Fixes alpha issue in lock screen shortcuts.

This bug was introduced in ag/21077389 where we implemented "dimming" of
the views to support the remote rendering of the screen preview that's
shown in the wallpaper picker but never tested that it doesn't affect
the views when shown in the normal lock screen.

This CL fixes that.

Fix: 266875410
Test: manually verified that pulling the shade down or the bouncer up
properly fades out the lock screen shortcuts
Test: manually verified that the appropriate "dimming" of the
currently-not-selected button is working as expected in the wallpaper
picker

Change-Id: I9f3e6f7ec600567065d10e6f94a87096607817bf

packages/SystemUI/src/com/android/systemui/keyguard/ui/binder/KeyguardBottomAreaViewBinder.kt

@@ -49,6 +49,7 @@ import kotlin.math.pow
 import kotlin.math.sqrt
 import kotlin.time.Duration.Companion.milliseconds
 import kotlinx.coroutines.ExperimentalCoroutinesApi
+import kotlinx.coroutines.flow.Flow
 import kotlinx.coroutines.flow.MutableStateFlow
 import kotlinx.coroutines.flow.combine
 import kotlinx.coroutines.flow.flatMapLatest
@@ -163,11 +164,25 @@ object KeyguardBottomAreaViewBinder {
 
                         ambientIndicationArea?.alpha = alpha
                         indicationArea.alpha = alpha
-                        startButton.alpha = alpha
-                        endButton.alpha = alpha
                     }
                 }
 
+                launch {
+                    updateButtonAlpha(
+                        view = startButton,
+                        viewModel = viewModel.startButton,
+                        alphaFlow = viewModel.alpha,
+                    )
+                }
+
+                launch {
+                    updateButtonAlpha(
+                        view = endButton,
+                        viewModel = viewModel.endButton,
+                        alphaFlow = viewModel.alpha,
+                    )
+                }
+
                 launch {
                     viewModel.indicationAreaTranslationX.collect { translationX ->
                         indicationArea.translationX = translationX
@@ -321,7 +336,6 @@ object KeyguardBottomAreaViewBinder {
             .animate()
             .scaleX(if (viewModel.isSelected) SCALE_SELECTED_BUTTON else 1f)
             .scaleY(if (viewModel.isSelected) SCALE_SELECTED_BUTTON else 1f)
-            .alpha(if (viewModel.isDimmed) DIM_ALPHA else 1f)
             .start()
 
         view.isClickable = viewModel.isClickable
@@ -341,6 +355,17 @@ object KeyguardBottomAreaViewBinder {
         view.isSelected = viewModel.isSelected
     }
 
+    private suspend fun updateButtonAlpha(
+        view: View,
+        viewModel: Flow<KeyguardQuickAffordanceViewModel>,
+        alphaFlow: Flow<Float>,
+    ) {
+        combine(viewModel.map { it.isDimmed }, alphaFlow) { isDimmed, alpha ->
+                if (isDimmed) DIM_ALPHA else alpha
+            }
+            .collect { view.alpha = it }
+    }
+
     private class OnTouchListener(
         private val view: View,
         private val viewModel: KeyguardQuickAffordanceViewModel,