From a774cad033fdc371af9f89b9a787a30ea017481c Mon Sep 17 00:00:00 2001
From: Gabriel Schneider <gbrls@0x4200.cafe>
Date: Mon, 3 Aug 2026 01:34:50 -0300
Subject: animate anchored theme colors on native and tty backends

---
 src/gui/gui.zig | 46 ++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 46 insertions(+)

(limited to 'src/gui')

diff --git a/src/gui/gui.zig b/src/gui/gui.zig
index 6bd2c715..983be262 100644
--- a/src/gui/gui.zig
+++ b/src/gui/gui.zig
@@ -111,6 +111,39 @@ const overlay_circle_vertices: usize = 16 * 3;
 const touch_click_flash_max_frames: u8 = 14;
 const touch_click_flash_vertices: usize = 1400;
 const touch_scroll_tick: f32 = 0.02;
+
+/// SDL input can wake the loop faster than display cadence, so ticking once
+/// per pass would make animation duration depend on pty traffic or mouse
+/// motion. This monotonic gate keeps it near 60 Hz without sleeping the event
+/// loop; the first frame after activation displays the exact source palette.
+const AnimationClock = struct {
+    next_ns: u64 = 0,
+
+    fn due(clock: *AnimationClock, active: bool, now_ns: u64) bool {
+        if (!active) {
+            clock.next_ns = 0;
+            return false;
+        }
+        if (clock.next_ns == 0) {
+            clock.next_ns = now_ns +| pardes.animation.frame_ns;
+            return false;
+        }
+        if (now_ns < clock.next_ns) return false;
+        clock.next_ns = now_ns +| pardes.animation.frame_ns;
+        return true;
+    }
+};
+
+test "GUI animation clock is active-only and cadence gated" {
+    var clock: AnimationClock = .{};
+    try std.testing.expect(!clock.due(false, 100));
+    try std.testing.expect(!clock.due(true, 100));
+    try std.testing.expect(!clock.due(true, 100 + pardes.animation.frame_ns - 1));
+    try std.testing.expect(clock.due(true, 100 + pardes.animation.frame_ns));
+    try std.testing.expect(!clock.due(false, 100 + 2 * pardes.animation.frame_ns));
+    try std.testing.expectEqual(@as(u64, 0), clock.next_ns);
+}
+
 /// Web tap-vs-scroll heuristic, measured after normalized coordinates have
 /// been mapped into backing pixels (12px = 8 CSS px at web_render_scale).
 const touch_tap_slop_px: f32 = 12.0;
@@ -1273,6 +1306,7 @@ fn runNative(init: std.process.Init, opts_in: pardes.Options) !void {
 
     var frame_arena: std.heap.ArenaAllocator = .init(gpa);
     defer frame_arena.deinit();
+    var animation_clock: AnimationClock = .{};
 
     while (!core.quit) {
         // 1. SDL input: block briefly for the first event, then drain the rest
@@ -1389,6 +1423,8 @@ fn runNative(init: std.process.Init, opts_in: pardes.Options) !void {
         // 7. render — apply the wheel batch LAST before it, while
         // core.surface still holds the frame the last pass drew
         stepScroll(&g, core, gpa);
+        if (animation_clock.due(core.themeAnimationActive(), c.SDL_GetTicksNS()))
+            core.update(.tick);
         _ = frame_arena.reset(.retain_capacity);
         const surface = try core.render(frame_arena.allocator());
         renderFrame(&g, gpa, surface, core.crt_on, core.show_debug) catch |err| log.err("render: {t}", .{err});
@@ -1410,6 +1446,7 @@ const WebState = struct {
     core: *pardes.Pardes,
     gpa: std.mem.Allocator,
     frame_arena: std.heap.ArenaAllocator,
+    animation_clock: AnimationClock = .{},
 };
 var live_web_state: ?*WebState = null;
 
@@ -1672,6 +1709,8 @@ fn webFrame(arg: ?*anyopaque) callconv(.c) void {
     if (updateCoreResize(core, cols, rows, g.cell_w, g.cell_h)) resetScroll(g);
     // 4. render — apply the wheel batch last, see runNative
     stepScroll(g, core, st.gpa);
+    if (st.animation_clock.due(core.themeAnimationActive(), c.SDL_GetTicksNS()))
+        core.update(.tick);
     _ = st.frame_arena.reset(.retain_capacity);
     const surface = core.render(st.frame_arena.allocator()) catch return;
     renderFrameGl(g, st.gpa, surface, core.show_debug) catch return;
@@ -1805,6 +1844,13 @@ fn runGrid(init: std.process.Init, opts_in: pardes.Options) !void {
         msgs.deinit(gpa);
         drainEffects(core, &ptys, &gens, io, gpa, &queue, &pipe_tasks, null, -1, &watches, true);
         pollCwds(core, &ptys);
+        // The grid harness polls stdin at the same 16 ms cadence as native
+        // SDL. Advancing here lets `stable` wait for exact endpoint colors;
+        // once inactive it resumes the old event-only frame contract.
+        if (core.themeAnimationActive()) {
+            core.update(.tick);
+            n_events += 1;
+        }
         if (n_events == 0) continue; // idle tick: nothing changed, no frame
         _ = frame_arena.reset(.retain_capacity);
         const surface = try core.render(frame_arena.allocator());
-- 
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