Default to drupal root and allow for base_url overrides.

Closes #2865185

src/Plugin/EntityPrint/PrintEngine/DomPdf.php

@@ -88,6 +88,7 @@ class DomPdf extends PdfEngineBase implements ContainerFactoryPluginInterface {
     $this->dompdfOptions->setFontDir($temp_dir);
     $this->dompdfOptions->setLogOutputFile($temp_dir . DIRECTORY_SEPARATOR . self::LOG_FILE_NAME);
     $this->dompdfOptions->setIsRemoteEnabled($this->configuration['enable_remote']);
+    $this->dompdfOptions->setChroot([\Drupal::getContainer()->getParameter('app.root')]);
     $this->dompdfOptions->setIsFontSubsettingEnabled($this->configuration['font_subsetting']);
     $this->dompdfOptions->setIsPhpEnabled($this->configuration['embedded_php']);
     $this->dompdfOptions->setDpi($this->configuration['dpi']);
@@ -100,6 +101,32 @@ class DomPdf extends PdfEngineBase implements ContainerFactoryPluginInterface {
     $this->dompdf
       ->setBaseHost($request->getHttpHost())
       ->setProtocol($request->getScheme() . '://');
+
+    // Take the base url setting into account.
+    if (!empty($this->configuration['base_url'])) {
+      $base_url = parse_url($this->configuration['base_url']);
+      if (!empty($base_url['scheme'])) {
+        $this->dompdf->setProtocol($base_url['scheme'] . '://');
+        if (!empty($base_url['host'])) {
+          $host = $base_url['host'];
+          if (!empty($base_url['port'])) {
+            $host .= ':' . $base_url['port'];
+          }
+          $this->dompdf->setBaseHost($host);
+          if (!empty($base_url['path'])) {
+            $this->dompdf->setBasePath($base_url['path']);
+          }
+        }
+        else {
+          // Assuming file protocol.
+          $this->dompdf->setBaseHost($base_url['path']);
+          // We need to make sure domPdf allows access to our file path.
+          $this->dompdfOptions->setChroot($base_url['path']);
+        }
+      }
+    }
+
+    $this->setupHttpContext();
   }
 
   /**