Doc change: More updates to the design guidelines.
Change-Id: Ia21cc7bfc97e7347f4dfa5d9d25d87c4be70be9d
diff --git a/docs/html/design/patterns/buttons.jd b/docs/html/design/patterns/buttons.jd
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+page.title=Buttons
+page.tags="buttons"
+@jd:body
+
+<p>
+ Some content is best experienced full screen, like videos, games, image
+ galleries, books, and slides in a presentation. You can engage users more
+ deeply with content in full screen by minimizing visual distraction from app
+ controls and protecting users from escaping the app accidentally.
+</p>
+
+<div style="margin:auto;padding:auto;text-align:center;">
+ <img src="{@docRoot}design/media/fullscreen_landing.png" style="margin:1em auto 2em auto;">
+</div>
+<p>
+ In version 4.4, Android offers two approaches for making your app go full
+ screen: Lean Back and Immersive. In both approaches, all persistent system
+ bars are hidden. The difference between them is how the user brings the bars
+ back into view.
+</p>
+
+<div class="layout-content-row">
+ <div class="layout-content-col span-6">
+ <h4>Lean Back</h4>
+ <p>Touch the screen anywhere to bring back system bars. </p>
+ <img src="{@docRoot}design/media/fullscreen_leanback.png" style="width:311px;">
+ </div>
+ <div class="layout-content-col span-6">
+ <h4>Immersive</h4>
+ <p>Swipe from the any edge of the screen with a hidden bar to bring back system bars. </p>
+ <img src="{@docRoot}design/media/fullscreen_immersive_swipe_bottom.png" style="width:160px;float:right">
+ <img src="{@docRoot}design/media/fullscreen_immersive_swipe_top.png" style="width:160px">
+ </div>
+</div>
+
+<h2 id="leanback">
+ Lean Back
+</h2>
+
+<p>
+ The Lean Back approach is for full-screen experiences in which users won't be
+ interacting heavily with the screen while consuming content, like while
+ watching a video.
+</p>
+
+<p>
+ In this type of experience, users are leaning back and watching the screen.
+ Then, when they need to bring back the bars, they simply touch anywhere. This
+ gesture is easy and intuitive.
+</p>
+
+ <img src="{@docRoot}design/media/fullscreen_leanback.png" style="width:311px;">
+
+<h2 id="immersive">
+ Immersive
+</h2>
+
+<p>
+ The Immersive approach is mainly intended for apps in which the user will be
+ heavily interacting with the full screen as part of the primary experience.
+ Examples are games, viewing images in a gallery, or reading paginated
+ content, like a book or slides in a presentation.
+</p>
+
+<p>
+ In this type of experience, when users need to bring back the system bars,
+ they swipe from any edge where a system bar is hidden. By requiring this more
+ deliberate gesture, the user's deep engagement with your app won't be
+ interrupted by accidental touches and swipes.
+</p>
+
+<div class="layout-content-row">
+ <div class="layout-content-col span-6">
+ <img src="{@docRoot}design/media/fullscreen_immersive_swipe_bottom.png" style="width:160px;float:right">
+ <img src="{@docRoot}design/media/fullscreen_immersive_swipe_top.png" style="width:160px">
+ </div>
+</div>
+
+<p>
+ The user learns about the gesture to bring back the system bars through a
+ message that appears the first time the app goes full screen.
+</p>
+
+<p>
+ If your app has its own controls that aren't needed when a user is immersed
+ in content, make them disappear and reappear in sync with the system bars.
+ This rule also applies to any app-specific gestures you might have for hiding
+ and showing app controls. For example, if touching anywhere on the screen
+ toggles the appearance of an action bar or a palette, then it must also
+ toggle the appearance of system bars.
+</p>
+
+<p>
+ You might be tempted to use this approach just to maximize screen real
+ estate. But be mindful of how often users jump in and out of apps to check
+ notifications, do impromptu searches, and more. This approach will cause
+ users to lose easy access to system navigation, so a little extra space
+ should not be the only benefit they're getting in return.
+</p>
+
+<h2 id="variation_using_edges">
+ Variation: Swiping from edges with bars also affects the app
+</h2>
+
+<p>
+ In the Immersive approach, any time a user swipes from an edge with a system
+ bar, the Android framework takes care of revealing the system bars. Your app
+ won't even be aware that this gesture occurred.
+</p>
+
+<p>
+ But in some apps, the user might occasionally need to swipe from the edge as
+ <strong>part of the primary app experience</strong>. Examples are games and
+ drawing applications.
+</p>
+
+<p>
+ For apps with this requirement, you can use a variation on the Immersive
+ approach: when a user swipes from an edge with a system bar, system bars are
+ shown and the gesture is passed to the app so the app can respond to the
+ gesture.
+</p>
+
+<p>
+ For example, in a drawing app that uses this approach, if a user wants to
+ draw a line that begins at the very edge of the screen, swiping from the edge
+ would reveal the system bars and also start drawing a line that begins at the
+ very edge.
+</p>
+
+<p>
+ In this approach, to minimize disruption while a user is deeply engaged in
+ the app, the system bars are semi-transparent. The bars automatically
+ disappear after a few seconds of no interaction or as soon as the user
+ touches or gestures anywhere outside the system bars.
+</p>
+
+<h2 id="lightsout">What About Lights Out Mode?</h2>
+
+<p>
+ Before Android 4.4, the design guideline was to use Lights Out mode, a mode
+ in which the Action Bar and Status Bar fades away and becomes unavailable
+ after a few seconds of inactivity. The Navigation Bar is still available and
+ responds to touches but appears dimmed.
+</p>
+
+<p>
+ Replace previous implementations of Lights Out mode with the Lean Back or
+ Immersive approaches. Continue to use Lights Out mode for implementations of
+ your app targeted for earlier releases.
+</p>
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