1. The keyguard force hides some windows when it is shown and as soon
as the keyguard goes away there windows are made visible. However,
the window transition that the keyguard is moving away is reported
before the force hidden windows are shown which makes the screen
magnifier compute the magnified region with an incomplete list of
windows of interest.
bug:7215285
Change-Id: I3abc4d97b7a74de8183ad20477dadf66c82da037
1. The way for computing the magnified region was simplistic and
incorrect. It was ignoring window layering resulting in broken
behavior. For example, if the IME is up, then the everything else
is magnifed and the IME not. Now the keyguard appears and covers
the IME but the magnified region does not expand while it would
since the keyguard completely covers the not magnified IME window.
bug:7138937
Change-Id: I21414635aefab700ce75d40f3e913c1472cba202
1. When the screen goes off the user will be in a completely
different context upon turning the screen on. Therefore,
if magnification auto update is enabled magnification
will be disengaged on screen off.
bug:7139088
Change-Id: I790cfa5b3cf31d34e95fc9548e6246a84096c37b
1. If screen magnification is enabled the user has to triple tap
and lift or triple tap and hold to engage magnification. Hence,
we delay the touch events until we are sure that it is no longer
possible for the user to perform a multi-tap to engage
magnification. While such a delay is unavoidable it feels a
bit longer than it should be. This change reduces the delay
between taps to be considered a multi-tap, essentially making
the click delay shorter.
bug:7139918
Change-Id: I2100945171fff99600766193f0effdaef1f1db8f
1. If the user changes the magnification level while moving the
viewport the magnification is locked. The gesture handle has
to put device back into a viewport moving state if this was
the last state.
bug:7139363
Change-Id: I24992b973bb15624580114353b004efdb35c2faa
1. Before in magnified state the user was able to only scale or
pan. Based on user input this change allows performing pan
or scale or both. If the user scales more than a threshold
we are performing a scale and independently of that if the
use pans more than a threshold we are performing a pan.
bug:7138928
Change-Id: Ic1511500ba3369091dcfd070669d3e4f0286fbe5
1. Due to frequent changes of the behavior of ScaleGestureDetector
this patch rolls in a gesture detector used for changing the
screen magnification level. It has an improved algorithm which
uses the diameter of min circle around the points as the span, the
center of this circle as the focal point, and the average slop
of the lines from each pointer to the center to determine the
angle of the diameter used when computing the span x and y.
Change-Id: I5cee8dba84032a0702016b8f9632f78139024bbe
1. If screen magnification is disabled when the screen is in a
magnified state we have to zoom out since otherwise the user
is stuck in a magnified state without ability to pan/zoom/
toggle magnification which renders the device useless.
bug:7131030
Change-Id: I8f3339f31310448ec8742f3101c1fdc61a6a5f83
1. If screen magnification is disabled when the screen is in a
magnified state we have to zoom out since otherwise the user
is stuck in a magnified state without ability to pan/zoom/
toggle magnification which renders the device useless.
bug:7131030
Change-Id: Ia620954fbd594e7cd470e43b89d9ed04c0397c3c
This change is the initial check in of the screen magnification
feature. This feature enables magnification of the screen via
global gestures (assuming it has been enabled from settings)
to allow a low vision user to efficiently use an Android device.
Interaction model:
1. Triple tap toggles permanent screen magnification which is magnifying
the area around the location of the triple tap. One can think of the
location of the triple tap as the center of the magnified viewport.
For example, a triple tap when not magnified would magnify the screen
and leave it in a magnified state. A triple tapping when magnified would
clear magnification and leave the screen in a not magnified state.
2. Triple tap and hold would magnify the screen if not magnified and enable
viewport dragging mode until the finger goes up. One can think of this
mode as a way to move the magnified viewport since the area around the
moving finger will be magnified to fit the screen. For example, if the
screen was not magnified and the user triple taps and holds the screen
would magnify and the viewport will follow the user's finger. When the
finger goes up the screen will clear zoom out. If the same user interaction
is performed when the screen is magnified, the viewport movement will
be the same but when the finger goes up the screen will stay magnified.
In other words, the initial magnified state is sticky.
3. Pinching with any number of additional fingers when viewport dragging
is enabled, i.e. the user triple tapped and holds, would adjust the
magnification scale which will become the current default magnification
scale. The next time the user magnifies the same magnification scale
would be used.
4. When in a permanent magnified state the user can use two or more fingers
to pan the viewport. Note that in this mode the content is panned as
opposed to the viewport dragging mode in which the viewport is moved.
5. When in a permanent magnified state the user can use three or more
fingers to change the magnification scale which will become the current
default magnification scale. The next time the user magnifies the same
magnification scale would be used.
6. The magnification scale will be persisted in settings and in the cloud.
Note: Since two fingers are used to pan the content in a permanently magnified
state no other two finger gestures in touch exploration or applications
will work unless the uses zooms out to normal state where all gestures
works as expected. This is an intentional tradeoff to allow efficient
panning since in a permanently magnified state this would be the dominant
action to be performed.
Design:
1. The window manager exposes APIs for setting accessibility transformation
which is a scale and offsets for X and Y axis. The window manager queries
the window policy for which windows will not be magnified. For example,
the IME windows and the navigation bar are not magnified including windows
that are attached to them.
2. The accessibility features such a screen magnification and touch
exploration are now impemented as a sequence of transformations on the
event stream. The accessibility manager service may request each
of these features or both. The behavior of the features is not changed
based on the fact that another one is enabled.
3. The screen magnifier keeps a viewport of the content that is magnified
which is surrounded by a glow in a magnified state. Interactions outside
of the viewport are delegated directly to the application without
interpretation. For example, a triple tap on the letter 'a' of the IME
would type three letters instead of toggling magnified state. The viewport
is updated on screen rotation and on window transitions. For example,
when the IME pops up the viewport shrinks.
4. The glow around the viewport is implemented as a special type of window
that does not take input focus, cannot be touched, is laid out in the
screen coordiates with width and height matching these of the screen.
When the magnified region changes the root view of the window draws the
hightlight but the size of the window does not change - unless a rotation
happens. All changes in the viewport size or showing or hiding it are
animated.
5. The viewport is encapsulated in a class that knows how to show,
hide, and resize the viewport - potentially animating that.
This class uses the new animation framework for animations.
6. The magnification is handled by a magnification controller that
keeps track of the current trnasformation to be applied to the screen
content and the desired such. If these two are not the same it is
responsibility of the magnification controller to reconcile them by
potentially animating the transition from one to the other.
7. A dipslay content observer wathces for winodw transitions, screen
rotations, and when a rectange on the screen has been reqeusted. This
class is responsible for handling interesting state changes such
as changing the viewport bounds on IME pop up or screen rotation,
panning the content to make a requested rectangle visible on the
screen, etc.
8. To implement viewport updates the window manger was updated with APIs
to watch for window transitions and when a rectangle has been requested
on the screen. These APIs are protected by a signature level permission.
Also a parcelable and poolable window info class has been added with
APIs for getting the window info given the window token. This enables
getting some useful information about a window. There APIs are also
signature protected.
bug:6795382
Change-Id: Iec93da8bf6376beebbd4f5167ab7723dc7d9bd00
