shakakira / snap.js

A Library for creating beautiful mobile shelfs in Javascript

Usage

var snapper = new Snap({
  element: document.getElementById('content')
});

Settings and Defaults

settings = {
    element: null,
    resistance: 0.5,
    flickThreshold: 50,
    transitionSpeed: 0.3,
    easing: 'ease',
    maxPosition: 266,
    minPosition: -266,
    tapToClose: true,
    slideIntent: 40
}

• element: The element which the user will be sliding side to side
• resistance: The cooeficcient used to slow sliding when user has passed max or min threshold
• flickThreshold: Number of pixels the user needs to swiftly travel to activate a "flick" open
• transitionSpeed: The speed at which the pane slides open or closed
• easing: The CSS3 Easing method you want to use for transitions
• maxPosition: Maximum number of pixels the pane may be slid to the right
• minPosition: Maximum number of pixels the pane may be slid to the left
• tapToClose: If true, tapping an open pane will close it
• slideIntent: The number of degrees the user must initiate sliding in towards the left or right (see diagram below)

Notes on Slide Intent: The slide intent is an int between 0 and 90, and represents the degrees in the first quadrant of a circle that you would like to have mirrored on the X and Y axis. For example, if you have 40 set as your slideIntent value, the user would only be able to slide the pane by dragging in the blue area in the diagram below. Once intent has been defined, it will not change until the user releases.

Public Methods

open: Opens the pane to the specified side

snapper.open('left');
// OR
snapper.open('right');

close: Closes the pane

snapper.close();

on: Adds an event hook

snapper.on('start', function(){
  // Do Something
});

The available methods to hook into are as follows:

• start: Fired when touching down on the draggable pane and it begins to move
• drag: Fired when the pane has been moved or slid
• stop: Fired when the pane has been let go od
• animating: Fired when the pane is animating
• animated: Fired when the pane is finished it's animations
• ignore: Fired when trying to drag the pane but ended up dragging on an ignored element

off: Removes an event hook

snapper.off('drag');

The event names listed above apply for the off method.

state: Returns detailed information about the state of the pane

var data = snapper.state();

The data returned from the state method will look like the following:

{
    state: "closed", // State of the Pane
    info:{
        opening: "left", // Side which user intends to open
        towards: "right", // Direction user is dragging towards
        hyperExtending: false, // True if user is pulling past predefined bounds
        halfway: false, // True if pane is at least halfway open
        flick: false, // True if user has moved pane X amount of pixels in the open/close direction without changing directions
        translation:{
            absolute: 20, // Pixels pane has translated
            relative: 21, // Pixels pane has translated relative to starting translation
            sinceDirectionChange: 10 // Pixels pane has translated since the direction of the pane has changed
        }
    }
} 

Gotchas

Layout

The layout itself is what most people will have a hard time emulating, so the simplest approach I have found is as follows:

Two absolute elements, one to represent all the content, and another to represent all the drawers. The content has a higher z-index than the drawers. Within the drawers element, it's direct children should represent the containers for the drawers, these should be fixed or absolute. Assigning classes to your drawers to specify which side it is on is recommended. All absolutely positioned elements should have 0 for top, left, right, bottom properties, excluding your panes which will have auto set to their respective sides and a width assigned. The width of your drawers is usually the same number you want to use for minPosition and maxPosition

div.drawers {position: absolute;}
    div.left-drawer  {position: absolute;}
        [content]
    div.right-drawer  {position: absolute;}
        [content]
div#content {position: absolute;}
    [top-bars]
    [content] {overflow: auto}
    [bottom-bars]

A sample layout is found in demo/apps/default.html.

Independent Scrolling

Some CSS is required to get some smooth ass scrolling. Utilize the CSS below to apply this to any of your elements:

.scrollable{
	overflow: auto;
	-webkit-transition-property: top, bottom;
	transition-property: top, bottom;
	-webkit-transition-duration: .2s, .2s;
	transition-duration: .2s, .2s;
	-webkit-transition-timing-function: linear, linear;
	transition-timing-function: linear, linear;
	-webkit-overflow-scrolling: touch;
}

Z-Indexes and Display

Because of the nature of this code, drawers are just kind of stacked behind the content. To bring the proper drawer to the fron, you can hook into Snaps event system:

var UpdateDrawers = function(){
  var state = snapper.state(),
		towards = state.info.towards,
		opening = state.info.opening;
	if(opening=='right' && towards=='left'){
		// Revealing Right Drawer, apply CSS to that droor to bring it to the front.
    // Usually, display:block works if you set all panes to display:none;
	} else if(opening=='left' && towards=='right') {
		// Revealing left Drawer
	}
};

// Bind Events
snapper.on('drag', UpdateDrawers);
snapper.on('animating', UpdateDrawers);
snapper.on('animated', UpdateDrawers);

An example of this code in action can be found in demo/apps/ratchet/template.html