From 733e0a1e542dec42325d1110688848d4fecf4f56 Mon Sep 17 00:00:00 2001
From: Rossmaxx <74815851+Rossmaxx@users.noreply.github.com>
Date: Mon, 18 Sep 2023 22:14:08 +0530
Subject: [PATCH] Fix invalid use of iterators in piano roll (#6869)

---
 src/gui/editors/PianoRoll.cpp | 26 +++++++++++++-------------
 1 file changed, 13 insertions(+), 13 deletions(-)

diff --git a/src/gui/editors/PianoRoll.cpp b/src/gui/editors/PianoRoll.cpp
index 751fb9d2a..1da6aa3df 100644
--- a/src/gui/editors/PianoRoll.cpp
+++ b/src/gui/editors/PianoRoll.cpp
@@ -1719,10 +1719,10 @@ void PianoRoll::mousePressEvent(QMouseEvent * me )
 			const NoteVector & notes = m_midiClip->notes();
 
 			// will be our iterator in the following loop
-			auto it = notes.begin() + notes.size() - 1;
+			auto it = notes.rbegin();
 
 			// loop through whole note-vector...
-			for( int i = 0; i < notes.size(); ++i )
+			while (it != notes.rend())
 			{
 				Note *note = *it;
 				TimePos len = note->length();
@@ -1747,7 +1747,7 @@ void PianoRoll::mousePressEvent(QMouseEvent * me )
 				{
 					break;
 				}
-				--it;
+				++it;
 			}
 
 			// first check whether the user clicked in note-edit-
@@ -1769,7 +1769,7 @@ void PianoRoll::mousePressEvent(QMouseEvent * me )
 				Note * created_new_note = nullptr;
 				// did it reach end of vector because
 				// there's no note??
-				if( it == notes.begin()-1 )
+				if (it == notes.rend())
 				{
 					is_new_note = true;
 					m_midiClip->addJournalCheckPoint();
@@ -1816,8 +1816,8 @@ void PianoRoll::mousePressEvent(QMouseEvent * me )
 					// reset it so that it can be used for
 					// ops (move, resize) after this
 					// code-block
-					it = notes.begin();
-					while( it != notes.end() && *it != created_new_note )
+					it = notes.rbegin();
+					while (it != notes.rend() && *it != created_new_note)
 					{
 						++it;
 					}
@@ -1933,7 +1933,7 @@ void PianoRoll::mousePressEvent(QMouseEvent * me )
 			{
 				// erase single note
 				m_mouseDownRight = true;
-				if( it != notes.begin()-1 )
+				if (it != notes.rend())
 				{
 					m_midiClip->addJournalCheckPoint();
 					m_midiClip->removeNote( *it );
@@ -2513,7 +2513,7 @@ void PianoRoll::mouseMoveEvent( QMouseEvent * me )
 			bool altPressed = me->modifiers() & Qt::AltModifier;
 			// We iterate from last note in MIDI clip to the first,
 			// chronologically
-			auto it = notes.begin() + notes.size() - 1;
+			auto it = notes.rbegin();
 			for( int i = 0; i < notes.size(); ++i )
 			{
 				Note* n = *it;
@@ -2556,7 +2556,7 @@ void PianoRoll::mouseMoveEvent( QMouseEvent * me )
 				}
 
 
-				--it;
+				++it;
 			}
 
 			// Emit MIDI clip has changed
@@ -2575,10 +2575,10 @@ void PianoRoll::mouseMoveEvent( QMouseEvent * me )
 			const NoteVector & notes = m_midiClip->notes();
 
 			// will be our iterator in the following loop
-			auto it = notes.begin() + notes.size() - 1;
+			auto it = notes.rbegin();
 
 			// loop through whole note-vector...
-			for( int i = 0; i < notes.size(); ++i )
+			while (it != notes.rend())
 			{
 				Note *note = *it;
 				// and check whether the cursor is over an
@@ -2591,12 +2591,12 @@ void PianoRoll::mouseMoveEvent( QMouseEvent * me )
 				{
 					break;
 				}
-				--it;
+				++it;
 			}
 
 			// did it reach end of vector because there's
 			// no note??
-			if( it != notes.begin()-1 )
+			if (it != notes.rend())
 			{
 				Note *note = *it;
 				// x coordinate of the right edge of the note