Kinetic.js – creating a grid

Question

I'm new to Kintetic.js and I'm trying to do a grid. The width is 800px and the height is 400px. And I want squares (20x20) to cover that area. Every square has a 1px border. So something like this:

var box = new Kinetic.Rect({
  width: 20,
  height: 20,
  fill: 'transparent',
  stroke: 'rgba(0, 0, 0, 0.02)'
});

And to fill the canvas, I have a crappy for-loop like this:

for (var i = 0; i <= this.field.getWidth(); i = i + 20) {
  for (var i2 = 0; i2 <= this.field.getHeight(); i2 = i2 + 20) {
    var cbox = box.clone({x: i, y: i2});
    this.grid.add(cbox);
  }
}

this.grid is a Kinetic.Layer. The first problem with this code is that it is very slow and I get like a 500ms delay before the grid shows up. But the worst thing is that if I put an mouseover and mouseout event on the cbox to change the fill color, that renders really really slow. This is how I do it:

cbox.on('mouseover', function () {
  this.setFill('black');
  self.grid.draw();
});

cbox.on('mouseout', function () {
  this.setFill('transparent');
  self.grid.draw();
});

So my question is how can I improve the code and performance of this?

Answer 1

How about to make grid with lines and use one rect for cursor highlighting? Here i wrote the example for you: http://jsfiddle.net/e_aksenov/R72Xu/30/

var CELL_SIZE = 35,
w = 4,
h = 5,
W = w * CELL_SIZE,
H = h * CELL_SIZE;

var make_grid = function(layer) {
var back = new Kinetic.Rect({
    x: 0,
    y: 0,
    width: W,
    height: H,
    fill: "yellow"
});
layer.add(back);
for (i = 0; i < w + 1; i++) {
    var I = i * CELL_SIZE;
    var l = new Kinetic.Line({
        stroke: "black",
        points: [I, 0, I, H]
    });
    layer.add(l);
}

for (j = 0; j < h + 1; j++) {
    var J = j * CELL_SIZE;
    var l2 = new Kinetic.Line({
        stroke: "black",
        points: [0, J, W, J]
    });
    layer.add(l2);
}
    return back; //to attach mouseover listener
};

var cursor_bind = function(layer, grid_rect, rect) {

grid_rect.on('mouseover', function(e) {
    var rx = Math.floor(e.x / CELL_SIZE);
    var ry = Math.floor(e.y / CELL_SIZE);
    rect.setPosition(rx * CELL_SIZE, ry * CELL_SIZE);
    layer.draw();
});
};

var stage = new Kinetic.Stage({
container: "kinetic",
width: 800,
height: 600,
draggable: true
});

var layer = new Kinetic.Layer();

var rect = new Kinetic.Rect({
x: 0,
y: 0,
width: CELL_SIZE,
height: CELL_SIZE,
fill: "#00D2FF",
stroke: "black",
strokeWidth: 4
});

var gr = make_grid(layer);
cursor_bind(layer, gr, rect);

// add the shape to the layer
layer.add(rect);

// add the layer to the stage
stage.add(layer);​