jamescook, pkotwicz August 2013 User Experience Immersive fullscreen is a fullscreen mode for the Chrome OS Ash window manager. It allows users with small screens to use almost the entire screen for web content, but still access the tab strip and app shelf when needed.

The tabs (and location bar) are collapsed into a small strip at the top of the screen. The shelf is similarly collapsed at the bottom of the screen. Showing the strip gives the user a visual target for the mouse.

Mousing to the top of the screen slides in the top controls, which are fully interactive. For a detailed description of the user experience, see Ben’s [original proposal](https://docs.google.com/a/google.com/document/d/1dequH51rwf8YpU6s5v6htmEozk8VBB5FbtM1jFDOwt4/edit). Top of screen implementation We introduce a TopContainerView that holds the tab strip and location bar. BrowserView continues to hold the page contents and download shelf. TopContainerView sometimes contains the bookmark bar. If the bookmark bar is visible (“attached” under the location bar) it should slide down over the page. However, on the new tab page the bookmark bar is visually part of the page contents, so the top controls must slide down over it. Therefore the bookmark bar is reparented between the BrowserView and the TopContainerView as needed. Infobars (“Save this password?”) are considered part of the page contents. The TopContainerView always slides over infobars. These are the states for the top controls. “Closed” is the steady state.

During the sliding and revealed states the TopContainerView paints to a compositor layer to allow it to be stacked above the web contents layer. Revealing the top controls The top controls need to feel like they slide open when the user presses the top of the screen, but not trigger accidentally when the user is mousing past web content at the top of the page. A reveal is triggered when the mouse is at the top of screen past a time delay and is moving slowly (or not at all) in a horizontal direction. In addition to revealing when the user mouses to the top of the screen there are a variety of situations in the UI when the top controls need to be visible. For example: When focus is in the location bar (so the user can see what he types) Making a bookmark (the dialog relies on the location bar to show the URL) Opening the tools menu (so the menu is visually attached to the 3-lines button) In these situations the top controls need to stay visible even if the mouse moves away from the screen edge. Getting these situations correct was one of the hardest parts of this feature. pkotwicz@ introduced a clever ImmersiveRevealedLock class to deal with the visibility issue. Various parts of Chrome code can acquire a lock and hold it until their UI is dismissed. The ImmersiveModeController handles sliding closed the top controls when all locks are destroyed and the mouse is away from the screen edge. The top controls also stay visible when any child control has focus, which handles the location bar and several other situations. Painting the collapsed controls The white strips in the collapsed controls (the “light bar”) help reinforce to the user that their tabs are still present. It also provides a place to show loading animations. The light-bar uses the existing TabStrip for painting, but with a special painting style flag set. This allows the existing tab layout code to be used for the light bar, so the tab positions exactly match. We also recycle most of the loading animation code. The disadvantaged of this approach is that it requires resizing, relayout and repainting of the tab strip whenever the reveal state changes. However, we decided the benefits of reusing the layout and animation code outweighed this cost. Browser and tab fullscreen Chrome supports two internal fullscreen concepts “browser fullscreen” and “tab fullscreen”. Browser fullscreen is entered via UI commands (e.g. Tools menu > Fullscreen). Tab fullscreen is entered when a web page requests fullscreen (e.g. Docs presentations). Immersive fullscreen is only tied to browser fullscreen. This has two advantages: 1. From the user’s perspective, immersive fullscreen is the only fullscreen state in the Ash window manager. In particular we avoid the confusion Mac OS creates with its two separate “fullscreen” and “presentation mode” commands. 2. Fullscreen videos, presentations and games don’t display the light-bars at the top and bottom of the screen, and the user doesn’t need to do anything special for this to happen. See chrome/browser/ui/fullscreen/fullscreen_controller.h for details on the two fullscreen modes. Test coverage Immersive fullscreen is covered by both unit tests and browser tests. The browser tests are used primarily to verify integration with the rest of the browser’s fullscreen mechanisms. See c/b/ui/views/frame/immersive_mode_controller_ash_unittest.cc and c/b/ui/views/frame/immersive_mode_controller_ash_browsertest.cc. Appendix During the development of immersive fullscreen the instant-extended project (“1993”) experimented with using web content to display the auto-complete suggetsions under the location bar. This presented challenges for layout in immersive fullscreen, as the suggestions were sometimes in a separate web view and sometimes (on the new tab page) part of the primary web content. The suggestions list has been reverted back to a native UI widget. However, if it becomes web content again this is how the layout code will need to change: Tab contents position, without 1993:

Regular window	Immersive fullscreen
Bookmark bar hidden	bottom of omnibox (top_container)	3 pixels from top (omnibox hidden, bookmarks hidden)
Bookmark bar attached	bottom of bookmark bar (top_container)	3 pixels from top (omnibox hidden, bookmarks bar shown during reveals)
New tab page with bookmark bar detached	bottom of bookmark bar (not top_container)	below bookmarks

Tab contents position, with 1993:

Regular window	Immersive fullscreen
No suggestions	bottom of omnibox	3 pixels from top
Suggestions (in overlay)	bottom of omnibox	3 pixels from top, overlay contents below top_container
NTP suggestions (in active)	bottom of omnibox (unless suggestions won’t cover bookmarks, then at top)	bottom of omnibox (unless suggestions won’t cover bookmarks, then at top)