Stop assuming xwidget views will only be displayed in TEXT_AREA

* src/xterm.c (x_scroll_run): Use view->area when calculating
xwidget view clipping.

* src/xwidget.c (x_draw_xwidget_glyph_string): Set view->area
to s->area and use that instead.

* src/xwidget.h (struct xwidget_view): Add glyph row area field.

src/xterm.c

@@ -4439,7 +4439,7 @@ x_scroll_run (struct window *w, struct run *run)
 		  int text_area_x, text_area_y, text_area_width, text_area_height;
 		  int clip_top, clip_bottom;
 
-		  window_box (w, TEXT_AREA, &text_area_x, &text_area_y,
+		  window_box (w, view->area, &text_area_x, &text_area_y,
 			      &text_area_width, &text_area_height);
 
 		  view->y = y;

src/xwidget.c

@@ -1631,7 +1631,9 @@ x_draw_xwidget_glyph_string (struct glyph_string *s)
     }
 #endif
 
-  window_box (s->w, TEXT_AREA, &text_area_x, &text_area_y,
+  xv->area = s->area;
+
+  window_box (s->w, xv->area, &text_area_x, &text_area_y,
               &text_area_width, &text_area_height);
 
   clip_left = max (0, text_area_x - x);

src/xwidget.h

@@ -104,6 +104,8 @@ struct xwidget_view
   /* The "live" instance isn't drawn.  */
   bool hidden;
 
+  enum glyph_row_area area;
+
 #if defined (USE_GTK)
   Display *dpy;
   Window wdesc;