Add support for device emulation in the Gallery app

This CL adds support for device emulation in the Gallery app so that we
can easily emulate any device on another device, e.g. emulate a phone on
a tablet or a emulate tablet on a phone.

The emulation is done at the device level, so that might even be useful
outside of the Gallery app, e.g. when working on SystemUI.

See b/231131244#comment11 for a quick video.

Bug: 231131244
Test: Manual
Change-Id: I64094369c32b796ad41a274d23e0910b7c61a3b0

packages/SystemUI/compose/gallery/AndroidManifest.xml

@@ -17,5 +17,6 @@
 
 <manifest xmlns:android="http://schemas.android.com/apk/res/android"
     package="com.android.systemui.compose.gallery">
-
+    <!-- To emulate a display size and density. -->
+    <uses-permission android:name="android.permission.WRITE_SECURE_SETTINGS" />
 </manifest>

packages/SystemUI/compose/gallery/app/AndroidManifest.xml

@@ -16,7 +16,7 @@
 -->
 
 <manifest xmlns:android="http://schemas.android.com/apk/res/android"
-    package="com.android.systemui.compose.gallery">
+    package="com.android.systemui.compose.gallery.app">
     <application
         android:allowBackup="true"
         android:icon="@mipmap/ic_launcher"
@@ -25,7 +25,7 @@
         android:supportsRtl="true"
         android:theme="@style/Theme.SystemUIGallery">
         <activity
-            android:name=".GalleryActivity"
+            android:name="com.android.systemui.compose.gallery.GalleryActivity"
             android:exported="true"
             android:label="@string/app_name">
             <intent-filter>

packages/SystemUI/compose/gallery/src/com/android/systemui/compose/gallery/ConfigurationControls.kt

@@ -1,5 +1,10 @@
 package com.android.systemui.compose.gallery
 
+import android.graphics.Point
+import android.os.UserHandle
+import android.view.Display
+import android.view.WindowManagerGlobal
+import androidx.compose.foundation.layout.RowScope
 import androidx.compose.foundation.layout.Spacer
 import androidx.compose.foundation.layout.width
 import androidx.compose.foundation.lazy.LazyRow
@@ -9,14 +14,25 @@ import androidx.compose.material.icons.filled.BrightnessLow
 import androidx.compose.material.icons.filled.FormatSize
 import androidx.compose.material.icons.filled.FormatTextdirectionLToR
 import androidx.compose.material.icons.filled.FormatTextdirectionRToL
+import androidx.compose.material.icons.filled.Smartphone
+import androidx.compose.material.icons.filled.Tablet
+import androidx.compose.material3.Button
+import androidx.compose.material3.ButtonDefaults
 import androidx.compose.material3.Icon
 import androidx.compose.material3.Text
 import androidx.compose.material3.TextButton
 import androidx.compose.runtime.Composable
+import androidx.compose.runtime.LaunchedEffect
+import androidx.compose.runtime.getValue
+import androidx.compose.runtime.mutableStateOf
+import androidx.compose.runtime.saveable.rememberSaveable
+import androidx.compose.runtime.setValue
 import androidx.compose.ui.Modifier
 import androidx.compose.ui.graphics.vector.ImageVector
 import androidx.compose.ui.unit.LayoutDirection
 import androidx.compose.ui.unit.dp
+import kotlin.math.max
+import kotlin.math.min
 
 enum class FontScale(val scale: Float) {
     Small(0.85f),
@@ -35,6 +51,39 @@ fun ConfigurationControls(
     onChangeLayoutDirection: () -> Unit,
     onChangeFontScale: () -> Unit,
 ) {
+    // The display we are emulating, if any.
+    var emulatedDisplayName by rememberSaveable { mutableStateOf<String?>(null) }
+    val emulatedDisplay =
+        emulatedDisplayName?.let { name -> EmulatedDisplays.firstOrNull { it.name == name } }
+
+    LaunchedEffect(emulatedDisplay) {
+        val wm = WindowManagerGlobal.getWindowManagerService()
+
+        val defaultDisplayId = Display.DEFAULT_DISPLAY
+        if (emulatedDisplay == null) {
+            wm.clearForcedDisplayDensityForUser(defaultDisplayId, UserHandle.myUserId())
+            wm.clearForcedDisplaySize(defaultDisplayId)
+        } else {
+            val density = emulatedDisplay.densityDpi
+
+            // Emulate the display and make sure that we use the maximum available space possible.
+            val initialSize = Point()
+            wm.getInitialDisplaySize(defaultDisplayId, initialSize)
+            val width = emulatedDisplay.width
+            val height = emulatedDisplay.height
+            val minOfSize = min(width, height)
+            val maxOfSize = max(width, height)
+            if (initialSize.x < initialSize.y) {
+                wm.setForcedDisplaySize(defaultDisplayId, minOfSize, maxOfSize)
+            } else {
+                wm.setForcedDisplaySize(defaultDisplayId, maxOfSize, minOfSize)
+            }
+            wm.setForcedDisplayDensityForUser(defaultDisplayId, density, UserHandle.myUserId())
+        }
+    }
+
+    // TODO(b/231131244): Fork FlowRow from Accompanist and use that instead to make sure that users
+    // don't miss any available configuration.
     LazyRow {
         // Dark/light theme.
         item {
@@ -82,5 +131,70 @@ fun ConfigurationControls(
                 }
             }
         }
+
+        // Display emulation.
+        EmulatedDisplays.forEach { display ->
+            item {
+                DisplayButton(
+                    display,
+                    emulatedDisplay == display,
+                    { emulatedDisplayName = it?.name },
+                )
+            }
+        }
     }
 }
+
+@Composable
+private fun DisplayButton(
+    display: EmulatedDisplay,
+    selected: Boolean,
+    onChangeEmulatedDisplay: (EmulatedDisplay?) -> Unit,
+) {
+    val onClick = {
+        if (selected) {
+            onChangeEmulatedDisplay(null)
+        } else {
+            onChangeEmulatedDisplay(display)
+        }
+    }
+
+    val content: @Composable RowScope.() -> Unit = {
+        Icon(display.icon, null)
+        Spacer(Modifier.width(8.dp))
+        Text(display.name)
+    }
+
+    if (selected) {
+        Button(onClick, contentPadding = ButtonDefaults.TextButtonContentPadding, content = content)
+    } else {
+        TextButton(onClick, content = content)
+    }
+}
+
+/** The displays that can be emulated from this Gallery app. */
+private val EmulatedDisplays =
+    listOf(
+        EmulatedDisplay(
+            "Phone",
+            Icons.Default.Smartphone,
+            width = 1440,
+            height = 3120,
+            densityDpi = 560,
+        ),
+        EmulatedDisplay(
+            "Tablet",
+            Icons.Default.Tablet,
+            width = 2560,
+            height = 1600,
+            densityDpi = 320,
+        ),
+    )
+
+private data class EmulatedDisplay(
+    val name: String,
+    val icon: ImageVector,
+    val width: Int,
+    val height: Int,
+    val densityDpi: Int,
+)