Question

I’ve tried to create a ’tile stamper’ application that allows you to select a tile from the top and then ‘stamp’ that tile onto the canvas area below. You can basically think of this as a map editor for an HTML5 game.

Everything is working except for the selecting and stamping: http://www.exeneva.com/html5/tileStamper

The JS error console says my event listeners aren’t correct, but I am 100% sure they are valid:

// Event listeners
theCanvas.addEventListener("mousemove", onMouseMove, false);   
theCanvas.addEventListener("click", onMouseClick, false);

Here is my mouse movement and mouse click handling code:

function onMouseMove(e) {
  // Accounts for the canvas not being at the top left of screen
  mouseX = e.clientX - theCanvas.offsetLeft;
  mouseY = e.clientY - theCanvas.offsetTop;
}

function onMouseClick(e) {
  console.log("click: " + mouseX + "," + mouseY);
  if (mouseY < 128) {
    // Find tile to highlight
    var totalRows = 7; // 8 total rows, but relative zero means we use 7
    var col = Math.floor(mouseX / tileLength);
    var row = Math.floor(mouseY / tileLength);
    var tileId = (row * totalRows) + (col + row);
    highlightTile(tileId, col * tileLength, row * tileLength);
  } else {
    // stamp the selected tile
    var col = Math.floor(mouseX / tileLength);
    var row = Math.floor(mouseY / tileLength);
    context.putImageData(imageData, col * tileLength, row * tileLength);
  }
}

Here is the tile highlighting code:

function highlightTile(tileId, x, y) {
  // redraw tilesheet and highlight selected tile
  context.fillStyle = "#aaaaaa";
  context.fillRect(0, 0, 256, 128);
  drawTileSheet();

  imageData = context.getImageData(x, y, 32, 32);
  // set alpha to 128
  for (j = 3; j < imageData.data.length; j += 4) {
    imageData.data[j] = 128;
  }

  // draw red line around selected tile
  var startX = Math.floor(tileId % 8) * 32;
  var startY = Math.floor(tileId / 8) * 32;
  context.strokeStyle = "red";
  context.strokeRect(startX, startY, 32, 32);
}

Can someone help me figure out why this isn’t working?

Answer 1

According to this line:

var theCanvas = $("#canvasOne");

theCanvas is jquery wrapper, not a pure DOM Element.So it does not have addEventListener method.
You could try like this:

theCanvas[0].addEventListener("mousemove", onMouseMove, false);   
theCanvas[0].addEventListener("click", onMouseClick, false);