feat: accelerated paint (#16)

**CEF supports** hardware-accelerated off-screen rendering by enabling `shared_texture_enabled` via `WindowInfo` and passing `--off-screen-rendering-enabled --shared-texture-enabled` as arguments.
- https://bitbucket.org/chromiumembedded/cef/pull-requests/734
- https://github.com/chromiumembedded/cef/blob/2c411892e273c564dfb6650dcee8fea458849178/include/cef_render_handler.h#L151-L173.

Author: 1zun4

java/org/cef/CefBrowserSettings.java

@@ -20,12 +20,29 @@ public class CefBrowserSettings {
      */
     public int windowless_frame_rate = 0;
 
+    /**
+     * Set to true to enable shared texture rendering. When enabled, the browser
+     * will render to a shared texture that can be accessed by the host application
+     * for hardware-accelerated compositing. This is supported on Windows via D3D11,
+     * macOS via Metal/OpenGL, and Linux via native buffers.
+     */
+    public boolean shared_texture_enabled = false;
+
+    /**
+     * Set to true to enable external begin frame scheduling. When enabled, the
+     * client must call CefBrowserHost::SendExternalBeginFrame to trigger frame
+     * rendering at the specified frame rate.
+     */
+    public boolean external_begin_frame_enabled = false;
+
     public CefBrowserSettings() {}
 
     @Override
     public CefBrowserSettings clone() {
         CefBrowserSettings tmp = new CefBrowserSettings();
         tmp.windowless_frame_rate = windowless_frame_rate;
+        tmp.shared_texture_enabled = shared_texture_enabled;
+        tmp.external_begin_frame_enabled = external_begin_frame_enabled;
         return tmp;
     }
 }

java/org/cef/CefClient.java

@@ -87,7 +87,7 @@ public CefBrowser createBrowser(String url, boolean isTransparent,
     }
 
     public CefBrowser createBrowser(String url, boolean isTransparent,
-            CefRequestContext context, CefBrowserSettings settings) {
+                                    CefRequestContext context, CefBrowserSettings settings) {
         if (isDisposed_)
             throw new IllegalStateException("Can't create browser. CefClient is disposed");
         return CefBrowserFactory.create(
@@ -122,7 +122,7 @@ protected CefDialogHandler getDialogHandler() {
     protected CefDisplayHandler getDisplayHandler() {
         return this;
     }
-    
+
     @Override
     protected CefAudioHandler getAudioHandler() {
         return this;
@@ -230,7 +230,7 @@ public void removeDialogHandler() {
     @Override
     public boolean onFileDialog(CefBrowser browser, FileDialogMode mode, String title,
                                 String defaultFilePath, Vector<String> acceptFilters, Vector<String> acceptExtensions,
-            Vector<String> acceptDescriptions, CefFileDialogCallback callback) {
+                                Vector<String> acceptDescriptions, CefFileDialogCallback callback) {
         if (dialogHandler_ != null && browser != null) {
             return dialogHandler_.onFileDialog(browser, mode, title, defaultFilePath, acceptFilters,
                     acceptExtensions, acceptDescriptions, callback);
@@ -322,7 +322,7 @@ public void removeDownloadHandler() {
 
     @Override
     public boolean onBeforeDownload(CefBrowser browser, CefDownloadItem downloadItem,
-                                 String suggestedName, CefBeforeDownloadCallback callback) {
+                                    String suggestedName, CefBeforeDownloadCallback callback) {
         if (downloadHandler_ != null && browser != null)
             return downloadHandler_.onBeforeDownload(
                     browser, downloadItem, suggestedName, callback);
@@ -693,6 +693,15 @@ public void onPaint(CefBrowser browser, boolean popup, Rectangle[] dirtyRects,
             realHandler.onPaint(browser, popup, dirtyRects, buffer, width, height);
     }
 
+    @Override
+    public void onAcceleratedPaint(CefBrowser browser, boolean popup, Rectangle[] dirtyRects, CefAcceleratedPaintInfo info) {
+        if (browser == null) return;
+
+        CefRenderHandler realHandler = browser.getRenderHandler();
+        if (realHandler != null)
+            realHandler.onAcceleratedPaint(browser, popup, dirtyRects, info);
+    }
+
     @Override
     public void addOnPaintListener(Consumer<CefPaintEvent> listener) {}
 
@@ -702,6 +711,15 @@ public void setOnPaintListener(Consumer<CefPaintEvent> listener) {}
     @Override
     public void removeOnPaintListener(Consumer<CefPaintEvent> listener) {}
 
+    @Override
+    public void addOnAcceleratedPaintListener(Consumer<CefAcceleratedPaintEvent> listener) {}
+
+    @Override
+    public void setOnAcceleratedPaintListener(Consumer<CefAcceleratedPaintEvent> listener) {}
+
+    @Override
+    public void removeOnAcceleratedPaintListener(Consumer<CefAcceleratedPaintEvent> listener) {}
+
     @Override
     public boolean startDragging(CefBrowser browser, CefDragData dragData, int mask, int x, int y) {
         if (browser == null) return false;
@@ -808,39 +826,39 @@ public void onMouseEvent(
     public boolean getScreenInfo(CefBrowser arg0, CefScreenInfo arg1) {
         return false;
     }
-    
+
     // CefAudioHandler
-    
+
     public CefClient addAudioHandler(CefAudioHandler handler) {
         if (audioHandler_ == null) audioHandler_ = handler;
         return this;
     }
-    
+
     public void removeAudioHandler() {
         audioHandler_ = null;
     }
-    
+
     @Override
     public boolean getAudioParameters(CefBrowser browser, CefAudioParameters params) {
         if (audioHandler_ != null) return audioHandler_.getAudioParameters(browser, params);
         return false;
     }
-    
+
     @Override
     public void onAudioStreamStarted(CefBrowser browser, CefAudioParameters params, int channels) {
         if (audioHandler_ != null) audioHandler_.onAudioStreamStarted(browser, params, channels);
     }
-    
+
     @Override
     public void onAudioStreamPacket(CefBrowser browser, DataPointer data, int frames, long pts) {
         if (audioHandler_ != null) audioHandler_.onAudioStreamPacket(browser, data, frames, pts);
     }
-    
+
     @Override
     public void onAudioStreamStopped(CefBrowser browser) {
         if (audioHandler_ != null) audioHandler_.onAudioStreamStopped(browser);
     }
-    
+
     @Override
     public void onAudioStreamError(CefBrowser browser, String text) {
         if (audioHandler_ != null) audioHandler_.onAudioStreamError(browser, text);

java/org/cef/browser/CefAcceleratedPaintEvent.java

@@ -0,0 +1,48 @@
+// Copyright (c) 2024 The Chromium Embedded Framework Authors. All rights
+// reserved. Use of this source code is governed by a BSD-style license that
+// can be found in the LICENSE file.
+
+package org.cef.browser;
+
+import org.cef.handler.CefAcceleratedPaintInfo;
+
+import java.awt.*;
+
+public class CefAcceleratedPaintEvent {
+    private final CefBrowser browser;
+    private final boolean popup;
+    private final Rectangle[] dirtyRects;
+    private final CefAcceleratedPaintInfo acceleratedPaintInfo;
+
+    public CefAcceleratedPaintEvent(CefBrowser browser, boolean popup, Rectangle[] dirtyRects,
+            CefAcceleratedPaintInfo acceleratedPaintInfo) {
+        this.browser = browser;
+        this.popup = popup;
+        this.dirtyRects = dirtyRects;
+        this.acceleratedPaintInfo = acceleratedPaintInfo;
+    }
+
+    public CefBrowser getBrowser() {
+        return browser;
+    }
+
+    public boolean getPopup() {
+        return popup;
+    }
+
+    public Rectangle[] getDirtyRects() {
+        return dirtyRects;
+    }
+
+    public CefAcceleratedPaintInfo getAcceleratedPaintInfo() {
+        return acceleratedPaintInfo;
+    }
+
+    public int getWidth() {
+        return acceleratedPaintInfo.width;
+    }
+
+    public int getHeight() {
+        return acceleratedPaintInfo.height;
+    }
+}

java/org/cef/browser/CefBrowser.java

@@ -398,6 +398,15 @@ public void runFileDialog(FileDialogMode mode, String title, String defaultFileP
      */
     public void setWindowlessFrameRate(int frameRate);
 
+    /**
+     * Send an external begin frame to trigger frame rendering when external begin frame
+     * scheduling is enabled. This method should be called at the desired frame rate when
+     * CefBrowserSettings.external_begin_frame_enabled is set to true.
+     *
+     * @throws UnsupportedOperationException if not supported
+     */
+    public void sendExternalBeginFrame();
+
     /**
      * Returns the maximum rate in frames per second (fps) that {@code CefRenderHandler::onPaint}
      * will be called for a windowless browser. The actual fps may be lower if the browser cannot