+
+ /**
+ * Add Link headers for preloading the wiki's logo.
+ *
+ * @since 1.26
+ */
+ protected function addLogoPreloadLinkHeaders() {
+ $logo = $this->getConfig()->get( 'Logo' ); // wgLogo
+ $logoHD = $this->getConfig()->get( 'LogoHD' ); // wgLogoHD
+
+ $tags = [];
+ $logosPerDppx = [];
+ $logos = [];
+
+ $logosPerDppx['1.0'] = $logo;
+
+ if ( !$logoHD ) {
+ // No media queries required if we only have one variant
+ $this->addLinkHeader( '<' . $logo . '>;rel=preload;as=image' );
+ return;
+ }
+
+ foreach ( $logoHD as $dppx => $src ) {
+ // Only 1.5x and 2x are supported
+ // Note: Keep in sync with ResourceLoaderSkinModule
+ if ( in_array( $dppx, [ '1.5x', '2x' ] ) ) {
+ // LogoHD uses a string in this format: "1.5x"
+ $dppx = substr( $dppx, 0, -1 );
+ $logosPerDppx[$dppx] = $src;
+ }
+ }
+
+ // Because PHP can't have floats as array keys
+ uksort( $logosPerDppx, function ( $a , $b ) {
+ $a = floatval( $a );
+ $b = floatval( $b );
+
+ if ( $a == $b ) {
+ return 0;
+ }
+ // Sort from smallest to largest (e.g. 1x, 1.5x, 2x)
+ return ( $a < $b ) ? -1 : 1;
+ } );
+
+ foreach ( $logosPerDppx as $dppx => $src ) {
+ $logos[] = [ 'dppx' => $dppx, 'src' => $src ];
+ }
+
+ $logosCount = count( $logos );
+ // Logic must match ResourceLoaderSkinModule:
+ // - 1x applies to resolution < 1.5dppx
+ // - 1.5x applies to resolution >= 1.5dppx && < 2dppx
+ // - 2x applies to resolution >= 2dppx
+ // Note that min-resolution and max-resolution are both inclusive.
+ for ( $i = 0; $i < $logosCount; $i++ ) {
+ if ( $i === 0 ) {
+ // Smallest dppx
+ // min-resolution is ">=" (larger than or equal to)
+ // "not min-resolution" is essentially "<"
+ $media_query = 'not all and (min-resolution: ' . $logos[ 1 ]['dppx'] . 'dppx)';
+ } elseif ( $i !== $logosCount - 1 ) {
+ // In between
+ // Media query expressions can only apply "not" to the entire expression
+ // (e.g. can't express ">= 1.5 and not >= 2).
+ // Workaround: Use <= 1.9999 in place of < 2.
+ $upper_bound = floatval( $logos[ $i + 1 ]['dppx'] ) - 0.000001;
+ $media_query = '(min-resolution: ' . $logos[ $i ]['dppx'] .
+ 'dppx) and (max-resolution: ' . $upper_bound . 'dppx)';
+ } else {
+ // Largest dppx
+ $media_query = '(min-resolution: ' . $logos[ $i ]['dppx'] . 'dppx)';
+ }
+
+ $this->addLinkHeader(
+ '<' . $logos[$i]['src'] . '>;rel=preload;as=image;media=' . $media_query
+ );
+ }
+ }