From 8d28c3b3bdab63fab132b81e38d54bc4c132ea8a Mon Sep 17 00:00:00 2001
From: Daniel Sandler <dsandler@google.com>
Date: Thu, 20 Aug 2009 13:34:02 -0400
Subject: [PATCH] Address b/2064664 by setting mThumbOffset to half the width
 of the thumb by default.

mThumbOffset previously defaulted to 0, which caused drawing artifacts at
extrema of very long SeekBars.

The thumb offset can still be overridden by declaring android:thumbOffset in
layout or calling SeekBar.setThumbOffset(int).

Bug: 2064664
---
 core/java/android/widget/AbsSeekBar.java | 16 ++++++++++++----
 1 file changed, 12 insertions(+), 4 deletions(-)

diff --git a/core/java/android/widget/AbsSeekBar.java b/core/java/android/widget/AbsSeekBar.java
index f92eb997d3a4a..2a0e5e5161f58 100644
--- a/core/java/android/widget/AbsSeekBar.java
+++ b/core/java/android/widget/AbsSeekBar.java
@@ -64,10 +64,10 @@ public abstract class AbsSeekBar extends ProgressBar {
         TypedArray a = context.obtainStyledAttributes(attrs,
                 com.android.internal.R.styleable.SeekBar, defStyle, 0);
         Drawable thumb = a.getDrawable(com.android.internal.R.styleable.SeekBar_thumb);
-        setThumb(thumb);
+        setThumb(thumb); // will guess mThumbOffset if thumb != null...
+        // ...but allow layout to override this
         int thumbOffset =
-                a.getDimensionPixelOffset(com.android.internal.R.styleable.SeekBar_thumbOffset, 0);
-        setThumbOffset(thumbOffset);
+                a.getDimensionPixelOffset(com.android.internal.R.styleable.SeekBar_thumbOffset, getThumbOffset());
         a.recycle();
 
         a = context.obtainStyledAttributes(attrs,
@@ -77,13 +77,21 @@ public abstract class AbsSeekBar extends ProgressBar {
     }
 
     /**
-     * Sets the thumb that will be drawn at the end of the progress meter within the SeekBar
+     * Sets the thumb that will be drawn at the end of the progress meter within the SeekBar.
+     * <p>
+     * If the thumb is a valid drawable (i.e. not null), half its width will be
+     * used as the new thumb offset (@see #setThumbOffset(int)).
      * 
      * @param thumb Drawable representing the thumb
      */
     public void setThumb(Drawable thumb) {
         if (thumb != null) {
             thumb.setCallback(this);
+
+            // Assuming the thumb drawable is symmetric, set the thumb offset
+            // such that the thumb will hang halfway off either edge of the
+            // progress bar.
+            mThumbOffset = (int)thumb.getIntrinsicWidth() / 2;
         }
         mThumb = thumb;
         invalidate();