Jungfraujoch/viewer/image_viewer/JFJochImage.h

// SPDX-FileCopyrightText: 2025 Filip Leonarski, Paul Scherrer Institute <filip.leonarski@psi.ch>
// SPDX-License-Identifier: GPL-3.0-only

#pragma once

#include <cmath>
#include <memory>

#include <QElapsedTimer>
#include <QTimer>
#include <QGraphicsView>
#include <QGraphicsItem>
#include <QImage>
#include <QMouseEvent>
#include <QPainterPath>
#include <QTransform>
#include <QPointF>
#include "../../common/ColorScale.h"
#include "../../common/JFJochMessages.h"

// Q_DECLARE_METATYPE(ROIMessage)

// Maps one pixel value to a colour. Shared by the generic float path and by subclasses that
// colour straight out of their own buffer, so the two cannot drift apart. Apply() takes a
// real value; the callers handle their own gap/bad/saturated encoding.
struct PixelColorMap {
    const rgb *lut = nullptr;
    int lut_size = 0;
    float minv = 0.0f;
    float range = 0.0f;
    float inv_range = 0.0f;
    float inv_range_log = 0.0f;
    bool hdr = false;
    rgb gap{}, bad{}, saturated{};

    [[nodiscard]] rgb Apply(float v) const {
        float f;
        const float v_minv = v - minv;

        if (hdr) {
            if (v_minv <= 0.0f)
                f = 0.0f;
            else if (v_minv >= range)
                f = static_cast<float>(lut_size);
            else
                f = std::log1p(v_minv) * inv_range_log;
        } else
            f = v_minv * inv_range;

        if (f < 0.0f) f = 0.0f;

        auto idx = static_cast<int>(f + 0.5f);
        if (idx <= 0) idx = 0;
        else if (idx >= lut_size) idx = lut_size - 1;
        return lut[idx];
    }
};

// Draws a rendered frame. A QGraphicsPixmapItem would mean converting the whole image into a
// QPixmap on every recolour, which costs one extra allocation and a full pass over the pixels.
// The frame is held by shared_ptr so that several views can show the same pixels.
class JFJochImageItem : public QGraphicsItem {
    std::shared_ptr<const QImage> img_;
public:
    explicit JFJochImageItem(std::shared_ptr<const QImage> img) : img_(std::move(img)) {}
    QRectF boundingRect() const override;
    QPainterPath opaqueArea() const override;
    void paint(QPainter *painter, const QStyleOptionGraphicsItem *option, QWidget *widget) override;
    void refresh();   // the buffer behind the item changed
};

class JFJochImage : public QGraphicsView {
    Q_OBJECT

    bool m_adjustForegroundWithWheel = false;

    // Viewport-lock support: guard prevents the emit<->apply ping-pong between
    // two linked views, and the helper broadcasts the current transform+center.
    bool m_applyingViewport = false;
    void emitViewportChanged();

    void DrawROI();
    virtual void addCustomOverlay();
    void updateROI();
    void drawPixelLabels(QPainter *painter, const QRectF &rect);
    void wheelEvent(QWheelEvent* event) override;
    void resizeEvent(QResizeEvent *event) override;
    void contextMenuEvent(QContextMenuEvent *event) override;

    void mousePressEvent(QMouseEvent *event) override;
    void mouseMoveEvent(QMouseEvent *event) override;
    void mouseReleaseEvent(QMouseEvent *event) override;

protected:
    // Only the view that owns detector counts offers a region of interest; for the others a
    // shift-drag would draw a box that means nothing.
    [[nodiscard]] virtual bool AllowROI() const { return false; }

    bool show_saturation = false;

    bool auto_bg = false;
    bool auto_fg = false;
    bool hdr_mode = false;

    double scale_factor = 1.0;

    size_t W = 0, H = 0;
    size_t prev_W = 0, prev_H = 0;

    // Track initial fit state and last image size
    bool initial_fit_done_ = false;

    QColor feature_color = Qt::magenta;

    // Decimal places for non-integer per-pixel value labels. Float images are
    // unreadable with many decimals, so subclasses can lower this.
    int label_decimals_ = 3;

    float foreground = 10.0;
    float background = 0.0;
    ColorScale color_scale;
    std::vector<float> image_fp;
    // The rendered RGB frame. Reused across frames (no per-frame allocation) and held by
    // shared_ptr so follower views can display the very same pixels - see JFJochFollowerImage.
    // The pointer itself is stable for the lifetime of the widget; only its contents change.
    std::shared_ptr<QImage> frame_ = std::make_shared<QImage>();

    // Persistent image item — never destroyed/recreated on overlay update
    JFJochImageItem *image_item_ = nullptr;
    // Overlay items managed separately
    QList<QGraphicsItem *> overlay_items_;

    // Helper: add an overlay item to the scene and track it for selective removal
    void addOverlayItem(QGraphicsItem *item);

    enum class MouseEventType {None, Panning, DrawingROI, MovingROI, ResizingROI, EditingExternalROI};
    MouseEventType mouse_event_type = MouseEventType::None;

    // Hooks for editing a named, persistent ROI drawn by a subclass (the base only
    // owns the mouse events; the subclass knows the loaded ROIs). roiEditPress returns
    // true to claim the gesture for ROI editing.
    virtual bool roiEditPress(const QPointF &scenePos) { return false; }
    virtual void roiEditMove(const QPointF &scenePos) {}
    virtual void roiEditRelease() {}
    virtual void roiScratchDrawn() {}   // a shift/ctrl-drag finished drawing a new box/circle
    QPoint lastMousePos;  // To track panning movement

    // Resizing which edge/corner
    enum class ResizeHandle { None, Left, Right, Top, Bottom, TopLeft, TopRight, BottomLeft, BottomRight, Inside };
    ResizeHandle active_handle_ = ResizeHandle::None;
    ResizeHandle hover_handle_ = ResizeHandle::None;

    enum class RoiType {RoiBox, RoiCircle};
    RoiType roi_type = RoiType::RoiBox;
    QPointF roiStartPos;
    QPointF roiEndPos;
    QRectF roiBox;

    // Text for the per-pixel value label at (x, y). The base reads image_fp, which is what the
    // float-valued views hold; a view whose source is exact integers overrides this so the label
    // is exact and no float copy of the image has to exist at all.
    [[nodiscard]] virtual QString PixelLabel(int x, int y) const;
    void drawForeground(QPainter *painter, const QRectF &rect) override;

    static QPointF RoundPoint(const QPointF& p);
    virtual void mouseHover(const QPointF &scenePos, Qt::KeyboardModifiers modifiers) = 0;

    // Hover feedback (status bar, resolution readout, magnifier) used to be regenerated on every
    // single mouse motion. Each regeneration dirties the window, and on a remote X session every
    // repaint costs a full-window pixel upload, so the thing to minimise is the number of
    // repaints. ~15 Hz is far below the motion event rate and well above what the eye follows.
    //
    // The rate limit is applied inline rather than from a timer on purpose: running the update
    // inside the mouse event keeps its damage in the same repaint as anything else that event
    // triggers (a pan), instead of costing a second one. The timer only covers the tail, so the
    // final position is still reported once the pointer stops.
    static constexpr int kHoverIntervalMs = 66;
    void ScheduleHoverUpdate(const QPointF &scenePos, Qt::KeyboardModifiers modifiers);
    void UpdateHover();
    void leaveEvent(QEvent *event) override;
    QPointF hover_scene_pos_;
    Qt::KeyboardModifiers hover_modifiers_ = Qt::NoModifier;
    QElapsedTimer hover_rate_;
    QTimer *hover_tail_timer_ = nullptr;

    ResizeHandle hitTestROIHandle(const QPointF& scenePos, qreal tol = 3.0) const;

    void updateOverlay();
    void RenderImage();
    PixelColorMap MakeColorMap() const;
    // Colour one row into `out`. Called from worker threads, so it must stay const. The base
    // maps image_fp; a subclass whose source is already a compact buffer can map that directly
    // and skip materialising the float image.
    virtual void ColorRow(size_t y, const PixelColorMap &map, QRgb *out) const;
    // Re-render once the event queue drains. The foreground slider and the wheel emit far
    // faster than a large image can be recoloured, so intermediate values are dropped
    // instead of queueing a full recolour per event.
    void ScheduleRenderImage();
    bool render_pending_ = false;
    bool image_dirty_ = false;   // frame_ changed since the item was last refreshed
    void ClearFrame();           // drop the pixels and tell followers
    // Set while a pan/zoom moves the scrollbars, so onScroll() does not rebuild the overlay
    // once per scrollbar; the gesture rebuilds it once itself.
    bool suppress_overlay_update_ = false;
    void Redraw();

    // Invalidate image_item_ and overlay tracking after scene()->clear()
    void resetScenePointers();

    // Perform initial fit-to-view (shorter direction), once per image size
    void fitToViewShorterSideOnce();

    // Render the current frame to an image at native resolution, optionally including the overlay
    // (spots, predictions, rings, ROIs). Used by both the clipboard and save-to-file actions.
    QImage renderToImage(bool with_overlay);
    void copyImageToClipboard();
    void copyImageWithOverlayToClipboard();
    void saveImageToFile(bool with_overlay);
    void clearROIInternal();
signals:
    void autoForegroundChanged(bool input);
    void foregroundChanged(float v);
    void backgroundChanged(float v);
    void writeStatusBar(QString string, int timeout_ms = 0);
    void roiBoxUpdated(QRect box);
    void roiCircleUpdated(double x, double y, double radius);
    void viewportChanged(QTransform transform, QPointF center);
    void hoverScenePos(QPointF scenePos);
    // A new frame has been rendered into Frame(). Follower views repaint on this.
    void frameRendered();
private slots:
    void onScroll(int value);
public slots:
    void setFeatureColor(QColor input);
    void setColorMap(int color_map);
    virtual void changeForeground(float val);
    void changeBackground(float val);

    void SetROIBox(QRect box);
    void SetROICircle(double x, double y, double radius);

    void centerOnSpot(QPointF point);
    void applyViewport(QTransform transform, QPointF center);
    void fitToView();

    void adjustForeground(bool input);
    void setZoom(double input);
public:
    explicit JFJochImage(QWidget *parent = nullptr);
    double GetScaleFactor() const;
    // The rendered frame, for views that want to show the same pixels without redoing the work
    [[nodiscard]] std::shared_ptr<const QImage> Frame() const { return frame_; }
};