11/10/2023 0 Comments Windowmanager formatMost window managers are designed to help provide a desktop environment. Under Wayland clients always draw their own window decorations.Ī window manager is system software that controls the placement and appearance of windows within a windowing system in a graphical user interface. Under X11, when the window manager is not running, the window decorations are missing for most windows. The drawing of the content is the task of the client. The window decoration is either drawn by the window manager (X11) or by the client ( Wayland). Under X, the window manager and the display server are two distinct programs but under Wayland, the function of both is handled by the Wayland compositor. Also, they gave me a heads-up (thanks!) that “this behavior may change in a future release” - as it did in Android 4.4 that year.Type of system software Layers of the graphical user interface: In a reply a few weeks later, they don’t consider it a security vulnerability because the SYSTEM_ALERT_WINDOW permission “gates the behavior”. Shortly after I discovered the issue I contacted the Android Security Team mid-2013 since I considered it to be a security-related bug, making Denial-of-Service attacks possible by user apps blocking the navigation bar. I’d call it a bug, but here’s the background: This makes it impossible for user apps to place a Window over the shown navigation bar anymore. Effectively, this change disables FLAG_LAYOUT_NO_LIMITS for TYPE_SYSTEM_ERROR Windows. In Android 4.4 this behavior was changed. When this flag is set, a Window can be easily placed on top of the navigation bar, e.g., by setting the Window parameters gravity to Gravity.BOTTOM | Gravity.LEFT and the y coordinate to the negative navigation bar height. However, via the FLAG_LAYOUT_NO_LIMITS flag it is possible to allow Windows to extend beyond these boundaries. A Small Remaining Issueīy default, Windows can’t be laid out anywhere on the screen because the boundaries for screen content exclude the navigation bar. Windows a z-ordered depending on their type via the internal windowTypeToLayerLw method.Īs shown in this method, there exists a single Window type which is laid out on top of the navigation bar type and is available to user apps: However, it is possible (prior to Android 4.4): Generally, overlaying the navigation bar was considered impossible, e.g., in an answer to this question on StackOverflow. In the following two sections, such a flag will be used to put a Window on top of the navigation bar. Yet others control where the Window is shown or laid out. Others when the Window is shown, e.g., FLAG_SECURE Some of them control if the Window is (not) focusable There exist a lot of available Window flags, cf. LayoutParams ( width, height, xpos, ypos, type, flags, format ) // add the View to the WindowManager instance, creating a new Window wm. TRANSLUCENT // create the LayoutParams for the new Window WindowManager. FLAG_NOT_TOUCHABLE // the pixel format, here: translucent int format = PixelFormat. TYPE_SYSTEM_ALERT // make the Window receive no touch input events int flags = WindowManager. getSystemService ( WINDOW_SERVICE ) // create the (root) View for the new Window View v = new View ( context ) // // setup parameters for the Window // // create a system alert Window (requires the SYSTEM_ALERT_WINDOW permission) int type = WindowManager. Windows can be added via the WindowManager: // get the WindowManager for the context-specific Display WindowManager wm = ( WindowManager ) context. Others require the SYSTEM_ALERT_WINDOW permission, e.g.,įinally, there exist purely internal Window types, e.g., for the navigation bar. Some Window types can be used freely by any app, e.g., normal application Windows. (System) WindowsĪndroid uses a variety of different Window types (listed in the WindowManager.LayoutParams class) for different purposes.įor example, there exist types for normal application Windows, Starting with Android 5.0, the navigation bar also provides a button for keyboard/language switching. Instead, it mainly holds the home, back, and recents buttons.Īdditionally, a legacy menu button is shown when necessary. Starting with Android 4.0, the system bar is replaced by the navigation bar which doesn’t provide functionality of So-called software buttons, replacing hardware buttons.Īdditionally, it holds elements from the status bar, e.g., a clock and access to the notification area. This bar, usually located at the screen bottom, provides navigation controls as Thus, especially devices which likely won’t receive a system update can benefit from apps using the method described here. Still, at time of writing, nearly 50% of all Android devices run Android 4.0-4.3. The behavior which allowed this was changed in Android 4.4. Overlaying the System/Navigation Bar | by cygeryįirst off, the method described in this post only works on Android versions up to 4.3.
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