LibWeb: Make MouseEvent.offsetX/Y ignore transforms

That is what the spec calls it, at least.
In code, this manifests as making the offset very aware
of the element's transform, because the click position comes
relative to the viewport, not to the transformed element.
This commit is contained in:
Psychpsyo 2024-11-19 22:26:00 +01:00
parent 24a6fd3d76
commit 1921bba601
3 changed files with 58 additions and 4 deletions

View file

@ -136,13 +136,44 @@ static Gfx::StandardCursor cursor_css_to_gfx(Optional<CSS::Cursor> cursor)
} }
} }
// https://drafts.csswg.org/cssom-view/#dom-mouseevent-offsetx
static CSSPixelPoint compute_mouse_event_offset(CSSPixelPoint position, Layout::Node const& layout_node) static CSSPixelPoint compute_mouse_event_offset(CSSPixelPoint position, Layout::Node const& layout_node)
{ {
auto top_left_of_layout_node = layout_node.first_paintable()->box_type_agnostic_position(); // If the events dispatch flag is set,
return { // FIXME: Is this guaranteed to be dispatched?
position.x() - top_left_of_layout_node.x(),
position.y() - top_left_of_layout_node.y() // return the x-coordinate of the position where the event occurred,
Gfx::Point<float> precision_offset = {
position.x().to_double(),
position.y().to_double()
}; };
// ignoring the transforms that apply to the element and its ancestors,
if (layout_node.has_css_transform()) {
auto const& paintable_box = layout_node.dom_node()->paintable_box();
auto const affine_transform = Gfx::extract_2d_affine_transform(paintable_box->transform().inverse());
auto const& origin = paintable_box->transform_origin();
Gfx::Point<float> const precision_origin = {
origin.x().to_double(),
origin.y().to_double()
};
precision_offset.translate_by(-precision_origin);
precision_offset.transform_by(affine_transform);
precision_offset.translate_by(precision_origin);
}
// relative to the origin of the padding edge of the target node
auto const top_left_of_layout_node = layout_node.first_paintable()->box_type_agnostic_position();
CSSPixelPoint offset = {
CSSPixels(precision_offset.x()),
CSSPixels(precision_offset.y())
};
offset -= top_left_of_layout_node;
// and terminate these steps.
return offset;
} }
EventHandler::EventHandler(Badge<HTML::Navigable>, HTML::Navigable& navigable) EventHandler::EventHandler(Badge<HTML::Navigable>, HTML::Navigable& navigable)

View file

@ -0,0 +1,2 @@
offsetX: 45.75
offsetY: 57.078125

View file

@ -0,0 +1,21 @@
<!DOCTYPE html>
<style>
div {
width: 100px;
height: 100px;
background-color: gray;
transform: rotate(45deg);
}
</style>
<div onClick="
println(`offsetX: ${event.offsetX}`);
println(`offsetY: ${event.offsetY}`);
"></div>
<script src="../include.js"></script>
<script>
test(() => {
internals.click(50, 60);
});
</script>