[graphics/krita] libs/ui/tool: Nuke caching

Git commit a8d4b36a4f19923e80779815556a68bf244c9b4d by Emmet O'Neill, on behalf of Dat Le.
Committed on 13/08/2026 at 23:16.
Pushed by emmetoneill into branch 'master'.

Nuke caching

M  +11   -42   libs/ui/tool/KisAsyncColorSamplerHelper.cpp
M  +1    -3    libs/ui/tool/KisAsyncColorSamplerHelper.h
M  +4    -4    libs/ui/tool/strokes/kis_color_sampler_stroke_strategy.cpp
M  +3    -4    libs/ui/tool/strokes/kis_color_sampler_stroke_strategy.h

https://invent.kde.org/graphics/krita/-/commit/a8d4b36a4f19923e80779815556a68bf244c9b4d

diff --git a/libs/ui/tool/KisAsyncColorSamplerHelper.cpp b/libs/ui/tool/KisAsyncColorSamplerHelper.cpp
index 24a970e82bd..4ad99c522a6 100644
--- a/libs/ui/tool/KisAsyncColorSamplerHelper.cpp
+++ b/libs/ui/tool/KisAsyncColorSamplerHelper.cpp
@@ -83,7 +83,6 @@ struct KisAsyncColorSamplerHelper::Private
     QPainterPath cacheCrosshairPath;
     int cacheCirclePreviewDiameter;
     bool canvasPreviewFetchingStarted {false};
-    QRect oldCanvasPixelRect;
     bool zoomPreviewHasPainted {false};
 
     QColor currentColor;
@@ -415,7 +414,6 @@ void KisAsyncColorSamplerHelper::deactivate()
     m_d->cacheCanvasPreviewImage = QImage();
     m_d->cacheCanvasPreviewRect = QRect();
     m_d->canvasPreviewFetchingStarted = false;
-    m_d->oldCanvasPixelRect = QRect();
     m_d->zoomPreviewHasPainted = false;
 
     m_d->isActive = false;
@@ -710,15 +708,11 @@ void KisAsyncColorSamplerHelper::paintCircleCrosshair(QPainter &gc, const QRectF
     qreal luminance = KisPaintingTweaks::luminosityCoarse(currentColor);
     if (luminance < 0.5) crosshairColor = Qt::white;
 
-    qreal dpr = gc.device()->devicePixelRatioF();
-    qreal penWidth = 1.0 * dpr;
-    QPen pen = QPen(crosshairColor, penWidth);
-
     gc.save();
 
     gc.setRenderHints(QPainter::Antialiasing | QPainter::SmoothPixmapTransform);
     gc.setCompositionMode(QPainter::CompositionMode_SourceOver);
-    gc.setPen(pen);
+    gc.setPen(crosshairColor);
 
     QTransform tf;
     tf.translate(viewRectF.center().x(), viewRectF.center().y());
@@ -728,7 +722,7 @@ void KisAsyncColorSamplerHelper::paintCircleCrosshair(QPainter &gc, const QRectF
     gc.restore();
 }
 
-QImage KisAsyncColorSamplerHelper::cacheCanvasImage(QRect &canvasPixelRect) {
+QImage KisAsyncColorSamplerHelper::fetchCanvasPreview(QRect &canvasPixelRect) {
     KisImageWSP canvasImage = m_d->canvas->image();
 
     if (!canvasImage->bounds().intersects(canvasPixelRect)) {
@@ -736,40 +730,15 @@ QImage KisAsyncColorSamplerHelper::cacheCanvasImage(QRect &canvasPixelRect) {
         return QImage();
     }
 
-    // If already cached the whole canvas, just use it from now on
-    if (m_d->cacheCanvasPreviewRect == canvasImage->bounds()) {
-        return m_d->cacheCanvasPreviewImage;
-    }
-
-    if (m_d->cacheCanvasPreviewRect.isEmpty() || !m_d->cacheCanvasPreviewRect.contains(canvasPixelRect)) {
-        // Cache an area larger than the needed preview area to avoid rapid small dynamic allocations
-        // And also avoid frequent preview delay from repeatedly fetching canvas image asynchronously
-        qreal cacheScale = 1;
-
-        QRect cacheCanvasRect = canvasPixelRect;
-        cacheCanvasRect.setSize(canvasPixelRect.size() * cacheScale);
-        cacheCanvasRect.moveCenter(canvasPixelRect.center());
-
-        // if cache requirement is larger than canvas, then just copy whole canvas
-        if (cacheCanvasRect.width() >= canvasImage->width() || cacheCanvasRect.height() >= canvasImage->height()) {
-            cacheCanvasRect = canvasImage->bounds();
-        }
-
-        // If not already have a job fetching canvas image, then do it
-        // TODO: There's probably a better way to do this
-        if (!m_d->canvasPreviewFetchingStarted) {
-            m_d->canvasPreviewFetchingStarted = true;
-            m_d->strokesFacade()->addJob(m_d->strokeId,
-                new KisColorSamplerStrokeStrategy::GenerateCanvasZoomPreviewData(m_d->canvas, cacheCanvasRect, canvasImage->colorSpace()->profile()));
-        }
-
-        // Return the last valid canvas preview while we wait to fetch new canvas cache async
-        if (!m_d->oldCanvasPixelRect.isNull()) canvasPixelRect = m_d->oldCanvasPixelRect;
-        return m_d->cacheCanvasPreviewImage;
+    // If not already have a job fetching canvas image, then do it
+    if (!m_d->canvasPreviewFetchingStarted) {
+        m_d->canvasPreviewFetchingStarted = true;
+        m_d->strokesFacade()->addJob(m_d->strokeId,
+            new KisColorSamplerStrokeStrategy::GenerateCanvasZoomPreviewData(m_d->canvas, canvasPixelRect));
     }
 
-    canvasPixelRect.translate(-m_d->cacheCanvasPreviewRect.topLeft());
-    m_d->oldCanvasPixelRect = canvasPixelRect;
+    // Render the last frame if available
+    if (!m_d->cacheCanvasPreviewRect.isNull()) canvasPixelRect = m_d->cacheCanvasPreviewRect;
 
     return m_d->cacheCanvasPreviewImage;
 }
@@ -787,7 +756,7 @@ bool KisAsyncColorSamplerHelper::paintCircleCanvasPreview(QPainter &gc, const QR
     // Make sure the center is the pixel currently sampled because standardizing may change the shape
     canvasPixelRect.moveCenter(image->documentToImagePixelFloored(zoomDocRectF.center()));
 
-    QImage cachedImage = cacheCanvasImage(canvasPixelRect);
+    QImage cachedImage = fetchCanvasPreview(canvasPixelRect);
     // If cachedImage and canvasPixelRect is null, painting is not needed
     // If cachedImage is null and canvasPixelRect is not null, painting was deferred
     if (cachedImage.isNull()) return canvasPixelRect.isNull();
@@ -862,8 +831,8 @@ void KisAsyncColorSamplerHelper::paintCircleReferenceImagePreview(QPainter &gc,
 }
 
 void KisAsyncColorSamplerHelper::slotCanvasZoomPreviewUpdated(const QImage &canvasImage, QRect canvasRect) {
-    m_d->cacheCanvasPreviewImage = canvasImage;
     m_d->cacheCanvasPreviewRect = canvasRect;
+    m_d->cacheCanvasPreviewImage = canvasImage;
 
     m_d->canvasPreviewFetchingStarted = false;
 
diff --git a/libs/ui/tool/KisAsyncColorSamplerHelper.h b/libs/ui/tool/KisAsyncColorSamplerHelper.h
index 528d7797566..8f4ed364dfb 100644
--- a/libs/ui/tool/KisAsyncColorSamplerHelper.h
+++ b/libs/ui/tool/KisAsyncColorSamplerHelper.h
@@ -87,9 +87,7 @@ private:
     bool paintCircleCanvasPreview(QPainter &gc, const QRectF &viewRectF, const QRectF &zoomDocRectF, const QPainterPath &clip);
     void paintCircleReferenceImagePreview(QPainter &gc, const QRectF &viewRectF, const QRectF &zoomDocRectF, const QPainterPath &clip);
 
-    // Returns a QImage that should either contain the canvasPixelRect + caching, or the whole canvas if canvasPixelRect + caching > canvas size.
-    // Also modify the input rect to point to the same position relative to the returned image
-    QImage cacheCanvasImage(QRect &canvasPixelRect);
+    QImage fetchCanvasPreview(QRect &canvasPixelRect);
 
     struct Private;
     QScopedPointer<Private> m_d;
diff --git a/libs/ui/tool/strokes/kis_color_sampler_stroke_strategy.cpp b/libs/ui/tool/strokes/kis_color_sampler_stroke_strategy.cpp
index b3719928b7a..dbf9aec6fb6 100644
--- a/libs/ui/tool/strokes/kis_color_sampler_stroke_strategy.cpp
+++ b/libs/ui/tool/strokes/kis_color_sampler_stroke_strategy.cpp
@@ -59,13 +59,13 @@ void KisColorSamplerStrokeStrategy::doStrokeCallback(KisStrokeJobData *data)
         }
     } else if (previewData) {
         KisPaintDeviceSP dev = previewData->canvas->image()->projection();
-        KisPaintDeviceSP tmp = new KisPaintDevice(dev->colorSpace());
+        KisPaintDeviceSP tmpDev = new KisPaintDevice(dev->colorSpace());
 
-        tmp->makeCloneFromRough(dev, previewData->canvasPixelRect);
+        tmpDev->makeCloneFrom(dev, previewData->canvasPixelRect);
 
-        QImage image = previewData->canvas->displayColorConverter()->convertImageToDisplayColorSpace(tmp, previewData->canvasPixelRect, true);
+        QImage image = previewData->canvas->displayColorConverter()->convertImageToDisplayColorSpace(tmpDev, previewData->canvasPixelRect, true);
 
-        Q_EMIT sigCanvasZoomPreviewUpdated(image, previewData->canvasPixelRect);
+        Q_EMIT sigCanvasZoomPreviewUpdated(image, QRect(QPoint(0,0), previewData->canvasPixelRect.size()));
     }
 }
 
diff --git a/libs/ui/tool/strokes/kis_color_sampler_stroke_strategy.h b/libs/ui/tool/strokes/kis_color_sampler_stroke_strategy.h
index bdf761473a1..4b4117e915d 100644
--- a/libs/ui/tool/strokes/kis_color_sampler_stroke_strategy.h
+++ b/libs/ui/tool/strokes/kis_color_sampler_stroke_strategy.h
@@ -49,18 +49,17 @@ public:
 
     class GenerateCanvasZoomPreviewData : public KisStrokeJobData {
     public:
-        GenerateCanvasZoomPreviewData(KisCanvas2* _canvas, const QRect &_canvasPixelRect, const KoColorProfile *_colorProfile)
-            : canvas(_canvas), canvasPixelRect(_canvasPixelRect), colorProfile(_colorProfile)
+        GenerateCanvasZoomPreviewData(KisCanvas2* _canvas, const QRect &_canvasPixelRect)
+            : canvas(_canvas), canvasPixelRect(_canvasPixelRect)
         {}
 
         KisStrokeJobData* createLodClone(int levelOfDetail) override {
             Q_UNUSED(levelOfDetail);
-            return new GenerateCanvasZoomPreviewData(canvas, canvasPixelRect, colorProfile);
+            return new GenerateCanvasZoomPreviewData(canvas, canvasPixelRect);
         }
 
         KisCanvas2 *canvas;
         QRect canvasPixelRect;
-        const KoColorProfile *colorProfile;
     };
 public:
     KisColorSamplerStrokeStrategy(int radius, int blend, int lod = 0);