Ladybird+LibWebView+WebContent: Make the screenshot IPCs async

These IPCs are different than other IPCs in that we can't just set up a
callback function to be invoked when WebContent sends us the screenshot
data. There are multiple places that would set that callback, and they
would step on each other's toes.

Instead, the screenshot APIs on ViewImplementation now return a Promise
which callers can interact with to receive the screenshot (or an error).

Author: trflynn89

Ladybird/AppKit/UI/LadybirdWebView.mm

@@ -791,14 +791,16 @@ - (void)searchSelectedText:(id)sender
 
 - (void)takeVisibleScreenshot:(id)sender
 {
-    auto result = m_web_view_bridge->take_screenshot(WebView::ViewImplementation::ScreenshotType::Visible);
-    (void)result; // FIXME: Display an error if this failed.
+    m_web_view_bridge->take_screenshot(WebView::ViewImplementation::ScreenshotType::Visible)->when_rejected([](auto const& error) {
+        (void)error; // FIXME: Display the error.
+    });
 }
 
 - (void)takeFullScreenshot:(id)sender
 {
-    auto result = m_web_view_bridge->take_screenshot(WebView::ViewImplementation::ScreenshotType::Full);
-    (void)result; // FIXME: Display an error if this failed.
+    m_web_view_bridge->take_screenshot(WebView::ViewImplementation::ScreenshotType::Full)->when_rejected([](auto const& error) {
+        (void)error; // FIXME: Display the error.
+    });
 }
 
 - (void)openLink:(id)sender

Ladybird/Qt/Tab.cpp

@@ -310,19 +310,19 @@ Tab::Tab(BrowserWindow* window, WebContentOptions const& web_content_options, St
     auto* take_visible_screenshot_action = new QAction("Take &Visible Screenshot", this);
     take_visible_screenshot_action->setIcon(load_icon_from_uri("resource://icons/16x16/filetype-image.png"sv));
     QObject::connect(take_visible_screenshot_action, &QAction::triggered, this, [this]() {
-        if (auto result = view().take_screenshot(WebView::ViewImplementation::ScreenshotType::Visible); result.is_error()) {
-            auto error = MUST(String::formatted("{}", result.error()));
-            QMessageBox::warning(this, "Ladybird", qstring_from_ak_string(error));
-        }
+        view().take_screenshot(WebView::ViewImplementation::ScreenshotType::Visible)->when_rejected([this](auto const& error) {
+            auto error_message = MUST(String::formatted("{}", error));
+            QMessageBox::warning(this, "Ladybird", qstring_from_ak_string(error_message));
+        });
     });
 
     auto* take_full_screenshot_action = new QAction("Take &Full Screenshot", this);
     take_full_screenshot_action->setIcon(load_icon_from_uri("resource://icons/16x16/filetype-image.png"sv));
     QObject::connect(take_full_screenshot_action, &QAction::triggered, this, [this]() {
-        if (auto result = view().take_screenshot(WebView::ViewImplementation::ScreenshotType::Full); result.is_error()) {
-            auto error = MUST(String::formatted("{}", result.error()));
-            QMessageBox::warning(this, "Ladybird", qstring_from_ak_string(error));
-        }
+        view().take_screenshot(WebView::ViewImplementation::ScreenshotType::Full)->when_rejected([this](auto const& error) {
+            auto error_message = MUST(String::formatted("{}", error));
+            QMessageBox::warning(this, "Ladybird", qstring_from_ak_string(error_message));
+        });
     });
 
     m_page_context_menu = new QMenu("Context menu", this);

Userland/Applications/Browser/Tab.cpp

@@ -657,20 +657,20 @@ Tab::Tab(BrowserWindow& window)
 
     auto take_visible_screenshot_action = GUI::Action::create(
         "Take &Visible Screenshot"sv, g_icon_bag.filetype_image, [this](auto&) {
-            if (auto result = view().take_screenshot(WebView::ViewImplementation::ScreenshotType::Visible); result.is_error()) {
-                auto error = String::formatted("{}", result.error()).release_value_but_fixme_should_propagate_errors();
-                GUI::MessageBox::show_error(&this->window(), error);
-            }
+            view().take_screenshot(WebView::ViewImplementation::ScreenshotType::Visible)->when_rejected([this](auto const& error) {
+                auto error_message = MUST(String::formatted("{}", error));
+                GUI::MessageBox::show_error(&this->window(), error_message);
+            });
         },
         this);
     take_visible_screenshot_action->set_status_tip("Save a screenshot of the visible portion of the current tab to the Downloads directory"_string);
 
     auto take_full_screenshot_action = GUI::Action::create(
         "Take &Full Screenshot"sv, g_icon_bag.filetype_image, [this](auto&) {
-            if (auto result = view().take_screenshot(WebView::ViewImplementation::ScreenshotType::Full); result.is_error()) {
-                auto error = String::formatted("{}", result.error()).release_value_but_fixme_should_propagate_errors();
-                GUI::MessageBox::show_error(&this->window(), error);
-            }
+            view().take_screenshot(WebView::ViewImplementation::ScreenshotType::Full)->when_rejected([this](auto const& error) {
+                auto error_message = MUST(String::formatted("{}", error));
+                GUI::MessageBox::show_error(&this->window(), error_message);
+            });
         },
         this);
     take_full_screenshot_action->set_status_tip("Save a screenshot of the entirety of the current tab to the Downloads directory"_string);

Userland/Libraries/LibWebView/InspectorClient.cpp

@@ -254,10 +254,13 @@ void InspectorClient::context_menu_screenshot_dom_node()
 {
     VERIFY(m_context_menu_data.has_value());
 
-    if (auto result = m_content_web_view.take_dom_node_screenshot(m_context_menu_data->dom_node_id); result.is_error())
-        append_console_warning(MUST(String::formatted("Warning: {}", result.error())));
-    else
-        append_console_message(MUST(String::formatted("Screenshot saved to: {}", result.value())));
+    m_content_web_view.take_dom_node_screenshot(m_context_menu_data->dom_node_id)
+        ->when_resolved([this](auto const& path) {
+            append_console_message(MUST(String::formatted("Screenshot saved to: {}", path)));
+        })
+        .when_rejected([this](auto const& error) {
+            append_console_warning(MUST(String::formatted("Warning: {}", error)));
+        });
 
     m_context_menu_data.clear();
 }

Userland/Libraries/LibWebView/ViewImplementation.cpp

@@ -370,27 +370,65 @@ static ErrorOr<LexicalPath> save_screenshot(Gfx::ShareableBitmap const& bitmap)
     return path;
 }
 
-ErrorOr<LexicalPath> ViewImplementation::take_screenshot(ScreenshotType type)
+NonnullRefPtr<Core::Promise<LexicalPath>> ViewImplementation::take_screenshot(ScreenshotType type)
 {
+    auto promise = Core::Promise<LexicalPath>::construct();
+
+    if (m_pending_screenshot) {
+        // For simplicitly, only allow taking one screenshot at a time for now. Revisit if we need
+        // to allow spamming screenshot requests for some reason.
+        promise->reject(Error::from_string_literal("A screenshot request is already in progress"));
+        return promise;
+    }
+
     Gfx::ShareableBitmap bitmap;
 
     switch (type) {
     case ScreenshotType::Visible:
-        if (auto* visible_bitmap = m_client_state.has_usable_bitmap ? m_client_state.front_bitmap.bitmap.ptr() : m_backup_bitmap.ptr())
-            bitmap = visible_bitmap->to_shareable_bitmap();
+        if (auto* visible_bitmap = m_client_state.has_usable_bitmap ? m_client_state.front_bitmap.bitmap.ptr() : m_backup_bitmap.ptr()) {
+            if (auto result = save_screenshot(visible_bitmap->to_shareable_bitmap()); result.is_error())
+                promise->reject(result.release_error());
+            else
+                promise->resolve(result.release_value());
+        }
         break;
+
     case ScreenshotType::Full:
-        bitmap = client().take_document_screenshot();
+        m_pending_screenshot = promise;
+        client().async_take_document_screenshot();
         break;
     }
 
-    return save_screenshot(bitmap);
+    return promise;
+}
+
+NonnullRefPtr<Core::Promise<LexicalPath>> ViewImplementation::take_dom_node_screenshot(i32 node_id)
+{
+    auto promise = Core::Promise<LexicalPath>::construct();
+
+    if (m_pending_screenshot) {
+        // For simplicitly, only allow taking one screenshot at a time for now. Revisit if we need
+        // to allow spamming screenshot requests for some reason.
+        promise->reject(Error::from_string_literal("A screenshot request is already in progress"));
+        return promise;
+    }
+
+    m_pending_screenshot = promise;
+    client().async_take_dom_node_screenshot(node_id);
+
+    return promise;
 }
 
-ErrorOr<LexicalPath> ViewImplementation::take_dom_node_screenshot(i32 node_id)
+void ViewImplementation::did_receive_screenshot(Badge<WebContentClient>, Gfx::ShareableBitmap const& screenshot)
 {
-    auto bitmap = client().take_dom_node_screenshot(node_id);
-    return save_screenshot(bitmap);
+    VERIFY(m_pending_screenshot);
+
+    if (auto result = save_screenshot(screenshot); result.is_error())
+        m_pending_screenshot->reject(result.release_error());
+    else
+        m_pending_screenshot->resolve(result.release_value());
+
+    m_pending_screenshot = nullptr;
 }
 
 ErrorOr<LexicalPath> ViewImplementation::dump_gc_graph()

Userland/Libraries/LibWebView/ViewImplementation.h

@@ -11,6 +11,7 @@
 #include <AK/Function.h>
 #include <AK/LexicalPath.h>
 #include <AK/String.h>
+#include <LibCore/Promise.h>
 #include <LibGfx/Forward.h>
 #include <LibGfx/StandardCursor.h>
 #include <LibWeb/Forward.h>
@@ -95,8 +96,9 @@ class ViewImplementation {
         Visible,
         Full,
     };
-    ErrorOr<LexicalPath> take_screenshot(ScreenshotType);
-    ErrorOr<LexicalPath> take_dom_node_screenshot(i32);
+    NonnullRefPtr<Core::Promise<LexicalPath>> take_screenshot(ScreenshotType);
+    NonnullRefPtr<Core::Promise<LexicalPath>> take_dom_node_screenshot(i32);
+    virtual void did_receive_screenshot(Badge<WebContentClient>, Gfx::ShareableBitmap const&);
 
     ErrorOr<LexicalPath> dump_gc_graph();
 
@@ -229,6 +231,8 @@ class ViewImplementation {
 
     size_t m_crash_count = 0;
     RefPtr<Core::Timer> m_repeated_crash_timer;
+
+    RefPtr<Core::Promise<LexicalPath>> m_pending_screenshot;
 };
 
 }

Userland/Libraries/LibWebView/WebContentClient.cpp

@@ -231,6 +231,11 @@ void WebContentClient::did_get_dom_node_html(String const& html)
         m_view.on_received_dom_node_html(html);
 }
 
+void WebContentClient::did_take_screenshot(Gfx::ShareableBitmap const& screenshot)
+{
+    m_view.did_receive_screenshot({}, screenshot);
+}
+
 void WebContentClient::did_output_js_console_message(i32 message_index)
 {
     if (m_view.on_received_console_message)

Userland/Libraries/LibWebView/WebContentClient.h

@@ -58,6 +58,7 @@ class WebContentClient final
     virtual void did_get_hovered_node_id(i32 node_id) override;
     virtual void did_finish_editing_dom_node(Optional<i32> const& node_id) override;
     virtual void did_get_dom_node_html(String const& html) override;
+    virtual void did_take_screenshot(Gfx::ShareableBitmap const& screenshot) override;
     virtual void did_output_js_console_message(i32 message_index) override;
     virtual void did_get_js_console_messages(i32 start_index, Vector<ByteString> const& message_types, Vector<ByteString> const& messages) override;
     virtual void did_change_favicon(Gfx::ShareableBitmap const&) override;

Userland/Services/WebContent/ConnectionFromClient.cpp

@@ -854,33 +854,37 @@ void ConnectionFromClient::js_console_request_messages(i32 start_index)
         m_top_level_document_console_client->send_messages(start_index);
 }
 
-Messages::WebContentServer::TakeDocumentScreenshotResponse ConnectionFromClient::take_document_screenshot()
+void ConnectionFromClient::take_document_screenshot()
 {
     auto* document = page().page().top_level_browsing_context().active_document();
-    if (!document || !document->document_element())
-        return Gfx::ShareableBitmap {};
+    if (!document || !document->document_element()) {
+        async_did_take_screenshot({});
+        return;
+    }
 
     auto const& content_size = page().content_size();
     Web::DevicePixelRect rect { { 0, 0 }, content_size };
 
     auto bitmap = Gfx::Bitmap::create(Gfx::BitmapFormat::BGRA8888, rect.size().to_type<int>()).release_value_but_fixme_should_propagate_errors();
     page().paint(rect, *bitmap);
 
-    return bitmap->to_shareable_bitmap();
+    async_did_take_screenshot(bitmap->to_shareable_bitmap());
 }
 
-Messages::WebContentServer::TakeDomNodeScreenshotResponse ConnectionFromClient::take_dom_node_screenshot(i32 node_id)
+void ConnectionFromClient::take_dom_node_screenshot(i32 node_id)
 {
     auto* dom_node = Web::DOM::Node::from_unique_id(node_id);
-    if (!dom_node || !dom_node->paintable_box())
-        return Gfx::ShareableBitmap {};
+    if (!dom_node || !dom_node->paintable_box()) {
+        async_did_take_screenshot({});
+        return;
+    }
 
     auto rect = page().page().enclosing_device_rect(dom_node->paintable_box()->absolute_border_box_rect());
 
     auto bitmap = Gfx::Bitmap::create(Gfx::BitmapFormat::BGRA8888, rect.size().to_type<int>()).release_value_but_fixme_should_propagate_errors();
     page().paint(rect, *bitmap, { .paint_overlay = Web::PaintOptions::PaintOverlay::No });
 
-    return bitmap->to_shareable_bitmap();
+    async_did_take_screenshot(bitmap->to_shareable_bitmap());
 }
 
 Messages::WebContentServer::DumpGcGraphResponse ConnectionFromClient::dump_gc_graph()

Userland/Services/WebContent/ConnectionFromClient.h

@@ -121,8 +121,8 @@ class ConnectionFromClient final
 
     virtual void enable_inspector_prototype() override;
 
-    virtual Messages::WebContentServer::TakeDocumentScreenshotResponse take_document_screenshot() override;
-    virtual Messages::WebContentServer::TakeDomNodeScreenshotResponse take_dom_node_screenshot(i32 node_id) override;
+    virtual void take_document_screenshot() override;
+    virtual void take_dom_node_screenshot(i32 node_id) override;
 
     virtual Messages::WebContentServer::DumpGcGraphResponse dump_gc_graph() override;