69 lines
1.9 KiB
C#
69 lines
1.9 KiB
C#
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using Microsoft.Xna.Framework;
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using Microsoft.Xna.Framework.Graphics;
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namespace Theriapolis.Game.Screens;
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/// <summary>
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/// Manages a stack of IScreen instances.
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/// Only the top screen receives Update and Draw calls.
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/// Push/Pop are deferred to the start of the next frame to avoid mid-loop mutation.
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/// </summary>
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public sealed class ScreenManager
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{
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private readonly Game1 _game;
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private readonly Stack<IScreen> _stack = new();
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private IScreen? _pendingPush;
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private int _pendingPops; // count rather than bool — multiple Pops queued in one frame all apply
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public ScreenManager(Game1 game)
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{
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_game = game;
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}
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public IScreen? Current => _stack.Count > 0 ? _stack.Peek() : null;
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public void Push(IScreen screen)
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{
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_pendingPush = screen;
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}
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public void Pop()
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{
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_pendingPops++;
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}
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/// <summary>Process any pending push/pop, then update the current screen.</summary>
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public void Update(GameTime gameTime)
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{
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// Apply deferred transitions — drain all pending pops before any push.
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bool popped = false;
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while (_pendingPops > 0 && _stack.Count > 0)
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{
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var top = _stack.Pop();
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top.Deactivate();
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_pendingPops--;
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popped = true;
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}
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_pendingPops = 0;
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// Only call Reactivate once after a pop chain — not every frame.
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if (popped && _stack.TryPeek(out var back)) back.Reactivate();
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if (_pendingPush is not null)
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{
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_stack.TryPeek(out var cur);
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cur?.Deactivate();
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_pendingPush.Initialize(_game);
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_stack.Push(_pendingPush);
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_pendingPush = null;
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}
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Current?.Update(gameTime);
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}
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public void Draw(GameTime gameTime, SpriteBatch spriteBatch)
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{
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Current?.Draw(gameTime, spriteBatch);
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}
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}
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