From ffa123e5ba835bb68b063b017df144fb7f5d05ce Mon Sep 17 00:00:00 2001
From: Thomas White <taw@physics.org>
Date: Sun, 18 Mar 2018 16:15:53 +0100
Subject: Disallow insertion and deletion unless scblock==rscblock

---
 src/frame.c     | 39 +++++++++++++++++++++++++++++++++++++++
 src/frame.h     |  2 ++
 src/sc_editor.c | 20 +++++++++++---------
 src/sc_interp.c |  2 +-
 4 files changed, 53 insertions(+), 10 deletions(-)

diff --git a/src/frame.c b/src/frame.c
index 27e2210..a125ce6 100644
--- a/src/frame.c
+++ b/src/frame.c
@@ -961,6 +961,40 @@ size_t pos_trail_to_offset(Paragraph *para, size_t offs, int trail)
 }
 
 
+int position_editable(struct frame *fr, struct edit_pos cp)
+{
+	Paragraph *para;
+	int run;
+	size_t paraoffs;
+
+	if ( fr == NULL ) {
+		fprintf(stderr, "Frame is NULL.\n");
+		return 0;
+	}
+
+	if ( cp.para >= fr->n_paras ) {
+		fprintf(stderr, "Paragraph number is too high!\n");
+		return 0;
+	}
+
+	para = fr->paras[cp.para];
+
+	if ( para->scblock != para->rscblock ) {
+		fprintf(stderr, "Paragraph is not editable.\n");
+		return 0;
+	}
+
+	paraoffs = pos_trail_to_offset(para, cp.pos, cp.trail);
+	run = which_run(para, paraoffs);
+	if ( run == para->n_runs ) {
+		fprintf(stderr, "Couldn't find run!\n");
+		return 0;
+	}
+
+	return (para->runs[run].scblock == para->runs[run].rscblock);
+}
+
+
 void insert_text_in_paragraph(Paragraph *para, size_t offs, const char *t)
 {
 	int nrun;
@@ -1391,6 +1425,11 @@ void delete_text_from_frame(struct frame *fr, struct edit_pos p1, struct edit_po
 
 	sort_positions(&p1, &p2);
 
+	if ( !position_editable(fr, p1) || !position_editable(fr, p2) ) {
+		fprintf(stderr, "Block delete outside editable region\n");
+		return;
+	}
+
 	/* Find SC positions for start and end */
 	p1scblock = pos_to_scblock(fr, p1, &type1);
 	p2scblock = pos_to_scblock(fr, p2, &type2);
diff --git a/src/frame.h b/src/frame.h
index 2548d6d..8eae26a 100644
--- a/src/frame.h
+++ b/src/frame.h
@@ -164,6 +164,8 @@ extern int positions_equal(struct edit_pos a, struct edit_pos b);
 extern int get_para_highlight(struct frame *fr, int cursor_para,
                               double *cx, double *cy, double *cw, double *ch);
 
+extern int position_editable(struct frame *fr, struct edit_pos cp);
+
 extern int get_cursor_pos(struct frame *fr, int cursor_para, int cursor_pos,
                           double *cx, double *cy, double *ch);
 
diff --git a/src/sc_editor.c b/src/sc_editor.c
index 065c76b..36ea899 100644
--- a/src/sc_editor.c
+++ b/src/sc_editor.c
@@ -748,9 +748,16 @@ static void do_backspace(struct frame *fr, SCEditor *e)
 			show_edit_pos(p1);
 			show_edit_pos(p2);
 
-			delete_text_from_frame(e->cursor_frame, p1, p2, wrapw);
+			if ( position_editable(e->cursor_frame, p1)
+			  && position_editable(e->cursor_frame, p2) )
+			{
 
-			e->cpos = p2;
+				delete_text_from_frame(e->cursor_frame, p1, p2, wrapw);
+				e->cpos = p2;
+
+			} else {
+				fprintf(stderr, "Deleting not editable.\n");
+			}
 
 		} else {
 
@@ -770,13 +777,8 @@ static void insert_text(char *t, SCEditor *e)
 {
 	Paragraph *para;
 
-	if ( e->cursor_frame == NULL ) {
-		fprintf(stderr, "Inserting text into no frame.\n");
-	        return;
-	}
-
-	if ( e->cpos.para >= e->cursor_frame->n_paras ) {
-		fprintf(stderr, "Cursor paragraph number is too high!\n");
+	if ( !position_editable(e->cursor_frame, e->cpos) ) {
+		fprintf(stderr, "Position not editable\n");
 		return;
 	}
 
diff --git a/src/sc_interp.c b/src/sc_interp.c
index 6914b13..55d5f34 100644
--- a/src/sc_interp.c
+++ b/src/sc_interp.c
@@ -243,7 +243,7 @@ static int check_callback(SCInterpreter *scin, SCBlock *bl)
 		if ( strcmp(cbl->names[i], name) != 0 ) continue;
 		r = cbl->box_funcs[i](scin, bl, &w, &h, &bvp, cbl->vps[i]);
 		if ( r )  {
-			add_callback_para(sc_interp_get_frame(scin), bl, w, h,
+			add_callback_para(sc_interp_get_frame(scin), bl, rbl, w, h,
 			                  cbl->draw_funcs[i], cbl->click_funcs[i],
 			                  bvp, cbl->vps[i]);
 		}
-- 
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