Set dark theme flag when initializing with Color

Users want to be able to use this flag and have been relying on
WallpaperColors#fromBitmap given that flags were not parsed by
the main constructor.

Fixes: 151717291
Test: atest WallpaperColorsTest
Change-Id: I0470a867c54756df9a758b24835a50bc67191050

core/java/android/app/WallpaperColors.java

@@ -222,6 +222,14 @@ public final class WallpaperColors implements Parcelable {
     public WallpaperColors(@NonNull Color primaryColor, @Nullable Color secondaryColor,
             @Nullable Color tertiaryColor) {
         this(primaryColor, secondaryColor, tertiaryColor, 0);
+
+        // Calculate dark theme support based on primary color.
+        final float[] tmpHsl = new float[3];
+        ColorUtils.colorToHSL(primaryColor.toArgb(), tmpHsl);
+        final float luminance = tmpHsl[2];
+        if (luminance < DARK_THEME_MEAN_LUMINANCE) {
+            mColorHints |= HINT_SUPPORTS_DARK_THEME;
+        }
     }
 
     /**

tests/Internal/src/android/app/WallpaperColorsTest.java

@@ -87,6 +87,14 @@ public class WallpaperColorsTest {
                 + "HINT_FROM_BITMAP.", fromBitmap);
     }
 
+    @Test
+    public void darkMainColorSupportsDarkTheme() {
+        final Color color = Color.valueOf(Color.BLACK);
+        WallpaperColors colors = new WallpaperColors(color, null, null);
+        Assert.assertTrue("Dark theme should be supported by dark main colors.",
+                (colors.getColorHints() & WallpaperColors.HINT_SUPPORTS_DARK_THEME) != 0);
+    }
+
     /**
      * WallpaperColors should not recycle bitmaps that it didn't create.
      */