G9: SelectionGlow, a soft halo round the body's selection

SelectionGlow on|off (off; a pixel shell's, Chrome.selection_glow): each
block of selected rows in a pane body casts Lift's soft kind in the
selection's own colour, the block its caster (never touched) and a cursor
beside it joined to the caster; clipped to the bodies (never a tag or a
grip); at most 22% (§8.2), less where the text round it would drop below
min(its contrast, 4.5); fading in over 100 ms with an ease-out, on the
core's continuous path (shell_continuous); none while panes move. Blocks
come from the cells in the theme's selection colour (documented).

Tests: the halo's colour, its clip to the body, nothing at its first frame
and up to its cap after 100 ms, fading done. Gates as G8. Feel review:
.scratch/render/selection/.

1 files changed, 13 insertions, 0 deletions

diff --git a/docs/effects.md b/docs/effects.md
index 2fc68c81..61b969c2 100644
--- a/docs/effects.md
+++ b/docs/effects.md
@@ -42,6 +42,7 @@ why. The verdict is the user's.
 | G6 smooth scroll | follows `Motion` (on through the default smooth; `Motion off` lands at once) | a mouse wheel's notch glides, a touchpad follows the finger | .scratch/render/scroll/ (glide-<flavour>.mp4, quarter speed, strips) | pending |
 | G7 panel transitions | `PanelSlide`, `PanelZoom`, `PanelVertical`, `PanelDissolve` (off) with `Motion` | a moving pane casts a shadow; a retargeted move keeps its speed; the GUI's dissolve is a crossfade | .scratch/render/transitions/ (slide smooth, bouncy, retargeted; dissolve) | pending |
 | G8 notice chips | follows `Motion` and `Lift` | a notice floats in tier 4 on a lift (shadow) while Lift is on, drops in easing out and dissolves easing in, quicker than it came (150 ms against 180) | .scratch/render/notices/ (acme, forge) | pending |
+| G9 selection glow | `SelectionGlow on\|off` (off) | a soft halo of the selection's colour round each block of it in a body, fading in over 100 ms | .scratch/render/selection/ (forge, acme, lapis; lapis-glow-zoom.png) | pending |
 
 ## Motion flavours
 
@@ -184,3 +185,15 @@ tier 4 with Lift's shadow at its fade while Lift is on, on the bodies
 alone. What G8 changed: leaving was slower than arriving (a 300 ms
 dissolve against a 180 ms fall); §8.1 wants leaving the quicker, in 100 to
 160 ms, so MessageDissolve now defaults to 150 (a test holds both bands).
+
+Notes on G9: the halo is Lift's soft kind in the selection's own colour,
+cast by each block of selected rows in a pane body (the rows that touch),
+with the block as its caster, so the selection itself is never touched;
+a cursor beside a block joins the caster, so it is never glowed over
+either. It stays on bodies (never a tag or a grip), is at most 22% (§8.2:
+coloured glows at most 25%) and less where the text round it would drop
+below min(its contrast, 4.5); it comes up over 100 ms with an ease-out
+(micro-feedback), on the core's continuous path, and is not drawn while
+panes move. The blocks are read from the cells painted in the theme's
+selection colour, a pixel shell's inference (§1.5, smell 4) until
+selections are regions.