LayoutLib: Fix ring rendering.

Bug: http://b.android.com/65503
Change-Id: I6ed901703cffee345f3083ea3ddeb52a28f4ac64
diff --git a/tools/layoutlib/bridge/src/android/graphics/drawable/GradientDrawable_Delegate.java b/tools/layoutlib/bridge/src/android/graphics/drawable/GradientDrawable_Delegate.java
new file mode 100644
index 0000000..a3ad2aa
--- /dev/null
+++ b/tools/layoutlib/bridge/src/android/graphics/drawable/GradientDrawable_Delegate.java
@@ -0,0 +1,73 @@
+/*
+ * Copyright (C) 2015 The Android Open Source Project
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package android.graphics.drawable;
+
+import com.android.tools.layoutlib.annotations.LayoutlibDelegate;
+
+import android.graphics.Path;
+import android.graphics.drawable.GradientDrawable.GradientState;
+
+import java.lang.reflect.Field;
+
+/**
+ * Delegate implementing the native methods of {@link GradientDrawable}
+ *
+ * Through the layoutlib_create tool, the original native methods of GradientDrawable have been
+ * replaced by calls to methods of the same name in this delegate class.
+ */
+public class GradientDrawable_Delegate {
+
+    /**
+     * The ring can be built either by drawing full circles, or by drawing arcs in case the
+     * circle isn't complete. LayoutLib cannot handle drawing full circles (requires path
+     * subtraction). So, if we need to draw full circles, we switch to drawing 99% circle.
+     */
+    @LayoutlibDelegate
+    /*package*/ static Path buildRing(GradientDrawable thisDrawable, GradientState st) {
+        boolean useLevel = st.mUseLevelForShape;
+        int level = thisDrawable.getLevel();
+        // 10000 is the max level. See android.graphics.drawable.Drawable#getLevel()
+        float sweep = useLevel ? (360.0f * level / 10000.0f) : 360f;
+        Field mLevel = null;
+        if (sweep >= 360 || sweep <= -360) {
+            st.mUseLevelForShape = true;
+            // Use reflection to set the value of the field to prevent setting the drawable to
+            // dirty again.
+            try {
+                mLevel = Drawable.class.getDeclaredField("mLevel");
+                mLevel.setAccessible(true);
+                mLevel.setInt(thisDrawable, 9999);  // set to one less than max.
+            } catch (NoSuchFieldException e) {
+                // The field has been removed in a recent framework change. Fall back to old
+                // buggy behaviour.
+            } catch (IllegalAccessException e) {
+                // We've already set the field to be accessible.
+                assert false;
+            }
+        }
+        Path path = thisDrawable.buildRing_Original(st);
+        st.mUseLevelForShape = useLevel;
+        if (mLevel != null) {
+            try {
+                mLevel.setInt(thisDrawable, level);
+            } catch (IllegalAccessException e) {
+                assert false;
+            }
+        }
+        return path;
+    }
+}
diff --git a/tools/layoutlib/create/src/com/android/tools/layoutlib/create/CreateInfo.java b/tools/layoutlib/create/src/com/android/tools/layoutlib/create/CreateInfo.java
index 9244310..c9bc62e 100644
--- a/tools/layoutlib/create/src/com/android/tools/layoutlib/create/CreateInfo.java
+++ b/tools/layoutlib/create/src/com/android/tools/layoutlib/create/CreateInfo.java
@@ -166,6 +166,7 @@
         "android.content.res.TypedArray#getValueAt",
         "android.content.res.TypedArray#obtain",
         "android.graphics.BitmapFactory#finishDecode",
+        "android.graphics.drawable.GradientDrawable#buildRing",
         "android.graphics.Typeface#getSystemFontConfigLocation",
         "android.os.Handler#sendMessageAtTime",
         "android.os.HandlerThread#run",