Merge branch 'tabs'

Closes #508

CHANGELOG.md

@@ -101,6 +101,8 @@
 * Reverse video (`\E[?5h`) now only swaps the default foreground and
   background colors. Cells with explicit foreground and/or background
   colors remain unchanged.
+* Tabs (`\t`) are now preserved when the window is resized, and when
+  copying text (https://codeberg.org/dnkl/foot/issues/508).
 
 
 ### Deprecated

csi.c

@@ -1120,7 +1120,10 @@ csi_dispatch(struct terminal *term, uint8_t final)
                     }
                 }
                 xassert(new_col >= term->grid->cursor.point.col);
+
+                bool lcf = term->grid->cursor.lcf;
                 term_cursor_right(term, new_col - term->grid->cursor.point.col);
+                term->grid->cursor.lcf = lcf;
             }
             break;
         }

extract.c

@@ -9,6 +9,7 @@ struct extraction_context {
     wchar_t *buf;
     size_t size;
     size_t idx;
+    size_t tab_spaces_left;
     size_t empty_count;
     size_t newline_count;
     bool strip_trailing_empty;
@@ -191,8 +192,17 @@ extract_one(const struct terminal *term, const struct row *row,
             }
             ctx->empty_count = 0;
         }
+
+        ctx->tab_spaces_left = 0;
     }
 
+    if (cell->wc == L' ' && ctx->tab_spaces_left > 0) {
+        ctx->tab_spaces_left--;
+        return true;
+    }
+
+    ctx->tab_spaces_left = 0;
+
     if (cell->wc == 0) {
         ctx->empty_count++;
         ctx->last_row = row;
@@ -231,6 +241,19 @@ extract_one(const struct terminal *term, const struct row *row,
         if (!ensure_size(ctx, 1))
             goto err;
         ctx->buf[ctx->idx++] = cell->wc;
+
+        if (cell->wc == L'\t') {
+            int next_tab_stop = term->cols - 1;
+            tll_foreach(term->tab_stops, it) {
+                if (it->item > col) {
+                    next_tab_stop = it->item;
+                    break;
+                }
+            }
+
+            xassert(next_tab_stop >= col);
+            ctx->tab_spaces_left = next_tab_stop - col;
+        }
     }
 
     ctx->last_row = row;

render.c

@@ -620,7 +620,7 @@ render_cell(struct terminal *term, pixman_image_t *pix,
     if (has_cursor && term->cursor_style == CURSOR_BLOCK && term->kbd_focus)
         draw_cursor(term, cell, font, pix, &fg, &bg, x, y, cell_cols);
 
-    if (cell->wc == 0 || cell->wc >= CELL_SPACER ||
+    if (cell->wc == 0 || cell->wc >= CELL_SPACER || cell->wc == L'\t' ||
         (unlikely(cell->attrs.conceal) && !is_selected))
     {
         goto draw_cursor;

vt.c

@@ -162,20 +162,58 @@ action_execute(struct terminal *term, uint8_t c)
 
     case '\t': {
         /* HT - horizontal tab */
+        int start_col = term->grid->cursor.point.col;
         int new_col = term->cols - 1;
+
         tll_foreach(term->tab_stops, it) {
-            if (it->item > term->grid->cursor.point.col) {
+            if (it->item > start_col) {
                 new_col = it->item;
                 break;
             }
         }
-        xassert(new_col >= term->grid->cursor.point.col);
+        xassert(new_col >= start_col);
+        xassert(new_col < term->cols);
+
+        struct row *row = term->grid->cur_row;
+
+        bool emit_tab_char = (row->cells[start_col].wc == 0 ||
+                              row->cells[start_col].wc == L' ');
+
+        /* Check if all cells from here until the next tab stop are empty */
+        for (const struct cell *cell = &row->cells[start_col + 1];
+             cell < &row->cells[new_col];
+             cell++)
+        {
+            if (!(cell->wc == 0 || cell->wc == L' ')) {
+                emit_tab_char = false;
+                break;
+            }
+        }
+
+        /*
+         * Emit a tab in current cell, and write spaces to the
+         * subsequent cells, all the way until the next tab stop.
+         */
+        if (emit_tab_char) {
+            row->dirty = true;
+
+            row->cells[start_col].wc = '\t';
+            row->cells[start_col].attrs.clean = 0;
+
+            for (struct cell *cell = &row->cells[start_col + 1];
+                 cell < &row->cells[new_col];
+                 cell++)
+            {
+                cell->wc = L' ';
+                cell->attrs.clean = 0;
+            }
+        }
 
         /* According to the specification, HT _should_ cancel LCF. But
          * XTerm, and nearly all other emulators, don't. So we follow
          * suit */
         bool lcf = term->grid->cursor.lcf;
-        term_cursor_right(term, new_col - term->grid->cursor.point.col);
+        term_cursor_right(term, new_col - start_col);
         term->grid->cursor.lcf = lcf;
         break;
     }