Add StatusBarColorNestedScrollConnection.

app/src/main/java/org/thoughtcrime/securesms/compose/StatusBarColorNestedScrollConnection.kt

@@ -0,0 +1,80 @@
+package org.thoughtcrime.securesms.compose
+
+import android.animation.ValueAnimator
+import android.app.Activity
+import androidx.compose.ui.geometry.Offset
+import androidx.compose.ui.input.nestedscroll.NestedScrollConnection
+import androidx.compose.ui.input.nestedscroll.NestedScrollSource
+import androidx.compose.ui.unit.Velocity
+import androidx.core.content.ContextCompat
+import com.google.android.material.animation.ArgbEvaluatorCompat
+import org.thoughtcrime.securesms.R
+import org.thoughtcrime.securesms.util.WindowUtil
+import kotlin.math.abs
+
+/**
+ * Controls status-bar color based off a nested scroll
+ */
+class StatusBarColorNestedScrollConnection(
+  private val activity: Activity
+) : NestedScrollConnection {
+  private var animator: ValueAnimator? = null
+
+  private val normalColor = ContextCompat.getColor(activity, R.color.signal_colorBackground)
+  private val scrollColor = ContextCompat.getColor(activity, R.color.signal_colorSurface2)
+
+  private var contentOffset = 0f
+
+  override suspend fun onPostFling(consumed: Velocity, available: Velocity): Velocity {
+    return Velocity.Zero
+  }
+
+  override fun onPostScroll(consumed: Offset, available: Offset, source: NestedScrollSource): Offset {
+    val oldContentOffset = contentOffset
+    if (consumed.y == 0f && available.y > 0f) {
+      contentOffset = 0f
+    } else {
+      contentOffset += consumed.y
+    }
+
+    if (oldContentOffset.isNearZero() xor contentOffset.isNearZero()) {
+      applyState()
+    }
+
+    return Offset.Zero
+  }
+
+  fun setColorImmediate() {
+    val end = when {
+      contentOffset.isNearZero() -> normalColor
+      else -> scrollColor
+    }
+
+    animator?.cancel()
+    WindowUtil.setStatusBarColor(
+      activity.window,
+      end
+    )
+  }
+
+  private fun applyState() {
+    val (start, end) = when {
+      contentOffset.isNearZero() -> scrollColor to normalColor
+      else -> normalColor to scrollColor
+    }
+
+    animator?.cancel()
+    animator = ValueAnimator.ofFloat(0f, 1f).apply {
+      duration = 200
+      addUpdateListener {
+        WindowUtil.setStatusBarColor(
+          activity.window,
+          ArgbEvaluatorCompat.getInstance().evaluate(it.animatedFraction, start, end)
+        )
+      }
+      start()
+    }
+  }
+
+  private fun Float.isNearZero(): Boolean = abs(this) < 0.001
+}