G11: HoverGlow, a soft underline of light under a look-hover's word

HoverGlow on|off (off, a pixel shell's; Chrome.glows bit 1, SelectionGlow
bit 0 now that there are two): under the word a look-hover would open (its
cells in the affordance's tint) a strip three logical pixels tall along
its foot, blurred by one, in the theme's accent, at most 22% and under
the text's contrast floor, fading in over 80 ms; kept to the bodies and
split round a cursor. glowBlocks serves G9 and G11. The strip is cast from
a row away so addSoft's caster cut-out misses it.

Tests: the glow comes up by 90 ms and never falls on the cursor's cell.
Gates as G10 (a loaded machine shifted the GUI goldens a scene once; a
rerun matched 01-08). Feel review: .scratch/render/hover/.

1 files changed, 9 insertions, 3 deletions

diff --git a/src/config.zig b/src/config.zig
index 229c70ea..4e159d01 100644
--- a/src/config.zig
+++ b/src/config.zig
@@ -123,6 +123,7 @@ pub const leader_path = paths: {
     if (builtins.capabilities.ligatures) table.set(.Ligatures, null);
     if (builtins.capabilities.lift) table.set(.CursorBlink, null);
     if (builtins.capabilities.lift) table.set(.SelectionGlow, null);
+    if (builtins.capabilities.lift) table.set(.HoverGlow, null);
     if (builtins.capabilities.lift) table.set(.Lift, null);
     table.set(.Motion, null);
     table.set(.InactiveDim, null);
@@ -670,6 +671,9 @@ pub const Runtime = struct {
     /// G9: a soft halo round the selection in the body, fading in over
     /// 100 ms, a pixel shell's (docs/effects.md).
     selection_glow: bool = false,
+    /// G11: a soft glow under the word a look-hover would open, fading in
+    /// over 80 ms, a pixel shell's.
+    hover_glow: bool = false,
     /// How long a message stays after the key or click that dismisses it.
     message_linger_ms: u16 = 800,
     /// How long its fall into the row takes, easing out (§8.1: arriving,
@@ -893,7 +897,7 @@ pub const Runtime = struct {
     /// The message timings a setting word sets, each in milliseconds.
     pub const MessageTime = enum { linger, fall, dissolve };
 
-    pub const Toggle = enum { colors, wrap, tree_context_tag_style, tag_bottom, debug, focus_tint, syntax_bold, verbose, message_animation, ligatures, cursor_blink, selection_glow };
+    pub const Toggle = enum { colors, wrap, tree_context_tag_style, tag_bottom, debug, focus_tint, syntax_bold, verbose, message_animation, ligatures, cursor_blink, selection_glow, hover_glow };
     /// A bundled post pass, a Shadertoy file in shaders/post/: the CRT, and
     /// G4's bloom, vignette and grain (docs/effects.md).
     pub const Scene = enum { crt, bloom, vignette, grain };
@@ -953,6 +957,7 @@ pub const Runtime = struct {
         .{ .word = "Ligatures", .action = .{ .toggle = .ligatures }, .availability = .ligatures, .doc = "A font's programming ligatures draw across their cells, on or off." },
         .{ .word = "CursorBlink", .action = .{ .toggle = .cursor_blink }, .availability = .lift, .doc = "The cursor blinks, solid while typing, on or off." },
         .{ .word = "SelectionGlow", .action = .{ .toggle = .selection_glow }, .availability = .lift, .doc = "A soft halo of the selection's colour round it in the body, on or off." },
+        .{ .word = "HoverGlow", .action = .{ .toggle = .hover_glow }, .availability = .lift, .doc = "A soft underline of light under the word a look-hover would open, on or off." },
         .{ .word = "Lift", .action = .lift, .availability = .lift, .doc = "How the focused pane stands off the page: off, shadow, rim or auto." },
         .{ .word = "Motion", .action = .motion, .doc = "How animations move: off, crisp, smooth, bouncy or playful." },
         .{ .word = "InactiveDim", .action = .inactive_dim, .doc = "Fade the unfocused panes' text by a percentage, 0 through 100, 0 off." },
@@ -1029,9 +1034,9 @@ pub const Runtime = struct {
                 .toggle => |field| if (field == .ligatures) {
                     if (setting.availability != .ligatures)
                         @compileError("the ligatures toggle must use the ligatures capability");
-                } else if (field == .cursor_blink or field == .selection_glow) {
+                } else if (field == .cursor_blink or field == .selection_glow or field == .hover_glow) {
                     if (setting.availability != .lift)
-                        @compileError("CursorBlink and SelectionGlow must use the lift capability (a pixel shell's)");
+                        @compileError("CursorBlink, SelectionGlow and HoverGlow must use the lift capability (a pixel shell's)");
                 } else if (setting.availability != null)
                     @compileError("unconditional toggles cannot carry a backend capability"),
                 else => if (setting.availability != null)
@@ -1687,6 +1692,7 @@ pub const Runtime = struct {
                     .ligatures => "Ligatures off\n",
                     .cursor_blink => "CursorBlink off\n",
                     .selection_glow => "SelectionGlow on\n",
+                    .hover_glow => "HoverGlow on\n",
                 },
                 .shell => "Shell requested (new panes) fish\n",
                 .tagline_size => "TaglineSize 73\n",