Display Cutouts

Android 9 adds support for implementing different types of display cutouts on devices. Display cutouts allow you to create immersive, edge-to-edge experiences while still allowing space for important sensors on the front of devices.

Top center display cutout

Figure 1. Top center display cutout

Android 9 supports the following types of cutouts:

  • Top center: Cutout at the center of the top edge
  • Top uncentered: Cutout may be in the corner or slightly off-center
  • Bottom: Cutout at the bottom
  • Dual: One cutout on top and one on the bottom

Examples and source

The following window manager code at PhoneWindowManager.java shows how display frames are inset to the safe area when LAYOUT_IN_DISPLAY_CUTOUT_MODE_ALWAYS is not set.

// Ensure that windows with a DEFAULT or NEVER display cutout mode are laid out in
// the cutout safe zone.
if (cutoutMode != LAYOUT_IN_DISPLAY_CUTOUT_MODE_ALWAYS) {
    final Rect displayCutoutSafeExceptMaybeBars = mTmpDisplayCutoutSafeExceptMaybeBarsRect;
    displayCutoutSafeExceptMaybeBars.set(displayFrames.mDisplayCutoutSafe);
    if (layoutInScreen && layoutInsetDecor && !requestedFullscreen
            && cutoutMode == LAYOUT_IN_DISPLAY_CUTOUT_MODE_DEFAULT) {
        // At the top we have the status bar, so apps that are
        // LAYOUT_IN_SCREEN | LAYOUT_INSET_DECOR but not FULLSCREEN
        // already expect that there's an inset there and we don't need to exclude
        // the window from that area.
        displayCutoutSafeExceptMaybeBars.top = Integer.MIN_VALUE;
    }
    if (layoutInScreen && layoutInsetDecor && !requestedHideNavigation
            && cutoutMode == LAYOUT_IN_DISPLAY_CUTOUT_MODE_DEFAULT) {
        // Same for the navigation bar.
        switch (mNavigationBarPosition) {
            case NAV_BAR_BOTTOM:
                displayCutoutSafeExceptMaybeBars.bottom = Integer.MAX_VALUE;
                break;
            case NAV_BAR_RIGHT:
                displayCutoutSafeExceptMaybeBars.right = Integer.MAX_VALUE;
                break;
            case NAV_BAR_LEFT:
                displayCutoutSafeExceptMaybeBars.left = Integer.MIN_VALUE;
                break;
        }
    }
    if (type == TYPE_INPUT_METHOD && mNavigationBarPosition == NAV_BAR_BOTTOM) {
        // The IME can always extend under the bottom cutout if the navbar is there.
        displayCutoutSafeExceptMaybeBars.bottom = Integer.MAX_VALUE;
    }
    // Windows that are attached to a parent and laid out in said parent already avoid
    // the cutout according to that parent and don't need to be further constrained.
    // Floating IN_SCREEN windows get what they ask for and lay out in the full screen.
    // They will later be cropped or shifted using the displayFrame in WindowState,
    // which prevents overlap with the DisplayCutout.
    if (!attachedInParent && !floatingInScreenWindow) {
        mTmpRect.set(pf);
        pf.intersectUnchecked(displayCutoutSafeExceptMaybeBars);
        parentFrameWasClippedByDisplayCutout |= !mTmpRect.equals(pf);
    }
    // Make sure that NO_LIMITS windows clipped to the display don't extend under the
    // cutout.
    df.intersectUnchecked(displayCutoutSafeExceptMaybeBars);
}

SystemUI renders in the cutout area, and needs to determine where it can draw. PhoneStatusBarView.java provides an example of a view that determines where the display cutout is, how big it is, and whether or not the inset from the nav bar avoids the cutout area.

By overriding onApplyWindowInsets(), a view can determine where the cutout is and update its layout accordingly.

@Override
    public WindowInsets onApplyWindowInsets(WindowInsets insets) {
        if (updateOrientationAndCutout(mLastOrientation)) {
            updateLayoutForCutout();
            requestLayout();
        }
        return super.onApplyWindowInsets(insets);
    }

These methods outline how cutouts are handled in the status bar in all cases (i.e. top center, top uncentered, bottom, and dual-cutouts in all rotations).

Requirements

To ensure that apps are not negatively impacted by cutouts, you must ensure that:

  • The status bar extends to at least the height of the cutout in portrait mode
  • The cutout area must be letterboxed in fullscreen and landscape modes

Your device can have up to one cutout on each short edge (top and bottom).

For more information, see the CDD.

Implementation

To implement display cutouts on your device, you must configure the following values for System UI.

Value Description
quick_qs_offset_height

Defines the top margin for the quick settings panel. The clock and battery are displayed in the space above the panel.

In values-land, set to status_bar_height_landscape, and in portrait set to either the default of 48dp, or the height of the cutout, whichever is larger. Can optionally be taller than the cutout if desired.

quick_qs_total_height

Total height of the quick-quick settings panel (collapsed quick settings panel) when the notification shade is expanded, including the space above the panel containing the clock.

Because of the way quick settings is laid out, the total height of the quick-quick settings panel (including the offset) must be known statically, so this value must be adjusted by the same delta quick_qs_offset_height. Values-land defaults this to 152dp, while the portrait default is 176dp.

status_bar_height_portrait

The default height of the status bar from the framework's perspective.

In most devices, this defaults to 24dp. When there is a cutout, set this value to the height of the cutout. Can optionally be taller than the cutout if desired.

status_bar_height_landscape

The height of the status bar in landscape. Cutouts are only supported on the short edges of the device, so this will always be an unaltered status bar height.

In a device with no cutout, this is equivalent to status_bar_height_portrait. When a cutout is present, keep this value at the default status bar height.

config_mainBuiltInDisplayCutout

The path defining the shape of the cutout. This is a string parsable by android.util.PathParser, and is how the size and shape of the cutout is defined to the system.

@dp can be specified on the path to emulate a shape targeting different devices. Because physical cutouts have an exact pixel size, do not use the @dp specifier when defining the path for a hardware notch.

config_fillMainBuiltinDisplayCutout

A boolean value that determines whether to draw the cutout path (defined above) in software. Can be used to emulate a cutout, or to fill in a physical cutout to achieve anti-aliasing.

If true, config_mainBuiltInDisplayCutout is filled in black.

See these dimens files for the default definitions:

Example overlay for an emulated cutout:

<resources xmlns:xliff="urn:oasis:names:tc:xliff:document:1.2">

    <!-- The bounding path of the cutout region of the main built-in display.
         Must either be empty if there is no cutout region, or a string that is parsable by
         {@link android.util.PathParser}.

         The path is assumed to be specified in display coordinates with pixel units and in
         the display's native orientation, with the origin of the coordinate system at the
         center top of the display.

         To facilitate writing device-independent emulation overlays, the marker `@dp` can be
         appended after the path string to interpret coordinates in dp instead of px units.
         Note that a physical cutout should be configured in pixels for the best results.
         -->
    <string translatable="false" name="config_mainBuiltInDisplayCutout">
        M 0,0
        L -48, 0
        L -44.3940446283, 36.0595537175
        C -43.5582133885, 44.4178661152 -39.6, 48.0 -31.2, 48.0
        L 31.2, 48.0
        C 39.6, 48.0 43.5582133885, 44.4178661152 44.3940446283, 36.0595537175
        L 48, 0
        Z
        @dp
    </string>

    <!-- Whether the display cutout region of the main built-in display should be forced to
         black in software (to avoid aliasing or emulate a cutout that is not physically existent).
     -->
    <bool name="config_fillMainBuiltInDisplayCutout">true</bool>

    <!-- Height of the status bar -->
    <dimen name="status_bar_height_portrait">48dp</dimen>
    <dimen name="status_bar_height_landscape">28dp</dimen>
    <!-- Height of area above QQS where battery/time go (equal to status bar height if > 48dp) -->
    <dimen name="quick_qs_offset_height">48dp</dimen>
    <!-- Total height of QQS (quick_qs_offset_height + 128) -->
    <dimen name="quick_qs_total_height">176dp</dimen>

</resources>

Validation

To validate your implementation of display cutouts, run the CTS tests at tests/framework/base/windowmanager/src/android/server/wm.