Optimize GraphemeClusterSegmentFinder performance

This CL utilized minikin:isGraphemeBreak to compute all grapheme break indices when creating GraphemeClusterSegmentFinder. This makes all methods (such as #nextStartBoundary) of GraphemeClusterSegmentFinder O(1) instead of O(n).

Bug: 271004887
Test: atest TextViewHandwritingGestureTest
Change-Id: I61c1f2c45123a584456b4860b72cd4fdc84c5f1c

1 files changed, 59 insertions, 0 deletions

diff --git a/graphics/java/android/graphics/text/GraphemeBreak.java b/graphics/java/android/graphics/text/GraphemeBreak.java
new file mode 100644
index 000000000000..f82b2fd659cc
--- /dev/null
+++ b/graphics/java/android/graphics/text/GraphemeBreak.java
@@ -0,0 +1,59 @@
+/*
+ * Copyright (C) 2023 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.text;
+
+/** @hide */
+public class GraphemeBreak {
+    private GraphemeBreak() { }
+
+    /**
+     * Util method that checks if the offsets in given range are grapheme break.
+     *
+     * @param advances the advances of characters in the given text. It contains the font
+     *                information used by the algorithm to determine the grapheme break. It's useful
+     *                 when some character is missing in the font. For example, if the smile emoji
+     *                 "0xD83D 0xDE0A" is not found in the font and is displayed as 2 characters.
+     *                 We can't treat it as a single grapheme cluster.
+     * @param text the text to be processed.
+     * @param start the start offset of the queried range, inclusive.
+     * @param end the end offset of the queried range, exclusive.
+     * @param isGraphemeBreak the array to receive the result. The i-th element of the
+     *                       array will be set to true if the offset (start + i) is a grapheme
+     *                       break; otherwise, it will be set to false.
+     */
+    public static void isGraphemeBreak(float[] advances, char[] text, int start, int end,
+            boolean[] isGraphemeBreak) {
+        if (start > end) {
+            throw new IllegalArgumentException("start is greater than end: start = " + start
+                    + " end = " + end);
+        }
+        if (advances.length < end) {
+            throw new IllegalArgumentException("the length of advances is less than end"
+                    + "advances.length = " + advances.length
+                    + " end = " + end);
+        }
+        if (isGraphemeBreak.length < end - start) {
+            throw new IndexOutOfBoundsException("isGraphemeBreak doesn't have enough space to "
+                    + "receive the result, isGraphemeBreak.length: " + isGraphemeBreak.length
+                    + " needed space: " + (end - start));
+        }
+        nIsGraphemeBreak(advances, text, start, end, isGraphemeBreak);
+    }
+
+    private static native void nIsGraphemeBreak(float[] advances, char[] text, int start, int end,
+            boolean[] isGraphemeBreak);
+}