qsg2dlodpolicy.h

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#ifndef OPENSWMM_RENDER_QSG2DLODPOLICY_H
#define OPENSWMM_RENDER_QSG2DLODPOLICY_H
 
#include <QtGlobal>
 
#include <limits>
 
namespace OpenSWMM::Render
{
 
struct Qsg2DLodInputs
{
    // ── View ────────────────────────────────────────────────────────────
    double viewportWidthPx  = 0.0;  
    double viewportHeightPx = 0.0;
    double extentWidth      = 0.0;  
    double extentHeight     = 0.0;
 
    // ── Mesh density ────────────────────────────────────────────────────
    qint64 cellCount    = 0;    
    double meshBBoxArea = 0.0;  
    double visibleFraction = 1.0;
 
    // ── Sublayer intents (user-facing visibility toggles) ───────────────
    bool wantFill          = true;
    bool wantEdges         = false;
    bool wantVertexMarkers = false;
    bool wantContours      = false;
    bool wantContourLabels = false;
    bool wantVelocity      = false;
    bool haveSelection     = false;
 
    // ── Hysteresis anchors (previous decision; defaults = none) ─────────
    int previousBucket   = -1;
    int previousZoomStep = std::numeric_limits<int>::min();
 
    double farMaxCellAreaPx = 8.0;   // = Qsg2DLodPolicy::kFarMaxCellAreaPx
 
    double edgeMinCellAreaPx   = 32.0;   // = Qsg2DLodPolicy::kEdgeMinCellAreaPx
    double markerMinCellAreaPx = 200.0;  // = Qsg2DLodPolicy::kMarkerMinCellAreaPx
};
 
struct Qsg2DLodDecision
{
    enum Bucket { Far = 0, Mid = 1, Near = 2 };
 
    Bucket bucket        = Near;
    int    zoomStep      = 0;      
    double avgCellAreaPx = 0.0;    
 
    // Per-pass verdicts — already combined with the user intents, i.e.
    // false either because the user turned the pass off or because the
    // bucket suppresses it.
    bool drawFill             = true;
    bool drawEdges            = false;
    bool drawVertexMarkers    = false;
    bool drawContours         = false;   
    bool drawContourLabels    = false;
    bool drawVelocityVectors  = false;
    bool drawSelectedOverlays = false;   
 
    bool useAggregateFill = false;
 
    bool exactContourBands = false;
 
    bool   denseVelocityAllowed = false;
    qint64 maxVelocityGlyphs    = 0;
    int    maxContourLabels     = 0;
 
    [[nodiscard]] quint64 contentKey() const
    {
        return (quint64(quint32(zoomStep)) << 2) | quint64(bucket);
    }
};
 
class Qsg2DLodPolicy
{
public:
    // Bucket thresholds on the mean projected cell area (px²). A cell
    // whose area is below kFarMaxCellAreaPx spans < ~3 px — subpixel-ish,
    // wireframe/markers are pure noise. Above kNearMinCellAreaPx a cell
    // spans ≥ ~13 px and exact detail reads clearly.
    static constexpr double kFarMaxCellAreaPx   = 8.0;
    static constexpr double kNearMinCellAreaPx  = 160.0;
    static constexpr double kEdgeMinCellAreaPx  = 32.0;
    static constexpr double kMarkerMinCellAreaPx = 200.0;
    static constexpr double kBucketHysteresis   = 0.25;
    static constexpr double kZoomStepHysteresis = 0.08;
    static constexpr qint64 kDenseVelocityCellCap = 20000;
    static constexpr int    kMidMaxContourLabels  = 40;
    static constexpr int    kNearMaxContourLabels = 400;
 
    [[nodiscard]] static Qsg2DLodDecision decide(const Qsg2DLodInputs &in);
};
 
} // namespace OpenSWMM::Render
 
#endif // OPENSWMM_RENDER_QSG2DLODPOLICY_H