Add unit movement slide animation

scripts/core/battle_state.gd

@@ -7,6 +7,7 @@ signal changed
 signal log_added(message: String)
 signal dialogue_requested(lines: Array)
 signal combat_feedback_requested(unit_id: String, text: String, kind: String)
+signal unit_motion_requested(unit_id: String, from_cell: Vector2i, to_cell: Vector2i)
 
 const TEAM_PLAYER := "player"
 const TEAM_ENEMY := "enemy"
@@ -539,8 +540,10 @@ func try_move_selected(cell: Vector2i) -> bool:
 	if not get_unit_at(cell).is_empty():
 		return false
 
+	var from_cell: Vector2i = unit["pos"]
 	unit["pos"] = cell
 	unit["moved"] = true
+	unit_motion_requested.emit(str(unit.get("id", "")), from_cell, cell)
 	_emit_log("%s moved to %s." % [unit["name"], _format_cell(cell)])
 	_run_events("unit_reaches_tile", str(unit.get("team", "")), turn_number, unit)
 	_check_battle_status()
@@ -1837,8 +1840,10 @@ func _enemy_take_action(enemy: Dictionary) -> void:
 			best_cell = cell
 
 	if best_cell != enemy["pos"]:
+		var from_cell: Vector2i = enemy["pos"]
 		enemy["pos"] = best_cell
 		enemy["moved"] = true
+		unit_motion_requested.emit(str(enemy.get("id", "")), from_cell, best_cell)
 		_emit_log("%s advances to %s." % [enemy["name"], _format_cell(best_cell)])
 		_run_events("unit_reaches_tile", str(enemy.get("team", "")), turn_number, enemy)
 		if battle_status != STATUS_ACTIVE:

scripts/scenes/battle_scene.gd

@@ -33,6 +33,7 @@ const SFX_VOLUME_DB := -4.0
 const UI_SFX_VOLUME_DB := -8.0
 const FLOATING_TEXT_LIFETIME := 1.0
 const FLOATING_TEXT_RISE := 42.0
+const UNIT_MOVE_ANIMATION_DURATION := 0.18
 
 var state: BattleState = BattleStateScript.new()
 var campaign_state: CampaignState = CampaignStateScript.new()
@@ -110,6 +111,7 @@ var bgm_player: AudioStreamPlayer
 var current_bgm_key := ""
 var last_announced_battle_status := ""
 var floating_texts: Array[Dictionary] = []
+var unit_motion_by_unit: Dictionary = {}
 
 
 func _ready() -> void:
@@ -119,6 +121,7 @@ func _ready() -> void:
 	state.log_added.connect(_on_log_added)
 	state.dialogue_requested.connect(_on_dialogue_requested)
 	state.combat_feedback_requested.connect(_on_combat_feedback_requested)
+	state.unit_motion_requested.connect(_on_unit_motion_requested)
 	campaign_state.load_campaign(CAMPAIGN_PATH)
 	campaign_state.load_or_start(campaign_state.get_start_scenario_id())
 	if campaign_state.has_pending_post_battle_choice():
@@ -738,16 +741,30 @@ func _handle_key(event: InputEventKey) -> void:
 
 
 func _process(delta: float) -> void:
-	if floating_texts.is_empty():
-		return
-	var active_texts: Array[Dictionary] = []
-	for popup in floating_texts:
-		var next_popup := popup.duplicate(true)
-		next_popup["age"] = float(next_popup.get("age", 0.0)) + delta
-		if float(next_popup["age"]) < float(next_popup.get("duration", FLOATING_TEXT_LIFETIME)):
-			active_texts.append(next_popup)
-	floating_texts = active_texts
-	queue_redraw()
+	var needs_redraw := false
+	if not floating_texts.is_empty():
+		var active_texts: Array[Dictionary] = []
+		for popup in floating_texts:
+			var next_popup := popup.duplicate(true)
+			next_popup["age"] = float(next_popup.get("age", 0.0)) + delta
+			if float(next_popup["age"]) < float(next_popup.get("duration", FLOATING_TEXT_LIFETIME)):
+				active_texts.append(next_popup)
+		floating_texts = active_texts
+		needs_redraw = true
+
+	if not unit_motion_by_unit.is_empty():
+		var active_motion := {}
+		for unit_id in unit_motion_by_unit.keys():
+			var motion: Dictionary = unit_motion_by_unit[unit_id]
+			var next_motion := motion.duplicate(true)
+			next_motion["age"] = float(next_motion.get("age", 0.0)) + delta
+			if float(next_motion["age"]) < float(next_motion.get("duration", UNIT_MOVE_ANIMATION_DURATION)):
+				active_motion[unit_id] = next_motion
+		unit_motion_by_unit = active_motion
+		needs_redraw = true
+
+	if needs_redraw:
+		queue_redraw()
 
 
 func _can_select(unit: Dictionary) -> bool:
@@ -815,7 +832,7 @@ func _draw_units() -> void:
 		if not unit.get("alive", false) or not unit.get("deployed", true):
 			continue
 
-		var rect := _rect_for_cell(unit["pos"])
+		var rect := _visual_rect_for_unit(unit)
 		var center := rect.position + rect.size * 0.5
 		var team_color := PLAYER_COLOR if unit.get("team", "") == BattleState.TEAM_PLAYER else ENEMY_COLOR
 		var body_color := team_color.darkened(0.35) if unit.get("acted", false) else team_color
@@ -836,6 +853,26 @@ func _draw_units() -> void:
 			draw_arc(center, 29, 0.0, TAU, 48, Color(1.0, 0.92, 0.25), 3.0)
 
 
+func _visual_rect_for_unit(unit: Dictionary) -> Rect2:
+	var cell: Vector2i = unit.get("pos", Vector2i(-1, -1))
+	var rect := _rect_for_cell(cell)
+	var unit_id := str(unit.get("id", ""))
+	if unit_id.is_empty() or not unit_motion_by_unit.has(unit_id):
+		return rect
+
+	var motion: Dictionary = unit_motion_by_unit[unit_id]
+	var from_cell: Vector2i = motion.get("from", cell)
+	var to_cell: Vector2i = motion.get("to", cell)
+	var duration := max(0.01, float(motion.get("duration", UNIT_MOVE_ANIMATION_DURATION)))
+	var age := float(motion.get("age", 0.0))
+	var progress := clampf(age / duration, 0.0, 1.0)
+	var smooth_progress := progress * progress * (3.0 - 2.0 * progress)
+	var from_rect := _rect_for_cell(from_cell)
+	var to_rect := _rect_for_cell(to_cell)
+	rect.position = from_rect.position.lerp(to_rect.position, smooth_progress)
+	return rect
+
+
 func _draw_floating_texts() -> void:
 	if floating_texts.is_empty():
 		return
@@ -1262,6 +1299,18 @@ func _on_combat_feedback_requested(unit_id: String, text: String, kind: String)
 	queue_redraw()
 
 
+func _on_unit_motion_requested(unit_id: String, from_cell: Vector2i, to_cell: Vector2i) -> void:
+	if unit_id.is_empty() or from_cell == to_cell:
+		return
+	unit_motion_by_unit[unit_id] = {
+		"from": from_cell,
+		"to": to_cell,
+		"age": 0.0,
+		"duration": UNIT_MOVE_ANIMATION_DURATION
+	}
+	queue_redraw()
+
+
 func _floating_text_origin(cell: Vector2i) -> Vector2:
 	var rect := _rect_for_cell(cell)
 	return rect.position + Vector2(TILE_SIZE * 0.5, 18.0)
@@ -1447,6 +1496,7 @@ func _on_restart_pressed() -> void:
 	battle_result_summary.clear()
 	post_battle_dialogue_started = false
 	floating_texts.clear()
+	unit_motion_by_unit.clear()
 	shop_sell_mode = false
 	selected_skill_id = ""
 	selected_item_id = ""
@@ -1491,6 +1541,7 @@ func _load_scenario(scenario_id: String) -> void:
 	battle_result_summary.clear()
 	post_battle_dialogue_started = false
 	floating_texts.clear()
+	unit_motion_by_unit.clear()
 	selected_skill_id = ""
 	selected_item_id = ""
 	_hide_tactic_menu()
@@ -2370,6 +2421,7 @@ func _show_campaign_complete() -> void:
 	battle_result_summary.clear()
 	post_battle_dialogue_started = true
 	floating_texts.clear()
+	unit_motion_by_unit.clear()
 	move_cells.clear()
 	attack_cells.clear()
 	skill_cells.clear()