Frame X test: the corner-to-corner lines from main's split canvas frames module

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

crates/ui-egui/src/canvas.rs

@@ -30,7 +30,7 @@ mod view;
 use column_guides::{COLUMN_DRAG, ColumnDrag, column_guide_at, spread_x_across};
 use frames::{draw_frames, draw_selection};
 #[cfg(test)]
-use frames::{item_canvas_xf, overset_frames, overset_marks, ported_frames, text_frames_in};
+use frames::{frame_x, item_canvas_xf, overset_frames, overset_marks, ported_frames, text_frames_in};
 use guides::{GUIDE_DRAG, GUIDE_PRESS, GuideDrag, GuidePress, guide_readout, guide_spot, moving_guides, readout_at};
 #[cfg(test)]
 use guides::{guide_at, guide_drag_delta, guide_measure};

crates/ui-egui/src/canvas/frames.rs

@@ -135,7 +135,7 @@ fn draw_item_edges(painter: &egui::Painter, xf: &Xf, doc: &Document, it: &Item,
 /// The X of an empty graphic frame, in its own space: a four-cornered frame joins its opposite
 /// corners, so a frame slanted with Direct Selection keeps its X corner to corner, as InDesign
 /// draws it; other shapes span their bounds.
-fn frame_x(it: &Item) -> [(Point, Point); 2] {
+pub(super) fn frame_x(it: &Item) -> [(Point, Point); 2] {
     // A rectangle (slanted or not: four corner points, no handles). Ellipses, polygons (a
     // four-sided one is a diamond) and curved paths keep the X across their bounds. Edited points
     // make any of them a path: a four-cornered one whose corners would cross as a plus (a diamond,