14.20: the Navigator minimap from 300%

src/Document/EditorSession+Navigator.cpp

@@ -0,0 +1,54 @@
+#include "Document/EditorSession.h"
+#include "Document/BrushStroke.h"
+#include "IO/ImageExporter.h"
+#include "Logging.h"
+#include <QPainter>
+#include <cmath>
+
+// Swift's EditorSession+Navigator.swift: the document in small.
+namespace {
+// Every layer and placed mask scaled; blurs shrink with them.
+CanvasDocument placed(const CanvasDocument &document, double x, double y, int width, int height)
+{
+    const auto scaled = [x, y](LayerTransform transform) {
+        transform.origin = QPointF(transform.origin.x() * x, transform.origin.y() * y);
+        transform.size = QSizeF(transform.size.width() * x, transform.size.height() * y);
+        return transform;
+    };
+    CanvasDocument small = document;
+    small.width = width;
+    small.height = height;
+    for (ImageLayer &layer : small.layers) {
+        layer.transform = scaled(layer.transform);
+        if (layer.mask && layer.mask->placement)
+            layer.mask->placement = scaled(*layer.mask->placement);
+        if (layer.adjustment && layer.adjustment->blurRadius)
+            layer.adjustment->blurRadius = *layer.adjustment->blurRadius * x;
+        if (layer.adjustment && layer.adjustment->motionDistance)
+            layer.adjustment->motionDistance = *layer.adjustment->motionDistance * x;
+    }
+    return small;
+}
+}
+
+// At the picture's size: adjustment surfaces take what they draw.
+std::optional<QImage> EditorSession::navigatorImage(int maxSide) const
+{
+    if (!m_document || m_document->width <= 0 || m_document->height <= 0 || maxSide <= 0)
+        return std::nullopt;
+    const CanvasDocument &document = *m_document;
+    const double scale = std::min(1.0, double(maxSide) / std::max(document.width, document.height));
+    const int width = std::max(1, int(std::lround(document.width * scale))), height = std::max(1, int(std::lround(document.height * scale)));
+    QImage context;
+    try {
+        context = BrushRaster::context(width, height, false);
+    } catch (const ExportError &error) {
+        qCWarning(lcRendering) << "the navigator's picture could not be made:" << error.what();
+        return std::nullopt;
+    }
+    QPainter painter(&context);
+    // A bare session: edits in progress stay out.
+    EditorSession().drawLiveComposite(placed(document, double(width) / document.width, double(height) / document.height, width, height), painter);
+    painter.end();
+    return context;
+}

src/Document/EditorSession+Navigator.h

@@ -0,0 +1,4 @@
+// Swift's EditorSession+Navigator extension: the document in small.
+public:
+    // Its longer side `maxSide` at most, never enlarged.
+    std::optional<QImage> navigatorImage(int maxSide) const;

src/Document/EditorSession.h

@@ -313,6 +313,7 @@ public:
 #include "Document/Guides+Session.h"
 #include "Document/ObjectSelection+Session.h"
 #include "Document/ColorRangeSelection+Session.h"
+#include "Document/EditorSession+Navigator.h"
 signals:
     void changed();