8231286: HTML font size too large with high-DPI scaling and W3C_LENGTH_UNITS

Reviewed-by: aivanov, psadhukhan

Author: mperktold

src/java.desktop/share/classes/javax/swing/JEditorPane.java

@@ -1621,7 +1621,7 @@ private void writeObject(ObjectOutputStream s) throws IOException {
 
     /**
      * Key for a client property used to indicate whether
-     * <a href="http://www.w3.org/TR/CSS21/syndata.html#length-units">
+     * <a href="https://www.w3.org/TR/CSS22/syndata.html#length-units">
      * w3c compliant</a> length units are used for html rendering.
      * <p>
      * By default this is not enabled; to enable

src/java.desktop/share/classes/javax/swing/text/html/CSS.java

@@ -27,7 +27,6 @@
 
 import java.awt.Color;
 import java.awt.Font;
-import java.awt.HeadlessException;
 import java.awt.Image;
 import java.awt.Toolkit;
 import java.io.IOException;
@@ -2881,18 +2880,14 @@ static class LengthUnit implements Serializable {
             lengthMapping.put("cm", 28.3464f);
             lengthMapping.put("pc", 12f);
             lengthMapping.put("in", 72f);
-            int res = 72;
-            try {
-                res = Toolkit.getDefaultToolkit().getScreenResolution();
-            } catch (HeadlessException e) {
-            }
-            // mapping according to the CSS2 spec
-            w3cLengthMapping.put("pt", res / 72f);
-            w3cLengthMapping.put("px", 1f);
-            w3cLengthMapping.put("mm", res / 25.4f);
-            w3cLengthMapping.put("cm", res / 2.54f);
-            w3cLengthMapping.put("pc", res / 6f);
-            w3cLengthMapping.put("in", (float) res);
+            // Mapping according to the CSS2.2 spec
+            // https://www.w3.org/TR/CSS22/syndata.html#x39
+            w3cLengthMapping.put("pt", 96f / 72f);         // 1/72 of 1in
+            w3cLengthMapping.put("px", 1f);                // 1/96 of 1in
+            w3cLengthMapping.put("mm", 96f / 2.54f / 10f); // 1/10 of 1cm
+            w3cLengthMapping.put("cm", 96f / 2.54f);       // 96px/2.54
+            w3cLengthMapping.put("pc", 96f / 6f);          // 1/6 of 1in
+            w3cLengthMapping.put("in", 96f);               // 96px
         }
 
         LengthUnit(String value, short defaultType, float defaultValue) {

test/jdk/javax/swing/text/html/CSS/8231286/HtmlFontSizeTest.java

@@ -0,0 +1,81 @@
+/*
+ * Copyright (c) 2021, 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 8231286
+ * @summary  Verifies if HTML font size too large with high-DPI scaling and W3C_LENGTH_UNITS
+ * @run main/othervm -Dsun.java2d.uiScale=1.0 HtmlFontSizeTest
+ */
+
+import java.awt.Dimension;
+import java.util.Locale;
+
+import javax.swing.JEditorPane;
+import javax.swing.SwingUtilities;
+import javax.swing.text.Document;
+import javax.swing.text.html.HTMLEditorKit;
+
+public class HtmlFontSizeTest {
+    static volatile Dimension w3cFrameSize;
+    static volatile Dimension stdFrameSize;
+
+    private static Dimension test(boolean w3ccheck) {
+        JEditorPane htmlPane = new JEditorPane();
+        htmlPane.setEditable(false);
+
+        if (w3ccheck) {
+            htmlPane.putClientProperty(JEditorPane.W3C_LENGTH_UNITS, Boolean.TRUE);
+        }
+
+        HTMLEditorKit kit = new HTMLEditorKit();
+        htmlPane.setEditorKit(kit);
+
+        String htmlString = "<html>\n"
+            + "<body style=\"font-family:SansSerif; font-size:16pt\">\n"
+            + "<p>This should be 16 pt.</p>\n"
+            + "</body>\n"
+            + "</html>";
+
+        Document doc = kit.createDefaultDocument();
+        htmlPane.setDocument(doc);
+        htmlPane.setText(htmlString);
+
+        return htmlPane.getPreferredSize();
+    }
+
+    public static void main(String[] args) throws Exception {
+        SwingUtilities.invokeAndWait(() -> {
+            w3cFrameSize = test(true);
+            stdFrameSize = test(false);
+        });
+        System.out.println("size with W3C:" + w3cFrameSize);
+        System.out.println("size without W3C:" + stdFrameSize);
+
+        float ratio = (float)w3cFrameSize.width / (float)stdFrameSize.width;
+        System.out.println("w3cFrameSize.width/stdFrameSize.width " + ratio);
+
+        if (!"1.3".equals(String.format(Locale.ENGLISH, "%.1f", ratio))) {
+            throw new RuntimeException("HTML font size too large with high-DPI scaling and W3C_LENGTH_UNITS");
+        }
+    }
+}