jquery.byteLimit: Handle characters outside BMP (surrogate pairs) when trimming

[lhc/web/wiklou.git] / resources / src / jquery / jquery.byteLimit.js

diff --git a/resources/src/jquery/jquery.byteLimit.js b/resources/src/jquery/jquery.byteLimit.js
index c75246c..3ce6e7f 100644 (file)
--- a/resources/src/jquery/jquery.byteLimit.js
+++ b/resources/src/jquery/jquery.byteLimit.js
@@ -14,6 +14,20 @@
                'blur.byteLimit'
        ].join( ' ' );
 
+       // Like String#charAt, but return the pair of UTF-16 surrogates for characters outside of BMP.
+       function codePointAt( string, offset, backwards ) {
+               // We don't need to check for offsets at the beginning or end of string,
+               // String#slice will simply return a shorter (or empty) substring.
+               var maybePair = backwards ?
+                       string.slice( offset - 1, offset + 1 ) :
+                       string.slice( offset, offset + 2 );
+               if ( /^[\uD800-\uDBFF][\uDC00-\uDFFF]$/.test( maybePair ) ) {
+                       return maybePair;
+               } else {
+                       return string.charAt( offset );
+               }
+       }
+
        /**
         * Utility function to trim down a string, based on byteLimit
         * and given a safe start position. It supports insertion anywhere
@@ -32,7 +46,7 @@
         * @return {boolean} return.trimmed
         */
        $.trimByteLength = function ( safeVal, newVal, byteLimit, fn ) {
-               var startMatches, endMatches, matchesLen, inpParts,
+               var startMatches, endMatches, matchesLen, inpParts, chopOff, oldChar, newChar,
                        oldVal = safeVal;
 
                // Run the hook if one was provided, but only on the length
@@ -61,18 +75,22 @@
 
                // Count same characters from the left, first.
                // (if "foo" -> "foofoo", assume addition was at the end).
-               while (
-                       startMatches < matchesLen &&
-                       oldVal.charAt( startMatches ) === newVal.charAt( startMatches )
-               ) {
-                       startMatches += 1;
+               while ( startMatches < matchesLen ) {
+                       oldChar = codePointAt( oldVal, startMatches, false );
+                       newChar = codePointAt( newVal, startMatches, false );
+                       if ( oldChar !== newChar ) {
+                               break;
+                       }
+                       startMatches += oldChar.length;
                }
 
-               while (
-                       endMatches < ( matchesLen - startMatches ) &&
-                       oldVal.charAt( oldVal.length - 1 - endMatches ) === newVal.charAt( newVal.length - 1 - endMatches )
-               ) {
-                       endMatches += 1;
+               while ( endMatches < ( matchesLen - startMatches ) ) {
+                       oldChar = codePointAt( oldVal, oldVal.length - 1 - endMatches, true );
+                       newChar = codePointAt( newVal, newVal.length - 1 - endMatches, true );
+                       if ( oldChar !== newChar ) {
+                               break;
+                       }
+                       endMatches += oldChar.length;
                }
 
                inpParts = [
@@ -89,11 +107,15 @@
                if ( fn ) {
                        // stop, when there is nothing to slice - T43450
                        while ( $.byteLength( fn( inpParts.join( '' ) ) ) > byteLimit && inpParts[ 1 ].length > 0 ) {
-                               inpParts[ 1 ] = inpParts[ 1 ].slice( 0, -1 );
+                               // Do not chop off halves of surrogate pairs
+                               chopOff = /[\uD800-\uDBFF][\uDC00-\uDFFF]$/.test( inpParts[ 1 ] ) ? 2 : 1;
+                               inpParts[ 1 ] = inpParts[ 1 ].slice( 0, -chopOff );
                        }
                } else {
                        while ( $.byteLength( inpParts.join( '' ) ) > byteLimit ) {
-                               inpParts[ 1 ] = inpParts[ 1 ].slice( 0, -1 );
+                               // Do not chop off halves of surrogate pairs
+                               chopOff = /[\uD800-\uDBFF][\uDC00-\uDFFF]$/.test( inpParts[ 1 ] ) ? 2 : 1;
+                               inpParts[ 1 ] = inpParts[ 1 ].slice( 0, -chopOff );
                        }
                }