Enable setting large WebView content

android/src/toga_android/widgets/internal/webview.py

@@ -1,14 +1,42 @@
 import weakref
 
-from android.webkit import WebResourceRequest, WebView as A_WebView, WebViewClient
-from java import Override, jboolean, jvoid, static_proxy
+from android.webkit import (
+    WebResourceRequest,
+    WebResourceResponse,
+    WebView as A_WebView,
+    WebViewClient,
+)
+from androidx.webkit import WebViewAssetLoader
+from java import Override, dynamic_proxy, jboolean, jvoid, static_proxy
+from java.io import FileInputStream
 from java.lang import String as jstring
 
+import toga
+
+
+class TogaCachePathHandler(dynamic_proxy(WebViewAssetLoader.PathHandler)):
+    def __init__(self, impl):
+        super().__init__()
+        self.impl = impl
+
+    @Override(WebResourceResponse, [jstring])
+    def handle(self, path):
+        filepath = toga.App.app.paths.cache / path
+        if filepath.exists():
+            return WebResourceResponse(
+                "text/html", "utf-8", FileInputStream(str(filepath))
+            )
+        return None
+
 
 class TogaWebClient(static_proxy(WebViewClient)):
     def __init__(self, impl):
         self._interface_ref = weakref.ref(impl.interface)
         self._impl_ref = weakref.ref(impl)
+        pathHandler = TogaCachePathHandler(impl._native_activity)
+        self.cache_assetLoader = (
+            WebViewAssetLoader.Builder().addPathHandler("/cache/", pathHandler).build()
+        )
         super().__init__()
 
     @property
@@ -46,3 +74,7 @@ def onPageFinished(self, webview, url):
         if self.impl and self.impl.loaded_future:  # pragma: no-branch
             self.impl.loaded_future.set_result(None)
             self.impl.loaded_future = None
+
+    @Override(WebResourceResponse, [A_WebView, WebResourceRequest])
+    def shouldInterceptRequest(self, webview, request):
+        return self.cache_assetLoader.shouldInterceptRequest(request.getUrl())

android/src/toga_android/widgets/webview.py

@@ -1,10 +1,13 @@
+import hashlib
 import json
+import shutil
 from http.cookiejar import CookieJar
 
 from android.webkit import ValueCallback, WebView as A_WebView, WebViewClient
 from java import dynamic_proxy
 from java.lang import NoClassDefFoundError
 
+import toga
 from toga.widgets.webview import CookiesResult, JavaScriptResult
 
 from .base import Widget
@@ -63,6 +66,17 @@ def create(self):
         self.settings.setBuiltInZoomControls(True)
         self.settings.setDisplayZoomControls(False)
 
+        # folder for temporary storing content larger than 2 MB
+        self._large_content_dir = (
+            toga.App.app.paths.cache / f"toga/webview-{self.interface.id}"
+        )
+        # base URL for accessing the cached files
+        self._large_content_base_url = f"https://appassets.androidplatform.net/cache/toga/webview-{self.interface.id}/"
+
+    def __del__(self):  # pragma: nocover
+        """Cleaning up the cached files for large content"""
+        shutil.rmtree(self._large_content_dir, ignore_errors=True)
+
     def get_url(self):
         url = self.native.getUrl()
         if url == "about:blank" or url.startswith("data:"):
@@ -77,10 +91,20 @@ def set_url(self, value, future=None):
         self.native.loadUrl(value)
 
     def set_content(self, root_url, content):
-        # There is a loadDataWithBaseURL method, but it's inconsistent about whether
-        # getUrl returns the given URL or a data: URL. Rather than support this feature
-        # intermittently, it's better to not support it at all.
-        self.native.loadData(content, "text/html", "utf-8")
+        if len(content) > 2 * 1024 * 1024:
+            self._large_content_dir.mkdir(parents=True, exist_ok=True)
+            h = hashlib.new("sha1")
+            h.update(bytes(self.interface.id, "utf-8"))
+            h.update(bytes(root_url, "utf-8"))
+            file_name = h.hexdigest() + ".html"
+            file_path = self._large_content_dir / file_name
+            file_path.write_text(content, encoding="utf-8")
+            self.set_url(self._large_content_base_url + file_name)
+        else:
+            # There is a loadDataWithBaseURL method, but it's inconsistent about
+            # whether getUrl returns the given URL or a data: URL. Rather than support
+            # this feature intermittently, it's better to not support it at all.
+            self.native.loadData(content, "text/html", "utf-8")
 
     def get_user_agent(self):
         return self.settings.getUserAgentString()

android/tests_backend/widgets/webview.py

@@ -1,3 +1,4 @@
+import os
 from http.cookiejar import CookieJar
 
 from android.webkit import WebView
@@ -15,3 +16,8 @@ class WebViewProbe(SimpleProbe):
     def extract_cookie(self, cookie_jar, name):
         assert isinstance(cookie_jar, CookieJar)
         skip("Cookie retrieval not implemented on Android")
+
+    def get_large_content_dir(self, widget):
+        for f in os.listdir(widget._impl._large_content_dir):
+            url = widget._impl._large_content_base_url + f
+        return url

changes/4062.bugfix.md

@@ -0,0 +1 @@
+The 2MB size limit for setting static WebView content has been removed for Windows.

examples/webview/pyproject.toml

@@ -51,6 +51,7 @@ base_theme = "Theme.MaterialComponents.Light.DarkActionBar"
 
 build_gradle_dependencies = [
     "com.google.android.material:material:1.12.0",
+    "androidx.webkit:webkit:1.15.0",
 ]
 
 build_gradle_extra_content="""

examples/webview/webview/app.py

@@ -80,6 +80,13 @@ def on_set_content(self, widget, **kwargs):
             ),
         )
 
+    def on_set_large_content(self, widget, **kwargs):
+        # according to the Microsoft documentation, the max content size is
+        # 2 MB but in fact, the limit seems to be at about 1.5 MB
+        large_content = f"<p>{'lorem ipsum ' * 200000}</p>"
+        print(f"content length: {len(large_content)}")
+        self.webview.set_content("https://example.com", large_content)
+
     def on_get_agent(self, widget, **kwargs):
         self.label.text = self.webview.user_agent
 
@@ -112,6 +119,9 @@ def startup(self):
                         toga.Button("good js", on_press=self.on_good_js),
                         toga.Button("bad js", on_press=self.on_bad_js),
                         toga.Button("set content", on_press=self.on_set_content),
+                        toga.Button(
+                            "set large content", on_press=self.on_set_large_content
+                        ),
                     ],
                 ),
                 toga.Box(

qt/src/toga_qt/widgets/webview.py

@@ -1,10 +1,13 @@
+import hashlib
+import shutil
 from http.cookiejar import Cookie, CookieJar
 
 from PySide6.QtCore import QUrl, Signal
 from PySide6.QtWebEngineCore import QWebEnginePage
 from PySide6.QtWebEngineWidgets import QWebEngineView
 from travertino.size import at_least
 
+import toga
 from toga.widgets.webview import CookiesResult, JavaScriptResult
 
 from .base import Widget
@@ -84,6 +87,15 @@ def create(self):
         )
         self.native.loadFinished.connect(self.qt_on_webview_load)
 
+        # folder for temporary storing content larger than 2 MB
+        self._large_content_dir = (
+            toga.App.app.paths.cache / f"toga/webview-{self.interface.id}"
+        )
+
+    def __del__(self):  # pragma: nocover
+        """Cleaning up the cached files for large content"""
+        shutil.rmtree(self._large_content_dir, ignore_errors=True)
+
     def qt_on_webview_load(self, ok: bool):
         self.interface.on_webview_load()
         if self.load_future:
@@ -134,7 +146,17 @@ def set_user_agent(self, value):
         return self.native.page().profile().setHttpUserAgent(value)
 
     def set_content(self, root_url, content):
-        self.native.setHtml(content, baseUrl=root_url)
+        if len(content) > 2 * 1024 * 1024:
+            self._large_content_dir.mkdir(parents=True, exist_ok=True)
+            h = hashlib.new("sha1")
+            h.update(bytes(self.interface.id, "utf-8"))
+            h.update(bytes(root_url, "utf-8"))
+            file_name = h.hexdigest() + ".html"
+            file_path = self._large_content_dir / file_name
+            file_path.write_text(content, encoding="utf-8")
+            self.set_url(file_path.as_uri())
+        else:
+            self.native.setHtml(content, baseUrl=root_url)
 
     def get_cookies(self):
         result = CookiesResult()

qt/tests_backend/widgets/webview.py

@@ -1,3 +1,5 @@
+import os
+
 from PySide6.QtWebEngineWidgets import QWebEngineView
 
 from .base import SimpleProbe
@@ -11,3 +13,8 @@ class WebViewProbe(SimpleProbe):
 
     def extract_cookie(self, cookie_jar, name):
         return next((c for c in cookie_jar if c.name == name), None)
+
+    def get_large_content_dir(self, widget):
+        for f in os.listdir(widget._impl._large_content_dir):
+            p = widget._impl._large_content_dir / f
+        return p.as_uri().replace("%20", " ")

testbed/pyproject.toml

@@ -105,6 +105,22 @@ requires = [
 ]
 
 [tool.briefcase.app.testbed.android]
+template = "https://github.com/mhsmith/briefcase-android-gradle-template"
+template_branch = "pip-options-newlines"
+test_requires = [
+    "coverage==7.13.1",
+    "coverage-conditional-plugin == 0.9.0",
+    # fonttools is only needed by Android, but we need to use sys.platform == 'linux'
+    # for < 3.13 there's no dependency identifier that can target Android exclusively
+    # before 3.13.
+    "fonttools==4.61.1 ; python_version < '3.13' and sys_platform == 'linux'",
+    "fonttools==4.61.1 ; python_version >= '3.13' and sys_platform == 'android'",
+    "psutil==7.2.1 ; python_version >= '3.13' and (sys_platform == 'linux' or sys_platform == 'darwin' or sys_platform == 'win32')",
+    "pillow==11.0.0",
+    "pytest==9.0.2",
+    "pytest-asyncio==1.3.0",
+    "pytest-retry==1.7.0",
+]
 test_sources = [
     "../android/tests_backend",
 ]
@@ -118,6 +134,7 @@ build_gradle_dependencies = [
     "com.google.android.material:material:1.12.0",
     "androidx.swiperefreshlayout:swiperefreshlayout:1.1.0",
     "org.osmdroid:osmdroid-android:6.1.20",
+    "androidx.webkit:webkit:1.15.0",
 ]
 
 build_gradle_extra_content = """\

testbed/tests/widgets/test_webview.py

@@ -205,6 +205,25 @@ async def test_static_content(widget, probe, on_load):
     )
 
 
+async def test_static_large_content(widget, probe, on_load):
+    """Static large content can be loaded into the page"""
+    large_content = f"<p>{'lorem ipsum ' * 200000}</p>"
+    url = "https://example.com/"
+    widget.set_content(url, large_content)
+    if hasattr(probe, "get_large_content_dir"):  # pragma: no branch
+        url = probe.get_large_content_dir(widget)
+
+    # DOM loads aren't instantaneous; wait for the URL to appear
+    await assert_content_change(
+        widget,
+        probe,
+        message="Webview has static large content",
+        url=url,
+        content=large_content,
+        on_load=on_load,
+    )
+
+
 async def test_user_agent(widget, probe):
     "The user agent can be customized"
 

winforms/src/toga_winforms/widgets/webview.py

@@ -1,4 +1,6 @@
+import hashlib
 import json
+import shutil
 import webbrowser
 from http.cookiejar import Cookie, CookieJar
 
@@ -102,6 +104,15 @@ def create(self):
         # user on_navigation_starting handler
         self._allowed_url = None
 
+        # folder for temporary storing content larger than 2 MB
+        self._large_content_dir = (
+            toga.App.app.paths.cache / f"toga/webview-{self.interface.id}"
+        )
+
+    def __del__(self):  # pragma: nocover
+        """Cleaning up the cached files for large content"""
+        shutil.rmtree(self._large_content_dir, ignore_errors=True)
+
     # Any non-trivial use of the WebView requires the CoreWebView2 object to be
     # initialized, which is asynchronous. Since most of this class's methods are not
     # asynchronous, they cannot handle this using `await`. Instead, they add a callable
@@ -232,8 +243,20 @@ def set_content(self, root_url, content):
         if self.interface.on_navigation_starting._raw:
             # mark URL as being allowed
             self._allowed_url = "about:blank"
-        # There appears to be no way to pass the root_url.
-        self.native.NavigateToString(content)
+        if len(content) > 1572834:
+            # according to the Microsoft documentation, the max content size is
+            # 2 MB, but in fact, the limit seems to be at about 1.5 MB
+            self._large_content_dir.mkdir(parents=True, exist_ok=True)
+            h = hashlib.new("sha1")
+            h.update(bytes(self.interface.id, "utf-8"))
+            h.update(bytes(root_url, "utf-8"))
+            file_name = h.hexdigest() + ".html"
+            file_path = self._large_content_dir / file_name
+            file_path.write_text(content, encoding="utf-8")
+            self.set_url(file_path.as_uri())
+        else:
+            # There appears to be no way to pass the root_url.
+            self.native.NavigateToString(content)
 
     def get_user_agent(self):
         if self.corewebview2_available:

winforms/tests_backend/widgets/webview.py

@@ -1,3 +1,5 @@
+import os
+
 from Microsoft.Web.WebView2.WinForms import WebView2
 
 from .base import SimpleProbe
@@ -17,3 +19,8 @@ class WebViewProbe(SimpleProbe):
 
     def extract_cookie(self, cookie_jar, name):
         return next((c for c in cookie_jar if c.name == name), None)
+
+    def get_large_content_dir(self, widget):
+        for f in os.listdir(widget._impl._large_content_dir):
+            p = widget._impl._large_content_dir / f
+        return p.as_uri().replace("%20", " ")