Update scrollbars to match Material spec

Adds a minimum touch target size to the fast scroller so that we can
edge-align an 8dp thumb but still maintain a 48dp touch target.

BUG: 18467743
Change-Id: I31e9cf1948856f5fce7d75383b84a9359684ebe5

core/java/android/widget/FastScroller.java

@@ -106,6 +106,9 @@ class FastScroller {
      */
     private final int[] mPreviewResId = new int[2];
 
+    /** The minimum touch target size in pixels. */
+    private final int mMinimumTouchTarget;
+
     /**
      * Padding in pixels around the preview text. Applied as layout margins to
      * the preview text and padding to the preview image.
@@ -254,6 +257,9 @@ public FastScroller(AbsListView listView, int styleResId) {
         mPrimaryText = createPreviewTextView(context);
         mSecondaryText = createPreviewTextView(context);
 
+        mMinimumTouchTarget = listView.getResources().getDimensionPixelSize(
+                com.android.internal.R.dimen.fast_scroller_minimum_touch_target);
+
         setStyle(styleResId);
 
         final ViewGroupOverlay overlay = listView.getOverlay();
@@ -1474,18 +1480,31 @@ private boolean isPointInside(float x, float y) {
     }
 
     private boolean isPointInsideX(float x) {
+        final float offset = mThumbImage.getTranslationX();
+        final float left = mThumbImage.getLeft() + offset;
+        final float right = mThumbImage.getRight() + offset;
+
+        // Apply the minimum touch target size.
+        final float targetSizeDiff = mMinimumTouchTarget - (right - left);
+        final float adjust = targetSizeDiff > 0 ? targetSizeDiff : 0;
+
         if (mLayoutFromRight) {
-            return x >= mThumbImage.getLeft();
+            return x >= mThumbImage.getLeft() - adjust;
         } else {
-            return x <= mThumbImage.getRight();
+            return x <= mThumbImage.getRight() + adjust;
         }
     }
 
     private boolean isPointInsideY(float y) {
         final float offset = mThumbImage.getTranslationY();
         final float top = mThumbImage.getTop() + offset;
         final float bottom = mThumbImage.getBottom() + offset;
-        return y >= top && y <= bottom;
+
+        // Apply the minimum touch target size.
+        final float targetSizeDiff = mMinimumTouchTarget - (bottom - top);
+        final float adjust = targetSizeDiff > 0 ? targetSizeDiff / 2 : 0;
+
+        return y >= (top - adjust) && y <= (bottom + adjust);
     }
 
     /**

core/res/res/drawable/fastscroll_thumb_material.xml

@@ -16,11 +16,17 @@
 
 <selector xmlns:android="http://schemas.android.com/apk/res/android">
     <item android:state_pressed="true">
-        <bitmap android:src="@drawable/fastscroll_thumb_mtrl_alpha"
-            android:tint="?attr/colorControlActivated" />
+        <shape android:tint="?attr/colorControlActivated"
+               android:shape="rectangle">
+            <solid android:color="@color/white" />
+            <size android:width="8dp" android:height="48dp" />
+        </shape>
     </item>
     <item>
-        <bitmap android:src="@drawable/fastscroll_thumb_mtrl_alpha"
-            android:tint="?attr/colorControlNormal" />
+        <shape android:tint="?attr/colorControlNormal"
+               android:shape="rectangle">
+            <solid android:color="@color/white" />
+            <size android:width="8dp" android:height="48dp" />
+        </shape>
     </item>
 </selector>

core/res/res/drawable/fastscroll_track_material.xml

@@ -14,6 +14,9 @@
      limitations under the License.
 -->
 
-<nine-patch xmlns:android="http://schemas.android.com/apk/res/android"
-    android:src="@drawable/fastscroll_track_mtrl_alpha"
-    android:tint="?attr/colorControlNormal" />
+<shape xmlns:android="http://schemas.android.com/apk/res/android"
+       android:tint="?attr/colorControlNormal"
+       android:shape="rectangle">
+    <solid android:color="#21ffffff" />
+    <size android:width="8dp" />
+</shape>

core/res/res/drawable/scrollbar_handle_material.xml

@@ -14,6 +14,9 @@
      limitations under the License.
 -->
 
-<nine-patch xmlns:android="http://schemas.android.com/apk/res/android"
-    android:src="@drawable/scrollbar_handle_mtrl_alpha"
-    android:tint="?attr/colorControlNormal" />
+<shape xmlns:android="http://schemas.android.com/apk/res/android"
+       android:tint="?attr/colorControlNormal"
+       android:shape="rectangle">
+    <solid android:color="#42ffffff" />
+    <size android:width="4dp" />
+</shape>

core/res/res/values/dimens.xml

@@ -397,6 +397,9 @@
     <dimen name="datepicker_header_height">30dp</dimen>
     <dimen name="datepicker_header_text_size">14dp</dimen>
 
+    <!-- Minimum size of the fast scroller thumb's touch target. -->
+    <dimen name="fast_scroller_minimum_touch_target">48dp</dimen>
+
     <!-- width of ImmersiveModeConfirmation (-1 for match_parent) -->
     <dimen name="immersive_mode_cling_width">-1px</dimen>
 

core/res/res/values/symbols.xml

@@ -2126,5 +2126,6 @@
   <java-symbol type="string" name="android_system_label" />
   <java-symbol type="string" name="system_error_wipe_data" />
   <java-symbol type="string" name="system_error_manufacturer" />
+  <java-symbol type="dimen" name="fast_scroller_minimum_touch_target" />
 
 </resources>