LibWeb: Allow scrolling overflowed content with the mouse wheel :^)

This is rather crude, but you can now use the mouse wheel to scroll up
and down in block-level boxes with clipped overflowing content.
There's no limit to how far you can scroll in either direction, since
we don't yet track how much overflow there is. But it's a start. :^)

1 files changed, 16 insertions, 0 deletions

diff --git a/Userland/Libraries/LibWeb/Layout/BlockBox.cpp b/Userland/Libraries/LibWeb/Layout/BlockBox.cpp
index c0a05cae33..a23d33d1e2 100644
--- a/Userland/Libraries/LibWeb/Layout/BlockBox.cpp
+++ b/Userland/Libraries/LibWeb/Layout/BlockBox.cpp
@@ -68,6 +68,7 @@ void BlockBox::paint(PaintContext& context, PaintPhase phase)
         context.painter().save();
         // FIXME: Handle overflow-x and overflow-y being different values.
         context.painter().add_clip_rect(enclosing_int_rect(padded_rect()));
+        context.painter().translate(-m_scroll_offset.to_type<int>());
     }
 
     for (auto& line_box : m_line_boxes) {
@@ -141,4 +142,19 @@ void BlockBox::split_into_lines(InlineFormattingContext& context, LayoutMode lay
     line_box->add_fragment(*this, 0, 0, border_box_width(), height());
 }
 
+void BlockBox::set_scroll_offset(const Gfx::FloatPoint& offset)
+{
+    if (m_scroll_offset == offset)
+        return;
+    m_scroll_offset = offset;
+    set_needs_display();
+}
+
+void BlockBox::handle_mousewheel(Badge<EventHandler>, const Gfx::IntPoint&, unsigned int, unsigned int, int wheel_delta)
+{
+    auto new_offset = m_scroll_offset;
+    new_offset.move_by(0, wheel_delta);
+    set_scroll_offset(new_offset);
+}
+
 }