com.google.gwt.i18n.shared.BidiFormatter Maven / Gradle / Ivy
/*
* Copyright 2010 Google Inc.
*
* Licensed under the Apache License, Version 2.0 (the "License"); you may not
* use this file except in compliance with the License. You may obtain a copy of
* the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
* WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
* License for the specific language governing permissions and limitations under
* the License.
*/
package com.google.gwt.i18n.shared;
import com.google.gwt.i18n.client.HasDirection.Direction;
import com.google.gwt.i18n.client.LocaleInfo;
/**
* Utility class for formatting text for display in a potentially
* opposite-direction context without garbling. The direction of the context is
* set at formatter creation and the direction of the text can be either
* estimated or passed in when known. Provides the following functionality:
*
* 1. BiDi Wrapping: When text in one language is mixed into a document in
* another, opposite-direction language, e.g. when an English business name is
* embedded in a Hebrew web page, both the inserted string and the text
* following it may be displayed incorrectly unless the inserted string is
* explicitly separated from the surrounding text in a "wrapper" that declares
* its direction at the start and then resets it back at the end. This wrapping
* can be done in HTML mark-up (e.g. a 'span dir=rtl' tag) or - only in contexts
* where mark-up cannot be used - in Unicode BiDi formatting codes (LRE|RLE and
* PDF). Optionally, the mark-up can be inserted even when the direction is the
* same, in order to keep the DOM structure more stable. Providing such wrapping
* services is the basic purpose of the BiDi formatter.
*
* 2. Direction estimation: How does one know whether a string about to be
* inserted into surrounding text has the same direction? Well, in many cases,
* one knows that this must be the case when writing the code doing the
* insertion, e.g. when a localized message is inserted into a localized page.
* In such cases there is no need to involve the BiDi formatter at all. In some
* other cases, it need not be the same as the context, but is either constant
* (e.g. urls are always LTR) or otherwise known. In the remaining cases, e.g.
* when the string is user-entered or comes from a database, the language of the
* string (and thus its direction) is not known a priori, and must be estimated
* at run-time. The BiDi formatter can do this automatically.
*
* 3. Escaping: When wrapping plain text - i.e. text that is not already HTML or
* HTML-escaped - in HTML mark-up, the text must first be HTML-escaped to
* prevent XSS attacks and other nasty business. This of course is always true,
* but the escaping can not be done after the string has already been wrapped in
* mark-up, so the BiDi formatter also serves as a last chance and includes
* escaping services.
*
* Thus, in a single call, the formatter will escape the input string as
* specified, determine its direction, and wrap it as necessary. It is then up
* to the caller to insert the return value in the output.
*
*/
public class BidiFormatter {
/**
* A container class for direction-related string constants, e.g. Unicode
* formatting characters.
*/
static final class Format {
/**
* "left" string constant.
*/
public static final String LEFT = "left";
/**
* Unicode "Left-To-Right Embedding" (LRE) character.
*/
public static final char LRE = '\u202A';
/**
* Unicode "Left-To-Right Mark" (LRM) character.
*/
public static final char LRM = '\u200E';
/**
* String representation of LRM.
*/
public static final String LRM_STRING = Character.toString(LRM);
/**
* Unicode "Pop Directional Formatting" (PDF) character.
*/
public static final char PDF = '\u202C';
/**
* "right" string constant.
*/
public static final String RIGHT = "right";
/**
* Unicode "Right-To-Left Embedding" (RLE) character.
*/
public static final char RLE = '\u202B';
/**
* Unicode "Right-To-Left Mark" (RLM) character.
*/
public static final char RLM = '\u200F';
/**
* String representation of RLM.
*/
public static final String RLM_STRING = Character.toString(RLM);
// Not instantiable.
private Format() {
}
}
/**
* Factory for creating an instance of BidiFormatter given the context
* direction. The default behavior of {@link #spanWrap} and its variations is
* set to avoid span wrapping unless it's necessary ('dir' attribute needs to
* be set).
*
* @param rtlContext Whether the context direction is RTL.
* In one simple use case, the context direction would simply be the
* locale direction, which can be retrieved using
* {@code LocaleInfo.getCurrentLocale().isRTL()}
*/
public static BidiFormatter getInstance(boolean rtlContext) {
return getInstance(rtlContext, false);
}
/**
* Factory for creating an instance of BidiFormatter given the context
* direction and the desired span wrapping behavior (see below).
*
* @param rtlContext Whether the context direction is RTL. See an example of
* a simple use case at {@link #getInstance(boolean)}
* @param alwaysSpan Whether {@link #spanWrap} (and its variations) should
* always use a 'span' tag, even when the input direction is neutral
* or matches the context, so that the DOM structure of the output
* does not depend on the combination of directions
*/
public static BidiFormatter getInstance(boolean rtlContext,
boolean alwaysSpan) {
return new BidiFormatter(rtlContext ? Direction.RTL : Direction.LTR,
alwaysSpan);
}
/**
* Factory for creating an instance of BidiFormatter given the context
* direction. The default behavior of {@link #spanWrap} and its variations is
* set to avoid span wrapping unless it's necessary ('dir' attribute needs to
* be set).
*
* @param contextDir The context direction. See an example of a simple use
* case at {@link #getInstance(boolean)}. Note: Direction.DEFAULT
* indicates unknown context direction. Try not to use it, since it
* is impossible to reset the direction back to the context when it
* is unknown
*/
public static BidiFormatter getInstance(Direction contextDir) {
return getInstance(contextDir, false);
}
/**
* Factory for creating an instance of BidiFormatter given the context
* direction and the desired span wrapping behavior (see below).
*
* @param contextDir The context direction. See an example of a simple use
* case at {@link #getInstance(boolean)}. Note: Direction.DEFAULT
* indicates unknown context direction. Try not to use it, since it
* is impossible to reset the direction back to the context when it
* is unknown
* @param alwaysSpan Whether {@link #spanWrap} (and its variations) should
* always use a 'span' tag, even when the input direction is neutral
* or matches the context, so that the DOM structure of the output
* does not depend on the combination of directions
*/
public static BidiFormatter getInstance(Direction contextDir,
boolean alwaysSpan) {
return new BidiFormatter(contextDir, alwaysSpan);
}
/**
* Factory for creating an instance of BidiFormatter whose context direction
* matches the current locale's direction. The default behavior of {@link
* #spanWrap} and its variations is set to avoid span wrapping unless it's
* necessary ('dir' attribute needs to be set).
*/
public static BidiFormatter getInstanceForCurrentLocale() {
return getInstanceForCurrentLocale(false);
}
/**
* Factory for creating an instance of BidiFormatter whose context direction
* matches the current locale's direction, and given the desired span wrapping
* behavior (see below).
*
* @param alwaysSpan Whether {@link #spanWrap} (and its variations) should
* always use a 'span' tag, even when the input direction is neutral
* or matches the context, so that the DOM structure of the output
* does not depend on the combination of directions
*/
public static BidiFormatter getInstanceForCurrentLocale(boolean alwaysSpan) {
return getInstance(LocaleInfo.getCurrentLocale().isRTL(), alwaysSpan);
}
private boolean alwaysSpan;
private Direction contextDir;
/**
* @param contextDir The context direction
* @param alwaysSpan Whether {@link #spanWrap} (and its variations) should
* always use a 'span' tag, even when the input direction is neutral
* or matches the context, so that the DOM structure of the output
* does not depend on the combination of directions
*/
private BidiFormatter(Direction contextDir, boolean alwaysSpan) {
this.contextDir = contextDir;
this.alwaysSpan = alwaysSpan;
}
/**
* Like {@link #dirAttr(String, boolean)}, but assumes {@code isHtml} is
* false.
*
* @param str String whose direction is to be estimated
* @return "dir=rtl" for RTL text in non-RTL context; "dir=ltr" for LTR text
* in non-LTR context; else, the empty string.
*/
public String dirAttr(String str) {
return dirAttr(str, false);
}
/**
* Returns "dir=ltr" or "dir=rtl", depending on {@code str}'s estimated
* direction, if it is not the same as the context direction. Otherwise,
* returns the empty string.
*
* @param str String whose direction is to be estimated
* @param isHtml Whether {@code str} is HTML / HTML-escaped
* @return "dir=rtl" for RTL text in non-RTL context; "dir=ltr" for LTR text
* in non-LTR context; else, the empty string.
*/
public String dirAttr(String str, boolean isHtml) {
return knownDirAttr(BidiUtils.get().estimateDirection(str, isHtml));
}
/**
* Returns "left" for RTL context direction. Otherwise (LTR or default /
* unknown context direction) returns "right".
*/
public String endEdge() {
return contextDir == Direction.RTL ? Format.LEFT : Format.RIGHT;
}
/**
* Like {@link #estimateDirection(String, boolean)}, but assumes {@code
* isHtml} is false.
*
* @param str String whose direction is to be estimated
* @return {@code str}'s estimated overall direction
*/
public Direction estimateDirection(String str) {
return BidiUtils.get().estimateDirection(str);
}
/**
* Estimates the direction of a string using the best known general-purpose
* method, i.e. using relative word counts. Direction.DEFAULT return value
* indicates completely neutral input.
*
* @param str String whose direction is to be estimated
* @param isHtml Whether {@code str} is HTML / HTML-escaped
* @return {@code str}'s estimated overall direction
*/
public Direction estimateDirection(String str, boolean isHtml) {
return BidiUtils.get().estimateDirection(str, isHtml);
}
/**
* Returns whether the span structure added by the formatter should be stable,
* i.e., spans added even when the direction does not need to be declared.
*/
public boolean getAlwaysSpan() {
return alwaysSpan;
}
/**
* Returns the context direction.
*/
public Direction getContextDir() {
return contextDir;
}
/**
* Returns whether the context direction is RTL.
*/
public boolean isRtlContext() {
return contextDir == Direction.RTL;
}
/**
* Returns "dir=ltr" or "dir=rtl", depending on the given direction, if it is
* not the same as the context direction. Otherwise, returns the empty string.
*
* @param dir Given direction
* @return "dir=rtl" for RTL text in non-RTL context; "dir=ltr" for LTR text
* in non-LTR context; else, the empty string.
*/
public String knownDirAttr(Direction dir) {
if (dir != contextDir) {
return dir == Direction.LTR ? "dir=ltr" : dir == Direction.RTL
? "dir=rtl" : "";
}
return "";
}
/**
* Returns the Unicode BiDi mark matching the context direction (LRM for LTR
* context direction, RLM for RTL context direction), or the empty string for
* default / unknown context direction.
*/
public String mark() {
return contextDir == Direction.LTR ? Format.LRM_STRING
: contextDir == Direction.RTL ? Format.RLM_STRING : "";
}
/**
* Like {@link #markAfter(String, boolean)}, but assumes {@code isHtml} is
* false.
*
* @param str String after which the mark may need to appear
* @return LRM for RTL text in LTR context; RLM for LTR text in RTL context;
* else, the empty string.
*/
public String markAfter(String str) {
return markAfter(str, false);
}
/**
* Returns a Unicode BiDi mark matching the context direction (LRM or RLM) if
* either the direction or the exit direction of {@code str} is opposite to
* the context direction. Otherwise returns the empty string.
*
* @param str String after which the mark may need to appear
* @param isHtml Whether {@code str} is HTML / HTML-escaped
* @return LRM for RTL text in LTR context; RLM for LTR text in RTL context;
* else, the empty string.
*/
public String markAfter(String str, boolean isHtml) {
str = BidiUtils.get().stripHtmlIfNeeded(str, isHtml);
return dirResetIfNeeded(str, BidiUtils.get().estimateDirection(str), false,
true);
}
/**
* Like {@link #spanWrap(String, boolean, boolean)}, but assumes {@code
* isHtml} is false and {@code dirReset} is true.
*
* @param str The input string
* @return Input string after applying the above processing.
*/
public String spanWrap(String str) {
return spanWrap(str, false, true);
}
/**
* Like {@link #spanWrap(String, boolean, boolean)}, but assumes {@code
* dirReset} is true.
*
* @param str The input string
* @param isHtml Whether {@code str} is HTML / HTML-escaped
* @return Input string after applying the above processing.
*/
public String spanWrap(String str, boolean isHtml) {
return spanWrap(str, isHtml, true);
}
/**
* Formats a string of unknown direction for use in HTML output of the context
* direction, so an opposite-direction string is neither garbled nor garbles
* what follows it.
*
* The algorithm: estimates the direction of input argument {@code str}. In
* case its direction doesn't match the context direction, wraps it with a
* 'span' tag and adds a "dir" attribute (either 'dir=rtl' or 'dir=ltr').
*
* If {@code setAlwaysSpan(true)} was used, the input is always wrapped with
* 'span', skipping just the dir attribute when it's not needed.
*
* If {@code dirReset}, and if the overall direction or the exit direction of
* {@code str} are opposite to the context direction, a trailing unicode BiDi
* mark matching the context direction is appended (LRM or RLM).
*
* If !{@code isHtml}, HTML-escapes {@code str} regardless of wrapping.
*
* @param str The input string
* @param isHtml Whether {@code str} is HTML / HTML-escaped
* @param dirReset Whether to append a trailing unicode bidi mark matching the
* context direction, when needed, to prevent the possible garbling
* of whatever may follow {@code str}
* @return Input string after applying the above processing.
*/
public String spanWrap(String str, boolean isHtml, boolean dirReset) {
Direction dir = BidiUtils.get().estimateDirection(str, isHtml);
return spanWrapWithKnownDir(dir, str, isHtml, dirReset);
}
/**
* Like {@link #spanWrapWithKnownDir(HasDirection.Direction, String, boolean, boolean)},
* but assumes {@code isHtml} is false and {@code dirReset} is true.
*
* @param dir {@code str}'s direction
* @param str The input string
* @return Input string after applying the above processing.
*/
public String spanWrapWithKnownDir(Direction dir, String str) {
return spanWrapWithKnownDir(dir, str, false, true);
}
/**
* Like {@link #spanWrapWithKnownDir(HasDirection.Direction, String, boolean, boolean)},
* but assumes {@code dirReset} is true.
*
* @param dir {@code str}'s direction
* @param str The input string
* @param isHtml Whether {@code str} is HTML / HTML-escaped
* @return Input string after applying the above processing.
*/
public String spanWrapWithKnownDir(Direction dir, String str, boolean isHtml) {
return spanWrapWithKnownDir(dir, str, isHtml, true);
}
/**
* Formats a string of given direction for use in HTML output of the context
* direction, so an opposite-direction string is neither garbled nor garbles
* what follows it.
*
* The algorithm: estimates the direction of input argument {@code str}. In
* case its direction doesn't match the context direction, wraps it with a
* 'span' tag and adds a "dir" attribute (either 'dir=rtl' or 'dir=ltr').
*
* If {@code setAlwaysSpan(true)} was used, the input is always wrapped with
* 'span', skipping just the dir attribute when it's not needed.
*
* If {@code dirReset}, and if the overall direction or the exit direction of
* {@code str} are opposite to the context direction, a trailing unicode BiDi
* mark matching the context direction is appended (LRM or RLM).
*
* If !{@code isHtml}, HTML-escapes {@code str} regardless of wrapping.
*
* @param dir {@code str}'s direction
* @param str The input string
* @param isHtml Whether {@code str} is HTML / HTML-escaped
* @param dirReset Whether to append a trailing unicode bidi mark matching the
* context direction, when needed, to prevent the possible garbling
* of whatever may follow {@code str}
* @return Input string after applying the above processing.
*/
public String spanWrapWithKnownDir(Direction dir, String str, boolean isHtml,
boolean dirReset) {
boolean dirCondition = dir != Direction.DEFAULT && dir != contextDir;
String origStr = str;
if (!isHtml) {
str = htmlEscape(str);
}
StringBuilder result = new StringBuilder();
if (alwaysSpan || dirCondition) {
result.append("" + str + "");
} else {
result.append(str);
}
// origStr is passed (more efficient when isHtml is false).
result.append(dirResetIfNeeded(origStr, dir, isHtml, dirReset));
return result.toString();
}
/**
* Returns "right" for RTL context direction. Otherwise (LTR or default /
* unknown context direction) returns "left".
*/
public String startEdge() {
return contextDir == Direction.RTL ? Format.RIGHT : Format.LEFT;
}
/**
* Like {@link #unicodeWrap(String, boolean, boolean)}, but assumes {@code
* isHtml} is false and {@code dirReset} is true.
*
* @param str The input string
* @return Input string after applying the above processing.
*/
public String unicodeWrap(String str) {
return unicodeWrap(str, false, true);
}
/**
* Like {@link #unicodeWrap(String, boolean, boolean)}, but assumes {@code
* dirReset} is true.
*
* @param str The input string
* @param isHtml Whether {@code str} is HTML / HTML-escaped
* @return Input string after applying the above processing.
*/
public String unicodeWrap(String str, boolean isHtml) {
return unicodeWrap(str, isHtml, true);
}
/**
* Formats a string of unknown direction for use in plain-text output of the
* context direction, so an opposite-direction string is neither garbled nor
* garbles what follows it. As opposed to {@link #spanWrap}, this makes use of
* Unicode BiDi formatting characters. In HTML, its *only* valid use is inside
* of elements that do not allow mark-up, e.g. an 'option' tag.
*
* The algorithm: estimates the direction of input argument {@code str}. In
* case it doesn't match the context direction, wraps it with Unicode BiDi
* formatting characters: RLE+{@code str}+PDF for RTL text, or LRE+ {@code
* str}+PDF for LTR text.
*
* If {@code opt_dirReset}, and if the overall direction or the exit direction
* of {@code str} are opposite to the context direction, a trailing unicode
* BiDi mark matching the context direction is appended (LRM or RLM).
*
* Does *not* do HTML-escaping regardless of the value of {@code isHtml}.
*
* @param str The input string
* @param isHtml Whether {@code str} is HTML / HTML-escaped
* @param dirReset Whether to append a trailing unicode bidi mark matching the
* context direction, when needed, to prevent the possible garbling
* of whatever may follow {@code str}
* @return Input string after applying the above processing.
*/
public String unicodeWrap(String str, boolean isHtml, boolean dirReset) {
Direction dir = BidiUtils.get().estimateDirection(str, isHtml);
return unicodeWrapWithKnownDir(dir, str, isHtml, dirReset);
}
/**
* Like {@link #unicodeWrapWithKnownDir(HasDirection.Direction, String, boolean, boolean)},
* but assumes {@code isHtml} is false and {@code dirReset} is true.
*
* @param dir {@code str}'s direction
* @param str The input string
* @return Input string after applying the above processing.
*/
public String unicodeWrapWithKnownDir(Direction dir, String str) {
return unicodeWrapWithKnownDir(dir, str, false, true);
}
/**
* Like {@link #unicodeWrapWithKnownDir(HasDirection.Direction, String, boolean, boolean)},
* but assumes {@code dirReset} is true.
*
* @param dir {@code str}'s direction
* @param str The input string
* @param isHtml Whether {@code str} is HTML / HTML-escaped
* @return Input string after applying the above processing.
*/
public String unicodeWrapWithKnownDir(Direction dir, String str,
boolean isHtml) {
return unicodeWrapWithKnownDir(dir, str, isHtml, true);
}
/**
* Formats a string of given direction for use in plain-text output of the
* context direction, so an opposite-direction string is neither garbled nor
* garbles what follows it. As opposed to {@link #spanWrapWithKnownDir}, this
* makes use of unicode BiDi formatting characters. In HTML, its *only* valid
* use is inside of elements that do not allow mark-up, e.g. an 'option' tag.
*
* The algorithm: estimates the direction of input argument {@code str}. In
* case it doesn't match the context direction, wraps it with Unicode BiDi
* formatting characters: RLE+{@code str}+PDF for RTL text, or LRE+ {@code
* str}+PDF for LTR text.
*
* If {@code opt_dirReset}, and if the overall direction or the exit direction
* of {@code str} are opposite to the context direction, a trailing unicode
* BiDi mark matching the context direction is appended (LRM or RLM).
*
* Does *not* do HTML-escaping regardless of the value of {@code isHtml}.
*
* @param dir {@code str}'s direction
* @param str The input string
* @param isHtml Whether {@code str} is HTML / HTML-escaped
* @param dirReset Whether to append a trailing unicode bidi mark matching the
* context direction, when needed, to prevent the possible garbling
* of whatever may follow {@code str}
* @return Input string after applying the above processing.
*/
public String unicodeWrapWithKnownDir(Direction dir, String str,
boolean isHtml, boolean dirReset) {
StringBuilder result = new StringBuilder();
if (dir != Direction.DEFAULT && dir != contextDir) {
result.append(dir == Direction.RTL ? Format.RLE : Format.LRE);
result.append(str);
result.append(Format.PDF);
} else {
result.append(str);
}
result.append(dirResetIfNeeded(str, dir, isHtml, dirReset));
return result.toString();
}
/**
* Returns a unicode BiDi mark matching the context direction (LRM or RLM) if
* {@code dirReset}, and if the overall direction or the exit direction of
* {@code str} are opposite to the context direction. Otherwise returns the
* empty string.
*
* @param str The input string
* @param dir {@code str}'s overall direction
* @param isHtml Whether {@code str} is HTML / HTML-escaped
* @param dirReset Whether to perform the reset
* @return A unicode BiDi mark or the empty string.
*/
private String dirResetIfNeeded(String str, Direction dir, boolean isHtml,
boolean dirReset) {
// endsWithRtl and endsWithLtr are called only if needed (short-circuit).
if (dirReset
&& ((contextDir == Direction.LTR &&
(dir == Direction.RTL ||
BidiUtils.get().endsWithRtl(str, isHtml))) ||
(contextDir == Direction.RTL &&
(dir == Direction.LTR ||
BidiUtils.get().endsWithLtr(str, isHtml))))) {
return contextDir == Direction.LTR ? Format.LRM_STRING
: Format.RLM_STRING;
} else {
return "";
}
}
private String htmlEscape(String str) {
// TODO(tomerigo): use a proper escaper class once such exists.
return str.replace("&", "&").replace("<", "<").replace(">", ">").replace("\n", "
");
}
}