T7: the scroll thumb flashes as a terminal pane scrolls

ThumbFlash (off by default) brightens a body's scroll thumb toward the ink
when its view moves and fades it back over 250 ms, truecolor only. The tty
present path now clears shell_continuous once before its effects and each
effect only raises it, so the trail and the flash no longer mask each other.

1 files changed, 7 insertions, 1 deletions

diff --git a/src/config.zig b/src/config.zig
index 316ed3a0..1b432415 100644
--- a/src/config.zig
+++ b/src/config.zig
@@ -129,6 +129,7 @@ pub const leader_path = paths: {
     if (builtins.capabilities.lift) table.set(.Afterglow, null);
     table.set(.JumpTrail, null);
     table.set(.ChipShadow, null);
+    table.set(.ThumbFlash, null);
     if (builtins.capabilities.lift) table.set(.Lift, null);
     table.set(.Motion, null);
     table.set(.InactiveDim, null);
@@ -694,6 +695,9 @@ pub const Runtime = struct {
     /// T1: in a terminal, a notice chip casts a cell's shadow right and
     /// down (truecolor terminals).
     chip_shadow: bool = false,
+    /// T7: in a terminal, a pane's scroll thumb brightens as it scrolls and
+    /// fades back (truecolor terminals).
+    thumb_flash: 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,
@@ -917,7 +921,7 @@ 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, hover_glow, occlusion, parallax, afterglow, jump_trail, chip_shadow };
+    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, occlusion, parallax, afterglow, jump_trail, chip_shadow, thumb_flash };
     /// 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 };
@@ -983,6 +987,7 @@ pub const Runtime = struct {
         .{ .word = "Afterglow", .action = .{ .toggle = .afterglow }, .availability = .lift, .doc = "Text that changes glows for a moment and fades, on or off." },
         .{ .word = "JumpTrail", .action = .{ .toggle = .jump_trail }, .doc = "In a terminal, a jump of the cursor leaves a short trail that fades, on or off." },
         .{ .word = "ChipShadow", .action = .{ .toggle = .chip_shadow }, .doc = "In a terminal, a notice chip casts a cell's shadow right and down, on or off." },
+        .{ .word = "ThumbFlash", .action = .{ .toggle = .thumb_flash }, .doc = "In a terminal, a pane's scroll thumb brightens as it scrolls and fades back, 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." },
@@ -1723,6 +1728,7 @@ pub const Runtime = struct {
                     .afterglow => "Afterglow on\n",
                     .jump_trail => "JumpTrail on\n",
                     .chip_shadow => "ChipShadow on\n",
+                    .thumb_flash => "ThumbFlash on\n",
                 },
                 .shell => "Shell requested (new panes) fish\n",
                 .tagline_size => "TaglineSize 73\n",