JavaFX Transparent WebView PATCH

TransparentWebViewPatch.java

/**
 * @author Riccardo Balbo
 * @description This patch aims to make the WebView capable to correctly render transparent pages.
 * @license
 *  Copyright (c) 2015 Riccardo Balbo < riccardo @ forkforge . net >
 *
 *          This software is provided 'as-is', without any express or implied
 *          warranty. In no event will the authors be held liable for any
 *          damages arising from the use of this software.
 *
 *          Permission is granted to anyone to use this software for any
 *          purpose, including commercial applications, and to alter it and
 *          redistribute it freely, subject to the following restrictions:
 *
 *          1. The origin of this software must not be misrepresented; you must
 *          not claim that you wrote the original software. If you use this
 *          software in a product, an acknowledgment in the product
 *          documentation would be appreciated but is not required.
 *
 *          2. Altered source versions must be plainly marked as such, and must
 *          not be misrepresented as being the original software.
 *
 *          3. This notice may not be removed or altered from any source
 *          distribution.
 */

import java.io.ByteArrayInputStream;
import java.lang.instrument.ClassFileTransformer;
import java.lang.instrument.IllegalClassFormatException;
import java.security.ProtectionDomain;
import java.lang.instrument.Instrumentation;
import javassist.ClassPool;
import javassist.CtClass;
import javassist.CtMethod;

public class TransparentWebViewPatch implements ClassFileTransformer{
    private final ClassPool _CLASS_POOL=ClassPool.getDefault();

    public static void premain(String agentArguments,Instrumentation instrumentation){
        instrumentation.addTransformer(new TransparentWebViewPatch());
    }

    // This patch aims to make the WebView capable to correctly render
    // transparent pages.

    @Override
    public byte[] transform(ClassLoader loader, String class_name, Class<?> class_being_redefined, ProtectionDomain protection_domain, byte[] byte_code) throws IllegalClassFormatException {
        if(class_name.equals("com/sun/webkit/WebPage")){
            System.out.println("> Patching "+class_name+" ...");
            try{
                CtClass ct_class=_CLASS_POOL.makeClass(new ByteArrayInputStream(byte_code));

                // First thing to do is edit the fireLoadEvent in order to force
                // the page to set its own
                // background to transparent black (0x00000000 argb) each time
                // it changes
                CtMethod fireLoadEvent_method=ct_class.getDeclaredMethod("fireLoadEvent");
                fireLoadEvent_method.insertBefore("{\n"+"    "
                        + "setBackgroundColor(0);\n"
                +"}");

                // DEPRECATED CODE: NOT WORKING FROM JAVA 1.8.0_66
                // Then, we edit the the paint2GC method in order to call
                // clearRect every time right before it
                // start to draw a clip (clips are parts of the rendered frame).
                // We need this because when the webpage is rendered with the
                // backbuffer enabled,
                // every clip is just drawn over the old rendered frame without
                // care about the alpha channel.
                // NOTE: there is a system property
                // com.sun.webkit.pagebackbuffer that could do the trick without
                // this entire patch, but i didn't succeed in getting anything
                // useful out of it...
                // CtMethod
                // paint2GC_method=ct_class.getDeclaredMethod("paint2GC");
                // paint2GC_method.insertAt(696,
                // "{\n" +
                // " com.sun.webkit.graphics.WCRectangle clip=$1.getClip(); \n"
                // +
                // "
                // $1.clearRect(clip.getX(),clip.getY(),clip.getWidth(),clip.getHeight());\n"
                // +
                // "}"
                // );
                // END OF DEPRECATED CODE

                // Then we replace the scroll method body in order to force the
                // repaint of the entire frame
                // when the page is scrolled
                CtMethod scroll_method=ct_class.getDeclaredMethod("scroll");
                scroll_method.setBody(
                        "{\n"+"   "
                        + "addDirtyRect(new com.sun.webkit.graphics.WCRectangle(0f,0f,(float)width,(float)height));\n"
                        +"}"
                );
                byte_code=ct_class.toBytecode();
                ct_class.detach();
            }catch(Exception e){
                System.out.println("/!\\ "+class_name+" patching failed :(");
                e.printStackTrace();
                return byte_code;
            }
            System.out.println("> "+class_name+" patching succeeded!");
        }else if(class_name.equals("com/sun/javafx/webkit/prism/WCGraphicsPrismContext")){
            System.out.println("> Patching "+class_name+" ...");
            try{
                CtClass ct_class=_CLASS_POOL.makeClass(new ByteArrayInputStream(byte_code));

                // Then, we edit the the WCGraphicsPrismContext.setClip method
                // in order to call clearRect over the area of the clip.
                CtClass signature[]=new CtClass[]{_CLASS_POOL.get("com.sun.webkit.graphics.WCRectangle")};
                CtMethod setClip_method=ct_class.getDeclaredMethod("setClip",signature);
                setClip_method.insertBefore(
                        "{"+"  "
                        + " $0.clearRect($1.getX(),$1.getY(),$1.getWidth(),$1.getHeight());"
                        +"}");
                byte_code=ct_class.toBytecode();
                ct_class.detach();
            }catch(Exception e){
                System.out.println("/!\\ "+class_name+" patching failed :(");
                e.printStackTrace();
                return byte_code;
            }
            System.out.println("> "+class_name+" patching succeeded!");
        }

        return byte_code;
    }
}

build.sh

origin_dir=$PWD
rm -R build
mkdir build

rm -R /tmp/buildTransparentWebViewPatch
mkdir /tmp/buildTransparentWebViewPatch
cp TransparentWebViewPatch.java /tmp/buildTransparentWebViewPatch
cd  /tmp/buildTransparentWebViewPatch

echo "Downloading jboss javassist..."
wget https://github.com/jboss-javassist/javassist/releases/download/rel_3_20_0_ga/javassist.jar  > /dev/null 2>&1

echo "Compiling..."
javac -cp javassist.jar TransparentWebViewPatch.java 

echo "Building jar..."
sed -n '/\/\*\*/,/\*\//p' TransparentWebViewPatch.java > INFO.txt 
echo "Premain-Class: TransparentWebViewPatch" > manifest.txt
jar -cvfm TransparentWebViewPatch.jar manifest.txt INFO.txt TransparentWebViewPatch.class TransparentWebViewPatch.java 
cp TransparentWebViewPatch.jar $origin_dir/build/
cp javassist.jar $origin_dir/build/
rm -R /tmp/buildTransparentWebViewPatch
echo "Done!"

Hi axel1200.
I have used your version.
Console show msg.

Patching com/sun/webkit/WebPage ...
com/sun/webkit/WebPage patching succeeded!
Patching com/sun/javafx/webkit/prism/WCGraphicsPrismContext ...
com/sun/javafx/webkit/prism/WCGraphicsPrismContext patching succeeded!

But the webview background still not transparent
I use JDK 14, javaassist 3.27.0-GA, and Java Fx 14.
Can you tell me what u are using? Thank a lot.

I used jdk 11 :D not sure if that creates an issue. As javafx 14 says it needs jdk 11+. Not sure about the rest but you should find it in the repo

javassist.version=3.23.1-GA

And these vm parameters of which many should not be related -DnativeDir=build/resources/native -Dprism.dirtyopts=false -Xms128m -Xmx712m -XX:MinHeapFreeRatio=15 -XX:MaxHeapFreeRatio=33 -XX:+HeapDumpOnOutOfMemoryError -XX:+UseStringDeduplication -javaagent:webview-patch/build/libs/webview-patch.jar -Djava.net.preferIPv4Stack=true -XX:TieredStopAtLevel=1 -noverify