includes/media/MediaHandler.php

   1 <?php
   2 /**
   3  * Media-handling base classes and generic functionality.
   4  *
   5  * This program is free software; you can redistribute it and/or modify
   6  * it under the terms of the GNU General Public License as published by
   7  * the Free Software Foundation; either version 2 of the License, or
   8  * (at your option) any later version.
   9  *
  10  * This program is distributed in the hope that it will be useful,
  11  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  12  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
  13  * GNU General Public License for more details.
  14  *
  15  * You should have received a copy of the GNU General Public License along
  16  * with this program; if not, write to the Free Software Foundation, Inc.,
  17  * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.
  18  * http://www.gnu.org/copyleft/gpl.html
  19  *
  20  * @file
  21  * @ingroup Media
  22  */
  23
  24 /**
  25  * Base media handler class
  26  *
  27  * @ingroup Media
  28  */
  29 abstract class MediaHandler {
  30         const TRANSFORM_LATER = 1;
  31         const METADATA_GOOD = true;
  32         const METADATA_BAD = false;
  33         const METADATA_COMPATIBLE = 2; // for old but backwards compatible.
  34         /**
  35          * Max length of error logged by logErrorForExternalProcess()
  36          */
  37         const MAX_ERR_LOG_SIZE = 65535;
  38
  39         /** @var MediaHandler[] Instance cache with array of MediaHandler */
  40         protected static $handlers = array();
  41
  42         /**
  43          * Get a MediaHandler for a given MIME type from the instance cache
  44          *
  45          * @param string $type
  46          * @return MediaHandler
  47          */
  48         static function getHandler( $type ) {
  49                 global $wgMediaHandlers;
  50                 if ( !isset( $wgMediaHandlers[$type] ) ) {
  51                         wfDebug( __METHOD__ . ": no handler found for $type.\n" );
  52
  53                         return false;
  54                 }
  55                 $class = $wgMediaHandlers[$type];
  56                 if ( !isset( self::$handlers[$class] ) ) {
  57                         self::$handlers[$class] = new $class;
  58                         if ( !self::$handlers[$class]->isEnabled() ) {
  59                                 self::$handlers[$class] = false;
  60                         }
  61                 }
  62
  63                 return self::$handlers[$class];
  64         }
  65
  66         /**
  67          * Get an associative array mapping magic word IDs to parameter names.
  68          * Will be used by the parser to identify parameters.
  69          */
  70         abstract function getParamMap();
  71
  72         /**
  73          * Validate a thumbnail parameter at parse time.
  74          * Return true to accept the parameter, and false to reject it.
  75          * If you return false, the parser will do something quiet and forgiving.
  76          *
  77          * @param string $name
  78          * @param mixed $value
  79          */
  80         abstract function validateParam( $name, $value );
  81
  82         /**
  83          * Merge a parameter array into a string appropriate for inclusion in filenames
  84          *
  85          * @param array $params Array of parameters that have been through normaliseParams.
  86          * @return string
  87          */
  88         abstract function makeParamString( $params );
  89
  90         /**
  91          * Parse a param string made with makeParamString back into an array
  92          *
  93          * @param string $str The parameter string without file name (e.g. 122px)
  94          * @return array|bool Array of parameters or false on failure.
  95          */
  96         abstract function parseParamString( $str );
  97
  98         /**
  99          * Changes the parameter array as necessary, ready for transformation.
 100          * Should be idempotent.
 101          * Returns false if the parameters are unacceptable and the transform should fail
 102          * @param File $image
 103          * @param array $params
 104          */
 105         abstract function normaliseParams( $image, &$params );
 106
 107         /**
 108          * Get an image size array like that returned by getimagesize(), or false if it
 109          * can't be determined.
 110          *
 111          * @param File $image The image object, or false if there isn't one
 112          * @param string $path the filename
 113          * @return array Follow the format of PHP getimagesize() internal function.
 114          *   See http://www.php.net/getimagesize
 115          */
 116         abstract function getImageSize( $image, $path );
 117
 118         /**
 119          * Get handler-specific metadata which will be saved in the img_metadata field.
 120          *
 121          * @param File $image The image object, or false if there isn't one.
 122          *   Warning, FSFile::getPropsFromPath might pass an (object)array() instead (!)
 123          * @param string $path The filename
 124          * @return string
 125          */
 126         function getMetadata( $image, $path ) {
 127                 return '';
 128         }
 129
 130         /**
 131          * Get metadata version.
 132          *
 133          * This is not used for validating metadata, this is used for the api when returning
 134          * metadata, since api content formats should stay the same over time, and so things
 135          * using ForiegnApiRepo can keep backwards compatibility
 136          *
 137          * All core media handlers share a common version number, and extensions can
 138          * use the GetMetadataVersion hook to append to the array (they should append a unique
 139          * string so not to get confusing). If there was a media handler named 'foo' with metadata
 140          * version 3 it might add to the end of the array the element 'foo=3'. if the core metadata
 141          * version is 2, the end version string would look like '2;foo=3'.
 142          *
 143          * @return string Version string
 144          */
 145         static function getMetadataVersion() {
 146                 $version = array( '2' ); // core metadata version
 147                 wfRunHooks( 'GetMetadataVersion', array( &$version ) );
 148
 149                 return implode( ';', $version );
 150         }
 151
 152         /**
 153          * Convert metadata version.
 154          *
 155          * By default just returns $metadata, but can be used to allow
 156          * media handlers to convert between metadata versions.
 157          *
 158          * @param string|array $metadata Metadata array (serialized if string)
 159          * @param int $version Target version
 160          * @return array Serialized metadata in specified version, or $metadata on fail.
 161          */
 162         function convertMetadataVersion( $metadata, $version = 1 ) {
 163                 if ( !is_array( $metadata ) ) {
 164
 165                         //unserialize to keep return parameter consistent.
 166                         wfSuppressWarnings();
 167                         $ret = unserialize( $metadata );
 168                         wfRestoreWarnings();
 169
 170                         return $ret;
 171                 }
 172
 173                 return $metadata;
 174         }
 175
 176         /**
 177          * Get a string describing the type of metadata, for display purposes.
 178          * @param File $image
 179          * @return string
 180          */
 181         function getMetadataType( $image ) {
 182                 return false;
 183         }
 184
 185         /**
 186          * Check if the metadata string is valid for this handler.
 187          * If it returns MediaHandler::METADATA_BAD (or false), Image
 188          * will reload the metadata from the file and update the database.
 189          * MediaHandler::METADATA_GOOD for if the metadata is a-ok,
 190          * MediaHanlder::METADATA_COMPATIBLE if metadata is old but backwards
 191          * compatible (which may or may not trigger a metadata reload).
 192          * @param File $image
 193          * @param array $metadata
 194          * @return bool
 195          */
 196         function isMetadataValid( $image, $metadata ) {
 197                 return self::METADATA_GOOD;
 198         }
 199
 200         /**
 201          * Get an array of standard (FormatMetadata type) metadata values.
 202          *
 203          * The returned data is largely the same as that from getMetadata(),
 204          * but formatted in a standard, stable, handler-independent way.
 205          * The idea being that some values like ImageDescription or Artist
 206          * are universal and should be retrievable in a handler generic way.
 207          *
 208          * The specific properties are the type of properties that can be
 209          * handled by the FormatMetadata class. These values are exposed to the
 210          * user via the filemetadata parser function.
 211          *
 212          * Details of the response format of this function can be found at
 213          * https://www.mediawiki.org/wiki/Manual:File_metadata_handling
 214          * tl/dr: the response is an associative array of
 215          * properties keyed by name, but the value can be complex. You probably
 216          * want to call one of the FormatMetadata::flatten* functions on the
 217          * property values before using them, or call
 218          * FormatMetadata::getFormattedData() on the full response array, which
 219          * transforms all values into prettified, human-readable text.
 220          *
 221          * Subclasses overriding this function must return a value which is a
 222          * valid API response fragment (all associative array keys are valid
 223          * XML tagnames).
 224          *
 225          * Note, if the file simply has no metadata, but the handler supports
 226          * this interface, it should return an empty array, not false.
 227          *
 228          * @param File $file
 229          * @return array|bool False if interface not supported
 230          * @since 1.23
 231          */
 232         public function getCommonMetaArray( File $file ) {
 233                 return false;
 234         }
 235
 236         /**
 237          * Get a MediaTransformOutput object representing an alternate of the transformed
 238          * output which will call an intermediary thumbnail assist script.
 239          *
 240          * Used when the repository has a thumbnailScriptUrl option configured.
 241          *
 242          * Return false to fall back to the regular getTransform().
 243          * @param File $image
 244          * @param string $script
 245          * @param array $params
 246          * @return bool|ThumbnailImage
 247          */
 248         function getScriptedTransform( $image, $script, $params ) {
 249                 return false;
 250         }
 251
 252         /**
 253          * Get a MediaTransformOutput object representing the transformed output. Does not
 254          * actually do the transform.
 255          *
 256          * @param File $image The image object
 257          * @param string $dstPath Filesystem destination path
 258          * @param string $dstUrl Destination URL to use in output HTML
 259          * @param array $params Arbitrary set of parameters validated by $this->validateParam()
 260          * @return MediaTransformOutput
 261          */
 262         final function getTransform( $image, $dstPath, $dstUrl, $params ) {
 263                 return $this->doTransform( $image, $dstPath, $dstUrl, $params, self::TRANSFORM_LATER );
 264         }
 265
 266         /**
 267          * Get a MediaTransformOutput object representing the transformed output. Does the
 268          * transform unless $flags contains self::TRANSFORM_LATER.
 269          *
 270          * @param File $image The image object
 271          * @param string $dstPath Filesystem destination path
 272          * @param string $dstUrl Destination URL to use in output HTML
 273          * @param array $params Arbitrary set of parameters validated by $this->validateParam()
 274          *   Note: These parameters have *not* gone through $this->normaliseParams()
 275          * @param int $flags A bitfield, may contain self::TRANSFORM_LATER
 276          * @return MediaTransformOutput
 277          */
 278         abstract function doTransform( $image, $dstPath, $dstUrl, $params, $flags = 0 );
 279
 280         /**
 281          * Get the thumbnail extension and MIME type for a given source MIME type
 282          *
 283          * @param string $ext Extension of original file
 284          * @param string $mime MIME type of original file
 285          * @param array $params Handler specific rendering parameters
 286          * @return array thumbnail extension and MIME type
 287          */
 288         function getThumbType( $ext, $mime, $params = null ) {
 289                 $magic = MimeMagic::singleton();
 290                 if ( !$ext || $magic->isMatchingExtension( $ext, $mime ) === false ) {
 291                         // The extension is not valid for this mime type and we do
 292                         // recognize the mime type
 293                         $extensions = $magic->getExtensionsForType( $mime );
 294                         if ( $extensions ) {
 295                                 return array( strtok( $extensions, ' ' ), $mime );
 296                         }
 297                 }
 298
 299                 // The extension is correct (true) or the mime type is unknown to
 300                 // MediaWiki (null)
 301                 return array( $ext, $mime );
 302         }
 303
 304         /**
 305          * Get useful response headers for GET/HEAD requests for a file with the given metadata
 306          *
 307          * @param mixed $metadata Result of the getMetadata() function of this handler for a file
 308          * @return array
 309          */
 310         public function getStreamHeaders( $metadata ) {
 311                 return array();
 312         }
 313
 314         /**
 315          * True if the handled types can be transformed
 316          *
 317          * @param File $file
 318          * @return bool
 319          */
 320         function canRender( $file ) {
 321                 return true;
 322         }
 323
 324         /**
 325          * True if handled types cannot be displayed directly in a browser
 326          * but can be rendered
 327          *
 328          * @param File $file
 329          * @return bool
 330          */
 331         function mustRender( $file ) {
 332                 return false;
 333         }
 334
 335         /**
 336          * True if the type has multi-page capabilities
 337          *
 338          * @param File $file
 339          * @return bool
 340          */
 341         function isMultiPage( $file ) {
 342                 return false;
 343         }
 344
 345         /**
 346          * Page count for a multi-page document, false if unsupported or unknown
 347          *
 348          * @param File $file
 349          * @return bool
 350          */
 351         function pageCount( $file ) {
 352                 return false;
 353         }
 354
 355         /**
 356          * The material is vectorized and thus scaling is lossless
 357          *
 358          * @param File $file
 359          * @return bool
 360          */
 361         function isVectorized( $file ) {
 362                 return false;
 363         }
 364
 365         /**
 366          * The material is an image, and is animated.
 367          * In particular, video material need not return true.
 368          * @note Before 1.20, this was a method of ImageHandler only
 369          *
 370          * @param File $file
 371          * @return bool
 372          */
 373         function isAnimatedImage( $file ) {
 374                 return false;
 375         }
 376
 377         /**
 378          * If the material is animated, we can animate the thumbnail
 379          * @since 1.20
 380          *
 381          * @param File $file
 382          * @return bool If material is not animated, handler may return any value.
 383          */
 384         function canAnimateThumbnail( $file ) {
 385                 return true;
 386         }
 387
 388         /**
 389          * False if the handler is disabled for all files
 390          * @return bool
 391          */
 392         function isEnabled() {
 393                 return true;
 394         }
 395
 396         /**
 397          * Get an associative array of page dimensions
 398          * Currently "width" and "height" are understood, but this might be
 399          * expanded in the future.
 400          * Returns false if unknown.
 401          *
 402          * It is expected that handlers for paged media (e.g. DjVuHandler)
 403          * will override this method so that it gives the correct results
 404          * for each specific page of the file, using the $page argument.
 405          *
 406          * @note For non-paged media, use getImageSize.
 407          *
 408          * @param File $image
 409          * @param int $page What page to get dimensions of
 410          * @return array|bool
 411          */
 412         function getPageDimensions( $image, $page ) {
 413                 $gis = $this->getImageSize( $image, $image->getLocalRefPath() );
 414                 if ( $gis ) {
 415                         return array(
 416                                 'width' => $gis[0],
 417                                 'height' => $gis[1]
 418                         );
 419                 } else {
 420                         return false;
 421                 }
 422         }
 423
 424         /**
 425          * Generic getter for text layer.
 426          * Currently overloaded by PDF and DjVu handlers
 427          * @param File $image
 428          * @param int $page Page number to get information for
 429          * @return bool|string Page text or false when no text found.
 430          */
 431         function getPageText( $image, $page ) {
 432                 return false;
 433         }
 434
 435         /**
 436          * Get an array structure that looks like this:
 437          *
 438          * array(
 439          *    'visible' => array(
 440          *       'Human-readable name' => 'Human readable value',
 441          *       ...
 442          *    ),
 443          *    'collapsed' => array(
 444          *       'Human-readable name' => 'Human readable value',
 445          *       ...
 446          *    )
 447          * )
 448          * The UI will format this into a table where the visible fields are always
 449          * visible, and the collapsed fields are optionally visible.
 450          *
 451          * The function should return false if there is no metadata to display.
 452          */
 453
 454         /**
 455          * @todo FIXME: This interface is not very flexible. The media handler
 456          * should generate HTML instead. It can do all the formatting according
 457          * to some standard. That makes it possible to do things like visual
 458          * indication of grouped and chained streams in ogg container files.
 459          * @param File $image
 460          * @return array|bool
 461          */
 462         function formatMetadata( $image ) {
 463                 return false;
 464         }
 465
 466         /** sorts the visible/invisible field.
 467          * Split off from ImageHandler::formatMetadata, as used by more than
 468          * one type of handler.
 469          *
 470          * This is used by the media handlers that use the FormatMetadata class
 471          *
 472          * @param array $metadataArray Metadata array
 473          * @return array for use displaying metadata.
 474          */
 475         function formatMetadataHelper( $metadataArray ) {
 476                 $result = array(
 477                         'visible' => array(),
 478                         'collapsed' => array()
 479                 );
 480
 481                 $formatted = FormatMetadata::getFormattedData( $metadataArray );
 482                 // Sort fields into visible and collapsed
 483                 $visibleFields = $this->visibleMetadataFields();
 484                 foreach ( $formatted as $name => $value ) {
 485                         $tag = strtolower( $name );
 486                         self::addMeta( $result,
 487                                 in_array( $tag, $visibleFields ) ? 'visible' : 'collapsed',
 488                                 'exif',
 489                                 $tag,
 490                                 $value
 491                         );
 492                 }
 493
 494                 return $result;
 495         }
 496
 497         /**
 498          * Get a list of metadata items which should be displayed when
 499          * the metadata table is collapsed.
 500          *
 501          * @return array of strings
 502          */
 503         function visibleMetadataFields() {
 504                 return FormatMetadata::getVisibleFields();
 505         }
 506
 507         /**
 508          * This is used to generate an array element for each metadata value
 509          * That array is then used to generate the table of metadata values
 510          * on the image page
 511          *
 512          * @param array &$array An array containing elements for each type of visibility
 513          *   and each of those elements being an array of metadata items. This function adds
 514          *   a value to that array.
 515          * @param string $visibility ('visible' or 'collapsed') if this value is hidden
 516          *   by default.
 517          * @param string $type Type of metadata tag (currently always 'exif')
 518          * @param string $id The name of the metadata tag (like 'artist' for example).
 519          *   its name in the table displayed is the message "$type-$id" (Ex exif-artist ).
 520          * @param string $value Thingy goes into a wikitext table; it used to be escaped but
 521          *   that was incompatible with previous practise of customized display
 522          *   with wikitext formatting via messages such as 'exif-model-value'.
 523          *   So the escaping is taken back out, but generally this seems a confusing
 524          *   interface.
 525          * @param bool|string $param Value to pass to the message for the name of the field
 526          *   as $1. Currently this parameter doesn't seem to ever be used.
 527          *
 528          * Note, everything here is passed through the parser later on (!)
 529          */
 530         protected static function addMeta( &$array, $visibility, $type, $id, $value, $param = false ) {
 531                 $msg = wfMessage( "$type-$id", $param );
 532                 if ( $msg->exists() ) {
 533                         $name = $msg->text();
 534                 } else {
 535                         // This is for future compatibility when using instant commons.
 536                         // So as to not display as ugly a name if a new metadata
 537                         // property is defined that we don't know about
 538                         // (not a major issue since such a property would be collapsed
 539                         // by default).
 540                         wfDebug( __METHOD__ . ' Unknown metadata name: ' . $id . "\n" );
 541                         $name = wfEscapeWikiText( $id );
 542                 }
 543                 $array[$visibility][] = array(
 544                         'id' => "$type-$id",
 545                         'name' => $name,
 546                         'value' => $value
 547                 );
 548         }
 549
 550         /**
 551          * Used instead of getLongDesc if there is no handler registered for file.
 552          *
 553          * @param File $file
 554          * @return string
 555          */
 556         function getShortDesc( $file ) {
 557                 global $wgLang;
 558
 559                 return htmlspecialchars( $wgLang->formatSize( $file->getSize() ) );
 560         }
 561
 562         /**
 563          * Short description. Shown on Special:Search results.
 564          *
 565          * @param File $file
 566          * @return string
 567          */
 568         function getLongDesc( $file ) {
 569                 global $wgLang;
 570
 571                 return wfMessage( 'file-info', htmlspecialchars( $wgLang->formatSize( $file->getSize() ) ),
 572                         $file->getMimeType() )->parse();
 573         }
 574
 575         /**
 576          * Long description. Shown under image on image description page surounded by ().
 577          *
 578          * @param File $file
 579          * @return string
 580          */
 581         static function getGeneralShortDesc( $file ) {
 582                 global $wgLang;
 583
 584                 return $wgLang->formatSize( $file->getSize() );
 585         }
 586
 587         /**
 588          * Used instead of getShortDesc if there is no handler registered for file.
 589          *
 590          * @param File $file
 591          * @return string
 592          */
 593         static function getGeneralLongDesc( $file ) {
 594                 global $wgLang;
 595
 596                 return wfMessage( 'file-info', $wgLang->formatSize( $file->getSize() ),
 597                         $file->getMimeType() )->parse();
 598         }
 599
 600         /**
 601          * Calculate the largest thumbnail width for a given original file size
 602          * such that the thumbnail's height is at most $maxHeight.
 603          * @param int $boxWidth Width of the thumbnail box.
 604          * @param int $boxHeight Height of the thumbnail box.
 605          * @param int $maxHeight Maximum height expected for the thumbnail.
 606          * @return int
 607          */
 608         public static function fitBoxWidth( $boxWidth, $boxHeight, $maxHeight ) {
 609                 $idealWidth = $boxWidth * $maxHeight / $boxHeight;
 610                 $roundedUp = ceil( $idealWidth );
 611                 if ( round( $roundedUp * $boxHeight / $boxWidth ) > $maxHeight ) {
 612                         return floor( $idealWidth );
 613                 } else {
 614                         return $roundedUp;
 615                 }
 616         }
 617
 618         /**
 619          * Shown in file history box on image description page.
 620          *
 621          * @param File $file
 622          * @return String Dimensions
 623          */
 624         function getDimensionsString( $file ) {
 625                 return '';
 626         }
 627
 628         /**
 629          * Modify the parser object post-transform.
 630          *
 631          * This is often used to do $parser->addOutputHook(),
 632          * in order to add some javascript to render a viewer.
 633          * See TimedMediaHandler or OggHandler for an example.
 634          *
 635          * @param Parser $parser
 636          * @param File $file
 637          */
 638         function parserTransformHook( $parser, $file ) {
 639         }
 640
 641         /**
 642          * File validation hook called on upload.
 643          *
 644          * If the file at the given local path is not valid, or its MIME type does not
 645          * match the handler class, a Status object should be returned containing
 646          * relevant errors.
 647          *
 648          * @param string $fileName The local path to the file.
 649          * @return Status object
 650          */
 651         function verifyUpload( $fileName ) {
 652                 return Status::newGood();
 653         }
 654
 655         /**
 656          * Check for zero-sized thumbnails. These can be generated when
 657          * no disk space is available or some other error occurs
 658          *
 659          * @param string $dstPath The location of the suspect file
 660          * @param int $retval Return value of some shell process, file will be deleted if this is non-zero
 661          * @return bool True if removed, false otherwise
 662          */
 663         function removeBadFile( $dstPath, $retval = 0 ) {
 664                 if ( file_exists( $dstPath ) ) {
 665                         $thumbstat = stat( $dstPath );
 666                         if ( $thumbstat['size'] == 0 || $retval != 0 ) {
 667                                 $result = unlink( $dstPath );
 668
 669                                 if ( $result ) {
 670                                         wfDebugLog( 'thumbnail',
 671                                                 sprintf( 'Removing bad %d-byte thumbnail "%s". unlink() succeeded',
 672                                                         $thumbstat['size'], $dstPath ) );
 673                                 } else {
 674                                         wfDebugLog( 'thumbnail',
 675                                                 sprintf( 'Removing bad %d-byte thumbnail "%s". unlink() failed',
 676                                                         $thumbstat['size'], $dstPath ) );
 677                                 }
 678
 679                                 return true;
 680                         }
 681                 }
 682
 683                 return false;
 684         }
 685
 686         /**
 687          * Remove files from the purge list.
 688          *
 689          * This is used by some video handlers to prevent ?action=purge
 690          * from removing a transcoded video, which is expensive to
 691          * regenerate.
 692          *
 693          * @see LocalFile::purgeThumbnails
 694          *
 695          * @param array $files
 696          * @param array $options Purge options. Currently will always be
 697          *  an array with a single key 'forThumbRefresh' set to true.
 698          */
 699         public function filterThumbnailPurgeList( &$files, $options ) {
 700                 // Do nothing
 701         }
 702
 703         /*
 704          * True if the handler can rotate the media
 705          * @since 1.21
 706          * @return bool
 707          */
 708         public static function canRotate() {
 709                 return false;
 710         }
 711
 712         /**
 713          * On supporting image formats, try to read out the low-level orientation
 714          * of the file and return the angle that the file needs to be rotated to
 715          * be viewed.
 716          *
 717          * This information is only useful when manipulating the original file;
 718          * the width and height we normally work with is logical, and will match
 719          * any produced output views.
 720          *
 721          * For files we don't know, we return 0.
 722          *
 723          * @param File $file
 724          * @return int 0, 90, 180 or 270
 725          */
 726         public function getRotation( $file ) {
 727                 return 0;
 728         }
 729
 730         /**
 731          * Log an error that occurred in an external process
 732          *
 733          * Moved from BitmapHandler to MediaHandler with MediaWiki 1.23
 734          *
 735          * @since 1.23
 736          * @param int $retval
 737          * @param string $err Error reported by command. Anything longer than
 738          * MediaHandler::MAX_ERR_LOG_SIZE is stripped off.
 739          * @param string $cmd
 740          */
 741         protected function logErrorForExternalProcess( $retval, $err, $cmd ) {
 742                 # Keep error output limited (bug 57985)
 743                 $errMessage = trim( substr( $err, 0, self::MAX_ERR_LOG_SIZE ) );
 744
 745                 wfDebugLog( 'thumbnail',
 746                         sprintf( 'thumbnail failed on %s: error %d "%s" from "%s"',
 747                                         wfHostname(), $retval, $errMessage, $cmd ) );
 748         }
 749
 750         /**
 751          * Get list of languages file can be viewed in.
 752          *
 753          * @param File $file
 754          * @return Array Array of language codes, or empty array if unsupported.
 755          * @since 1.23
 756          */
 757         public function getAvailableLanguages( File $file ) {
 758                 return array();
 759         }
 760
 761         /**
 762          * On file types that support renderings in multiple languages,
 763          * which language is used by default if unspecified.
 764          *
 765          * If getAvailableLanguages returns a non-empty array, this must return
 766          * a valid language code. Otherwise can return null if files of this
 767          * type do not support alternative language renderings.
 768          *
 769          * @param File $file
 770          * @return String language code or null if multi-language not supported for filetype.
 771          * @since 1.23
 772          */
 773         public function getDefaultRenderLanguage( File $file ) {
 774                 return null;
 775         }
 776 }