/*
window.addEventListener('load', eventWindowLoaded, false);

function eventWindowLoaded() {
    canvasApp(); //包含整个Canvas应用程序
}
function canvasSupport(e) {

    return !!e.getContext;

}*/
//function canvasApp() {

    /*
    var myCanvas = document.getElementById('myCanvas');

    if (!canvasSupport(myCanvas)) {
        return;
    }

    var ctx = myCanvas.getContext('2d');

    myCanvas.width = window.innerWidth;
    myCanvas.height = window.innerHeight;*/

    // Draw grid
function drawGrid(ctx, w, h, strokeStyle, step) {
    for (var x = 0.5; x < w; x += step) {
        ctx.moveTo(x, 0);
        ctx.lineTo(x, h);
    }

    for (var y = 0.5; y < h; y += step) {
        ctx.moveTo(0, y);
        ctx.lineTo(w, y);
    }

    ctx.strokeStyle = strokeStyle;
    ctx.stroke();
}

// From: http://www.dbp-consulting.com/tutorials/canvas/CanvasArrow.html
// Draw arrow head
function drawHead(ctx, x0, y0, x1, y1, x2, y2, style, color, width) {
    if (typeof (x0) == 'string') {
        x0 = parseInt(x0);
    }
    if (typeof (y0) == 'string') {
        y0 = parseInt(y0);
    }
    if (typeof (x1) == 'string') {
        x1 = parseInt(x1);
    }
    if (typeof (y1) == 'string') {
        y1 = parseInt(y1);
    }
    if (typeof (x2) == 'string') {
        x2 = parseInt(x2);
    }
    if (typeof (y2) == 'string') {
        y2 = parseInt(y2);
    }
    /*
    var radius = 3,
        twoPI = 2 * Math.PI;
        */
    ctx.save();
    ctx.beginPath();
    ctx.strokeStyle = color;
    ctx.fillStyle = color;
    ctx.lineWidth = width;
    ctx.moveTo(x0, y0);
    ctx.lineTo(x1, y1);
    ctx.lineTo(x2, y2);

    switch (style) {
        case 0:
            var backdist = Math.sqrt(((x2 - x0) * (x2 - x0)) + ((y2 - y0) * (y2 - y0)));
            ctx.arcTo(x1, y1, x0, y0, .55 * backdist);
            ctx.fill();
            break;
        case 1:
            ctx.beginPath();
            ctx.moveTo(x0, y0);
            ctx.lineTo(x1, y1);
            ctx.lineTo(x2, y2);
            ctx.lineTo(x0, y0);
            ctx.fill();
            break;
        case 2:
            ctx.stroke();
            break;
        case 3:
            var cpx = (x0 + x1 + x2) / 3;
            var cpy = (y0 + y1 + y2) / 3;
            ctx.quadraticCurveTo(cpx, cpy, x0, y0);
            ctx.fill();
            break;
        case 4:
            var cp1x, cp1y, cp2x, cp2y, backdist;
            var shiftamt = 5;
            if (x2 == x0) {
                backdist = y2 - y0;
                cp1x = (x1 + x0) / 2;
                cp2x = (x1 + x0) / 2;
                cp1y = y1 + backdist / shiftamt;
                cp2y = y1 - backdist / shiftamt;
            } else {
                backdist = Math.sqrt(((x2 - x0) * (x2 - x0)) + ((y2 - y0) * (y2 - y0)));
                var xback = (x0 + x2) / 2;
                var yback = (y0 + y2) / 2;
                var xmid = (xback + x1) / 2;
                var ymid = (yback + y1) / 2;
                var m = (y2 - y0) / (x2 - x0);
                var dx = (backdist / (2 * Math.sqrt(m * m + 1))) / shiftamt;
                var dy = m * dx;
                cp1x = xmid - dx;
                cp1y = ymid - dy;
                cp2x = xmid + dx;
                cp2y = ymid + dy;
            }
            ctx.bezierCurveTo(cp1x, cp1y, cp2x, cp2y, x0, y0);
            ctx.fill();
            break;
    }
    ctx.restore();
}

// draw arrow
function drawArrow(ctx, x1, y1, x2, y2, style, which, angle, d, color, width) {
    if (typeof (x1) == 'string') {
        x1 = parseInt(x1);
    }
    if (typeof (y1) == 'string') {
        y1 = parseInt(y1);
    }
    if (typeof (x2) == 'string') {
        x2 = parseInt(x2);
    }
    if (typeof (y2) == 'string') {
        y2 = parseInt(y2);
    }
    style = typeof (style) != 'undefined' ? style : 3;
    which = typeof (which) != 'undefined' ? which : 1;
    angle = typeof (angle) != 'undefined' ? angle : Math.PI / 9;
    d = typeof (d) != 'undefined' ? d : 10;
    color = typeof (color) != 'undefined' ? color : '#000';
    width = typeof (width) != 'undefined' ? width : 1;
    var toDrawHead = typeof (style) != 'function' ? drawHead : style;
    var dist = Math.sqrt((x2 - x1) * (x2 - x1) + (y2 - y1) * (y2 - y1));
    var ratio = (dist - d / 3) / dist;
    var tox, toy, fromx, fromy;
    if (which & 1) {
        tox = Math.round(x1 + (x2 - x1) * ratio);
        toy = Math.round(y1 + (y2 - y1) * ratio);
    } else {
        tox = x2;
        toy = y2;
    }

    if (which & 2) {
        fromx = x1 + (x2 - x1) * (1 - ratio);
        fromy = y1 + (y2 - y1) * (1 - ratio);
    } else {
        fromx = x1;
        fromy = y1;
    }

    ctx.beginPath();
    ctx.strokeStyle = color;
    ctx.lineWidth = width;
    ctx.moveTo(fromx, fromy);
    ctx.lineTo(tox, toy);
    ctx.stroke();

    var lineangle = Math.atan2(y2 - y1, x2 - x1);
    var h = Math.abs(d / Math.cos(angle));
    if (which & 1) {
        var angle1 = lineangle + Math.PI + angle;
        var topx = x2 + Math.cos(angle1) * h;
        var topy = y2 + Math.sin(angle1) * h;
        var angle2 = lineangle + Math.PI - angle;
        var botx = x2 + Math.cos(angle2) * h;
        var boty = y2 + Math.sin(angle2) * h;
        toDrawHead(ctx, topx, topy, x2, y2, botx, boty, style, color, width);
    }

    if (which & 2) {
        var angle1 = lineangle + angle;
        var topx = x1 + Math.cos(angle1) * h;
        var topy = y1 + Math.sin(angle1) * h;
        var angle2 = lineangle - angle;
        var botx = x1 + Math.cos(angle2) * h;
        var boty = y1 + Math.sin(angle2) * h;
        toDrawHead(ctx, topx, topy, x1, y1, botx, boty, style, color, width);
    }
}

// draw arced arrow
function drawArcedArrow(ctx, x, y, r, startangle, endangle, anticlockwise, style, which, angle, d, color, width) {
    style = typeof (style) != 'undefined' ? style : 3;
    which = typeof (which) != 'undefined' ? which : 1;
    angle = typeof (angle) != 'undefined' ? angle : Math.PI / 8;
    d = typeof (d) != 'undefined' ? d : 10;
    color = typeof (color) != 'undefined' ? color : '#000';
    width = typeof (width) != 'undefined' ? width : 1;

    ctx.save();
    ctx.beginPath();
    ctx.lineWidth = width;
    ctx.strokeStyle = color;
    ctx.arc(x, y, r, startangle, endangle, anticlockwise);
    ctx.stroke();
    var sx, sy, lineangle, destx, desty;
    ctx.strokeStyle = 'rgba(0,0,0,0)';
    if (which & 1) {
        sx = Math.cos(startangle) * r + x;
        sy = Math.sin(startangle) * r + y;
        lineangle = Math.atan2(x - sx, sy - y);
        if (anticlockwise) {
            destx = sx + 10 * Math.cos(lineangle);
            desty = sy + 10 * Math.sin(lineangle);
        } else {
            destx = sx - 10 * Math.cos(lineangle);
            desty = sy - 10 * Math.sin(lineangle);
        }
        drawArrow(ctx, sx, sy, destx, desty, style, 2, angle, d, color, width);
    }

    if (which & 2) {
        sx = Math.cos(endangle) * r + x;
        sy = Math.sin(endangle) * r + y;
        lineangle = Math.atan2(x - sx, sy - y);
        if (anticlockwise) {
            destx = sx - 10 * Math.cos(lineangle);
            desty = sy - 10 * Math.sin(lineangle);
        } else {
            destx = sx + 10 * Math.cos(lineangle);
            desty = sy + 10 * Math.sin(lineangle);
        }
        drawArrow(ctx, sx, sy, destx, desty, style, 2, angle, d, color, width);
    }
    ctx.restore();
}
function drawScreen(ctx) {
    drawArrow(ctx, 100, 50, 250, 50, 1, 1, 20, 10, 'red', 30);

    //drawGrid(ctx, myCanvas.width, myCanvas.height, 'gray', 10);

    //drawArrow(ctx, 100, 50, 250, 50, 1, 1, 20, 10, 'red', 4);
    //drawArrow(ctx, 300, 50, 450, 50, 2, 1, 20, 10, 'blue', 4);
    //drawArrow(ctx, 500, 50, 650, 50, 3, 1, 20, 10, 'orange', 4);
    //drawArrow(ctx, 700, 50, 850, 50, 4, 1, 20, 10, 'green', 4);

    //drawArrow(ctx, 100, 100, 250, 100, 1, 2, 20, 10, 'red', 4);
    //drawArrow(ctx, 300, 100, 450, 100, 2, 2, 20, 10, 'blue', 4);
    //drawArrow(ctx, 500, 100, 650, 100, 3, 2, 20, 10, 'orange', 4);
    //drawArrow(ctx, 700, 100, 850, 100, 4, 2, 20, 10, 'green', 4);

    //drawArrow(ctx, 100, 150, 250, 250, 1, 2, 20, 10, 'red', 4);
    //drawArrow(ctx, 300, 150, 450, 250, 2, 2, 20, 10, 'blue', 4);
    //drawArrow(ctx, 500, 150, 650, 250, 3, 2, 20, 10, 'orange', 4);
    //drawArrow(ctx, 700, 150, 850, 250, 4, 2, 20, 10, 'green', 4);


    //drawArcedArrow(ctx, 900, 200, 100, 20, 100, true, 1, 1, 20, 10, 'blue', 4);
}

    //drawScreen();

//}