1 files changed, 18 insertions, 3 deletions
diff --git a/src/gui/gui.zig b/src/gui/gui.zig
index ab1875b7..aa39cf32 100644
--- a/src/gui/gui.zig
+++ b/src/gui/gui.zig
@@ -4086,7 +4086,12 @@ fn waitInput(ctx: ?*anyopaque, timeout_ms: u32) void {
         const minimized = !s.test_mode and c.SDL_GetWindowFlags(g.window) & (c.SDL_WINDOW_MINIMIZED | c.SDL_WINDOW_OCCLUDED) != 0;
         // A latency trace is fed on stdin, whose poll below paces the loop:
         // waiting here too would make every tick cost two frames.
-        const ms: c_int = if (latency_fd >= 0) 0 else if (minimized) -1 else if (timeout_ms != 0) @intCast(timeout_ms) else if (polls) 16 else -1;
+        // A chain that moves on its own wakes once a display refresh.
+        const poll_ms: c_int = if (g.post.animating(core.settings.shader_animation))
+            @intCast(@max(1, refreshNs(g) / std.time.ns_per_ms))
+        else
+            16;
+        const ms: c_int = if (latency_fd >= 0) 0 else if (minimized) -1 else if (timeout_ms != 0) @min(@as(c_int, @intCast(@min(timeout_ms, std.math.maxInt(c_int)))), if (polls) poll_ms else std.math.maxInt(c_int)) else if (polls) poll_ms else -1;
         // The wait is the 9P connections' turn with the core.
         pardes.turn.rest();
         const got = c.SDL_WaitEventTimeout(&sev, ms);
@@ -4168,9 +4173,19 @@ fn pollFrame(ctx: ?*anyopaque) void {
     if (updateCoreResize(core, geom.cols, geom.rows, g.cell_w, g.cell_h, g.tagline_width, g.tagline_height)) resetScroll(g);
     stepScroll(g, core, s.gpa);
     g.post.sync(s.gpa, s.io, g.device, g.swapchain_format, core);
-    // Between the core's frames, a chain that moves on its own redraws alone.
+    // Between the core's frames, a chain that moves on its own redraws
+    // alone, once a refresh of the display the window is on (a millisecond
+    // early is on time: the wait that paces it is in whole milliseconds).
     if (g.post.animating(core.settings.shader_animation) and !core.needs_frame and s.presented and
-        c.SDL_GetTicksNS() -| g.post.last_ns >= pardes.animation.frame_ns) redrawPost(g, s.gpa);
+        c.SDL_GetTicksNS() -| g.post.last_ns + std.time.ns_per_ms >= refreshNs(g)) redrawPost(g, s.gpa);
+}
+
+/// One refresh of the display the window is on, in ns; a frame of the
+/// core's where the display does not say.
+fn refreshNs(g: *const Gui) u64 {
+    const mode = c.SDL_GetCurrentDisplayMode(c.SDL_GetDisplayForWindow(g.window)) orelse return pardes.animation.frame_ns;
+    if (!(mode.*.refresh_rate > 1)) return pardes.animation.frame_ns;
+    return @intFromFloat(@as(f64, std.time.ns_per_s) / mode.*.refresh_rate);
 }
 
 fn finishWindowOpacity(core: *pardes.Pardes, applied: *u8, failure: ?[]const u8) void {