From feecee0a30c8dda21232991b803de64992e8f8d4 Mon Sep 17 00:00:00 2001
From: Naseq <nasim.naseq@gmail.com>
Date: Tue, 27 Oct 2026 18:13:44 +0430
Subject: [PATCH] Slide show tests: check the pending preview and the
 one-render gate directly (#964)

A harness runs frames until no repaint is asked for, so the preview had
already landed when its first assertion ran. One raw frame now shows the
preview pending and one render started, and the paging test pins a pending
job and checks a page turn starts no other render.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
---
 crates/ui-egui/src/show/tests.rs | 25 ++++++++++++++++++++++---
 1 file changed, 22 insertions(+), 3 deletions(-)

diff --git a/crates/ui-egui/src/show/tests.rs b/crates/ui-egui/src/show/tests.rs
index 7d2e2aba..12ac1148 100644
--- a/crates/ui-egui/src/show/tests.rs
+++ b/crates/ui-egui/src/show/tests.rs
@@ -1001,7 +1001,14 @@ fn the_presenter_next_preview_arrives_without_blocking_the_frame() {
     let mut session = deckcraft_engine::Session::with_new();
     session.execute("slide.new", &json!({})).unwrap();
     let doc = session.active().unwrap().doc.clone();
-    let show = Show::new(&doc, 0, false, true);
+    // One frame on its own (a harness runs frames until the preview lands): it asks for the
+    // preview and returns without it.
+    let mut show = Show::new(&doc, 0, false, true);
+    let mut keep = true;
+    let ctx = egui::Context::default();
+    let _ = ctx.run_ui(egui::RawInput::default(), |ui| presenter_window(ui.ctx(), &mut show, &doc, 0.0, &mut keep));
+    assert!(show.next_job.is_some() && show.next_tex.is_none(), "the first frame leaves the preview pending");
+    assert_eq!(show.preview_spawns, 1);
     let mut harness = egui_kittest::Harness::builder().with_size(vec2(1100.0, 700.0)).build_ui_state(
         |ui, (doc, show, keep): &mut (std::sync::Arc<Presentation>, Show, bool)| {
             let now = ui.input(|i| i.time);
@@ -1009,8 +1016,6 @@ fn the_presenter_next_preview_arrives_without_blocking_the_frame() {
         },
         (doc, show, true),
     );
-    harness.step();
-    assert!(harness.state().1.next_job.is_some() || harness.state().1.next_tex.is_some());
     for _ in 0..200 {
         if harness.state().1.next_tex.is_some() {
             break;
@@ -1020,6 +1025,7 @@ fn the_presenter_next_preview_arrives_without_blocking_the_frame() {
     }
     assert_eq!(harness.state().1.next_tex.as_ref().map(|(_, n, _)| *n), Some(1));
     assert!(harness.state().1.next_job.is_none());
+    assert_eq!(harness.state().1.preview_spawns, 1, "the pending render landed; none started over");
 }
 
 /// #964: paging quickly keeps one preview render running, and the preview that lands is the
@@ -1060,6 +1066,19 @@ fn paging_quickly_renders_one_preview_at_a_time_and_lands_on_the_newest() {
     assert!(st.next_job.is_none());
     // A render starts only once the one before it has finished: never more than one per turn.
     assert!(st.preview_spawns <= turns + 1, "{} renders for {turns} turns", st.preview_spawns);
+
+    // While a render is pending, turning the page starts no other.
+    let (_tx, rx) = std::sync::mpsc::channel();
+    let doc = harness.state().0.clone();
+    let spawns = harness.state().1.preview_spawns;
+    harness.state_mut().1.next_tex = None;
+    harness.state_mut().1.next_job = Some((doc.clone(), 0, rx));
+    let a = harness.state_mut().1.state.prev(&doc);
+    harness.state_mut().1.apply(a, &doc, 0.0);
+    harness.step();
+    let st = &harness.state().1;
+    assert_eq!(st.preview_spawns, spawns, "no render starts while one is pending");
+    assert!(st.next_job.is_some());
 }
 
 /// A preview rendered from a presentation that has since been edited (replaced) is dropped,