+'-resize';
                break;
            case 'bottom':
                canvas.style.cursor= (rect.h>0?'s':'n')+'-resize';
                break;
            case 'right':
                canvas.style.cursor= (rect.w>0?'e':'w')+'-resize';
                break;
        }
    }else canvas.style.cursor='';
}

init();
draw();

<canvas id="canvas" width="500" height="500"></canvas>