Merge branch 'reverse-wrap' into master

Closes #150

CHANGELOG.md

@@ -16,6 +16,13 @@
 
 ## Unreleased
 ### Added
+
+* Implement reverse auto-wrap (_auto\_left\_margin_, _bw_, in
+  terminfo). This mode can be enabled/disabled with `CSI ? 45 h` and
+  `CSI `45 l`. It is **enabled** by default
+  (https://codeberg.org/dnkl/foot/issues/150).
+
+
 ### Changed
 
 * Default value of the **scrollback.multiplier** option in `foot.ini`

csi.c

@@ -399,6 +399,10 @@ decset_decrst(struct terminal *term, unsigned param, bool enable)
         term->hide_cursor = !enable;
         break;
 
+    case 45:
+        term->reverse_wrap = enable;
+        break;
+
     case 1000:
         if (enable)
             term->mouse_tracking = MOUSE_CLICK;
@@ -576,6 +580,7 @@ xtsave(struct terminal *term, unsigned param)
     }
 
     case 25: term->xtsave.show_cursor = !term->hide_cursor; break;
+    case 45: term->xtsave.reverse_wrap = term->reverse_wrap; break;
     case 1000: term->xtsave.mouse_click = term->mouse_tracking == MOUSE_CLICK; break;
     case 1001: break;
     case 1002: term->xtsave.mouse_drag = term->mouse_tracking == MOUSE_DRAG; break;
@@ -606,6 +611,7 @@ xtrestore(struct terminal *term, unsigned param)
     case 9: /* enable = term->xtsave.mouse_x10; break; */ return;
     case 12: enable = term->xtsave.cursor_blink; break;
     case 25: enable = term->xtsave.show_cursor; break;
+    case 45: enable = term->xtsave.reverse_wrap; break;
     case 1000: enable = term->xtsave.mouse_click; break;
     case 1001: return;
     case 1002: enable = term->xtsave.mouse_drag; break;

foot.info

@@ -14,6 +14,7 @@ foot-direct|foot with direct color indexing,
 foot+base|foot base fragment,
     am,
     bce,
+    bw,
     ccc,
     km,
     mir,

terminal.c

@@ -904,6 +904,7 @@ term_init(const struct config *conf, struct fdm *fdm, struct reaper *reaper,
                           : FCFT_SUBPIXEL_NONE),
         .cursor_keys_mode = CURSOR_KEYS_NORMAL,
         .keypad_keys_mode = KEYPAD_NUMERICAL,
+        .reverse_wrap = true,
         .auto_margin = true,
         .window_title_stack = tll_init(),
         .scale = 1,
@@ -1394,6 +1395,7 @@ term_reset(struct terminal *term, bool hard)
     term->keypad_keys_mode = KEYPAD_NUMERICAL;
     term->reverse = false;
     term->hide_cursor = false;
+    term->reverse_wrap = true;
     term->auto_margin = true;
     term->insert_mode = false;
     term->bracketed_paste = false;
@@ -1728,9 +1730,44 @@ 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 && term->auto_margin)) {
+
+            /* 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;
 }
 

terminal.h

@@ -237,6 +237,7 @@ struct terminal {
     enum keypad_keys keypad_keys_mode;
     bool reverse;
     bool hide_cursor;
+    bool reverse_wrap;
     bool auto_margin;
     bool insert_mode;
     bool bracketed_paste;
@@ -256,6 +257,7 @@ struct terminal {
         uint32_t application_cursor_keys:1;
         uint32_t reverse:1;
         uint32_t show_cursor:1;
+        uint32_t reverse_wrap:1;
         uint32_t auto_margin:1;
         uint32_t cursor_blink:1;
         uint32_t insert_mode:1;

vt.c

@@ -130,7 +130,10 @@ action_execute(struct terminal *term, uint8_t c)
 
     case '\b':
         /* backspace */
-        term_cursor_left(term, 1);
+        if (term->grid->cursor.lcf)
+            term->grid->cursor.lcf = false;
+        else
+            term_cursor_left(term, 1);
         break;
 
     case '\t': {