8028722: Render: Drawing strings with exactly 254 glyphs causes hangs

Reviewed-by: prr, bae

src/solaris/classes/sun/font/XRTextRenderer.java

@@ -36,6 +36,10 @@ import sun.java2d.xr.*;
  * @author Clemens Eisserer
  */
 public class XRTextRenderer extends GlyphListPipe {
+    // Workarround for a bug in libXrender.
+    // In case the number of glyphs of an ELT is a multiple of 254,
+    // a few garbage bytes are sent to the XServer causing hangs.
+    static final int MAX_ELT_GLYPH_COUNT = 253;
 
     XRGlyphCache glyphCache;
     XRCompositeManager maskBuffer;
@@ -92,8 +96,11 @@ public class XRTextRenderer extends GlyphListPipe {
 
                 int posX = 0, posY = 0;
                 if (gl.usePositions()
-                        || (cacheEntry.getXAdvance() != ((float) cacheEntry.getXOff()) || cacheEntry.getYAdvance() != ((float) cacheEntry.getYOff()))
-                        || eltIndex < 0 || glyphSet != activeGlyphSet) {
+                        || cacheEntry.getXAdvance() != ((float) cacheEntry.getXOff())
+                        || cacheEntry.getYAdvance() != ((float) cacheEntry.getYOff())
+                        || glyphSet != activeGlyphSet
+                        || eltIndex < 0
+                        || eltList.getCharCnt(eltIndex) == MAX_ELT_GLYPH_COUNT) {
 
                     eltIndex = eltList.getNextIndex();
                     eltList.setCharCnt(eltIndex, 1);
@@ -101,7 +108,7 @@ public class XRTextRenderer extends GlyphListPipe {
                     eltList.setGlyphSet(eltIndex, glyphSet);
 
                     if (gl.usePositions()) {
-                        // /*In this case advX only stores rounding errors*/
+                        // In this case advX only stores rounding errors
                         float x = positions[i * 2] + advX;
                         float y = positions[i * 2 + 1] + advY;
                         posX = (int) Math.floor(x);
@@ -120,16 +127,14 @@ public class XRTextRenderer extends GlyphListPipe {
                         posX = (int) Math.floor(advX);
                         posY = (int) Math.floor(advY);
 
-                        // Advance of ELT = difference between stored
-                        // relative
+                        // Advance of ELT = difference between stored relative
                         // positioning information and required float.
                         advX += (cacheEntry.getXAdvance() - cacheEntry.getXOff());
                         advY += (cacheEntry.getYAdvance() - cacheEntry.getYOff());
                     }
-                    /*
-                     * Offset of the current glyph is the difference to the last
-                     * glyph and this one
-                     */
+
+                    // Offset of the current glyph is the difference
+                    // to the last glyph and this one
                     eltList.setXOff(eltIndex, (posX - oldPosX));
                     eltList.setYOff(eltIndex, (posY - oldPosY));
 

test/java/awt/Graphics2D/DrawString/XRenderElt254TextTest.java

+/*
+ * Copyright (c) 2008, 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.
+ */
+
+import java.awt.*;
+import java.awt.MultipleGradientPaint.*;
+import java.awt.image.*;
+import java.io.*;
+
+import javax.imageio.*;
+import javax.swing.*;
+
+/**
+ * @test
+ * @bug 8028722
+ * @summary tests wether drawString with 254 characters causes the xrender
+ *          pipeline to hang.
+ * @author ceisserer
+ */
+public class XRenderElt254TextTest extends Frame implements Runnable {
+    public volatile boolean success = false;
+
+    public void run() {
+        Image dstImg = getGraphicsConfiguration().createCompatibleVolatileImage(400, 400);
+        Graphics2D g = (Graphics2D) dstImg.getGraphics();
+
+        StringBuilder strBuilder = new StringBuilder(254);
+        for (int c = 0; c < 254; c++) {
+          strBuilder.append('a');
+        }
+
+        for (int i = 0; i < 100; i++) {
+            g.drawString(strBuilder.toString(), 20, 20);
+            Toolkit.getDefaultToolkit().sync();
+        }
+        success = true;
+    }
+
+    public static void main(String[] args) throws Exception {
+        XRenderElt254TextTest test = new XRenderElt254TextTest();
+        new Thread(test).start();
+
+        for (int i = 0; i < 30; i++) {
+            Thread.sleep(1000);
+
+            if (test.success) {
+            return; // Test finished successful
+            }
+        }
+
+        throw new RuntimeException("Test Failed");
+    }
+}