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jquery-stage

jQuery Stage

(jQuery Stage Information)

Abstract

jQuery Stage is a jQuery plugin for detecting information about the "stage", the browser's viewport.

Demo

See the included sample/index.html for a small demonstration of jQuery Stage.

Motivation

A Single-Page Application (SPA) usually has to render its User Interface (UI) onto multiple kinds of stages, based on device size and current device orientation. For true responsive design you usually have to take the two dimensions "stage size" (e.g. phone, tablet and desktop) and "stage orientation" (e.g. portrait, square, and landscape) into account. The preferred way to determine this information and react upon it is via CSS Media Queries.

But there are multiple problems:

  • CSS for backward compatibility reasons always uses a hard-coded DPI setting of 96dpi, even if most devices have an effective DPI in the range of 100dpi to 450dpi. Also, CSS's DPI (dots per inch) is actually PPI (pixel per inch), as it is an input resolution and not an output resolution.

  • The "dots per pixel" ratio can be realiably queried via JavaScript, but even with this neither DPI nor PPI can be reliably determined.

  • Media Queries can only query on width/height but not on the diagonal. But the diagonal more conveniently discriminates the size of a device.

  • Media Queries can not take a treshold for orientation into account, i.e., if width and height differ by less than 5% the stage is nearly square and neither portrait nor landscape.

This is where jQuery Stage and its guessing algorithm comes into the play.

Solution

jQuery Stage provides stage information in the following form:

stage: {
    w:           Int;    // stage width           (px)
    h:           Int;    // stage height          (px)
    dp:          Int;    // stage diagonal length (px)
    dppx:        Float;  // stage dots per pixel  (factor)
    ppi:         Float;  // stage pixel per inch  (factor)
    di:          Float;  // stage diagonal length (inch)
    size:        String; // stage size            (string)
    orientation: String; // stage orientation     (string)
}

The parameters are determined as following:

  • w: This is the exact viewport width in pixels.
  • h: This is the exact viewport height in pixels.
  • dp: This is the exact viewport diagonal in pixels.
  • dppx: This is the exact device dots per pixel ratio (usually 1.0 but up to 3.0 for high-resolution/retina displays).
  • ppi: This is guessed pixel per inch of the device.
  • di: This is the guessed viewport diagonal in inch.
  • size: This is the guessed viewport type: "phone", "tablet" or "desktop".
  • orientation: This is the rounded viewport orientation: "portrait", "square", "landscape".

On every change of any of those parameters (usually either by resizing the viewport on a desktop device or changing the device orientation of a portable device), an event named "stage" is trigged on the global "window" object providing the new stage information and the old stage information. An application can use this information for responsive design aspects.

API

The Application Programming Interface (API) of jQuery Stage is (in TypeScript definition syntax):

/*  the jQuery Stage Callback function type  */
interface JQueryStageCB {
    (ev: JQueryEventObject, stage: JQueryStageInfo, stageOld: JQueryStageInfo): any;
}

/*  the jQuery Stage Information structure type  */
interface JQueryStageInfo {
    w:           number;
    h:           number;
    dp:          number;
    dppx:        number;
    ppi:         number;
    di:          number;
    size:        string;
    orientation: string;
}

/*  the jQuery Stage Settings structure type  */
interface JQueryStageSettings {
    ppi:         { [key: string]: string; };
    size:        { [key: string]: string; };
    orientation: { [key: string]: string; };
}

/*  extend the static jQuery API extension (provided by jquery.d.ts)  */
interface JQueryStatic {
    stage: {
        /*  fetch current stage information  */
        (): JQueryStageInfo;

        /*  global version number  */
        version: string;

        /*  global debug level  */
        debug: number;

        /*  configure the stage settings  */
        settings(settings: JQueryStageSettings): void;
    };
}

/*  extend the dynamic jQuery result object API extension (provided by jquery.d.ts)  */
interface JQuery {
    stage(cb: JQueryStageCB): JQuery;
}

Settings

The actual guessing of the "ppi", "size" and "orientation" fields of the stage information can be adjusted by the application. The default is the following:

$.stage.settings({
    ppi: {
        "100": "dp > 1024 && dppx <= 1.0",
        "130": "*",
        "160": "dp < 1024 && dppx >= 2.0"
    },
    size: {
        "phone":   "0.0 <= di && di <  6.5",
        "tablet":  "6.5 <= di && di < 12.0",
        "desktop": "*"
    },
    orientation: {
        "portrait":  "h > w * 1.2",
        "square":    "*",
        "landscape": "w > h * 1.2"
    }
});

Event Handling

Reacting on the stage event is up to the application. Usually one wants to react similar to CSS media queries. A simple example follows:

/*  foo.css  */
.phone.landscape   { ... }
.phone.portrait    { ... }
.tablet.landscape  { ... }
.tablet.portrait   { ... }
.desktop.landscape { ... }
.desktop.portrait  { ... }

/*  foo.js  */
$(window).bind("stage", function (stage, stageOld) {
    $("body")
        .removeClass(stageOld.size)
        .addClass   (stage.size)
        .removeClass(stageOld.orientation)
        .addClass   (stage.orientation);
});

Getting jQuery-Stage

You can conveniently get jQuery-Stage in various ways:

  • Git: directly clone the official jQuery-Stage repository

    $ git clone https://github.com/rse/jquery-stage.git

  • NPM: install as client component via the NPM package manager:

    $ npm install jquery-stage

  • Bower: install as client component via the Bower component manager:

    $ bower install jquery-stage

  • cURL: downloading only the main file from the repository

    $ curl -O https://raw.github.com/rse/jquery-stage/master/jquery.stage.js

Building jQuery Stage

You can pick the jQuery plugin in file "jquery.stage.js" as is for use, but for linting and minifying it yourself you need Node.js ("node") and its Node.js Package Manager ("npm") globally installed.

# approach 1: use convenient Makefile (author preference)
$ make

# approach 2: use Grunt locally (contributor recommendation)
$ npm install
$ node_modules/grunt-cli/bin/grunt

# approach 3: install and use Grunt globally (contributor alternative)
$ npm install -g grunt-cli
$ npm install
$ grunt

See Also

License

Copyright (c) 2013-2016 Ralf S. Engelschall (http://engelschall.com/)

Permission is hereby granted, free of charge, to any person obtaining a copy of this software and associated documentation files (the "Software"), to deal in the Software without restriction, including without limitation the rights to use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of the Software, and to permit persons to whom the Software is furnished to do so, subject to the following conditions:

The above copyright notice and this permission notice shall be included in all copies or substantial portions of the Software.

THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.