Notes from the Friday #TXDevFest talks I attended

txdevfestday1.txt

TX Dev Fest
Mastering <canvas>
  @johnathanhebert
    Skitch
  It's just pixels
    Immediate mode graphics surface
    No DOM
  Grid size independent from css size
  General process
    clear()
    draw()
    repeat()
  Coordinate system
    The Great Fixed Coordinate System in the Sky
      The initial <canvas> coordinate system is your friend
    Translate - moves origin
    Rotate - rotates canvas and coordinate system around origin
    Linear algebra - lets you change coordinate system with matrices
      3 things:
        Scale it
        Translate
          [1 0 tx [x    [x+tx
           0 1 ty  y  =  y+ty
           0 0 1 ] 1]    1   ]
          Homogeneous coordinates - transformation cannot be represented in 2D
          Transform method: context.transform(a,b,c,d,e,f)
          [a c e
           b d f
           0 0 1]
          transform() changes the coordinate system
          setTransform is *relative to the initial coordinate system*
       Translate point to origin, scale, then translate back to zoom in on point  
       but backward
       Operations have to be in reverse order because the vector has to be on the right for the vector math to work
       Spin: translate(100,100).rotate(3).translate(-100,-100);

NFC
  "The future is already here -- it's just not very evenly distributed"
  Crossing the Chasm by Geoffery A. Moore
    NFC sitting in a niche right now
  History
    RADAR - 1935
    Leon Theremin invents first passively-powered "bug" for espionage - 1945
    RFID implementations continue - 1950's
    1960's - identifiying remote objects
    1970's - preventing retail theft
    2003 - NFC grows out of RFID, recognized specification
      Previously "wild west" of protocols
      Ugly logo
    Frequency vs distance
      NFC is in HF range - 13.56 MHz
    2004 - NFC forum created
      NDEF
        NFC Data Exchange Format
    2005 - NFC capable "shells"
      Mostly used as id chip
    2006 - First NFC built in
    2010 - Galaxy Nexus S first NFC-enabled Android device
    Moral: Technology has a long evolution, window of opportunity not missed
  Most devices with NFC are Android phones
  Embedded Android surging
  What's different now than a few years ago
    More computing power
    Cheaper hardware
    User-friendly OS's/apps
    Better API's
      Write custom tags
      Launch apps
      Change settings
      BT pairing
      Peer-to-peer data
  Book chapter: Professional Android Sensor Programming - Chapter 11
    Sample code: github.com/pchen/nfc-starter-apps
    Docs: nfc.android.com
  Four supported types of tag
    Broadcom Topaz and MIFARE ultra light most common/cheapest, good for playing
    Sony FeliCa and NXP DESFire/SmartFX have more storage space, features
    MIFARE Classic has partial support, removed from Google phones as of Nexus 4
  Forms
    Stickers
    Sewable
    Keychain
    Plastic
    Made for putting on metal
    More stickers
    Passcard
      Presto card
  Uses
    Read and write NFC tags
      Simple URL's
      URL-based triggers
        Launch application from URI
        Sample intent filter shown in slides, probably in above Github URL
      Example: NFC tag sticker with simple label deep-linked to specific Evernote entry for recipies
      Moo beta testing NFC business cards
      Task automation
        tagstand.com
        snapguide.com/guides/enhance-a-phone-slip-case-with-nfc-part-2-1
          Slip in the phone one direction, ringer loud, flip other direction, sets to quiet
      NFC-enabled phones
      Bluetooth pairing
  Do not revolve experience around NFC - should make tech disappear, simple, passive
  Pandemic 1.0 by Lance Weiler
    Transmedia project
    50 Nexus S devices at Sundance, NFC tag scavenger hunt
  Case for NFC
    Create low friction interactions
    Augments physical objects (internet not required)
    Apps/tech more tangible
    Increase viralness of your app
    Possibility to be platform agnostic
Location Services on Android
  Android GPS is awesome
    3m accuracy
    1s updates
    Most devices have GNSS hardware
    Not silver bullet
      Not all devices have
      Eats battery (~135 mA according to "studies")
      Takes a long time to get initial position fix (Most in 1s-5s range according to mapmyfitness data, ~18% 5s-10s)
    Can retrieve quality of fix and # of satellites
  GPS will sometimes return junk coordinates
    Time, lat/lng, or accuracy == 0
  Accuracy numbers in meters
  TTFF tricks
    Read source com.android.server.location.GpsLocationProvider
    No guarantees, use at your own risk, but cool stuff
      Don't use in production app
      Code in slides to re-bootstrap GPS chip
  Android LocationManager
    provides API to allow use of multiple sources
    Pros
      Control of provider: gps or cell/wifi
      Does not require Play Store (Kindle, CM)
      Backward compatible to API 1 (wheee)
    Cons:
      Requires requesting updates from individual location providers
      Need to examine multiple factors for "best estimate"
    Fused location provider
      Uses all of above + sensor data
      Pros:
        No complicated strategies
        Uses sensor data for indoor position
        Battery optimized
      Cons:
        Limited control
        Doesn't work on devices w/o Play Store
      Code: checkGooglePlayServiceAvailability
        Recheck for onResume to make sure update in place
      Fewer outliers than GPS, but slower and slightly less accurate
      Accuracy vs power
        getLastLocation() vs LocationRequest
        Priority options
      LocationRequest
        setExpirationDuration(millis)
        setNumUpdates(numUpdates) (1 for one very accurate location)
        setSmallestDisplacement(meters)
        LocationRequest.create(), chainable
      Checking Providers
        Can't do that with Fused, use LocationManager to check if location services enabled
  WiFi Proximity Demo
    Custom provider
    Sometimes all you need is WiFi proximity
    Geofencing API maybe better fit
    Code
      Sticky service
        Runs until explicitly stopped
      Can start with click or on BOOT_COMPLETED intent
      WakeLock makes sure CPU doesn't sleep until we're done
        Partial wake lock for CPU, full wake lock for screen
        Release in finally block to make sure CPU doesn't keep running on failure
  Useful references at end of presentation
    Presentation: http://t.co/kz3qjWq5lP
  Code: https://t.co/5Yd1IAeN8g
Opera & Blink
  Chromium is whole package, Blink is rendering engine
Chrome Packaged Apps
  Sandboxed client-side applications
  User-approved access to local resources
    Full window control
    Filesystem
    Local and synced storage
    Networking
    Background processing
    Bluetooth
    Devices
  HTML/CSS/(JS|DART)
  MVC structure
  Files
    manifest.json
    background.js
      Create window
    index.html
      Angularisms
      Requires ng-csp on html tag
    Distribute through Chrome web store
Using Enyo to Make Chrome Apps
  @unwiredben
  Came out of work Palm did a while ago on HP TouchPad
  www.enyojs.com
    Javascript/CSS framework
    Reusable components
    Cross-platform strong
    Designed for single-page apps
    UI widgets
    Apache 2.0
    Bought by LG Electronics recently
      TV's
  Enyo Bootplate
    http://github.com/enyojs/bootplate
    Template with Enyo and common libs
    Clone, rename, push
    Includes minifier to make enyo.js and app.js
  http://enyojs.com/api
  App restriction
    CSP
    document.write
    *no inline event handlers
    no eval()
    no Function() constructors
    no strings for setTimeout/setInterval (same as eval)
    no inline <script> tags
  Openings
    XHR fetches will work in app bundle, unlike normal file://XHRs
      Request permission to do things like USB port handling (Arduino)
  background.js
    Can use boilerplate for most apps
    Hardest decision is default window size
  Links to other sites
    No default handling of off-app links
    _blank pushes to main browser window
  Testing
    Go to chrome://extensions page
    Developer tools checkbox
    Load unpacked extension
  Submit to store
    Zip, not .crx
    Must have manifest.json at root
    Must NOT contain any other manifest.json files
    Required images
      128x128 icon
      640x400 screenshot
      something else went too fast