GridList

Drag and drop library for a two-dimensional resizable and responsive list of items

Demo: http://ubervu.github.io/grid/

Disclaimer: The current implementation is for a horizontal grid. This means that the number of rows is configurable, whereas columns extend dynamically, based on the number, size and position of items placed inside the grid. While this is by design, most, if not all, logic was built around the idea that at any point the other axis could be supported with minor/moderate code changes, making both orientations available through the use of an single option.

The GridList library is split into two roles:

1. An agnostic GridList class that manages the two-dimensional positions from a list of items within a virtual matrix
2. A jQuery plugin built on top of the GridList class that translates the generic items positions into responsive DOM elements with drag and drop capabilities

GridList class

Jump to:

• API
• Primitives

API

new GridList(items, options)

var myGrid = new GridList(items, {rows: 3});

The first constructor parameter is an array of items to populate the grid with.

Supported options:

• rows - Number of rows for the grid

generateGrid()

myGrid.generateGrid();

Build the grid structure from scratch, using the positions of the given items. If items lack positional attributes (x and y), they will be misplaced, possibly overlapping. If you want to build a grid around a list of items that only have their size attributes defined (w and h), and rely on the library to position them two-dimensionally, use resizeGrid.

resizeGrid(rows)

myGrid.resizeGrid(4);

(Re)generate positions for the items inside a grid instance for a given number of rows. This method has two major use-cases:

1. Items are being represented two-dimensionally for the first time
2. Items already have 2d positions but need to be represented on a different grid size, maintaining as much as possible of their previous order

Given the horizontal orientation, positions inside the grid are generated left-to-right, top-to-bottom. So when looking for a new position inside the grid the topmost row from the leftmost column is chosen.

moveItemToPosition(item, position)

// Move item from [0, 0] to [1, 1]
var carefreeItem = myGrid.grid[0][0];
myGrid.moveItemToPosition(carefreeItem, [1, 1]);

Here are things that happen when moving an item inside the grid:

1. The item's previous position is cleared inside the 2d grid
2. The position inside the item object is updated
3. The item's new position is marked inside the 2d grid
4. Collisions are handled if the moved item overlaps with other item(s) from the grid

Collisions can be solved in two ways. First, an attempt to resolve them locally is made, meaning that the moved item tries to swap position with the overlapped item(s). This is the preferred fair trade. If this doesn't work out and after swapping we still have collisions inside the grid, the entire grid will be regenerated, starting with the moved item fixed in its new position. In the latter case, all the items around and to the right of the moved item might have their position slightly altered.

resizeItem(item, width)

// Resize item from position [0, 0] to span over 3 columns
var growthItem = myGrid.grid[0, 0];
myGrid.resizeItem(growthItem, 3);
console.log(growthItem.w); // will output "3"

Resizing an item is very similar to moving its position, in the sense that grid cells will be repopulated and collisions will be handled afterwards. See moveItemToPosition.

TODO: Implement resizing of item height

Primitives

Item

The item is the building block of GridList, and is a plain JavaScript object. The primary function of the GridList is to position such items two-dimentionally. Which brings us to the composition of an item: w and h for size, x and y for position. E.g.

{w: 3, h: 1, x: 0, y: 1}

Note that x and y (column and row) are abstract coords inside the grid, they are integer values starting from 0. Naturally, w and h (width and height) also take up space in the same coordinate system, which reveals the smallest unit of a grid: the cell. You could say, for example, that the featured item above takes up three grid cells.

gridList.items

A GridList instance works around an array of items. The items array is the first parameter of the class constructor and is always visible under the .items property. Here's a list of items for a grid with three 1x1 items on a column with three rows:

[{w: 1, h: 1, x: 0, y: 0},
 {w: 1, h: 1, x: 0, y: 1},
 {w: 1, h: 1, x: 0, y: 2}]

gridList.grid

Seeing how JavaScript doesn't support multidimensional arrays, the 2d grid inside GridList is represented by an array for columns, with each array entry containing another array with cells for each row. The cell is simply a pointer to an item that occupies it, or a null reference if no item is sitting on that cell's position. Note that more cells can point to the same item reference, because items occupy w * h cells. Here's a grid pseudo-representation:

col1	col2	col3	col4
1	2
1	3	4	4
1		4	4

Having the grid in a two-dimensional data structure, we can fetch item references directly by targeting any of the cells they cover inside the grid. E.g.

myGrid.grid[1][0] // reference to item #2
myGrid.grid[1][1] // reference to item #3
myGrid.grid[2][1] // reference to item #4
myGrid.grid[3][2] // still reference to item #4

PS. This grid would be generated by these items:

[{w: 1, h: 3, x: 0, y: 0},
 {w: 1, h: 1, x: 1, y: 0},
 {w: 1, h: 1, x: 1, y: 1},
 {w: 2, h: 2, x: 2, y: 1}]

$.fn.gridList

$('.my-list').gridList({rows: 3});

The jQuery plugin has two main functions:

• Render the GridList on top of a list of DOM elements. The list items are expected to have data-w and data-h attributes, and optionally data-x and data-y (if their positions have been previously generated and persisted)
• Drag and drop capabilities

The function takes an optional argument with options that will be passed to the draggables when constructing them.

$('.my-list').gridList({rows: 3}, {handle: '.title');

See jQuery UI Draggable API for details on all the available options.

The rendered list is responsive to its parent container, meaning that the width and height of the items are calculated based on the container height divided by the number of grid rows.

FAQ: Why not gridster?

• Their README reads Ducksboard is no longer active in their development. There are a few notable forks but it's hard to assert their reliability.
• gridster works vertically and our design is horizontal. We instigated a gridster pull request that attempted to make gridster work both ways and it didn't seem to stabilize any time soon, plus the code was too complex to approach. Our lib ended up having over than 5 times fewer code.
• gridster collisions are very basic, we pushed towards better UX and found alternative ways for dealing with collisions.
• We wanted out-of-the-box responsiveness, and the entire grid system was build fluid, relative to any parent container.
• We needed the grid logic to be a DOM-less lib outside the jQuery plugin. This allows us to compute grid positions on the server-side and run kick-ass fast tests with Node.
• Another more particular thing we needed was widgets that had height=0, which means they stretch on however many rows a grid has. We show timelines like this. The same can be easily adapted for width in vertical grids.

Please check demo page or code directly for investigating these assumptions.