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Pro HTML5 Programming Powerful APIs for Richer Internet Application Development

Pro HTML5 Programming Powerful APIs for Richer Internet Application Development. Chap 1. overview of html5. History of HTML5. HTML was first published as an Internet draft in 1993.

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Pro HTML5 Programming Powerful APIs for Richer Internet Application Development

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  1. Pro HTML5 ProgrammingPowerful APIs for Richer Internet Application Development

  2. Chap 1. overview of html5

  3. History of HTML5 • HTML was first published as an Internet draft in 1993. • Version 2.0, 3.2, 4.0 occurred in the same year, and finally 4.01 in 1999, W3C assumed control of the specification. • Then, HTML was considered a dead-end; web standards shifted to XML and XHTML. • HTML5 specification was created by Web Hypertext Application Working Group (WHATWG) in 2004. • W3C became involved with HTML again in 2006 and published first working draft in 2008, and XHTML 2 stopped in 2009. • Today, HTML5 solves very practical problems, browser vendors are feverishly implementing its new features, even though the specification has not been completely locked down.

  4. Myth of 2022 • HTML5 spec. is a working draft today (not final). • 2012: candidate recommendation. (HTML5 will be complete ) • 2022: proposed recommendation. • IE6 does not support many of new features. • Microsoft promises to design that browser with increased HTML5 support.

  5. Who is developing HTML5 • Web Hypertext Application Technology Working Group (WHATWG) • Founded in 2004 • Vendors: Apple, Mozilla, Google, Opera • World Wide Web Consortium (W3C) • Internet Engineering Task Force (IETF) • HTML5 defines a new WebSocket API that relies on a new WebSocket protocol.

  6. Characteristics of HTML5 • Compatibility • Utility - Separation of Presentation (CSS) and Content (HTML) • Most of presentational features of earlier versions of HTML are no longer supported (but will still work!). • Shortages of older versions of HTML • Poor accessibility • Unnecessary complexity (Harder to read code) • Large document size – slower loading pages • Interoperability - Simplify wherever possible • Native browser ability instead of complex JavaScript code • A new, simplified DOCTYPE and simplified character set declaration • Powerful yet simple HTML5 APIs • Universal access: • Accessibility • Media independence • Support for all world languages: Ex: <ruby> supports Ruby annotation

  7. A Plugin – Free Paradigm • Present problem of plugin • Cannot always be installed • Can be disabled or blocked (Ex: iPad does not ship with a Flash plugin) • Often blocked in controlled corporate environments • Users disable because of unwelcome advertising • A separate attack vector • Difficult to integrate with the rest of HTML document

  8. HTML5 Features • Scalable Vector Graphics (SVG) • WebSocketAPI and protocol • Web origin concept • Web Storage • Web SQL database • Web Workers • XMLHTTPRequest Level 2 • Canvas (2D or 3D) • Channel messaging • Cross-document messaging • Geolocation • MathML • Microdata • Server-Sent Event

  9. New DOCTYE and Character Set • DOCTYPE • <!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd"> • <!DOCTYPE html> • Character set • <meta http-equiv="Content-Type" content="text/html; charset=utf-8"> • <meta charset="utf-8">

  10. New and Deprecated Elements Deprecated Elements: Elements perform inline styling in favor of using CSS, Ex: big, center, font

  11. Semantic Markup • The sectioning content type is useful for search engine. • New sectioning HTML5 elements

  12. HTML5 Tag - <link> • <link> • Define the relationship between a document and an external resource • Placed at <head> • Attributes • Example: <link rel=“stylesheet” href=“html5.css”>

  13. CSS – webkit/moz • webkit and moz mean they are not W3C standard • webkit • Supported by Safari and Chrome • -webkit-box-shadow: 2px 2px 20px #888; (Shadow effect) • -webkit-transform: rotate(-45deg); (Rotate effect) • -webkit-transform: scale(0.5);(Change size) • -webkit-border-radius: 10px; • moz • Supported by Mozilla • -moz-box-shadow: 2px 2px 20px #888; (Shadow effect) • -moz-transform: rotate(-45deg); (Rotate effect) Excerise: Listing 1-1, 1-2

  14. Simplifying Section – Selectors API HTML4 HTML5 HTML5 Excerise: Listing 1-3

  15. Windows.JSON AND DOM LEVEL 3 • JSON • A relatively new and increasing popular way to represent data • Data is represented as objects • In older browsers, a JavaScript library (http://json.org) is necessary. Parsing and serializing are not always fast enough • Newer browsers have a native implementation of JSON • DOM Level 3 • Most browsers support standard APIs for events and elements, Internet Explorer differs. • IE9 will support DOM level 2 and 3 features.

  16. Chap 2. canvas api

  17. What is canvas • Dynamically generate and render graphics, charts, images and animations • SVG (Scalable Vector Graphics) vs. Canvas • Bitmap canvas • Images drawn on a canvas are final and not be resized • Objects drawn on a canvas are not part of the page’s DOM or any namespace • SVG images can be scaled seamlessly at different resolutions and allow hit detection • HTML5 Canvas API • It performs well because it does not have to store objects for every primitive it draws • Relatively easy to implement the Canvas API

  18. Canvas • Element: <canvas></canvas> • Coordinates:

  19. Checking browser support try { document.createElement("canvas").getContext("2d"); document.getElementById("support").innerHTML = "HTML5 Canvas is supported in your browser."; } catch (e) { document.getElementById("support").innerHTML = "HTML5 Canvas is not supported  in your browser."; }

  20. Canvas, Draw line • A basic canvas with solid border • <canvas id=“canvas" height="800" width="1000" style="border: 3px solid"></canvas> • Get the canvas element and its context var canvas = document.getElementById('canvas'); varcontext = canvas.getContext('2d'); • Draw line • Prepare graph context.beginPath(); context.moveTo(70, 140); context.lineTo(140, 70); • Stroke graph onto the canvas • context.stroke(); Excerise

  21. Transformation(translate, scale, rotate)

  22. translation • Get the canvas element and its context • Save the current drawing state context.save(); • Move to new coordinate, ex: (50, 100) context.translate(50, 100); • Draw line • Restore the old drawing state context.restore(); Excerise

  23. Path context.beginPath(); context.moveTo(-25, -50); context.lineTo(-10, -80); context.lineTo(-20, -80); context.lineTo(-5, -110; context.lineTo(-15, -110); context.lineTo(0, -140); context.lineTo(15, -110); context.lineTo(5, -110); context.lineTo(20, -80); context.lineTo(10, -80); context.lineTo(25, -50); ontext.closePath();

  24. Stroke style • Line width • context.lineWidth = 4; • Corner style at path joins (round:圓角, bevel:斜角, miter) • context.lineJoin = 'round'; • Line style at endpoints (round, square, butt:預設值) • Context.lineCap = ‘square'; • Stroke style • Change color • context.strokeStyle= '#663300'; • Background pattern • Fill Style • Change color • context.fillStyle= '#339900'; • Background pattern • Fill the region inside all the closed paths • context.fill(); • Fill rectangular content • context.fillRect(x, y, w, h); //ex: context.fillRect(-5, -50, 10, 50);

  25. Example – Draw a tree

  26. Quadratic Curve • Starting Point: current location • context.quadraticCurveTo(ControlPointX, ControlPointY, EndPointX, EndPointY); • Example: • context.save(); • context.translate(-10, 350); • cucontext.moveTo(0, 0); • context.quadraticCurveTo(170, -50, 260, -190); • context.quadraticCurveTo(310, -250, 410, -250); • context.lineWidth = 20; • context.strokeStyle= '#663300'; • ontext.stroke(); • context.restore();

  27. Image • Load image varimg = new Image(); img.src = “bark.jpg”; • Confirm the image is loaded img.onload = function(){ //Draw image onto canvas } • Draw image onto canvas • context.drawImage(image, dx, dy) • context.drawImage(image, dx, dy, dw, dh) • context.drawImage(image, sx, sy, sw, sh, dx, dy, dw, dh) • Example • var bark = new Image(); • bark.src= "bark.jpg"; • bark.onload= function(){ • context.drawImage(bark, -5, -50, 10, 50); • context.stroke(); • context.restore(); • }

  28. GRADIENT • Linear Gradient(漸層) • Usage • context.createLinearGradient(x0, y0, x1, y1) • x0, y0 - Line start • x1, y1 - Line end • gradient.addColorStop(offset, color) • offset - From 0.0 to 1.0 • color - Use rgba() or HEX • Example • vartrunkGradient = context.createLinearGradient(-5, -50, 5, -50); • trunkGradient.addColorStop(0, '#663300'); • trunkGradient.addColorStop(0.4, '#996600'); • trunkGradient.addColorStop(1, '#552200'); • context.fillStyle= trunkGradient; • context.fillRect(-5, -50, 10, 50); • Radical Gradient • Usage • Context.createRadicalGradient(x0, y0, r0, x1, y1, r1) • x0, y0, r0 – First circle center at (x0, y0) with radius r0 • x1, y1, r1 – Second circle center at (x1, y1) with radius r1

  29. Background Pattern • Usage • context.createPattern(image, repeat) • repeat - repeat, repeat-x, repeat-y, no-repeat • Example vargravel = new Image(); gravel.src= "gravel.jpg"; context.save(); context.translate(-10, 390); gravel.onload= function(){ context.beginPath(); context.moveTo(0, 0); context.quadraticCurveTo(170, -50, 260, -190); context.quadraticCurveTo(310, -250, 410, -250); context.lineWidth = 20; context.strokeStyle = context.createPattern(gravel, 'repeat'); context.stroke(); context.restore(); }

  30. Scale • Usage • context.scale(rx, ry); • rx – width scale ratio • ry – height scale ratio • Example • varcanvas = document.getElementById('canvas'); • varcontext = canvas.getContext('2d'); • context.save(); • context.translate(260, 500); • context.scale(2, 2); • drawTree(context); • context.restore();

  31. Rotate • Usage • context.rotate(angle) • angel can be express with Math.PI/180 * degree • Example • var canvas = document.getElementById('canvas'); • var context = canvas.getContext('2d'); • context.save(); • context.translate(260, 500); • context.rotate(Math.PI/180 * 40); • drawTree(context); • context.restore();

  32. Transform • Context.transform(rx, sy, sx, ry, dx, dy) • rx – width scale ratio • ry – height scale ratio • sy– vertical shear • sx– horizontal shear • Example • var canvas = document.getElementById('canvas'); • varcontext = canvas.getContext('2d'); • context.save(); • context.translate(130, 250); • context.transform(1, 0, -0.5, 1, 0, 0); • context.scale(1, 0.6); • context.fillStyle= 'rgb(0, 0, 0, 0.2)'; • context.fillRect(-5, -50, 10, 50); • createCanopyPath(context); • context.fill(); • context.restore();

  33. Canvas text • Usage • context.fillText(text, x, y, maxwidth) • context.strokeText(text, x, y, maxwidth) • Property • context.font = Font String • context.textAlign = start, end, left, right, center • context.textBaseLine = top, middle, bottom, … • Example • context.save(); • context.font= '60px 標楷體'; • context.fillStyle= '#996600'; • context.textAlign= 'center'; • context.fillText('快樂圖畫', 200, 60, 400); • context.restore();

  34. Shadows • Usage • shadowColor – Any CSS Color • shadowOffsetX – Pixel Count • shadowOffsetY – Pixel Count • Shadowblur – Gaussian blur • Example • context.shadowColor= 'rgba(0, 0, 0, 0.2)'; • context.shadowOffsetX= 15; • context.shadowOffsetY= -10; • context.shadowBlur= 2; • context.font= '60px 標楷體'; • context.fillStyle= '#996600'; • context.textAlign= 'center'; • context.fillText('快樂圖畫', 200, 60, 400);

  35. Chap 3. Audio/Video api

  36. Video Container • An audio or video file is really just a container file, similar to a ZIP archive file that contains a number of files. • Some of the popular video container formats include the following: • Audio Video Interleave (.avi) • Flash Video (.flv) • MPEG 4 (.mp4) • Matroska(.mkv) • Ogg(.ogv)

  37. Audio and Video Codecs • Audio and video coders/decoders (codecs) are algorithms used to encode and decode a particular audio or video stream so that they can be played back. • Some example audio codecs are the following: • AAC • MPEG-3 • OggVorbis • Example video codecs are the following: • H.264 • VP8 • OggTheora

  38. Restrictions • Streaming audio and video. • That is, there is currently no standard for bitrate switching in HTML5 video • Media is restricted by HTTP cross-origin resource sharing. • Full-screen video is not scriptable • Because it could be considered a security violation to let a scriptable element take over the full screen. • Accessibility for audio and video elements is not fully specified yet. • Work is underway on a specification called WebSRT for subtitle support based on the popular SRT format.

  39. Browser Support • Browser support for HTML5 Video • Checking for Browser Support • JavaScript • varhasVideo = !!(document.createElement('video').canPlayType); • HTML Fallback content • <video src="video.ogg" controls> • Your browser does not support HTML5 video. • </video>

  40. HTML USAGE • Audio • <audio controls> • <source src="johann_sebastian_bach_air.ogg"> • <source src="johann_sebastian_bach_air.mp3"> • An audio clip from Johann Sebastian Bach. • </audio> • Video • <video id="movies“ autoplayautobuffer="true" width="400px" height="300px"> • <source src="Intermission-Walk-in.ogv"> • <source src="Intermission-Walk-in_512kb.mp4"> • </video>

  41. Taking Control • Common control functions

  42. WORKING WITH Audio • <audio id="clickSound"> • <source src="johann_sebastian_bach_air.ogg"> • <source src="johann_sebastian_bach_air.mp3"> • </audio> • <button id="toggle" onclick="toggleSound()">Play</button> • <script type="text/javascript"> • function toggleSound(){ • var music = document.getElementById("clickSound"); • vartoggle = document.getElementById("toggle"); • if (music.paused) { //檢查是否已暫停 • music.play(); • toggle.innerHTML = "Pause"; • } else { • music.pause(); • toggle.innerHTML ="Play"; • } • } • </script>

  43. Chap 4. GeolocationAPI

  44. About Location Information • You can request users to share their location and, if they agree, you can providethem with instructions on how to get to a nearby store to pick up a new pair of shoes at a discountedrate. • You request a position and, if the useragrees, the browser returns location information. • The position is provided to the browser by the underlying device (for example, a laptop or a mobile phone) on which the HTML5 Geolocation–enabledbrowser is running. • IPAddress • Global Positioning System (GPS) • Wi-Fi with MAC addresses from RFID, Wi-Fi, and Bluetooth • GSM or CDMA cell phone IDs

  45. The pros and consof geolocation data

  46. Arachitecture & Privacy • The browser intercepts and requests user permission at step 2.

  47. Browser Support • Browser support for HTML5 Geolocation

  48. Checking for Browser Support • if(navigator.geolocation) { • document.getElementById("support").innerHTML = "HTML5 Geolocation supported."; • } else { • document.getElementById("support").innerHTML = "HTML5 Geolocation is not supported in your browser."; • }

  49. Positions requests • Theres are two type of position requests • One-shot position request • Repeated position updates

  50. One-Shot Position Requests • Usage • void getCurrentPosition(in PositionCallbacksuccessCallback, • in optional PositionErrorCallbackerrorCallback, • in optional PositionOptions options); • Example • navigator.geolocation.getCurrentPosition(updateLocation, handleLocationError, {timeout:10000}); • updateLocationis a PositionCallback function will implement later • handleLocationErroris a PositionErrorCallback function will implement later

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