Fix updating of text nodes in QQuickTextEdit

The update algorithm wasn't working correctly if there were
two disconnected dirty regions in the textNodeMap. This could
happend by e.g. programatically removing text at the beginning
and appending at the end.

Change-Id: I3de2c8efedb03c004c4c304d130360cbdb4485b7
Fixes: QTBUG-68863
Reviewed-by: Eskil Abrahamsen Blomfeldt <eskil.abrahamsen-blomfeldt@qt.io>

1 files changed, 12 insertions, 1 deletions

diff --git a/src/quick/items/qquicktextedit.cpp b/src/quick/items/qquicktextedit.cpp
index bfc9f4c769..328f7c9103 100644
--- a/src/quick/items/qquicktextedit.cpp
+++ b/src/quick/items/qquicktextedit.cpp
@@ -2044,11 +2044,22 @@ QSGNode *QQuickTextEdit::updatePaintNode(QSGNode *oldNode, UpdatePaintNodeData *
         int firstDirtyPos = 0;
         if (nodeIterator != d->textNodeMap.end()) {
             firstDirtyPos = nodeIterator->startPos();
+            // ### this could be optimized if the first and last dirty nodes are not connected
+            // as the intermediate text nodes would usually only need to be transformed differently.
+            int lastDirtyPos = firstDirtyPos;
+            auto it = d->textNodeMap.constEnd();
+            while (it != nodeIterator) {
+                --it;
+                if (it->dirty()) {
+                    lastDirtyPos = it->startPos();
+                    break;
+                }
+            }
             do {
                 rootNode->removeChildNode(nodeIterator->textNode());
                 delete nodeIterator->textNode();
                 nodeIterator = d->textNodeMap.erase(nodeIterator);
-            } while (nodeIterator != d->textNodeMap.end() && nodeIterator->dirty());
+            } while (nodeIterator != d->textNodeMap.constEnd() && nodeIterator->startPos() <= lastDirtyPos);
         }
 
         // FIXME: the text decorations could probably be handled separately (only updated for affected textFrames)