/*

File: gridview.js

Abstract: A JavaScript object that creates a simple grid view programmatically.

  Used to create the list of thumbnails in the image gallery.

Version: 1.1

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*/

// GridView creates a one- or two-dimensional grid of divs. The content of the thumbnails

// is obtained via the data source, and notifications about focus changes are sent to the

// delegate, both of which should be set by the client (SlideShow in this case).

function GridView(element)

{

  this._rowWidth = 800;

  this._rowElementWidth = 20;

  this._visibleColumns = 6;

  this._activeElementIndex = 0;

  this.currentLeftColumn = 0;

  this.element = element ? element :  document.createElement("div");

  this.element.addClassName('grid-view');

}

GridView.prototype.init = function(dataSource, delegate)

{

  this.dataSource = dataSource;

  this.delegate = delegate;

  // create the grid container

  this.gridContainer = document.createElement("div");

  this.gridContainer.addClassName('grid-container-view');

  this.element.appendChild(this.gridContainer);

  // Ask the data source how many elements we should contain.

  var numElements = this.dataSource.gridViewNumberOfElements(this);

  // Create the grid contents, asking the dataSource to create elements for us.

  for (var i=0; i < numElements; i++) {

    var el = this.dataSource.gridViewElementAtIndex(this, i);

    el.addClassName('grid-element');

    this.gridContainer.appendChild(el);

  }

  this.layout();

};

GridView.prototype.setRowWidth = function(newRowWidth)

{

  this._rowWidth = newRowWidth;

  this.layout();

};

GridView.prototype.setRowElementWidth = function(newRowElementWidth)

{

  this._rowElementWidth = newRowElementWidth;

  this.layout();

};

GridView.prototype.setVisibleColumns = function(visibleColumns)

{

  this._visibleColumns = visibleColumns;

  this.layout();

};

GridView.prototype.setActiveElementIndex = function(newActiveElementIndex)

{

  if (newActiveElementIndex >= 0 &&

      newActiveElementIndex < this.dataSource.gridViewNumberOfElements(this) &&

      newActiveElementIndex != this._activeElementIndex) {

    // Call delegate to inform blur of current active element

    if (objectHasMethod(this.delegate, 'gridViewDidBlurElementAtIndex'))

      this.delegate.gridViewDidBlurElementAtIndex(this, this._activeElementIndex);

    this._activeElementIndex = newActiveElementIndex;

    // Call delegate to inform focus of new active element

    if (objectHasMethod(this.delegate, 'gridViewDidFocusElementAtIndex'))

      this.delegate.gridViewDidFocusElementAtIndex(this, this._activeElementIndex);

    this.revealSelection();

  }

};

GridView.prototype.canMoveLeft = function()

{

  return (this._activeElementIndex > 0);

};

GridView.prototype.canMoveRight = function()

{

  return (this._activeElementIndex < (this.dataSource[GridViewNumberOfElements](this) - 1));

};

GridView.prototype.layout = function()

{

  this.positionCells();

  this.revealSelection();

};

GridView.prototype.positionCells = function()

{

  if (!this.dataSource)

    return;

  var numElements = this.dataSource.gridViewNumberOfElements(this);

  for (var i = 0; i < numElements; i++) {

    var x = this.gridXForElement(i);

    this.dataSource.gridViewElementAtIndex(this, i).style.webkitTransform = "translate3d(" + x + "px, 0, 0)";

  }

};

GridView.prototype.revealSelection = function()

{

  var offset;

  if (this.currentLeftColumn <= (this._activeElementIndex - this._visibleColumns)) {

    this.currentLeftColumn = this._activeElementIndex - this._visibleColumns + 1;

    offset = this.currentLeftColumn * this._rowElementWidth;

    this.gridContainer.style.webkitTransform = "translate3d(-" + offset + "px, 0, 0)";

  } else if (this.currentLeftColumn > this._activeElementIndex) {

    this.currentLeftColumn = this._activeElementIndex;

    offset = this.currentLeftColumn * this._rowElementWidth;

    this.gridContainer.style.webkitTransform = "translate3d(-" + offset + "px, 0, 0)";

  }

};

GridView.prototype.gridXForElement = function(index)

{

  return index * this._rowElementWidth;

};