[Framework] Add config to apply custom shadow on header images

To make text and status icons better visible with bright
images if required.

- Fix headershadow derp, thanks to @xyyx

Change-Id: I393d7eb55425e72a953947f0ce0a2b33f5ed3ef8

Author: maxwen

core/java/android/provider/Settings.java

@@ -3818,6 +3818,14 @@ public boolean validate(String value) {
          */
         public static final String STATUS_BAR_CUSTOM_HEADER = "status_bar_custom_header";
 
+        /**
+         *
+         * Whether to apply a shadow on top of the header image
+         * value is the alpha value of the shadow image is 0 -> no shadow -> 255 black
+         * @hide
+         */
+        public static final String STATUS_BAR_CUSTOM_HEADER_SHADOW = "status_bar_custom_header_shadow";
+
         /**
          * Current active provider
          * @hide

packages/SystemUI/src/com/android/systemui/statusbar/phone/PhoneStatusBar.java

@@ -607,6 +607,10 @@ protected void observe() {
             resolver.registerContentObserver(Settings.System.getUriFor(
                     Settings.System.QS_NUM_TILE_ROWS), false, this,
                     UserHandle.USER_ALL);
+            resolver.registerContentObserver(Settings.System.getUriFor(
+                    Settings.System.STATUS_BAR_CUSTOM_HEADER_SHADOW), false, this,
+                    UserHandle.USER_ALL);
+
             update();
         }
 

packages/SystemUI/src/com/android/systemui/statusbar/phone/StatusBarHeaderView.java

@@ -30,6 +30,7 @@
 import android.graphics.Outline;
 import android.graphics.Rect;
 import android.graphics.drawable.Animatable;
+import android.graphics.drawable.ColorDrawable;
 import android.graphics.drawable.Drawable;
 import android.graphics.drawable.RippleDrawable;
 import android.graphics.drawable.TransitionDrawable;
@@ -516,6 +517,7 @@ private void updateVisibilities() {
             mDockBatteryLevel.setForceShown(mExpanded && mShowBatteryTextExpanded);
             mDockBatteryLevel.setVisibility(View.VISIBLE);
         }
+        applyHeaderBackgroundShadow();
     }
 
     private void updateSignalClusterDetachment() {
@@ -1294,6 +1296,19 @@ private void setNotificationPanelHeaderBackground(final Drawable dw, final boole
         } else {
             mBackgroundImage.setImageDrawable(dw);
         }
+        applyHeaderBackgroundShadow();
+    }
+
+    private void applyHeaderBackgroundShadow() {
+        final int headerShadow = Settings.System.getIntForUser(mContext.getContentResolver(),
+                Settings.System.STATUS_BAR_CUSTOM_HEADER_SHADOW, 0,
+                UserHandle.USER_CURRENT);
+
+        if (mBackgroundImage != null) {
+            ColorDrawable shadow = new ColorDrawable(Color.BLACK);
+            shadow.setAlpha(headerShadow);
+            mBackgroundImage.setForeground(shadow);
+        }
     }
 
     @Override