sl0ppty: dashed borders and a deeper push-back while dragging

Two changes to the same moment, on opposite sides of the chrome boundary.

Every pane that is not being dragged now draws a dashed border, because every
one of them is somewhere the pane could be dropped and a dashed frame says so
without needing a legend. The pane in your hand keeps a solid one, so the two
states are distinguishable by shape and not only by colour — which matters on
a terminal whose palette makes the greying subtle, and to anyone who would not
see the greying at all. The pane actually under the pointer still takes the
existing drop-target highlight on top of the dashes: these are all targets,
that one is the one you are on.

Borders are chrome, so this is not a shader and could not have been. It lives
in draw_frame, keyed off the same drag.moved that gates the greying, so a press
that turns out to be a click neither greys nor dashes anything.

The greying itself gets a second pass: desaturated *and* darkened, rather than
only desaturated. Grey alone still competes for attention at the same
brightness, which is what made the dragged pane fail to pop. Two shaders
instead of one that does both, because "colourless" and "recessed" are
different things to want and want separate knobs — drag_grayscale 200 and
drag_dim 140. This is the first thing to actually use the chain, and it is
what the chain was for.

The knob that used to mean "off" no longer does, and the test that asserted it
caught that immediately: drag_grayscale 0 now leaves drag_dim still dimming.
Rather than couple them, the test became three — both off, each alone — which
is better coverage of a two-knob effect than the single case was of a one-knob
one.

1 files changed, 103 insertions, 5 deletions

diff --git a/tests/test_shaders.py b/tests/test_shaders.py
index be86d35..adf029a 100644
--- a/tests/test_shaders.py
+++ b/tests/test_shaders.py
@@ -219,18 +219,112 @@ def test_the_drag_greying_outranks_the_focus_dimming():
         s.settle(200)
 
 
-def test_drag_greying_can_be_turned_off():
-    with Session(SH, cols=90, rows=16, config=cfg("drag_grayscale 0\n")) as s:
+def drag_and_sample(conf):
+    """Colour of a non-dragged pane's content mid-drag, under `conf`."""
+    with Session(SH, cols=90, rows=16, config=cfg(conf)) as s:
         s.settle(200)
         left, right = split(s)
         s.settle(200)
+        press(s, left["x"] + 4, left["y"])
+        motion(s, right["x"] + 5, right["y"] + 3)
+        s.settle(120)
+        got = content_fg(s.snapshot(), right)
+        release(s, right["x"] + 5, right["y"] + 3)
+        s.settle(120)
+        return got
+
+
+def test_the_two_drag_knobs_are_independent():
+    both_off = drag_and_sample("drag_grayscale 0\ndrag_dim 0\n")
+    check("with both off a drag leaves every pane alone", both_off == GREEN,
+          str(both_off))
+
+    # Desaturate only: channels converge, brightness roughly survives.
+    gray_only = drag_and_sample("drag_grayscale 255\ndrag_dim 0\n")
+    ch = [int(gray_only[i:i + 2], 16) for i in (1, 3, 5)]
+    check("grayscale alone desaturates without darkening much",
+          ch[0] == ch[1] == ch[2] and ch[1] > 0x60, str(gray_only))
+
+    # Darken only: the hue survives, the brightness does not.
+    dim_only = drag_and_sample("drag_grayscale 0\ndrag_dim 200\n")
+    ch = [int(dim_only[i:i + 2], 16) for i in (1, 3, 5)]
+    check("dim alone darkens without desaturating",
+          ch[0] == 0 and ch[2] == 0 and 0 < ch[1] < 0x60, str(dim_only))
+
+
+def test_the_default_drag_look_is_grey_and_recessed():
+    """Both together: the dragged pane has to win on contrast, not just hue."""
+    got = drag_and_sample("")
+    ch = [int(got[i:i + 2], 16) for i in (1, 3, 5)]
+    check("a non-dragged pane is pushed well below full brightness",
+          max(ch) < 0x80, f"{got} max={max(ch):#x}")
+    check("and towards grey", max(ch) - min(ch) < 60,
+          f"{got} spread={max(ch) - min(ch)}")
+
+
+# ---- the drop-target border (chrome, not a shader) -------------------------
+
+DASH_H = "\u2504"
+SOLID_H = "\u2500"
+
+
+def test_non_dragged_panes_get_a_dashed_border():
+    with Session(SH, cols=90, rows=16) as s:
+        s.settle(200)
+        left, right = split(s)
+        s.settle(200)
+
+        snap = s.snapshot()
+        check("borders are solid when nothing is being dragged",
+              DASH_H not in snap.line(right["y"]), repr(snap.line(right["y"])))
 
         press(s, left["x"] + 4, left["y"])
         motion(s, right["x"] + 5, right["y"] + 3)
         s.settle(120)
         snap = s.snapshot()
-        check("drag_grayscale 0 leaves every pane alone",
-              content_fg(snap, right) == GREEN, str(content_fg(snap, right)))
+        top = snap.line(right["y"])[right["x"]:right["x"] + right["w"]]
+        dragged_top = snap.line(left["y"])[left["x"]:left["x"] + left["w"]]
+        check("a pane you could drop onto is dashed", DASH_H in top, repr(top))
+        check("the pane in your hand stays solid",
+              DASH_H not in dragged_top and SOLID_H in dragged_top,
+              repr(dragged_top))
+
+        release(s, right["x"] + 5, right["y"] + 3)
+        s.settle(200)
+        snap = s.snapshot()
+        for p in s.panes():
+            row = snap.line(p["y"])[p["x"]:p["x"] + p["w"]]
+            check(f"pane {p['id']} is solid again after the drop",
+                  DASH_H not in row, repr(row))
+
+
+def test_a_press_that_never_moves_dashes_nothing():
+    with Session(SH, cols=90, rows=16) as s:
+        s.settle(200)
+        left, right = split(s)
+        s.settle(200)
+        press(s, left["x"] + 4, left["y"])
+        s.settle(120)
+        snap = s.snapshot()
+        check("pressing without moving dashes nothing",
+              DASH_H not in snap.screen(), "")
+        release(s, left["x"] + 4, left["y"])
+        s.settle(120)
+
+
+def test_the_hovered_target_is_still_highlighted_over_the_dashes():
+    with Session(SH, cols=90, rows=16) as s:
+        s.settle(200)
+        left, right = split(s)
+        s.settle(200)
+        press(s, left["x"] + 4, left["y"])
+        motion(s, right["x"] + 5, right["y"] + 3)
+        s.settle(120)
+        snap = s.snapshot()
+        run = snap.style_at(right["x"], right["y"])
+        check("the pane under the pointer keeps its drop highlight",
+              run and run["fg"] == "#ff5fd7" and "bold" in run["attrs"],
+              str(run))
         release(s, right["x"] + 5, right["y"] + 3)
         s.settle(120)
 
@@ -280,7 +374,11 @@ if __name__ == "__main__":
     test_full_strength_is_a_true_grey()
     test_a_press_that_never_moves_greys_nothing()
     test_the_drag_greying_outranks_the_focus_dimming()
-    test_drag_greying_can_be_turned_off()
+    test_the_two_drag_knobs_are_independent()
+    test_the_default_drag_look_is_grey_and_recessed()
+    test_non_dragged_panes_get_a_dashed_border()
+    test_a_press_that_never_moves_dashes_nothing()
+    test_the_hovered_target_is_still_highlighted_over_the_dashes()
     test_a_drag_that_ends_off_a_pane_still_clears()
     test_a_keystroke_mid_drag_clears_the_greying()
     sys.exit(report())