resourceloader: Omit parameter 'lang' from image URLs when not vary

The parameter 'lang' is only added to the URL when the image vary on the
language or on the direction.

Also omit the parameter 'lang' when the value is equal to
ResourceLoaderContext::DEFAULT_LANG.

This change makes the URLs shorter and reduces the size of the
stylesheets.

This change also improves caching because the URLs do not vary on the
language for the same image.

Change-Id: Id7d8ecc7d95747f3c157f9abc12e8489e5085aff

diff --git a/includes/resourceloader/ResourceLoaderImage.php b/includes/resourceloader/ResourceLoaderImage.php
index c1b3dc3..7829b71 100644 (file)
--- a/includes/resourceloader/ResourceLoaderImage.php
+++ b/includes/resourceloader/ResourceLoaderImage.php
@@ -214,10 +214,13 @@ class ResourceLoaderImage {
                        'image' => $this->getName(),
                        'variant' => $variant,
                        'format' => $format,
-                       'lang' => $context->getLanguage(),
-                       'skin' => $context->getSkin(),
-                       'version' => $context->getVersion(),
                ];
+               if ( $this->varyOnLanguage() ) {
+                       $query['lang'] = $context->getLanguage();
+               }
+               // The following parameters are at the end to keep the original order of the parameters.
+               $query['skin'] = $context->getSkin();
+               $query['version'] = $context->getVersion();
 
                return wfAppendQuery( $script, $query );
        }
@@ -446,4 +449,16 @@ class ResourceLoaderImage {
                        return $png ?: false;
                }
        }
+
+       /**
+        * Check if the image depends on the language.
+        *
+        * @return bool
+        */
+       private function varyOnLanguage() {
+               return is_array( $this->descriptor ) && (
+                       isset( $this->descriptor['ltr'] ) ||
+                       isset( $this->descriptor['rtl'] ) ||
+                       isset( $this->descriptor['lang'] ) );
+       }
 }