fix(chatlog): update multi line selection on chatlog change

Fixes crash due to out of bound access. Fixes selection box jumping on history load.

Fix #5769

src/chatlog/chatlog.cpp

@@ -34,6 +34,9 @@
 #include <QShortcut>
 #include <QTimer>
 
+#include <algorithm>
+#include <cassert>
+
 /**
  * @var ChatLog::repNameAfter
  * @brief repetition interval sender name (sec)
@@ -454,6 +457,8 @@ void ChatLog::insertChatlinesOnTop(const QList<ChatLine::Ptr>& newLines)
 
     lines = combLines;
 
+    moveSelectionRectDownIfMulti(newLines.size());
+
     scene->setItemIndexMethod(oldIndexMeth);
 
     // redo layout
@@ -722,6 +727,51 @@ void ChatLog::reloadTheme()
     }
 }
 
+/**
+ * @brief Adjusts the multi line selection rectangle based on chatlog changing lines
+ * @param offset Amount to shift selection rect up by. Must be non-negative.
+  */
+void ChatLog::moveSelectionRectUpIfMulti(int offset)
+{
+    assert(offset >= 0);
+    if (selectionMode != Multi) {
+        return;
+    }
+    if (selLastRow < offset) { // entire selection now out of bounds
+        clearSelection();
+        return;
+    } else {
+        selLastRow -= offset;
+    }
+    selClickedRow = std::max(0, selClickedRow - offset);
+    selFirstRow = std::max(0, selFirstRow - offset);
+    updateMultiSelectionRect();
+    emit selectionChanged();
+}
+
+/**
+ * @brief Adjusts the multi line selection rectangle based on chatlog changing lines
+ * @param offset Amount to shift selection rect down by. Must be non-negative.
+  */
+void ChatLog::moveSelectionRectDownIfMulti(int offset)
+{
+    assert(offset >= 0);
+    if (selectionMode != Multi) {
+        return;
+    }
+    const int lastLine = lines.size() - 1;
+    if (selFirstRow + offset > lastLine) { // entire selection now out of bounds
+        clearSelection();
+        return;
+    } else {
+        selFirstRow += offset;
+    }
+    selClickedRow = std::min(lastLine, selClickedRow + offset);
+    selLastRow = std::min(lastLine, selLastRow + offset);
+    updateMultiSelectionRect();
+    emit selectionChanged();
+}
+
 void ChatLog::removeFirsts(const int num)
 {
     if (lines.size() > num) {
@@ -734,6 +784,8 @@ void ChatLog::removeFirsts(const int num)
     for (int i = 0; i < lines.size(); ++i) {
         lines[i]->setRow(i);
     }
+
+    moveSelectionRectUpIfMulti(num);
 }
 
 void ChatLog::removeLasts(const int num)

src/chatlog/chatlog.h

@@ -58,6 +58,8 @@ public:
     void selectAll();
     void fontChanged(const QFont& font);
     void reloadTheme();
+    void moveSelectionRectUpIfMulti(int offset);
+    void moveSelectionRectDownIfMulti(int offset);
     void removeFirsts(const int num);
     void removeLasts(const int num);
     void setScroll(const bool scroll);