stats_overlay.hpp

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// This file is part of the Rendering Engine project.
// Author: Alexander Obzherin <alexanderobzherin@gmail.com>
// Copyright (c) 2026 Alexander Obzherin
// Distributed under the terms of the zlib License. See LICENSE.md for details.
 
#pragma once
 
#include "actor_2d.hpp"
 
namespace rendering_engine
{
class Rectangle2D;
class TextBlock2D;
 
/**
 * @class StatsOverlay
 * @brief Displays real-time frame statistics as a 2D overlay.
 *
 * StatsOverlay renders a simple performance panel containing:
 * - FPS
 * - Frame duration (ms)
 * - Update time (ms)
 * - Draw time (ms)
 *
 * The overlay is drawn in screen space using Rectangle2D and TextBlock2D
 * subobjects. Values are updated every frame using FrameMetrics obtained
 * from the active application.
 *
 * Intended for debugging and performance diagnostics.
 */
class RE_API StatsOverlay : public Actor2D
{
public:
    /**
     * @brief Constructs a StatsOverlay actor.
     *
     * Reads configuration options and prepares internal state.
     *
     * @param scene Reference to the owning scene.
     */
    StatsOverlay(Scene& scene);
    /**
     * @brief Creates and positions overlay visual elements.
     *
     * Spawns background rectangle and label/value text blocks,
     * attaches them to the root component, and arranges them
     * in a two-column layout.
     */
    void Initialize() override;
    /**
     * @brief Updates displayed statistics each frame.
     *
     * Retrieves FrameMetrics from the active application and
     * updates value text blocks accordingly.
     *
     * @param deltaTime Time elapsed since previous frame (ms).
     */
    void Update(float deltaTime) override;
 
private:
    Rectangle2D* mBackGround;
 
    TextBlock2D* mFPSLabel;
    TextBlock2D* mFPSValue;
    
    TextBlock2D* mFrameLabel;
    TextBlock2D* mFrameValue;
 
    TextBlock2D* mUpdateLabel;
    TextBlock2D* mUpdateValue;
 
    TextBlock2D* mDrawLabel;
    TextBlock2D* mDrawValue;
 
    glm::vec4 mBgColor{ 0.0f, 0.0f, 1.0f, 0.9f };
    glm::vec4 mLabelColor{ 0.5f, 0.5f, 0.5f, 1.0f };
    glm::vec4 mValueColor{ 1.0f, 1.0f, 1.0f, 1.0f };
 
    bool bUseSmoothedFPS = true;
 
    float mTimeAccumulator = 0.0f;
    const float mUpdateInterval = 0.25f; // seconds
};
 
} // namespace rendering_engine