Add proper picture in picture support to compose CallScreen component.

app/src/main/java/org/thoughtcrime/securesms/components/webrtc/v2/CallScreen.kt

@@ -80,6 +80,7 @@ fun CallScreen(
   callRecipient: Recipient,
   webRtcCallState: WebRtcViewModel.State,
   isRemoteVideoOffer: Boolean,
+  isInPipMode: Boolean,
   callScreenState: CallScreenState,
   callControlsState: CallControlsState,
   callScreenController: CallScreenController = CallScreenController.rememberCallScreenController(
@@ -110,6 +111,16 @@ fun CallScreen(
       callStatus = callScreenState.callStatus,
       callScreenControlsListener = callScreenControlsListener
     )
+
+    return
+  }
+
+  if (isInPipMode) {
+    PictureInPictureCallScreen(
+      callParticipantsPagerState = callParticipantsPagerState,
+      callScreenController = callScreenController
+    )
+
     return
   }
 
@@ -532,6 +543,7 @@ private fun CallScreenPreview() {
       callRecipient = Recipient(systemContactName = "Test User"),
       webRtcCallState = WebRtcViewModel.State.CALL_CONNECTED,
       isRemoteVideoOffer = false,
+      isInPipMode = false,
       callScreenState = CallScreenState(),
       callControlsState = CallControlsState(
         displayMicToggle = true,

app/src/main/java/org/thoughtcrime/securesms/components/webrtc/v2/ComposeCallScreenMediator.kt

@@ -24,6 +24,7 @@ import kotlinx.coroutines.flow.MutableStateFlow
 import kotlinx.coroutines.flow.collectLatest
 import kotlinx.coroutines.flow.update
 import kotlinx.coroutines.launch
+import org.signal.core.ui.compose.rememberIsInPipMode
 import org.signal.core.ui.compose.theme.SignalTheme
 import org.signal.core.util.logging.Log
 import org.thoughtcrime.securesms.components.webrtc.CallParticipantListUpdate
@@ -122,6 +123,7 @@ class ComposeCallScreenMediator(private val activity: WebRtcCallActivity, viewMo
           callRecipient = recipient,
           webRtcCallState = webRtcCallState,
           isRemoteVideoOffer = viewModel.isAnswerWithVideoAvailable(),
+          isInPipMode = rememberIsInPipMode(),
           callScreenState = callScreenState,
           callControlsState = callControlsState,
           callScreenController = callScreenController,

app/src/main/java/org/thoughtcrime/securesms/components/webrtc/v2/PictureInPictureCallScreen.kt

@@ -0,0 +1,38 @@
+/*
+ * Copyright 2025 Signal Messenger, LLC
+ * SPDX-License-Identifier: AGPL-3.0-only
+ */
+
+package org.thoughtcrime.securesms.components.webrtc.v2
+
+import androidx.compose.foundation.clickable
+import androidx.compose.foundation.layout.fillMaxSize
+import androidx.compose.runtime.Composable
+import androidx.compose.runtime.rememberCoroutineScope
+import androidx.compose.ui.Modifier
+import kotlinx.coroutines.launch
+
+/**
+ * Displayed when the user minimizes the call screen while a call is ongoing.
+ */
+@Composable
+fun PictureInPictureCallScreen(
+  callParticipantsPagerState: CallParticipantsPagerState,
+  callScreenController: CallScreenController
+) {
+  val scope = rememberCoroutineScope()
+
+  CallParticipantsPager(
+    callParticipantsPagerState = callParticipantsPagerState,
+    modifier = Modifier
+      .fillMaxSize()
+      .clickable(
+        onClick = {
+          scope.launch {
+            callScreenController.handleEvent(CallScreenController.Event.TOGGLE_CONTROLS)
+          }
+        },
+        enabled = false
+      )
+  )
+}

core-ui/src/main/java/org/signal/core/ui/compose/ActivityComponents.kt

@@ -0,0 +1,44 @@
+/*
+ * Copyright 2025 Signal Messenger, LLC
+ * SPDX-License-Identifier: AGPL-3.0-only
+ */
+
+package org.signal.core.ui.compose
+
+import android.os.Build
+import androidx.appcompat.app.AppCompatActivity
+import androidx.compose.runtime.Composable
+import androidx.compose.runtime.DisposableEffect
+import androidx.compose.runtime.getValue
+import androidx.compose.runtime.mutableStateOf
+import androidx.compose.runtime.remember
+import androidx.compose.runtime.setValue
+import androidx.compose.ui.platform.LocalContext
+import androidx.core.app.PictureInPictureModeChangedInfo
+import androidx.core.util.Consumer
+
+/**
+ * Returns whether the screen is currently in the system picture-in-picture mode.
+ *
+ * This requires an AppCompatActivity context, so it cannot be utilized in Composables
+ * that require a preview.
+ */
+@Composable
+fun rememberIsInPipMode(): Boolean {
+  if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.O) {
+    val activity = LocalContext.current as AppCompatActivity
+    var pipMode: Boolean by remember { mutableStateOf(activity.isInPictureInPictureMode) }
+    DisposableEffect(activity) {
+      val observer = Consumer<PictureInPictureModeChangedInfo> { info ->
+        pipMode = info.isInPictureInPictureMode
+      }
+      activity.addOnPictureInPictureModeChangedListener(
+        observer
+      )
+      onDispose { activity.removeOnPictureInPictureModeChangedListener(observer) }
+    }
+    return pipMode
+  } else {
+    return false
+  }
+}