From b7e2f672cff33454556bab9c24bac597459d8675 Mon Sep 17 00:00:00 2001
From: Thomas Hartmann <thomas.hartmann@qt.io>
Date: Wed, 22 Feb 2017 18:27:35 +0100
Subject: [PATCH] QmlDesigner: Improve performance of nodeAtTextCursorPosition

We find candidates by a linear search using just the offset.
This way we have to calculate the length (which is slow) only for
a very few selected nodes.
The number of nodes we have to calulate the length for is bounded by
the maximum nesting, which is for any sane QML file smaller then 10.
Before we had to calculate the length for every node.

Change-Id: I53a03818e9986db4a224aef876b333444aa1c15b
Reviewed-by: Tim Jenssen <tim.jenssen@qt.io>
---
 .../designercore/include/rewriterview.h       |  2 ++
 .../designercore/model/rewriterview.cpp       | 34 +++++++++++--------
 2 files changed, 21 insertions(+), 15 deletions(-)

diff --git a/src/plugins/qmldesigner/designercore/include/rewriterview.h b/src/plugins/qmldesigner/designercore/include/rewriterview.h
index c7e20fea06e..5d5bc8bb282 100644
--- a/src/plugins/qmldesigner/designercore/include/rewriterview.h
+++ b/src/plugins/qmldesigner/designercore/include/rewriterview.h
@@ -176,6 +176,8 @@ protected: // functions
     void notifyErrorsAndWarnings(const QList<DocumentMessage> &errors);
 
 private: //variables
+    ModelNode nodeAtTextCursorPositionRekursive(const ModelNode &root, int cursorPosition) const;
+
     TextModifier *m_textModifier = nullptr;
     int transactionLevel = 0;
     bool m_modificationGroupActive = false;
diff --git a/src/plugins/qmldesigner/designercore/model/rewriterview.cpp b/src/plugins/qmldesigner/designercore/model/rewriterview.cpp
index 3bf0bfd4357..08a7d3629fe 100644
--- a/src/plugins/qmldesigner/designercore/model/rewriterview.cpp
+++ b/src/plugins/qmldesigner/designercore/model/rewriterview.cpp
@@ -556,24 +556,28 @@ static bool isInNodeDefinition(int nodeTextOffset, int nodeTextLength, int curso
     return (nodeTextOffset <= cursorPosition) && (nodeTextOffset + nodeTextLength > cursorPosition);
 }
 
-ModelNode RewriterView::nodeAtTextCursorPosition(int cursorPosition) const
+ModelNode RewriterView::nodeAtTextCursorPositionRekursive(const ModelNode &root, int cursorPosition) const
 {
-    const QList<ModelNode> allNodes = allModelNodes();
-
-    ModelNode nearestNode;
-    int nearestNodeTextOffset = -1;
-
-    foreach (const ModelNode &currentNode, allNodes) {
-        const int nodeTextOffset = nodeOffset(currentNode);
-        const int nodeTextLength = nodeLength(currentNode);
-        if (isInNodeDefinition(nodeTextOffset, nodeTextLength, cursorPosition)
-            && (nodeTextOffset > nearestNodeTextOffset)) {
-            nearestNode = currentNode;
-            nearestNodeTextOffset = nodeTextOffset;
-        }
+    ModelNode node = root;
+    foreach (const ModelNode &currentNode, node.directSubModelNodes()) {
+        const int offset = nodeOffset(currentNode);
+        if (offset < cursorPosition)
+            node = nodeAtTextCursorPositionRekursive(currentNode, cursorPosition);
+        else
+            break;
     }
 
-    return nearestNode;
+    const int nodeTextLength = nodeLength(node);
+    const int nodeTextOffset = nodeOffset(node);
+    if (isInNodeDefinition(nodeTextOffset, nodeTextLength, cursorPosition))
+        return node;
+
+    return root;
+}
+
+ModelNode RewriterView::nodeAtTextCursorPosition(int cursorPosition) const
+{
+    return nodeAtTextCursorPositionRekursive(rootModelNode(), cursorPosition);
 }
 
 bool RewriterView::renameId(const QString& oldId, const QString& newId)