From 633f1e6f96c407005ea44ca11766abf66c377069 Mon Sep 17 00:00:00 2001
From: Julian Winkler <julian.winkler1@web.de>
Date: Thu, 3 Oct 2024 22:42:12 +0200
Subject: [PATCH] WebView: implement file:///android_asset/... URIs

---
 src/api-impl-jni/util.c                       |  3 +++
 src/api-impl-jni/util.h                       |  4 +++
 .../widgets/android_webkit_WebView.c          | 25 +++++++++++++++++++
 src/api-impl/android/webkit/WebView.java      |  8 ++++++
 4 files changed, 40 insertions(+)

diff --git a/src/api-impl-jni/util.c b/src/api-impl-jni/util.c
index 6c2aefdb..0fa58623 100644
--- a/src/api-impl-jni/util.c
+++ b/src/api-impl-jni/util.c
@@ -161,6 +161,9 @@ void set_up_handle_cache(JNIEnv *env)
 
 	handle_cache.intent.class = _REF((*env)->FindClass(env, "android/content/Intent"));
 	handle_cache.intent.putExtraCharSequence = _METHOD(handle_cache.intent.class, "putExtra", "(Ljava/lang/String;Ljava/lang/CharSequence;)Landroid/content/Intent;");
+
+	handle_cache.webview.class = _REF((*env)->FindClass(env, "android/webkit/WebView"));
+	handle_cache.webview.internalGetAssetManager = _METHOD(handle_cache.webview.class, "internalGetAssetManager", "()Landroid/content/res/AssetManager;");
 }
 
 void extract_from_apk(const char *path, const char *target) {
diff --git a/src/api-impl-jni/util.h b/src/api-impl-jni/util.h
index 9e4a715d..5218e27e 100644
--- a/src/api-impl-jni/util.h
+++ b/src/api-impl-jni/util.h
@@ -111,6 +111,10 @@ struct handle_cache {
 		jclass class;
 		jmethodID putExtraCharSequence;
 	} intent;
+	struct {
+		jclass class;
+		jmethodID internalGetAssetManager;
+	} webview;
 };
 
 extern struct handle_cache handle_cache;
diff --git a/src/api-impl-jni/widgets/android_webkit_WebView.c b/src/api-impl-jni/widgets/android_webkit_WebView.c
index 6a29a59c..c8c84c60 100644
--- a/src/api-impl-jni/widgets/android_webkit_WebView.c
+++ b/src/api-impl-jni/widgets/android_webkit_WebView.c
@@ -1,5 +1,8 @@
 #include <gtk/gtk.h>
 #include <webkit/webkit.h>
+#include <gio/gunixinputstream.h>
+
+#include <androidfw/androidfw_c_api.h>
 
 #include "../defines.h"
 #include "../util.h"
@@ -9,6 +12,27 @@
 #include "../generated_headers/android_view_View.h"
 #include "../generated_headers/android_webkit_WebView.h"
 
+static void asset_uri_scheme_request_cb(WebKitURISchemeRequest *request, gpointer user_data)
+{
+	const gchar *path = webkit_uri_scheme_request_get_path(request);
+	if (path == NULL)
+		return;
+	path += 1; // remove the leading '/'
+	JNIEnv *env = get_jni_env();
+	WrapperWidget *wrapper = WRAPPER_WIDGET(gtk_widget_get_parent(GTK_WIDGET(webkit_uri_scheme_request_get_web_view(request))));
+	jobject asset_manager_obj = (*env)->CallObjectMethod(env, wrapper->jobj, handle_cache.webview.internalGetAssetManager);
+	struct AssetManager *asset_manager = _PTR(_GET_LONG_FIELD(asset_manager_obj, "mObject"));
+	struct Asset *asset = AssetManager_openNonAsset(asset_manager, path, ACCESS_STREAMING);
+	off_t offset;
+	off_t size;
+	int fd = Asset_openFileDescriptor(asset, &offset, &size);
+	Asset_delete(asset);
+	GInputStream *stream = g_unix_input_stream_new(fd, TRUE);
+	g_input_stream_skip(stream, offset, NULL, NULL);
+	webkit_uri_scheme_request_finish(request, stream, size, NULL);
+	g_object_unref(stream);
+}
+
 JNIEXPORT jlong JNICALL Java_android_webkit_WebView_native_1constructor(JNIEnv *env, jobject this, jobject context, jobject attrs)
 {
 	/* 
@@ -23,6 +47,7 @@ JNIEXPORT jlong JNICALL Java_android_webkit_WebView_native_1constructor(JNIEnv *
 	GtkWidget *webview = webkit_web_view_new();
 	wrapper_widget_set_child(WRAPPER_WIDGET(wrapper), webview);
 	wrapper_widget_set_jobject(WRAPPER_WIDGET(wrapper), env, this);
+	webkit_web_context_register_uri_scheme(webkit_web_view_get_context(WEBKIT_WEB_VIEW(webview)), "android-asset", asset_uri_scheme_request_cb, NULL, NULL);
 	return _INTPTR(webview);
 }
 
diff --git a/src/api-impl/android/webkit/WebView.java b/src/api-impl/android/webkit/WebView.java
index ffd650a0..eec02a6c 100644
--- a/src/api-impl/android/webkit/WebView.java
+++ b/src/api-impl/android/webkit/WebView.java
@@ -1,6 +1,7 @@
 package android.webkit;
 
 import android.content.Context;
+import android.content.res.AssetManager;
 import android.util.AttributeSet;
 import android.view.View;
 
@@ -47,6 +48,8 @@ public class WebView extends View {
 	public void destroy() {}
 
 	public void loadDataWithBaseURL(String baseUrl, String data, String mimeType, String encoding, String historyUrl) {
+		// webkit doesn't allow overwriting the file:// uri scheme. So we replace it with the android-asset:// scheme
+		data = data.replace("file:///android_asset/", "android-asset:///assets/");
 		native_loadDataWithBaseURL(widget, baseUrl, data, mimeType, encoding);
 	}
 
@@ -60,6 +63,11 @@ public class WebView extends View {
 
 	public void stopLoading() {}
 
+	// to be used by native code
+	AssetManager internalGetAssetManager() {
+		return getContext().getResources().getAssets();
+	}
+
 	@Override
 	protected native long native_constructor(Context context, AttributeSet attrs);
 	private native void native_loadDataWithBaseURL(long widget, String baseUrl, String data, String mimeType, String encoding);