KSPM: Simplify row removal handling

The KSelectionProxyModelPrivate::beginRemoveRows method is responsible
for figuring out the range in the proxy which is to be removed as a
result of removal in the source model.

There are some trivial cases which were made overcomplicated by the old
code.  The complex bit is figuring out the interaction with the
top-level.  I suspect that can be simplified further.

src/kselectionproxymodel.cpp

@@ -1149,87 +1149,57 @@ QPair<int, int> KSelectionProxyModelPrivate::beginRemoveRows(const QModelIndex &
 {
     Q_Q(const KSelectionProxyModel);
 
-    if (m_omitChildren && !m_startWithChildTrees && !m_includeAllSelected) {
-        // SubTreeRoots
-        if (m_rootIndexList.contains(parent) || isDescendantOf(m_rootIndexList, parent)) {
-            return qMakePair(-1, -1);
-        }
-    }
-
-    const QModelIndex proxyParent = mapParentFromSource(parent);
-
     if (!m_includeAllSelected && !m_omitChildren) {
         // SubTrees and SubTreesWithoutRoots
+        const QModelIndex proxyParent = mapParentFromSource(parent);
         if (proxyParent.isValid()) {
             return qMakePair(start, end);
         }
-        if (m_startWithChildTrees && m_rootIndexList.contains(parent)) {
-            // SubTreesWithoutRoots topLevel
-            const int proxyStartRow = getProxyInitialRow(parent) + start;
-            return qMakePair(proxyStartRow, proxyStartRow + (end - start));
-        }
     }
 
-    if (m_includeAllSelected && m_startWithChildTrees) {
-        // ChildrenOfExactSelection
-        int position = m_rootIndexList.indexOf(parent);
-        if (position != -1) {
-            const int proxyStartRow = getProxyInitialRow(parent) + start;
-            int proxyEndRow = proxyStartRow + (end - start);
-            ++position;
-            while (m_rootIndexList.size() < position) {
-                const QModelIndex idx = m_rootIndexList.at(position);
-                if (isDescendantOf(parent, idx)) {
-                    proxyEndRow += q->sourceModel()->rowCount(idx);
-                } else {
-                    break;
-                }
-            }
-            return qMakePair(proxyStartRow, proxyEndRow);
-        }
-        return qMakePair(-1, -1);
+    if (m_startWithChildTrees && m_rootIndexList.contains(parent)) {
+        const int proxyStartRow = getProxyInitialRow(parent) + start;
+        const int proxyEndRow = proxyStartRow + (end - start);
+        return qMakePair(proxyStartRow, proxyEndRow);
     }
 
     QList<QPersistentModelIndex>::const_iterator rootIt = m_rootIndexList.constBegin();
     const QList<QPersistentModelIndex>::const_iterator rootEnd = m_rootIndexList.constEnd();
-    int rootPosition = 0;
-    int rootStartRemove = -1;
-    int rootEndRemove = -1;
-    int siblingCount = 0;
-
-    for (; rootIt != rootEnd; ++rootIt, ++rootPosition) {
-        if (m_omitChildren && m_includeAllSelected) {
-            // ExactSelection
-            if (parent == rootIt->parent() && rootIt->row() <= end && rootIt->row() >= start) {
-                if (rootStartRemove == -1) {
-                    rootStartRemove = rootPosition;
-                }
-                ++rootEndRemove;
-            } else {
-                if (rootStartRemove != -1) {
-                    break;
-                }
-            }
+    int proxyStartRemove = 0;
+
+    for (; rootIt != rootEnd; ++rootIt) {
+        if (rootWillBeRemovedFrom(parent, start, end, *rootIt)) {
+            break;
         } else {
-            if (isDescendantOf(parent, *rootIt)) {
-                if (rootStartRemove == -1) {
-                    rootStartRemove = rootPosition;
-                }
-                ++rootEndRemove;
-                if (m_startWithChildTrees) {
-                    siblingCount += q->sourceModel()->rowCount(*rootIt);
-                }
+            if (m_startWithChildTrees) {
+                proxyStartRemove += q->sourceModel()->rowCount(*rootIt);
             } else {
-                if (rootStartRemove != -1) {
-                    break;
-                }
+                ++proxyStartRemove;
             }
         }
     }
-    if (rootStartRemove != -1) {
-        return qMakePair(siblingCount + rootStartRemove, siblingCount + rootEndRemove);
+
+    if (rootIt == rootEnd) {
+        return qMakePair(-1, -1);
     }
 
+    int proxyEndRemove = proxyStartRemove;
+
+    for (; rootIt != rootEnd; ++rootIt) {
+        if (!rootWillBeRemovedFrom(parent, start, end, *rootIt)) {
+            break;
+        }
+        if (m_startWithChildTrees) {
+            proxyEndRemove += q->sourceModel()->rowCount(*rootIt);
+        } else {
+            ++proxyEndRemove;
+        }
+    }
+
+    --proxyEndRemove;
+    if (proxyEndRemove >= 0) {
+        return qMakePair(proxyStartRemove, proxyEndRemove);
+    }
     return qMakePair(-1, -1);
 }