LibWeb: Allow layout nodes to receive and track mouse events

To implement form controls internally in LibWeb (necessary for multi
process forms), we'll need the ability to handle events since we can't
rely on LibGUI widgets anymore.

A LayoutNode can now override wants_mouse_events() and if it returns
true, it will now receive mousedown, mousemove and mouseup events. :^)

1 files changed, 44 insertions, 0 deletions

diff --git a/Libraries/LibWeb/Page/EventHandler.cpp b/Libraries/LibWeb/Page/EventHandler.cpp
index 32b750a821..57b73c9673 100644
--- a/Libraries/LibWeb/Page/EventHandler.cpp
+++ b/Libraries/LibWeb/Page/EventHandler.cpp
@@ -75,9 +75,20 @@ bool EventHandler::handle_mouseup(const Gfx::IntPoint& position, unsigned button
 {
     if (!layout_root())
         return false;
+
+    if (m_mouse_event_tracking_layout_node) {
+        m_mouse_event_tracking_layout_node->handle_mouseup({}, position, button, modifiers);
+        return true;
+    }
+
     bool handled_event = false;
 
     auto result = layout_root()->hit_test(position, HitTestType::Exact);
+
+    if (result.layout_node && result.layout_node->wants_mouse_events()) {
+        result.layout_node->handle_mouseup({}, position, button, modifiers);
+    }
+
     if (result.layout_node && result.layout_node->node()) {
         RefPtr<DOM::Node> node = result.layout_node->node();
         if (is<HTML::HTMLIFrameElement>(*node)) {
@@ -101,6 +112,12 @@ bool EventHandler::handle_mousedown(const Gfx::IntPoint& position, unsigned butt
 {
     if (!layout_root())
         return false;
+
+    if (m_mouse_event_tracking_layout_node) {
+        m_mouse_event_tracking_layout_node->handle_mousedown({}, position, button, modifiers);
+        return true;
+    }
+
     NonnullRefPtr document = *m_frame.document();
     auto& page_client = m_frame.page().client();
 
@@ -108,6 +125,11 @@ bool EventHandler::handle_mousedown(const Gfx::IntPoint& position, unsigned butt
     if (!result.layout_node)
         return false;
 
+    if (result.layout_node->wants_mouse_events()) {
+        result.layout_node->handle_mousedown({}, position, button, modifiers);
+        return true;
+    }
+
     RefPtr<DOM::Node> node = result.layout_node->node();
     document->set_hovered_node(node);
     if (!node)
@@ -171,6 +193,12 @@ bool EventHandler::handle_mousemove(const Gfx::IntPoint& position, unsigned butt
 {
     if (!layout_root())
         return false;
+
+    if (m_mouse_event_tracking_layout_node) {
+        m_mouse_event_tracking_layout_node->handle_mousemove({}, position, buttons, modifiers);
+        return true;
+    }
+
     auto& document = *m_frame.document();
     auto& page_client = m_frame.page().client();
 
@@ -180,6 +208,14 @@ bool EventHandler::handle_mousemove(const Gfx::IntPoint& position, unsigned butt
     auto result = layout_root()->hit_test(position, HitTestType::Exact);
     const HTML::HTMLAnchorElement* hovered_link_element = nullptr;
     if (result.layout_node) {
+
+        if (result.layout_node->wants_mouse_events()) {
+            result.layout_node->handle_mousemove({}, position, buttons, modifiers);
+            // FIXME: It feels a bit aggressive to always update the cursor like this.
+            page_client.page_did_request_cursor_change(Gfx::StandardCursor::None);
+            return true;
+        }
+
         RefPtr<DOM::Node> node = result.layout_node->node();
 
         if (node && is<HTML::HTMLIFrameElement>(*node)) {
@@ -313,4 +349,12 @@ bool EventHandler::handle_keydown(KeyCode key, unsigned modifiers, u32 code_poin
     return false;
 }
 
+void EventHandler::set_mouse_event_tracking_layout_node(LayoutNode* layout_node)
+{
+    if (layout_node)
+        m_mouse_event_tracking_layout_node = layout_node->make_weak_ptr();
+    else
+        m_mouse_event_tracking_layout_node = nullptr;
+}
+
 }