Added GSUB Table Type Implementation

src/FontLib/Table/Type/gsub.php

@@ -0,0 +1,203 @@
+<?php
+/**
+ * @package php-font-lib
+ * @link    https://github.com/dompdf/php-font-lib
+ * @license http://www.gnu.org/copyleft/lesser.html GNU Lesser General Public License
+ */
+
+namespace FontLib\Table\Type;
+use FontLib\Table\Table;
+
+/**
+ * `GSUB` font table (Glyph Substitution).
+ *
+ * @package php-font-lib
+ */
+class gsub extends Table {
+  private static $header_format = array(
+    "majorVersion"  => self::uint16,
+    "minorVersion"  => self::uint16,
+    "scriptList"    => self::uint16,
+    "featureList"   => self::uint16,
+    "lookupList"    => self::uint16,
+  );
+
+  protected function _parse() {
+    $font   = $this->getFont();
+    $offset = $font->pos();
+
+    $header = $font->unpack(self::$header_format);
+
+    $data = array(
+      "header"      => $header,
+      "scriptList"  => null,
+      "featureList" => null,
+      "lookupList"  => null,
+    );
+
+    if ($header["scriptList"]) {
+      $font->seek($offset + $header["scriptList"]);
+      $data["scriptList"] = $this->parseScriptList($font, $offset + $header["scriptList"]);
+    }
+
+    if ($header["featureList"]) {
+      $font->seek($offset + $header["featureList"]);
+      $data["featureList"] = $this->parseFeatureList($font, $offset + $header["featureList"]);
+    }
+
+    if ($header["lookupList"]) {
+      $font->seek($offset + $header["lookupList"]);
+      $data["lookupList"] = $this->parseLookupList($font, $offset + $header["lookupList"]);
+    }
+
+    $this->data = $data;
+  }
+
+  private function parseScriptList($font, $baseOffset) {
+    $scriptCount = $font->readUInt16();
+    $records = [];
+    for ($i = 0; $i < $scriptCount; $i++) {
+      $tag = $font->read(4);
+      $offset = $font->readUInt16();
+      $records[] = ["tag" => $tag, "offset" => $offset];
+    }
+    return ["scriptCount" => $scriptCount, "records" => $records];
+  }
+
+  private function parseFeatureList($font, $baseOffset) {
+    $featureCount = $font->readUInt16();
+    $records = [];
+    for ($i = 0; $i < $featureCount; $i++) {
+      $tag = $font->read(4);
+      $offset = $font->readUInt16();
+      $records[] = ["tag" => $tag, "offset" => $offset];
+    }
+    return ["featureCount" => $featureCount, "records" => $records];
+  }
+
+  private function parseLookupList($font, $baseOffset) {
+    $lookupCount = $font->readUInt16();
+    $lookups = [];
+    $offsets = $font->readUInt16Many($lookupCount);
+
+    foreach ($offsets as $lookupOffset) {
+      $font->seek($baseOffset + $lookupOffset);
+      $lookups[] = $this->parseLookup($font, $baseOffset + $lookupOffset);
+    }
+
+    return ["lookupCount" => $lookupCount, "lookups" => $lookups];
+  }
+
+  private function parseLookup($font, $baseOffset) {
+    $lookupType     = $font->readUInt16();
+    $lookupFlag     = $font->readUInt16();
+    $subtableCount  = $font->readUInt16();
+    $subtableOffsets = $font->readUInt16Many($subtableCount);
+
+    $subtables = [];
+    foreach ($subtableOffsets as $off) {
+      $font->seek($baseOffset + $off);
+      $subtables[] = $this->parseSubtable($font, $baseOffset + $off, $lookupType);
+    }
+
+    return [
+      "lookupType"    => $lookupType,
+      "lookupFlag"    => $lookupFlag,
+      "subtableCount" => $subtableCount,
+      "subtables"     => $subtables,
+    ];
+  }
+
+  private function parseSubtable($font, $baseOffset, $lookupType) {
+    switch ($lookupType) {
+      case 4:
+        return $this->parseLigatureSubst($font, $baseOffset);
+      default:
+        return ["raw" => "Unsupported lookupType $lookupType"];
+    }
+  }
+
+  private function parseLigatureSubst($font, $subtableBase) {
+    $substFormat   = $font->readUInt16();
+    if ($substFormat != 1) {
+      return ["format" => $substFormat, "unsupported" => true];
+    }
+
+    $coverageOffset = $font->readUInt16();
+    $ligSetCount    = $font->readUInt16();
+    $ligSetOffsets  = $font->readUInt16Many($ligSetCount);
+
+    $ligSets = [];
+    foreach ($ligSetOffsets as $offset) {
+      $font->seek($subtableBase + $offset);
+      $ligSets[] = $this->parseLigatureSet($font, $subtableBase + $offset);
+    }
+
+    $font->seek($subtableBase + $coverageOffset);
+    $coverageGlyphs = $this->parseCoverage($font);
+
+    return [
+      "format"         => $substFormat,
+      "coverageOffset" => $coverageOffset,
+      "coverageGlyphs" => $coverageGlyphs,
+      "ligSetCount"    => $ligSetCount,
+      "ligSets"        => $ligSets,
+    ];
+  }
+
+  private function parseCoverage($font) {
+    $coverageFormat = $font->readUInt16();
+    $glyphs = [];
+    if ($coverageFormat == 1) {
+        $glyphCount = $font->readUInt16();
+        for ($i = 0; $i < $glyphCount; $i++) {
+            $glyphs[] = $font->readUInt16();
+        }
+    } elseif ($coverageFormat == 2) {
+        $rangeCount = $font->readUInt16();
+        for ($i = 0; $i < $rangeCount; $i++) {
+            $startGlyph = $font->readUInt16();
+            $endGlyph   = $font->readUInt16();
+            $startCoverageIndex = $font->readUInt16(); // can be ignored for mapping
+            for ($g = $startGlyph; $g <= $endGlyph; $g++) {
+                $glyphs[] = $g;
+            }
+        }
+    }
+    return $glyphs;
+}
+
+
+  private function parseLigatureSet($font, $baseOffset) {
+    $ligatureCount  = $font->readUInt16();
+    $ligatureOffsets = $font->readUInt16Many($ligatureCount);
+
+    $ligatures = [];
+    foreach ($ligatureOffsets as $off) {
+      $font->seek($baseOffset + $off);
+      $ligatures[] = $this->parseLigature($font);
+    }
+
+    return [
+      "ligatureCount"  => $ligatureCount,
+      "ligatures"      => $ligatures,
+    ];
+  }
+
+  private function parseLigature($font) {
+    $ligGlyph   = $font->readUInt16();
+    $compCount  = $font->readUInt16();
+    $components = $font->readUInt16Many($compCount - 1);
+
+    return [
+      "ligatureGlyph" => $ligGlyph,
+      "compCount"     => $compCount,
+      "components"    => $components,
+    ];
+  }
+
+  function _encode() {
+    // This still needs to be implemented
+    throw new \Exception("Encoding GSUB not implemented yet.");
+  }
+}