/**
* 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 org.waveprotocol.wave.client.common.util;
import com.google.gwt.core.client.GWT;
/**
* Class to allow conditional compilation for different user agents.
*
* All methods should return values that are known at compile time.
* *
* TODO(user): Should this ever be thrown in for free with GWT, rather use
* their approach. A relevant thread is:
* http://groups.google.com/group/Google-Web-Toolkit-Contributors/browse_thread/thread/6745dee7a85eb585/bd58d1a9f2344b34
*
*/
public abstract class UserAgentStaticProperties {
static UserAgentStaticProperties get() {
return INSTANCE;
}
private static final UserAgentStaticProperties INSTANCE = createInstance();
/**
* Creates an instance of UserAgent.
*
* NOTE(danilatos): This method is designed to be statically evaluable by
* the compiler, such that the compiler can determine that
* only one subclass of UserAgent is ever used within a
* given permutation. This is possible because
* GWT.isClient() is replaced with true by the compiler,
* even though it is executed normally in unit tests.
* Testing the return value of GWT.create() is not adequate
* because only boolean values can be statically evaluated
* by the compiler at this time.
*
* @return an instance of UserAgent.
*/
private static UserAgentStaticProperties createInstance() {
if (GWT.isClient()) {
return GWT.create(UserAgentStaticProperties.class);
} else {
return new FirefoxImpl();
}
}
final boolean isWebkit() {
return isSafari() || isMobileWebkit();
}
/**
* @return true iff the user agent uses mobile webkit
*/
final boolean isMobileWebkit() {
return isAndroid() || isIPhone();
}
// Default instance methods: most return false, since they are intended to be overriden.
boolean isSafari() { return false; }
boolean isFirefox() { return false; }
boolean isIE() { return false; }
boolean isAndroid() { return false; }
boolean isIPhone() { return false; }
// NOTE(user): Created via deferred binding
public static class SafariImpl extends UserAgentStaticProperties {
@Override
protected boolean isSafari() {
return true;
}
}
// NOTE(user): Created via deferred binding
public static class FirefoxImpl extends UserAgentStaticProperties {
@Override
protected boolean isFirefox() {
return true;
}
}
// NOTE(user): Created via deferred binding
public static class IEImpl extends UserAgentStaticProperties {
@Override
protected boolean isIE() {
return true;
}
}
// NOTE(user): Created via deferred binding
public static class AndroidImpl extends UserAgentStaticProperties {
@Override
protected boolean isAndroid() {
return true;
}
}
// NOTE(user): Created via deferred binding
public static class IPhoneImpl extends UserAgentStaticProperties {
@Override
protected boolean isIPhone() {
return true;
}
}
}