Add a layering method to blend surface and onSurface colors without an alpha

value.

PiperOrigin-RevId: 218902432

Author: afohrman

lib/java/com/google/android/material/color/MaterialColors.java

@@ -27,7 +27,7 @@
 import android.view.View;
 
 /**
- * A utility class for common color variants used in Material themes
+ * A utility class for common color variants used in Material themes.
  *
  * @hide
  */
@@ -44,6 +44,18 @@ public static int getColor(View view, @AttrRes int colorAttributeResId) {
     return MaterialAttributes.resolveAttributeOrThrow(view, colorAttributeResId).data;
   }
 
+  /**
+   * Convenience method that calculates {@link MaterialColors#layer(View, int, int, float)} without
+   * an {@code overlayAlpha} value by passing in {@code 1f} for the alpha value.
+   */
+  @ColorInt
+  public static int layer(
+      View view,
+      @AttrRes int backgroundColorAttributeResId,
+      @AttrRes int overlayColorAttributeResId) {
+    return layer(view, backgroundColorAttributeResId, overlayColorAttributeResId, 1f);
+  }
+
   /**
    * Convenience method that wraps {@link MaterialColors#layer(int, int, float)} for layering colors
    * from theme attributes.
@@ -70,6 +82,15 @@ public static int layer(
       @FloatRange(from = 0.0, to = 1.0) float overlayAlpha) {
     int computedAlpha = Math.round(Color.alpha(overlayColor) * overlayAlpha);
     int computedOverlayColor = ColorUtils.setAlphaComponent(overlayColor, computedAlpha);
-    return ColorUtils.compositeColors(computedOverlayColor, backgroundColor);
+    return layer(backgroundColor, computedOverlayColor);
+  }
+
+  /**
+   * Calculates a color that represents the layering of the {@code overlayColor} on top of the
+   * {@code backgroundColor}.
+   */
+  @ColorInt
+  public static int layer(@ColorInt int backgroundColor, @ColorInt int overlayColor) {
+    return ColorUtils.compositeColors(overlayColor, backgroundColor);
   }
 }