esqueleto nivel 1

source/core/rendering/sprites/dissolve_sprite.hpp

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+#pragma once
+
+#include <SDL3/SDL.h>
+
+#include <memory>  // Para shared_ptr
+
+#include "core/rendering/sprites/animated_sprite.hpp"  // Para AnimatedSprite
+
+class Surface;
+
+// Direcció de la dissolució
+enum class DissolveDirection { NONE,
+    DOWN,
+    UP };
+
+// Sprite que pot dissoldre's o generar-se de forma aleatòria en X mil·lisegons.
+// progress_ va de 0.0 (totalment visible) a 1.0 (totalment invisible).
+class DissolveSprite : public AnimatedSprite {
+   public:
+    explicit DissolveSprite(const AnimationResource& data);
+    DissolveSprite(std::shared_ptr<Surface> surface, SDL_FRect pos);
+    ~DissolveSprite() override = default;
+
+    void update(float delta_time) override;
+    void render() override;
+
+    // Progrés manual [0.0 = totalment visible, 1.0 = totalment invisible]
+    void setProgress(float progress);
+    [[nodiscard]] auto getProgress() const -> float { return progress_; }
+
+    // Inicia una dissolució temporal (visible → invisible en duration_ms)
+    void startDissolve(float duration_ms, DissolveDirection dir = DissolveDirection::NONE);
+
+    // Inicia una generació temporal (invisible → visible en duration_ms)
+    void startGenerate(float duration_ms, DissolveDirection dir = DissolveDirection::NONE);
+
+    void stopTransition();
+    [[nodiscard]] auto isTransitionDone() const -> bool;
+
+    // Substitució de color: en reconstruir, substitueix source per target
+    void setColorReplace(Uint8 source, Uint8 target);
+
+   private:
+    enum class TransitionMode { NONE,
+        DISSOLVING,
+        GENERATING };
+
+    std::shared_ptr<Surface> surface_display_;  // Superfície amb els píxels filtrats
+
+    float progress_{0.0F};  // [0=visible, 1=invisible]
+    DissolveDirection direction_{DissolveDirection::NONE};
+    TransitionMode transition_mode_{TransitionMode::NONE};
+    float transition_duration_{0.0F};
+    float transition_elapsed_{0.0F};
+    SDL_FRect prev_clip_{.x = 0, .y = 0, .w = 0, .h = 0};
+    bool needs_rebuild_{false};
+    Uint8 source_color_{255};  // 255 = transparent = sense replace per defecte
+    Uint8 target_color_{0};
+
+    void rebuildDisplaySurface();
+    [[nodiscard]] static auto computePixelRank(int col, int row, int frame_h, DissolveDirection dir) -> float;
+};