term: cursor-left: reverse-wrap when cursor is at the left margin

Assuming the private mode ‘reverse-wrap’ has been enabled.

terminal.c

@@ -1728,9 +1728,44 @@ term_cursor_home(struct terminal *term)
 void
 term_cursor_left(struct terminal *term, int count)
 {
-    int move_amount = min(term->grid->cursor.point.col, count);
+    assert(count >= 0);
-    term->grid->cursor.point.col -= move_amount;
+    int new_col = term->grid->cursor.point.col - count;
-    assert(term->grid->cursor.point.col >= 0);
+
+    /* Reverse wrap */
+    if (unlikely(new_col < 0)) {
+        if (unlikely(term->reverse_wrap)) {
+
+            /* Number of rows to reverse wrap through */
+            int row_count = (abs(new_col) - 1) / term->cols + 1;
+
+            /* Row number cursor will end up on */
+            int new_row_no = term->grid->cursor.point.row - row_count;
+
+            /* New column number */
+            new_col = term->cols - ((abs(new_col) - 1) % term->cols + 1);
+            assert(new_col >= 0 && new_col < term->cols);
+
+            /* Don't back up past the scroll region */
+            /* TODO: should this be allowed? */
+            if (new_row_no < term->scroll_region.start) {
+                new_row_no = term->scroll_region.start;
+                new_col = 0;
+            }
+
+            struct row *new_row = grid_row(term->grid, new_row_no);
+            term->grid->cursor.point.col = new_col;
+            term->grid->cursor.point.row = new_row_no;
+            term->grid->cursor.lcf = false;
+            term->grid->cur_row = new_row;
+            return;
+        }
+
+        /* Reverse wrap disabled - don't let cursor move past first column */
+        new_col = 0;
+    }
+
+    assert(new_col >= 0);
+    term->grid->cursor.point.col = new_col;
     term->grid->cursor.lcf = false;
 }