slosh: paint the padding ring, so a float cannot be seen through

A tiled pane sits on a cleared screen, so unpainted padding looked fine by
accident; a float sits on whatever was composited under it, and every
unpainted cell let that show through. draw_frame now fills the ring between
border and contents with exactly what screen_clear leaves, and a suspended
pane's never-composed content rect gets the same treatment.

2 files changed, 52 insertions, 0 deletions

diff --git a/src/app_draw.c b/src/app_draw.c
index 24cc50d..04e8264 100644
--- a/src/app_draw.c
+++ b/src/app_draw.c
@@ -573,6 +573,25 @@ static void draw_frame(app_t *a, screen_t *s, node_t *leaf) {
     screen_text(s, x1, y, vbar, fg, NO_COLOR, attrs);
   }
 
+  /* The padding ring between the border and the contents, painted blank
+   * rather than left alone. A tiled pane sits on a cleared screen, so leaving
+   * it unpainted used to look the same by accident — but a float sits on
+   * whatever was composited under it, and every unpainted cell lets that show
+   * through. Blank-with-no-colour is exactly what screen_clear leaves, so a
+   * tiled pane looks as it always did, and with no padding configured the
+   * ring is empty and this writes nothing. */
+  {
+    rect_t c = leaf->content;
+    for (uint16_t y = (uint16_t)(r.y + 1); y < y1; y++)
+      for (uint16_t x = (uint16_t)(r.x + 1); x < x1; x++) {
+        if (x >= c.x && x < c.x + c.w && y >= c.y && y < c.y + c.h) {
+          x = (uint16_t)(c.x + c.w - 1); /* jump past the contents */
+          continue;
+        }
+        screen_text(s, x, y, " ", NO_COLOR, NO_COLOR, 0);
+      }
+  }
+
   /* A pane that rang, marked just inside its corner: the same place on every
    * pane, whatever its title is doing. */
   if (CFG.bell_indicator && pane_bell(leaf->pane) && r.w > 4)
@@ -1360,6 +1379,12 @@ static void draw_cb(node_t *n, void *ud) {
     /* Falls through to the shader pass rather than returning: a pane that has
      * not started is a state you can want to colour, and its label is the only
      * content it has. */
+    /* Nothing has ever composed into this content rect, so paint it blank
+     * first — for the same reason draw_frame paints the padding ring: a
+     * floating suspended pane must not show what is under it. */
+    for (uint16_t y = n->content.y; y < n->content.y + n->content.h; y++)
+      for (uint16_t x = n->content.x; x < n->content.x + n->content.w; x++)
+        screen_text(d->s, x, y, " ", NO_COLOR, NO_COLOR, 0);
     /* The pane exists, is laid out, and has run nothing. Say what it would. */
     const char *label = pane_label(n->pane);
     char line[256];
diff --git a/tests/test_float.py b/tests/test_float.py
index 1745ef7..b9e3233 100644
--- a/tests/test_float.py
+++ b/tests/test_float.py
@@ -912,6 +912,32 @@ def test_the_key_and_the_palette_both_run_it():
         check("running it floats the pane", len(floats(s)) == 1, str(here(s)))
 
 
+def test_the_padding_ring_hides_what_is_under_it():
+    """A float's padding is painted blank, not left unpainted. A tiled pane
+    sits on a cleared screen, so an unpainted ring looked fine by accident —
+    a float sits on whatever was composited below it, and every unpainted
+    cell let that show through."""
+    conf = cfg("padding 2\n")
+    filler = ["/bin/sh", "-c", 'printf "X%.0s" $(seq 1 4000); stty raw -echo; cat']
+    with Session(filler, cols=90, rows=24, config=conf) as s:
+        s.settle(50)
+        s.api("split", dir="cols")
+        s.settle(50)
+        s.api("float")
+        s.settle(100)
+        fl = floats(s)[0]
+        snap = s.snapshot()
+        # the ring between the border and the content, on a content row and
+        # on a padding row: all of it over the X-filled backdrop, all blank
+        row = snap.line(fl["content_y"])
+        left = row[fl["x"] + 1 : fl["content_x"]]
+        right = row[fl["content_x"] + fl["content_w"] : fl["x"] + fl["w"] - 1]
+        top = snap.line(fl["y"] + 1)[fl["x"] + 1 : fl["x"] + fl["w"] - 1]
+        check("the left padding is blank", set(left) <= {" "}, repr(left))
+        check("the right padding is blank", set(right) <= {" "}, repr(right))
+        check("a full padding row is blank", set(top) <= {" "}, repr(top))
+
+
 if __name__ == "__main__":
     test_floating_lifts_a_pane_out_of_the_layout()
     test_the_overlap_belongs_to_the_float()
@@ -946,4 +972,5 @@ if __name__ == "__main__":
     test_a_layout_of_only_floats_self_heals()
     test_a_float_is_not_a_drop_target()
     test_the_key_and_the_palette_both_run_it()
+    test_the_padding_ring_hides_what_is_under_it()
     sys.exit(report())