Make a transform tool work with Pass Through group layers

BUG:351548

krita/image/kis_projection_leaf.cpp

@@ -27,6 +27,9 @@
 
 #include "krita_utils.h"
 
+#include "kis_refresh_subtree_walker.h"
+#include "kis_async_merger.h"
+
 
 struct KisProjectionLeaf::Private
 {
@@ -46,6 +49,13 @@ struct KisProjectionLeaf::Private
     bool checkThisPassThrough() {
         return checkPassThrough(node);
     }
+
+    void temporarySetPassThrough(bool value) {
+        KisGroupLayer *group = qobject_cast<KisGroupLayer*>(node);
+        if (!group) return;
+
+        group->setPassThroughMode(value);
+    }
 };
 
 KisProjectionLeaf::KisProjectionLeaf(KisNode *node)
@@ -247,3 +257,25 @@ bool KisProjectionLeaf::isDroppedMask() const
     return qobject_cast<KisMask*>(m_d->node) &&
         m_d->checkParentPassThrough();
 }
+
+
+/**
+ * This method is rather slow and dangerous. It should be executes in
+ * exclusive environment only.
+ */
+void KisProjectionLeaf::explicitlyRegeneratePassThroughProjection()
+{
+    if (!m_d->checkThisPassThrough()) return;
+
+    m_d->temporarySetPassThrough(false);
+
+    const QRect updateRect = projection()->defaultBounds()->bounds();
+
+    KisRefreshSubtreeWalker walker(updateRect);
+    walker.collectRects(m_d->node, updateRect);
+
+    KisAsyncMerger merger;
+    merger.startMerge(walker);
+
+    m_d->temporarySetPassThrough(true);
+}

krita/image/kis_projection_leaf.h

@@ -62,6 +62,15 @@ public:
 
     bool isDroppedMask() const;
 
+    /**
+     * Regenerate projection of the current group layer iff it is
+     * pass-through mode.
+     *
+     * WARNING: must be called either under the image lock held
+     *          or in the context of an exclusive stroke job.
+     */
+    void explicitlyRegeneratePassThroughProjection();
+
 private:
     struct Private;
     const QScopedPointer<Private> m_d;

krita/plugins/tools/tool_transform2/strokes/transform_stroke_strategy.cpp

@@ -33,6 +33,8 @@
 #include "kis_transform_mask_adapter.h"
 #include "kis_transform_utils.h"
 
+#include "kis_projection_leaf.h"
+
 
 class ModifyTransformMaskCommand : public KUndo2Command {
 public:
@@ -102,8 +104,8 @@ TransformStrokeStrategy::TransformStrokeStrategy(KisNodeSP rootNode,
              * taken into account.
              */
             m_selection = 0;
-
         } else {
+            rootNode->projectionLeaf()->explicitlyRegeneratePassThroughProjection();
             device = rootNode->projection();
         }