Workaround to circumvent TYPO3 disturbing caching

 - Clear the stored page cache (for presentations viewer only!) on calling

UB-Mannheim/kitodo-presentation-docker#18
Signed-off-by: Christos Sidiropoulos <csidirop@runbox.com>

Classes/Plugin/PageView.php

@@ -397,6 +397,19 @@ protected function parseOCRengines(string $ocrEnginesPath):void{
         setcookie('tx-dlf-ocrEngines', self::$ocrEngines, ['SameSite' => 'lax']);
     }
 
+    /**
+     * This function is a workaround to circumvent TYPO3 disturbing caching.
+     * It clears the stored page cache (for presentations viewer only!) on calling.
+     * 
+     * @access protected
+     * 
+     * @return void
+     */
+    protected function clearPageCache():void{
+        $objectManager = GeneralUtility::makeInstance(\TYPO3\CMS\Extbase\Object\ObjectManager::class);
+        $objectManager->get(\TYPO3\CMS\Extbase\Service\CacheService::class)->clearPageCache($GLOBALS['TSFE']->id);
+    }
+
     /**
      * The main method of the PlugIn
      *
@@ -412,6 +425,7 @@ public function main($content, $conf)
         $this->init($conf);
         $this->loadDocument(); // Load current document
         $this->parseOCRengines(GeneralUtility::makeInstance(ExtensionConfiguration::class)->get('dlf')['ocrEngines']);
+        $this->clearPageCache();
         //Proccess request: Do OCR on given image(s):
         if ($_POST["request"]) {
             $this->generateFullText();