Canvas-2D-Context-API-Primer/grid.html at master · rroa/Canvas-2D-Context-API-Primer · GitHub

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<!--
To change this template use Tools | Templates.
-->
<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">
<html>
<head>
    <title>Keyboard Events - keypress</title>
    <meta charset="utf-8" />
    <meta name="viewport" content="width=1024" />
    <meta name="apple-mobile-web-app-capable" content="yes" />
    <style type="text/css">
        canvas.default { border: 1px solid black; }
        canvas.active { border: 1px solid red; }
        div.feedback { color: red; font-size: 1.0em; }

        body {
            /*background: lightblue;*/
        }

        canvas {
            background: #fff;
            margin: 20px;
        }
    </style>

    <!--SCRIPTS-->
    <script type="text/javascript">
        var x = 0;
        var y = 0;
        var kBoardWidth = 9;
        var kBoardHeight= 9;
        var kPieceWidth = 50;
        var kPieceHeight = 50;
        var kPixelWidth = 1 + (kBoardWidth * kPieceWidth);
        var kPixelHeight= 1 + (kBoardHeight * kPieceHeight);
        var fontXOffset = -15;
        var fontYOffset = 12;
        var currentPosition = { column:0, row:0 };
        var gContext;

        if (window.addEventListener) { // Mozilla, Netscape, Firefox
            window.addEventListener('load', WindowLoad, false);
        }
        else if (window.attachEvent) { // IE
            window.attachEvent('onload', WindowLoad);
        }

        function isInsideGrid(position) {
            return ( position.row >= 0 && position.row < kBoardWidth ) && ( position.column >= 0 && position.column < kBoardHeight );

        }

        function drawCharacter(position) {
            var column = position.column;
            var row = position.row;

            // transform row / column to grid coords
            var x = (column * kPieceWidth) + (kPieceWidth/2);
            var y = (row * kPieceHeight) + (kPieceHeight/2);

            // Radius based of the piece size
            var radius = (kPieceWidth/2) - (kPieceWidth/10);

            // draw
            gContext.strokeStyle = "#000";
            gContext.stroke();

            // Set the font
            gContext.font = "italic 200 36px/2 Unknown Font, sans-serif";

            // Draw the @ symbol in the center of the circle
            //
            gContext.fillStyle = 'black';
            gContext.fillText('@', x + fontXOffset, y + fontYOffset);

            //
            var up = { column: position.column, row: position.row - 1 };
            var down = { column: position.column, row: position.row + 1 };
            var left = { column: position.column - 1, row: position.row };
            var right = { column: position.column + 1, row: position.row };

            // Set the fill pattern
            gContext.fillStyle = '#ccc';

            if(isInsideGrid(up)){
                var x = (up.column * kPieceWidth) + (kPieceWidth/2);
                var y = (up.row * kPieceHeight) + (kPieceHeight/2);

                gContext.fillText('W', x + fontXOffset, y + fontYOffset);
            }

            if(isInsideGrid(down)){
                var x = (down.column * kPieceWidth) + (kPieceWidth/2);
                var y = (down.row * kPieceHeight) + (kPieceHeight/2);

                gContext.fillText('S', x + fontXOffset, y + fontYOffset);
            }

            if(isInsideGrid(left)){
                var x = (left.column * kPieceWidth) + (kPieceWidth/2);
                var y = (left.row * kPieceHeight) + (kPieceHeight/2);

                gContext.fillText('A', x + fontXOffset, y + fontYOffset);
            }

            if(isInsideGrid(right)){
                var x = (right.column * kPieceWidth) + (kPieceWidth/2);
                var y = (right.row * kPieceHeight) + (kPieceHeight/2);

                gContext.fillText('D', x + fontXOffset, y + fontYOffset);
            }
        }

        // This function was taken from an example of the book HTML5: Up and Running by Mark Pilgrim
        // http://www.amazon.com/HTML5-Up-Running-Mark-Pilgrim/dp/0596806027
        //
        function drawBoard() {

            gContext.clearRect(0, 0, kPixelWidth, kPixelHeight);
            gContext.beginPath();

            /* vertical lines */
            for (var x = 0; x <= kPixelWidth; x += kPieceWidth) {
	            gContext.moveTo(0.5 + x, 0);
	            gContext.lineTo(0.5 + x, kPixelHeight);
            }

            /* horizontal lines */
            for (var y = 0; y <= kPixelHeight; y += kPieceHeight) {
	            gContext.moveTo(0, 0.5 + y);
	            gContext.lineTo(kPixelWidth, 0.5 +  y);
            }

            /* draw it! */
            gContext.strokeStyle = "#ccc";
            gContext.stroke();

            drawCharacter(currentPosition);
        }

        document.addEventListener("keydown", function (e) {
            var newPosition = { column:0, row:0 };

            newPosition.column  = currentPosition.column;
            newPosition.row     = currentPosition.row;

            // A
            if( e.keyCode == 65 ){
                newPosition.column -= 1;
            }

            // D
            if( e.keyCode == 68 ){
                newPosition.column += 1;
            }

            // W
            if( e.keyCode == 87 ){
                newPosition.row -= 1;
            }

            // S
            if( e.keyCode == 83 ){
                newPosition.row += 1;
            }

            if(isInsideGrid(newPosition)){
                currentPosition = newPosition;
            }

            drawBoard();
        }, false);


        function WindowLoad(event) {
             var canvas = document.createElement('canvas');

             canvas.id = 'canvas';
             canvas.width = kPixelWidth;
             canvas.height = kPixelHeight;

             document.body.appendChild(canvas);

             var context = canvas.getContext("2d");
             gContext = context;

             drawBoard();
        }
    </script>
</head>
<body>
    <p>
        <a href="index.html">Back to index</a>
    </p>
</body>
</html>