sidebar: air between tabs (tab_gap)

A tab carrying three rows of wrapped status and the tab under it carrying
three more read as one column of text: the labels are in there, but the list
has stopped looking like a list. tab_gap is the blank rows between them, 0 by
default, which is exactly what the sidebar has always drawn.

It is the space *between* tabs and nothing else. Above the first tab is
tab_bar_pad's and before the button is newtab_pad's, so the gap is applied
before each label except the first and none of the three is ever paid twice.

Given up a row at a time when the list is short of room, ahead of every label
and the button, which is the same order the pad and the statuses already
follow: a gap that pushed a tab off the bottom would be spacing costing you
the thing it spaces. Paint rather than layout, so tuning it repaints without
reflowing any pane. Sidebars only -- the top strip is one row, and the space
between tabs there is the label's own padding.

2 files changed, 23 insertions, 0 deletions

diff --git a/src/app_draw.c b/src/app_draw.c
index 863b7f0..a363143 100644
--- a/src/app_draw.c
+++ b/src/app_draw.c
@@ -2188,6 +2188,23 @@ void draw_tab_sidebar(app_t *a, screen_t *s) {
   uint16_t btn_rows =
       (CFG.newtab_button && cells(CFG.newtab_mark)) ? (uint16_t)1 : (uint16_t)0;
   for (size_t i = 0; i < a->ntabs && y < limit; i++) {
+    /* Air between one tab and the next. Before the label rather than after
+     * the statuses, so it is the gap between two tabs and not a trailing
+     * margin under the last one -- the space before the first is
+     * tab_bar_pad's and the space before the button is newtab_pad's, and
+     * neither should be paid twice.
+     *
+     * Given up a row at a time when the list is short of room, ahead of
+     * anything that means something: a gap that pushed a tab off the bottom
+     * would be spacing costing you the thing it spaces. */
+    if (i) {
+      uint16_t g = CFG.tab_gap;
+      /* This tab's own label, the ones after it, and the button. */
+      uint16_t need = (uint16_t)(a->ntabs - i + btn_rows);
+      while (g && (uint16_t)(y + g + need) > limit) g--;
+      y = (uint16_t)(y + g);
+      if (y >= limit) break;
+    }
     draw_tab_cell(a, s, i, cx, y, cw, dragging_pane);
     y++;
     if (!cap) continue;
diff --git a/src/config.c b/src/config.c
index f3662fd..b9e3c29 100644
--- a/src/config.c
+++ b/src/config.c
@@ -954,6 +954,7 @@ void config_defaults(config_t *c) {
    * a gap nobody asked for. Still there for a bare sidebar, or for anyone
    * who wants room at the top for a borderless window's own buttons. */
   c->tab_bar_pad = 0;
+  c->tab_gap = 0; /* flush, the way the list has always read */
   /* Three is enough for "the build, the tests, and one more thing" without a
    * chatty tab pushing the list off the bottom. */
   c->tab_bar_status = 3;
@@ -1686,6 +1687,8 @@ char *config_render(const config_t *c) {
          c->tab_bar_width);
   cb_add(&b, "tab_bar_pad %u        // blank rows above a sidebar's tabs\n",
          c->tab_bar_pad);
+  cb_add(&b, "tab_gap %u            // blank rows between a sidebar's tabs\n",
+         c->tab_gap);
   cb_add(&b,
          "tab_bar_status %u     // pane status rows under each tab, 0 = off\n",
          c->tab_bar_status);
@@ -2017,6 +2020,7 @@ static const char *const KNOWN_TOP[] = {
     "tab_bar_status",
     "tab_bar_status_lines",
     "tab_bar_width",
+    "tab_gap",
     "theme",
     "title_align",
     "title_inset",
@@ -2229,6 +2233,8 @@ static bool load_into(config_t *c, const char *path, int depth, char *err,
                                            c->tab_bar_width);
   c->tab_bar_pad =
       (uint16_t)kdl_arg_int(kdl_child(root, "tab_bar_pad"), 0, c->tab_bar_pad);
+  c->tab_gap =
+      (uint16_t)kdl_arg_int(kdl_child(root, "tab_gap"), 0, c->tab_gap);
   c->tab_bar_status = (uint16_t)kdl_arg_int(kdl_child(root, "tab_bar_status"),
                                             0, c->tab_bar_status);
   c->tab_bar_status_lines = (uint16_t)kdl_arg_int(