sixel: implement private mode 8452 - cursor positioning after sixel

When disabled (the default), the cursor is positioned on a new line
after emitting a sixel image.

When enabled, the cursor is positioned to the right of the sixel
image.

Closes #363

CHANGELOG.md

@@ -47,6 +47,8 @@
   (https://codeberg.org/dnkl/foot/issues/347)
 * `DECSET 1070` - sixel private color palette
   (https://codeberg.org/dnkl/foot/issues/362).
+* `DECSET 8452` - position cursor to the right of sixels
+  (https://codeberg.org/dnkl/foot/issues/363).
 
 
 ### Changed

csi.c

@@ -552,6 +552,10 @@ decset_decrst(struct terminal *term, unsigned param, bool enable)
         term->bracketed_paste = enable;
         break;
 
+    case 8452:
+        term->sixel.cursor_right_of_graphics = enable;
+        break;
+
     case 27127:
         term->modify_escape_key = enable;
         break;
@@ -613,6 +617,7 @@ decrqm(const struct terminal *term, unsigned param, bool *enabled)
     case 1049: *enabled = term->grid == &term->alt; return true;
     case 1079: *enabled = term->sixel.use_private_palette; return true;
     case 2004: *enabled = term->bracketed_paste; return true;
+    case 8452: *enabled = term->sixel.cursor_right_of_graphics; return true;
     case 27127: *enabled = term->modify_escape_key; return true;
     case 737769: *enabled = term_ime_is_enabled(term); return true;
     }
@@ -653,6 +658,7 @@ xtsave(struct terminal *term, unsigned param)
     case 1049: term->xtsave.alt_screen = term->grid == &term->alt; break;
     case 1070: term->xtsave.sixel_private_palette = term->sixel.use_private_palette; break;
     case 2004: term->xtsave.bracketed_paste = term->bracketed_paste; break;
+    case 8452: term->xtsave.sixel_cursor_right_of_graphics = term->sixel.cursor_right_of_graphics; break;
     case 27127: term->xtsave.modify_escape_key = term->modify_escape_key; break;
     case 737769: term->xtsave.ime = term_ime_is_enabled(term); break;
     }
@@ -692,6 +698,7 @@ xtrestore(struct terminal *term, unsigned param)
     case 1049: enable = term->xtsave.alt_screen; break;
     case 1070: enable = term->xtsave.sixel_private_palette; break;
     case 2004: enable = term->xtsave.bracketed_paste; break;
+    case 8452: enable = term->xtsave.sixel_cursor_right_of_graphics; break;
     case 27127: enable = term->xtsave.modify_escape_key; break;
     case 737769: enable = term->xtsave.ime; break;
 

doc/foot-ctlseqs.5.scd

@@ -316,6 +316,9 @@ that corresponds to one of the following modes:
 |  2004
 :  xterm
 :  Wrap pasted text with start/end delimiters (bracketed paste mode)
+|  8452
+:  xterm
+:  Position cursor to the right of sixels, instead of on the next line
 |  737769
 :  foot
 :  Input Method Editor (IME) mode

sixel.c

@@ -767,9 +767,29 @@ sixel_unhook(struct terminal *term)
             {
                 row->cells[col].attrs.clean = 0;
             }
-            term_linefeed(term);
+
+            if (i < image.rows - 1 || !term->sixel.cursor_right_of_graphics)
+                term_linefeed(term);
         }
-        term_carriage_return(term);
+
+        /*
+         * Position cursor
+         *
+         * Private mode 8452 controls where we leave the cursor after
+         * emitting a sixel:
+         *
+         * When disabled (the default), the cursor is positioned on a
+         * new line.
+         *
+         * When enabled, the cursor is positioned to the right of the
+         * sixel.
+         */
+        term_cursor_to(
+            term,
+            term->grid->cursor.point.row,
+            (term->sixel.cursor_right_of_graphics
+             ? min(image.pos.col + image.cols, term->cols - 1)
+             : 0));
 
         _sixel_overwrite_by_rectangle(
             term, image.pos.row, image.pos.col, image.rows, image.cols);

terminal.h

@@ -361,6 +361,7 @@ struct terminal {
         uint32_t ime:1;
 
         uint32_t sixel_private_palette:1;
+        uint32_t sixel_cursor_right_of_graphics:1;
     } xtsave;
 
     char *window_title;
@@ -538,6 +539,8 @@ struct terminal {
         unsigned param;      /* Currently collecting parameter, for RASTER, COLOR_SPEC and REPEAT */
         unsigned param_idx;  /* Parameters seen */
 
+        bool cursor_right_of_graphics:1;  /* Private mode 8452 */
+
         /* Application configurable */
         unsigned palette_size;  /* Number of colors in palette */
         unsigned max_width;     /* Maximum image width, in pixels */