PDFBOX-3293 truetype hinting

debugger/src/main/java/org/apache/pdfbox/debugger/pagepane/PagePane.java

@@ -705,7 +705,7 @@ protected BufferedImage doInBackground() throws IOException
 
             PDFRenderer renderer = new PDFRenderer(document);
             renderer.setSubsamplingAllowed(ViewMenu.isAllowSubsampling());
-            //renderer.setHintingEnabled(ViewMenu.isHintingEnabled())
+            renderer.setHintingEnabled(ViewMenu.isHintingEnabled());
 
             long t0 = System.nanoTime();
             BufferedImage image = renderer.renderImage(pageIndex, scale, ImageTypeMenu.getImageType(), RenderDestinationMenu.getRenderDestination());

fontbox/src/main/java/org/apache/fontbox/ttf/BytecodeStream.java

@@ -0,0 +1,157 @@
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one or more
+ * contributor license agreements.  See the NOTICE file distributed with
+ * this work for additional information regarding copyright ownership.
+ * The ASF licenses this file to You 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 org.apache.fontbox.ttf;
+
+/**
+ * A bounds-checked cursor over a TrueType bytecode program (fpgm, prep, a glyph instruction stream, or
+ * a function body). It owns the program counter so individual opcode handlers never index the array by
+ * hand - this removes a whole class of off-by-one and overrun bugs and is trivially testable on its
+ * own. Reads past the end throw {@link HintingException} so the per-glyph fallback can catch cleanly.
+ *
+ * @author Apache PDFBox
+ */
+class BytecodeStream
+{
+    private final byte[] code;
+    private int ip;
+    private int instructionStart;
+    // exclusive upper bound for the program counter; a function body ends at its ENDF
+    private int limit;
+
+    /**
+     * @param code the bytecode program; not copied
+     */
+    public BytecodeStream(byte[] code)
+    {
+        this.code = code != null ? code : new byte[0];
+        this.limit = this.code.length;
+    }
+
+    /**
+     * @return the underlying bytecode array (not copied); used to record function entry points
+     */
+    public byte[] getCode()
+    {
+        return code;
+    }
+
+    /**
+     * @return true if there is at least one more byte to read
+     */
+    public boolean hasNext()
+    {
+        return ip < limit;
+    }
+
+    /**
+     * Restricts execution to {@code [0, end]}: the stream is exhausted after the byte at {@code end}
+     * (the {@code ENDF} of a function body) and a seek past it is an error, as a jump out of a
+     * function body is in FreeType.
+     *
+     * @param end the position of the last byte that may be executed
+     */
+    public void setEnd(int end)
+    {
+        this.limit = Math.min(code.length, end + 1);
+    }
+
+    /**
+     * @return the current program-counter position
+     */
+    public int position()
+    {
+        return ip;
+    }
+
+    /**
+     * Records the current position as the start of the instruction about to be read. Relative jumps
+     * ({@code JMPR}/{@code JROT}/{@code JROF}) are measured from here.
+     */
+    public void markInstructionStart()
+    {
+        instructionStart = ip;
+    }
+
+    /**
+     * @return the position recorded by the most recent {@link #markInstructionStart()}
+     */
+    public int instructionStart()
+    {
+        return instructionStart;
+    }
+
+    /**
+     * Moves the program counter to an absolute position.
+     *
+     * @param position the new position, within {@code [0, length]}
+     * @throws HintingException if the position is out of range
+     */
+    public void seek(int position)
+    {
+        if (position < 0 || position > limit)
+        {
+            throw new HintingException(
+                    "bytecode seek out of range: " + position + " of " + limit);
+        }
+        ip = position;
+    }
+
+    /**
+     * Advances the program counter by a relative amount (may be negative).
+     *
+     * @param delta the number of bytes to skip
+     * @throws HintingException if the result is out of range
+     */
+    public void skip(int delta)
+    {
+        seek(ip + delta);
+    }
+
+    /**
+     * Reads the next byte as an unsigned 0-255 value (an opcode, or push operand). Like
+     * {@link #seek(int)}, reads honour a function body's end, so a push reached by a jump into the
+     * middle of another push's operands cannot take bytes past the body's {@code ENDF}.
+     *
+     * @return the next unsigned byte
+     * @throws HintingException if the stream is exhausted
+     */
+    public int nextByte()
+    {
+        if (ip >= limit)
+        {
+            throw new HintingException("bytecode read past end at " + ip);
+        }
+        return code[ip++] & 0xFF;
+    }
+
+    /**
+     * Reads the next two bytes as a signed big-endian 16-bit word.
+     *
+     * @return the next signed word
+     * @throws HintingException if fewer than two bytes remain
+     */
+    public int nextWord()
+    {
+        if (ip + 1 >= limit)
+        {
+            throw new HintingException("bytecode word read past end at " + ip);
+        }
+        int hi = code[ip++] & 0xFF;
+        int lo = code[ip++] & 0xFF;
+        return (short) ((hi << 8) | lo);
+    }
+}

fontbox/src/main/java/org/apache/fontbox/ttf/ControlValueProgramTable.java

@@ -0,0 +1,65 @@
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one or more
+ * contributor license agreements.  See the NOTICE file distributed with
+ * this work for additional information regarding copyright ownership.
+ * The ASF licenses this file to You 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 org.apache.fontbox.ttf;
+
+import java.io.IOException;
+
+/**
+ * The 'prep' (Control Value Program, also known as the pre-program) table. It holds TrueType hinting
+ * bytecode that is executed whenever the point size or transform changes, to prepare the Control Value
+ * Table and graphics state for the new ppem. The bytecode is stored here as raw bytes and run by the
+ * interpreter.
+ *
+ * @author Apache PDFBox
+ */
+public class ControlValueProgramTable extends TTFTable
+{
+    /**
+     * A tag that identifies this table type.
+     */
+    public static final String TAG = "prep";
+
+    private byte[] program;
+
+    ControlValueProgramTable()
+    {
+    }
+
+    /**
+     * This will read the required data from the stream.
+     *
+     * @param ttf The font that is being read.
+     * @param data The stream to read the data from.
+     * @throws IOException If there is an error reading the data.
+     */
+    @Override
+    void read(TrueTypeFont ttf, TTFDataStream data) throws IOException
+    {
+        program = data.read((int) getLength());
+        initialized = true;
+    }
+
+    /**
+     * Returns the raw control value program bytecode.
+     *
+     * @return the bytecode of the pre-program
+     */
+    public byte[] getProgram()
+    {
+        return program;
+    }
+}

fontbox/src/main/java/org/apache/fontbox/ttf/ControlValueTable.java

@@ -0,0 +1,82 @@
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one or more
+ * contributor license agreements.  See the NOTICE file distributed with
+ * this work for additional information regarding copyright ownership.
+ * The ASF licenses this file to You 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 org.apache.fontbox.ttf;
+
+import java.io.IOException;
+
+/**
+ * The 'cvt ' (Control Value) table. It holds an array of reference values - stem widths, heights and
+ * similar control measurements - used by the TrueType hinting bytecode. The values are stored here in
+ * raw font units (signed FWords); they are scaled to the active ppem by the interpreter, not at parse
+ * time.
+ *
+ * @author Apache PDFBox
+ */
+public class ControlValueTable extends TTFTable
+{
+    /**
+     * A tag that identifies this table type.
+     */
+    public static final String TAG = "cvt ";
+
+    private int[] values;
+
+    ControlValueTable()
+    {
+    }
+
+    /**
+     * This will read the required data from the stream.
+     *
+     * @param ttf The font that is being read.
+     * @param data The stream to read the data from.
+     * @throws IOException If there is an error reading the data.
+     */
+    @Override
+    void read(TrueTypeFont ttf, TTFDataStream data) throws IOException
+    {
+        int count = (int) (getLength() / 2);
+        int[] cvt = new int[count];
+        for (int i = 0; i < count; i++)
+        {
+            cvt[i] = data.readSignedShort();
+        }
+        values = cvt;
+        initialized = true;
+    }
+
+    /**
+     * Returns the raw control values in font units (FWords). The interpreter scales these to the
+     * active ppem.
+     *
+     * @return the control values in font units
+     */
+    public int[] getValues()
+    {
+        return values;
+    }
+
+    /**
+     * Returns the number of control values in this table.
+     *
+     * @return the entry count
+     */
+    public int getValueCount()
+    {
+        return values != null ? values.length : 0;
+    }
+}