Reduce answer review scroll redraws

Reviewed-on: admin/step3#15

scripts/ui/question_player.gd

@@ -60,6 +60,8 @@ var stem_plain_text := ""
 var explanation_plain_text := ""
 var highlight_drag_source := ""
 var timer_color_state := ""
+var last_timer_bar_value := -1.0
+var last_timer_display_seconds := -1
 var pending_correct_advance := false
 var question_text_scale := 1.0
 var presented_choices: Array = []
@@ -1268,6 +1270,8 @@ func _load_question() -> void:
 	flagged = false
 	selected_choice = ""
 	current_answer = {}
+	last_timer_bar_value = -1.0
+	last_timer_display_seconds = -1
 	flag_button.button_pressed = false
 	_refresh_toolbar_state()
 	_clear_answer_review()
@@ -2094,7 +2098,10 @@ func _update_timer_bar() -> void:
 		return
 	var is_core_timer := BlockSessionService.session_kind == "core"
 	var ratio := BlockSessionService.get_session_timer_ratio()
-	timer_bar.value = ratio * 100.0
+	var next_value := ratio * 100.0
+	if last_timer_bar_value < 0.0 or absf(next_value - last_timer_bar_value) >= 0.1:
+		last_timer_bar_value = next_value
+		timer_bar.value = next_value
 	if is_core_timer and timer_label.visible:
 		_set_timer_display(int(floor(BlockSessionService.get_core_question_total_elapsed_seconds())))
 	var color_state := "blue"
@@ -2114,6 +2121,9 @@ func _set_timer_display(total_seconds: int) -> void:
 	if timer_label == null:
 		return
 	var safe_seconds := maxi(0, total_seconds)
+	if safe_seconds == last_timer_display_seconds:
+		return
+	last_timer_display_seconds = safe_seconds
 	timer_label.text = "%02d:%02d" % [int(floor(float(safe_seconds) / 60.0)), safe_seconds % 60]
 
 

tests/post_answer_review_test.gd

@@ -22,6 +22,7 @@ func _initialize() -> void:
 	_test_feedback_context_excludes_study_content()
 	_test_feedback_form_validation()
 	_test_revisitable_navigation_prefers_unanswered_questions()
+	_test_timer_text_avoids_redundant_frame_updates()
 	_test_submit_styles_keep_stable_geometry()
 	_test_core_timer_counts_up_and_remains_visible()
 	await _test_player_runtime_construction()
@@ -355,6 +356,20 @@ func _test_revisitable_navigation_prefers_unanswered_questions() -> void:
 	session.current_index = prior_index
 
 
+func _test_timer_text_avoids_redundant_frame_updates() -> void:
+	var player = load("res://scripts/ui/question_player.gd").new()
+	player.timer_label = Label.new()
+	player._set_timer_display(65)
+	_assert(player.timer_label.text == "01:05", "timer should render a changed second")
+	player.timer_label.text = "unchanged"
+	player._set_timer_display(65)
+	_assert(player.timer_label.text == "unchanged", "timer should not rewrite its label every frame")
+	player._set_timer_display(66)
+	_assert(player.timer_label.text == "01:06", "timer should render the next changed second")
+	player.timer_label.free()
+	player.free()
+
+
 func _test_player_runtime_construction() -> void:
 	var host := Control.new()
 	root.add_child(host)