8146324: Add sun.font.FontUtilities.isComplexCharCode or related method

Reviewed-by: serb, ssadetsky

jdk/src/java.desktop/share/classes/java/awt/Font.java

@@ -765,6 +765,49 @@ public class Font implements java.io.Serializable
         this.hasLayoutAttributes =  values.anyNonDefault(LAYOUT_MASK);
     }
 
+    /**
+     * Returns true if any part of the specified text is from a
+     * complex script for which the implementation will need to invoke
+     * layout processing in order to render correctly when using
+     * {@link Graphics#drawString(String,int,int) drawString(String,int,int)}
+     * and other text rendering methods. Measurement of the text
+     * may similarly need the same extra processing.
+     * The {@code start} and {@code end} indices are provided so that
+     * the application can request only a subset of the text be considered.
+     * The last char index examined is at {@code "end-1"},
+     * i.e a request to examine the entire array would be
+     * <pre>
+     * {@code Font.textRequiresLayout(chars, 0, chars.length);}
+     * </pre>
+     * An application may find this information helpful in
+     * performance sensitive code.
+     * <p>
+     * Note that even if this method returns {@code false}, layout processing
+     * may still be invoked when used with any {@code Font}
+     * for which {@link #hasLayoutAttributes()} returns {@code true},
+     * so that method will need to be consulted for the specific font,
+     * in order to obtain an answer which accounts for such font attributes.
+     *
+     * @param chars the text.
+     * @param start the index of the first char to examine.
+     * @param end the ending index, exclusive.
+     * @return {@code true} if the specified text will need special layout.
+     * @throws NullPointerException if {@code chars} is null.
+     * @throws ArrayIndexOutOfBoundsException if {@code start} is negative or
+     * {@code end} is greater than the length of the {@code chars} array.
+     * @since 9
+     */
+    public static boolean textRequiresLayout(char[] chars,
+                                             int start, int end) {
+        if (chars == null) {
+           throw new NullPointerException("null char array");
+        }
+        if (start < 0 || end > chars.length) {
+            throw new ArrayIndexOutOfBoundsException("start < 0 or end > len");
+        }
+        return FontUtilities.isComplexScript(chars, start, end);
+    }
+
     /**
      * Returns a {@code Font} appropriate to the attributes.
      * If {@code attributes} contains a {@code FONT} attribute

jdk/src/java.desktop/share/classes/sun/font/FontUtilities.java

@@ -182,6 +182,25 @@ public final class FontUtilities {
         return FontAccess.getFontAccess().getFont2D(font);
     }
 
+    /**
+     * Return true if there any characters which would trigger layout.
+     * This method considers supplementary characters to be simple,
+     * since we do not presently invoke layout on any code points in
+     * outside the BMP.
+     */
+    public static boolean isComplexScript(char [] chs, int start, int limit) {
+
+        for (int i = start; i < limit; i++) {
+            if (chs[i] < MIN_LAYOUT_CHARCODE) {
+                continue;
+            }
+            else if (isComplexCharCode(chs[i])) {
+                return true;
+            }
+        }
+        return false;
+    }
+
     /**
      * If there is anything in the text which triggers a case
      * where char->glyph does not map 1:1 in straightforward

jdk/test/java/awt/FontClass/TextRequiresLayoutTest.java

@@ -0,0 +1,85 @@
+/*
+ * Copyright (c) 2016, Oracle and/or its affiliates. All rights reserved.
+ * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
+ *
+ * This code is free software; you can redistribute it and/or modify it
+ * under the terms of the GNU General Public License version 2 only, as
+ * published by the Free Software Foundation.
+ *
+ * This code is distributed in the hope that it will be useful, but WITHOUT
+ * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
+ * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
+ * version 2 for more details (a copy is included in the LICENSE file that
+ * accompanied this code).
+ *
+ * You should have received a copy of the GNU General Public License version
+ * 2 along with this work; if not, write to the Free Software Foundation,
+ * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
+ *
+ * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
+ * or visit www.oracle.com if you need additional information or have any
+ * questions.
+ */
+
+/*
+ * @test
+ * @bug 8146324
+ * @summary Test Font.textRequiresLayout
+ */
+
+import java.awt.Font;
+
+public class TextRequiresLayoutTest {
+
+    public static void main(String args[]) {
+
+        String simpleStr = "Hello World";
+        String complexStr = "\u0641\u0642\u0643";
+        char[] simpleChars = simpleStr.toCharArray();
+        char[] complexChars = complexStr.toCharArray();
+
+        if (Font.textRequiresLayout(simpleChars, 0, simpleChars.length)) {
+            throw new RuntimeException("Simple text should not need layout");
+        }
+
+        if (!Font.textRequiresLayout(complexChars, 0, complexChars.length)) {
+            throw new RuntimeException("Complex text should need layout");
+        }
+
+        if (Font.textRequiresLayout(complexChars, 0, 0)) {
+            throw new RuntimeException("Empty text should not need layout");
+        }
+
+        boolean except = false;
+        try {
+             Font.textRequiresLayout(null, 0, 0);
+        } catch (NullPointerException npe) {
+           except = true;
+        }
+        if (!except) {
+            throw new RuntimeException("No expected IllegalArgumentException");
+        }
+
+        except = false;
+        try {
+             Font.textRequiresLayout(complexChars, -1, 0);
+        } catch (ArrayIndexOutOfBoundsException aioobe) {
+           except = true;
+        }
+        if (!except) {
+            throw new
+                RuntimeException("No expected ArrayIndexOutOfBoundsException");
+        }
+
+        except = false;
+        try {
+             Font.textRequiresLayout(complexChars, 0, complexChars.length+1);
+        } catch (ArrayIndexOutOfBoundsException aioobe) {
+           except = true;
+        }
+        if (!except) {
+            throw new
+                RuntimeException("No expected ArrayIndexOutOfBoundsException");
+        }
+    }
+}