TXT2MTXT: combine text into MText, with its settings dialog

TEXT and MTEXT objects are merged into one MTEXT (top-down or in
selection order, word-wrapped or one paragraph per object, with the
original pitch kept as line spacing) or each TEXT and MTEXT line becomes
an MTEXT of its own. The SEttings option opens the Combine Text settings
dialog; the settings persist as profile values and are exposed as the
TXT2MTXT* variables and the txt2mtxt_settings automation action.

Co-Authored-By: Claude Opus 5.5 <[email protected]>

src/entities/mtext.rs

@@ -114,6 +114,16 @@ fn display_text(t: &MText, document: &codec::CadDocument) -> String {
 /// click-to-select preview. Uses the exact same layout opts as `to_render`
 /// so the boxes line up with the rendered glyphs.
 pub fn glyph_boxes(t: &MText, document: &codec::CadDocument) -> Vec<GlyphBox> {
+    layout_of(t, document, true).glyph_boxes
+}
+
+/// The MTEXT laid out as it is drawn: its sub-lines, their widths and the
+/// first baseline, in the entity's own (pre-rotation) frame.
+pub fn layout_of(
+    t: &MText,
+    document: &codec::CadDocument,
+    want_glyph_boxes: bool,
+) -> crate::entities::text_support::MTextLayout {
     let resolved_style = resolve_text_style(&t.style, document);
     let attach_h_anchor: f32 = match t.attachment_point {
         AttachmentPoint::TopCenter
@@ -143,7 +153,7 @@ pub fn glyph_boxes(t: &MText, document: &codec::CadDocument) -> Vec<GlyphBox> {
     // A field shows its stored value: fields update on their evaluation
     // events (open, save, plot, regen, UPDATEFIELD), never on a redraw.
     let display = display_text(t, document);
-    let layout = layout_mtext(&MTextRenderOpts {
+    layout_mtext(&MTextRenderOpts {
         value: &display,
         insertion: [
             t.insertion_point.x,
@@ -165,10 +175,9 @@ pub fn glyph_boxes(t: &MText, document: &codec::CadDocument) -> Vec<GlyphBox> {
         vertical_text: matches!(t.drawing_direction, DrawingDirection::TopToBottom)
             || matches!(t.drawing_direction, DrawingDirection::ByStyle)
                 && resolved_style.is_vertical,
-        want_glyph_boxes: true,
+        want_glyph_boxes,
         columns: columns_of(t),
-    });
-    layout.glyph_boxes
+    })
 }
 
 fn to_render(t: &MText, document: &codec::CadDocument) -> RenderEntity {