viewer/image_viewer/JFJochDiffractionImage.cpp

@@ -43,11 +43,22 @@ void JFJochDiffractionImage::mouseHover(QMouseEvent *event) {
             .arg(coord.y(), 0, 'f', 1)
             .arg(intensity_str)
             .arg(res, 0, 'f', 2));
-        } else
+
+        // Update hovered resolution text without rebuilding the whole overlay
+        hover_resolution = res;
+        DrawResolutionText();
+        } else {
             emit writeStatusBar("");
 
+            // Clear hover resolution text when outside image
+            if (std::isfinite(hover_resolution)) {
+                hover_resolution = NAN;
+                DrawResolutionText();
+            }
+        }
 }
 
+
 void JFJochDiffractionImage::LoadImageInternal() {
     if (!image)
         return;
@@ -298,6 +309,8 @@ void JFJochDiffractionImage::addCustomOverlay() {
         DrawPredictions();
     if (show_saturation)
         DrawSaturation();
+
+    DrawResolutionText();
 }
 
 void JFJochDiffractionImage::loadImage(std::shared_ptr<const JFJochReaderImage> in_image) {
@@ -316,6 +329,9 @@ void JFJochDiffractionImage::loadImage(std::shared_ptr<const JFJochReaderImage>
         W = 0; H = 0;
         if (scene())
             scene()->clear();
+        hover_resolution = NAN;
+        hover_resolution_item = nullptr;
+
         CalcROI();
     }
 }
@@ -403,3 +419,64 @@ void JFJochDiffractionImage::setResolutionRingMode(RingMode mode) {
     ring_mode = mode;
     updateOverlay();
 }
+
+void JFJochDiffractionImage::DrawResolutionText() {
+    auto scn = scene();
+    if (!scn) {
+        hover_resolution_item = nullptr; // scene gone
+        return;
+    }
+
+    // Hide item if no valid hover resolution
+    if (!image || !std::isfinite(hover_resolution) || hover_resolution <= 0.0f) {
+        if (hover_resolution_item)
+            hover_resolution_item->setVisible(false);
+        return;
+    }
+
+    const QRectF visibleRect = mapToScene(viewport()->geometry()).boundingRect();
+
+    // Fixed on-screen font size (no dependence on scale_factor)
+    QFont font("Arial");
+    font.setPixelSize(32);  // big, constant size on screen
+
+    const QString label =
+        QString("d = %1 Å").arg(QString::number(hover_resolution, 'f', 2));
+
+    // Create the item if it does not exist yet; otherwise reuse it
+    if (!hover_resolution_item) {
+        hover_resolution_item = scn->addText(label, font);
+        hover_resolution_item->setZValue(10.0);
+        // Make the text ignore zooming / view transforms
+        hover_resolution_item->setFlag(QGraphicsItem::ItemIgnoresTransformations, true);
+    } else {
+        hover_resolution_item->setFont(font);
+        hover_resolution_item->setPlainText(label);
+    }
+
+    hover_resolution_item->setDefaultTextColor(feature_color);
+
+    // Keep a roughly constant ~10 px margin by compensating with scale_factor
+    const qreal margin_px = 10.0;
+    const qreal margin_scene = margin_px / std::max(0.0001, scale_factor);
+
+    QPointF topLeft(visibleRect.left() + margin_scene,
+                    visibleRect.top() + margin_scene);
+    hover_resolution_item->setPos(topLeft);
+    hover_resolution_item->setVisible(true);
+}
+
+void JFJochDiffractionImage::beforeOverlayCleared() {
+    // The scene is about to clear (and delete) all its items.
+    // Drop our non-owning pointer so we never touch a deleted item.
+    hover_resolution_item = nullptr;
+}
+
+void JFJochDiffractionImage::leaveEvent(QEvent *event) {
+    // Mouse left the view: clear hover resolution and hide text
+    if (std::isfinite(hover_resolution)) {
+        hover_resolution = NAN;
+        DrawResolutionText();
+    }
+    JFJochImage::leaveEvent(event);
+}

viewer/image_viewer/JFJochDiffractionImage.h

@@ -13,6 +13,8 @@ Q_OBJECT
     QColor prediction_color = Qt::darkRed;
     QColor ice_ring_color = Qt::cyan;
 
+    float hover_resolution = NAN;
+    QGraphicsTextItem* hover_resolution_item = nullptr; // big text in top-left
 public:
     enum class RingMode {Auto, Estimation, Manual, None, IceRings};
     Q_ENUM(RingMode)
@@ -28,8 +30,12 @@ private:
     void DrawBeamCenter();
     void DrawTopPixels();
     void DrawSaturation();
+    void DrawResolutionText();
     void DrawCross(float x, float y, float size, float width, float z = 1);
 
+    void beforeOverlayCleared() override;
+    void leaveEvent(QEvent *event) override;
+
     std::shared_ptr<const JFJochReaderImage> image;
 
     int32_t show_highest_pixels = 0;

viewer/image_viewer/JFJochImage.cpp

@@ -681,6 +681,8 @@ void JFJochImage::writePixelLabels() {
 void JFJochImage::updateOverlay() {
     if (!scene() || W * H <= 0) return;
 
+    beforeOverlayCleared();
+
     scene()->clear();
     scene()->addItem(new QGraphicsPixmapItem(pixmap));
 
@@ -828,3 +830,5 @@ void JFJochImage::fitToViewShorterSideOnce() {
 void JFJochImage::adjustForeground(bool input) {
     m_adjustForegroundWithWheel = input;
 }
+
+void JFJochImage::beforeOverlayCleared() {}

viewer/image_viewer/JFJochImage.h

@@ -30,6 +30,8 @@ class JFJochImage : public QGraphicsView {
     ROIMessage accumulateROI(int64_t xmin, int64_t xmax, int64_t ymin, int64_t ymax,
                           const std::function<bool(int64_t,int64_t)>& inside);
 protected:
+    virtual void beforeOverlayCleared();
+
     bool show_saturation = false;
 
     bool auto_bg = false;