Make the minimum code compile for Qt6

The following changes are applied to make the minimum build configuration compile:
*  Remove usage of a `QKeyEvent` constructor in `ColorChooser.h` by directly forwarding the original event.
* Change `QMap` to `QMulitMap` in several places in `ControlLayout.h` because that's what in fact is used.
* Change the parameter from `QEvent` to `QEnterEvent` in some `enterEvent` overrides.
* Add an include for `algorithm` in `MixHelpers.cpp`
* Fix a problem with string argument replacement in `embed.cpp`
* Introduce the usage of `QKeySequence` including the replacement of the `+` operator with the `|` operator.
* Add an include for `QActionGroup` in `ProjectNotes.cpp`.
* Use `QPalette::window` instead of `QPalette::background` in `ClipView.cpp`
* Use `qBound<panning_t>` instead of `qBound<int>` in `PianoRoll.cpp`. Add a cast.
* Replace the deprecated call to `QLayout::setMargin` with `QLayout::setContentsMargins`

Note: there are still lots of warnings when you compile this state with Qt6!

include/ColorChooser.h

@@ -55,8 +55,7 @@ class ColorChooser : public QColorDialog
 	//! Forward key events to the parent to prevent stuck notes when the dialog gets focus
 	void keyReleaseEvent(QKeyEvent *event) override
 	{
-		QKeyEvent ke(*event);
-		QApplication::sendEvent(parentWidget(), &ke);
+		QApplication::sendEvent(parentWidget(), event);
 	}
 private:
 	//! Copy the current QColorDialog palette into an array

include/ControlLayout.h

@@ -126,7 +126,7 @@ private slots:
 private:
 	int doLayout(const QRect &rect, bool testOnly) const;
 	int smartSpacing(QStyle::PixelMetric pm) const;
-	QMap<QString, QLayoutItem *>::const_iterator pairAt(int index) const;
+	QMultiMap<QString, QLayoutItem *>::const_iterator pairAt(int index) const;
 
 	QMultiMap<QString, QLayoutItem *> m_itemMap;
 	int m_hSpace;

include/FloatModelEditorBase.h

@@ -81,7 +81,7 @@ class LMMS_EXPORT FloatModelEditorBase : public QWidget, public FloatModelView
 	void paintEvent(QPaintEvent * me) override;
 	void wheelEvent(QWheelEvent * me) override;
 
-	void enterEvent(QEvent *event) override;
+	void enterEvent(QEnterEvent *event) override;
 	void leaveEvent(QEvent *event) override;
 
 	virtual float getValue(const QPoint & p);

include/PluginBrowser.h

@@ -66,7 +66,7 @@ class PluginDescWidget : public QWidget
 	void openInNewInstrumentTrack(QString value);
 
 protected:
-	void enterEvent( QEvent * _e ) override;
+	void enterEvent( QEnterEvent * _e ) override;
 	void leaveEvent( QEvent * _e ) override;
 	void mousePressEvent( QMouseEvent * _me ) override;
 	void paintEvent( QPaintEvent * _pe ) override;

src/core/MixHelpers.cpp

@@ -29,6 +29,8 @@
 #endif
 
 #include <cmath>
+#include <algorithm>
+
 #include <QtGlobal>
 
 #include "ValueBuffer.h"

src/gui/ControlLayout.cpp

@@ -141,7 +141,7 @@ int ControlLayout::count() const
 	return m_itemMap.size() - 1;
 }
 
-QMap<QString, QLayoutItem*>::const_iterator
+QMultiMap<QString, QLayoutItem*>::const_iterator
 ControlLayout::pairAt(int index) const
 {
 	if (index < 0) { return m_itemMap.cend(); }
@@ -151,7 +151,7 @@ ControlLayout::pairAt(int index) const
 		return item->widget()->objectName() == s_searchBarName;
 	};
 
-	QMap<QString, QLayoutItem*>::const_iterator itr = m_itemMap.cbegin();
+	QMultiMap<QString, QLayoutItem*>::const_iterator itr = m_itemMap.cbegin();
 	for (; itr != m_itemMap.cend() && (index > 0 || skip(itr.value())); ++itr)
 	{
 		if(!skip(itr.value())) { index--; }
@@ -242,7 +242,7 @@ int ControlLayout::doLayout(const QRect &rect, bool testOnly) const
 	const QString filterText = m_searchBar->text();
 	bool first = true;
 
-	QMapIterator<QString, QLayoutItem*> itr(m_itemMap);
+	QMultiMapIterator<QString, QLayoutItem*> itr(m_itemMap);
 	while (itr.hasNext())
 	{
 		itr.next();

src/gui/MainWindow.cpp

@@ -292,11 +292,11 @@ void MainWindow::finalize()
 	project_menu->addAction( embed::getIconPixmap( "project_save" ),
 					tr( "Save &As..." ),
 					this, SLOT(saveProjectAs()),
-					Qt::CTRL + Qt::SHIFT + Qt::Key_S );
+					QKeySequence(Qt::CTRL | Qt::SHIFT | Qt::Key_S));
 	project_menu->addAction( embed::getIconPixmap( "project_save" ),
 					tr( "Save as New &Version" ),
 					this, SLOT(saveProjectAsNewVersion()),
-					Qt::CTRL + Qt::ALT + Qt::Key_S );
+					QKeySequence(Qt::CTRL | Qt::ALT | Qt::Key_S));
 
 	project_menu->addAction( embed::getIconPixmap( "project_save" ),
 					tr( "Save as default template" ),
@@ -311,26 +311,26 @@ void MainWindow::finalize()
 					tr( "E&xport..." ),
 					this,
 					SLOT(onExportProject()),
-					Qt::CTRL + Qt::Key_E );
+					QKeySequence(Qt::CTRL | Qt::Key_E));
 	project_menu->addAction( embed::getIconPixmap( "project_export" ),
 					tr( "E&xport Tracks..." ),
 					this,
 					SLOT(onExportProjectTracks()),
-					Qt::CTRL + Qt::SHIFT + Qt::Key_E );
+					QKeySequence(Qt::CTRL | Qt::SHIFT | Qt::Key_E));
 
 	project_menu->addAction( embed::getIconPixmap( "midi_file" ),
 					tr( "Export &MIDI..." ),
 					this,
 					SLOT(onExportProjectMidi()),
-					Qt::CTRL + Qt::Key_M );
+					QKeySequence(Qt::CTRL | Qt::Key_M));
 
 // Prevent dangling separator at end of menu per https://bugreports.qt.io/browse/QTBUG-40071
 #if !(defined(LMMS_BUILD_APPLE) && (QT_VERSION < 0x050600))
 	project_menu->addSeparator();
 #endif
 	project_menu->addAction( embed::getIconPixmap( "exit" ), tr( "&Quit" ),
 					qApp, SLOT(closeAllWindows()),
-					Qt::CTRL + Qt::Key_Q );
+					QKeySequence(Qt::CTRL | Qt::Key_Q));
 
 	auto edit_menu = new QMenu(this);
 	menuBar()->addMenu( edit_menu )->setText( tr( "&Edit" ) );
@@ -343,13 +343,13 @@ void MainWindow::finalize()
 					this, SLOT(redo()),
 					QKeySequence::Redo );
 	// Ensure that both (Ctrl+Y) and (Ctrl+Shift+Z) activate redo shortcut regardless of OS defaults
-	if (QKeySequence(QKeySequence::Redo) != QKeySequence(Qt::CTRL + Qt::Key_Y))
+	if (QKeySequence(QKeySequence::Redo) != QKeySequence(Qt::CTRL | Qt::Key_Y))
 	{
-		new QShortcut( QKeySequence( Qt::CTRL + Qt::Key_Y ), this, SLOT(redo()));
+		new QShortcut( QKeySequence( Qt::CTRL | Qt::Key_Y ), this, SLOT(redo()));
 	}
-	if (QKeySequence(QKeySequence::Redo) != QKeySequence(Qt::CTRL + Qt::SHIFT + Qt::Key_Z ))
+	if (QKeySequence(QKeySequence::Redo) != QKeySequence(Qt::CTRL | Qt::SHIFT | Qt::Key_Z ))
 	{
-		new QShortcut( QKeySequence( Qt::CTRL + Qt::SHIFT + Qt::Key_Z ), this, SLOT(redo()));
+		new QShortcut( QKeySequence( Qt::CTRL | Qt::SHIFT | Qt::Key_Z ), this, SLOT(redo()));
 	}
 
 	edit_menu->addSeparator();
@@ -451,31 +451,31 @@ void MainWindow::finalize()
 	// window-toolbar
 	auto song_editor_window = new ToolButton(embed::getIconPixmap("songeditor"), tr("Song Editor") + " (Ctrl+1)", this,
 		SLOT(toggleSongEditorWin()), m_toolBar);
-	song_editor_window->setShortcut( Qt::CTRL + Qt::Key_1 );
+	song_editor_window->setShortcut(QKeySequence(Qt::CTRL | Qt::Key_1));
 
 	auto pattern_editor_window = new ToolButton(embed::getIconPixmap("pattern_track_btn"),
 		tr("Pattern Editor") + " (Ctrl+2)", this, SLOT(togglePatternEditorWin()), m_toolBar);
-	pattern_editor_window->setShortcut(Qt::CTRL + Qt::Key_2);
+	pattern_editor_window->setShortcut(QKeySequence(Qt::CTRL | Qt::Key_2));
 
 	auto piano_roll_window = new ToolButton(
 		embed::getIconPixmap("piano"), tr("Piano Roll") + " (Ctrl+3)", this, SLOT(togglePianoRollWin()), m_toolBar);
-	piano_roll_window->setShortcut( Qt::CTRL + Qt::Key_3 );
+	piano_roll_window->setShortcut(QKeySequence(Qt::CTRL | Qt::Key_3));
 
 	auto automation_editor_window = new ToolButton(embed::getIconPixmap("automation"),
 		tr("Automation Editor") + " (Ctrl+4)", this, SLOT(toggleAutomationEditorWin()), m_toolBar);
-	automation_editor_window->setShortcut( Qt::CTRL + Qt::Key_4 );
+	automation_editor_window->setShortcut(QKeySequence(Qt::CTRL | Qt::Key_4));
 
 	auto mixer_window = new ToolButton(
 		embed::getIconPixmap("mixer"), tr("Mixer") + " (Ctrl+5)", this, SLOT(toggleMixerWin()), m_toolBar);
-	mixer_window->setShortcut( Qt::CTRL + Qt::Key_5 );
+	mixer_window->setShortcut(QKeySequence(Qt::CTRL | Qt::Key_5));
 
 	auto controllers_window = new ToolButton(embed::getIconPixmap("controller"),
 		tr("Show/hide controller rack") + " (Ctrl+6)", this, SLOT(toggleControllerRack()), m_toolBar);
-	controllers_window->setShortcut( Qt::CTRL + Qt::Key_6 );
+	controllers_window->setShortcut(QKeySequence(Qt::CTRL | Qt::Key_6));
 
 	auto project_notes_window = new ToolButton(embed::getIconPixmap("project_notes"),
 		tr("Show/hide project notes") + " (Ctrl+7)", this, SLOT(toggleProjectNotesWin()), m_toolBar);
-	project_notes_window->setShortcut( Qt::CTRL + Qt::Key_7 );
+	project_notes_window->setShortcut(QKeySequence(Qt::CTRL | Qt::Key_7));
 
 	m_toolBarLayout->addWidget( song_editor_window, 1, 1 );
 	m_toolBarLayout->addWidget( pattern_editor_window, 1, 2 );

src/gui/PluginBrowser.cpp

@@ -260,7 +260,7 @@ void PluginDescWidget::paintEvent( QPaintEvent * )
 
 
 
-void PluginDescWidget::enterEvent( QEvent * _e )
+void PluginDescWidget::enterEvent( QEnterEvent * _e )
 {
 	m_mouseOver = true;
 

src/gui/ProjectNotes.cpp

@@ -26,6 +26,7 @@
 #include "ProjectNotes.h"
 
 #include <QAction>
+#include <QActionGroup>
 #include <QApplication>
 #include <QCloseEvent>
 #include <QColorDialog>

src/gui/clips/ClipView.cpp

@@ -356,7 +356,7 @@ void ClipView::selectColor()
 	// Get a color from the user
 	const auto newColor = ColorChooser{this}
 		.withPalette(ColorChooser::Palette::Track)
-		->getColor(m_clip->color().value_or(palette().background().color()));
+		->getColor(m_clip->color().value_or(palette().window().color()));
 	if (newColor.isValid()) { setColor(newColor); }
 }
 

src/gui/editors/AutomationEditor.cpp

@@ -2035,17 +2035,17 @@ AutomationEditorWindow::AutomationEditorWindow() :
 
 	auto editModeGroup = new ActionGroup(this);
 	m_drawAction = editModeGroup->addAction(embed::getIconPixmap("edit_draw"), tr("Draw mode (Shift+D)"));
-	m_drawAction->setShortcut(Qt::SHIFT | Qt::Key_D);
+	m_drawAction->setShortcut(QKeySequence(Qt::SHIFT | Qt::Key_D));
 	m_drawAction->setChecked(true);
 
 	m_eraseAction = editModeGroup->addAction(embed::getIconPixmap("edit_erase"), tr("Erase mode (Shift+E)"));
-	m_eraseAction->setShortcut(Qt::SHIFT | Qt::Key_E);
+	m_eraseAction->setShortcut(QKeySequence(Qt::SHIFT | Qt::Key_E));
 
 	m_drawOutAction = editModeGroup->addAction(embed::getIconPixmap("edit_draw_outvalue"), tr("Draw outValues mode (Shift+C)"));
-	m_drawOutAction->setShortcut(Qt::SHIFT | Qt::Key_C);
+	m_drawOutAction->setShortcut(QKeySequence(Qt::SHIFT | Qt::Key_C));
 
 	m_editTanAction = editModeGroup->addAction(embed::getIconPixmap("edit_tangent"), tr("Edit tangents mode (Shift+T)"));
-	m_editTanAction->setShortcut(Qt::SHIFT | Qt::Key_T);
+	m_editTanAction->setShortcut(QKeySequence(Qt::SHIFT | Qt::Key_T));
 	m_editTanAction->setEnabled(false);
 
 	m_flipYAction = new QAction(embed::getIconPixmap("flip_y"), tr("Flip vertically"), this);

src/gui/editors/PianoRoll.cpp

@@ -2454,11 +2454,11 @@ void PianoRoll::mouseMoveEvent( QMouseEvent * me )
 								( (float)( noteEditBottom() - noteEditTop() ) ) *
 								( MaxVolume - MinVolume ),
 											MaxVolume );
-				pan = qBound<int>( PanningLeft,
-								PanningLeft +
+				pan = qBound<panning_t>( PanningLeft,
+								static_cast<panning_t>(PanningLeft +
 								( (float)( noteEditBottom() - me->y() ) ) /
 								( (float)( noteEditBottom() - noteEditTop() ) ) *
-								( (float)( PanningRight - PanningLeft ) ),
+								( (float)( PanningRight - PanningLeft ) )),
 										  PanningRight);
 			}
 
@@ -3788,7 +3788,7 @@ void PianoRoll::wheelEvent(QWheelEvent * we )
 			{
 				for ( Note * n : nv )
 				{
-					panning_t pan = qBound<int>( PanningLeft, n->getPanning() + step, PanningRight );
+					panning_t pan = qBound<panning_t>( PanningLeft, n->getPanning() + static_cast<panning_t>(step), PanningRight );
 					n->setPanning( pan );
 				}
 				bool allPansEqual = std::all_of( nv.begin(), nv.end(),
@@ -4738,10 +4738,10 @@ PianoRollWindow::PianoRollWindow() :
 
 	drawAction->setChecked( true );
 
-	drawAction->setShortcut( Qt::SHIFT | Qt::Key_D );
-	eraseAction->setShortcut( Qt::SHIFT | Qt::Key_E );
-	selectAction->setShortcut( Qt::SHIFT | Qt::Key_S );
-	pitchBendAction->setShortcut( Qt::SHIFT | Qt::Key_T );
+	drawAction->setShortcut(QKeySequence(Qt::SHIFT | Qt::Key_D ));
+	eraseAction->setShortcut(QKeySequence(Qt::SHIFT | Qt::Key_E));
+	selectAction->setShortcut(QKeySequence(Qt::SHIFT | Qt::Key_S));
+	pitchBendAction->setShortcut(QKeySequence(Qt::SHIFT | Qt::Key_T));
 
 	connect( editModeGroup, SIGNAL(triggered(int)), m_editor, SLOT(setEditMode(int)));
 
@@ -4800,9 +4800,9 @@ PianoRollWindow::PianoRollWindow() :
 
 	auto pasteAction = new QAction(embed::getIconPixmap("edit_paste"), tr("Paste (%1+V)").arg(UI_CTRL_KEY), this);
 
-	cutAction->setShortcut( Qt::CTRL | Qt::Key_X );
-	copyAction->setShortcut( Qt::CTRL | Qt::Key_C );
-	pasteAction->setShortcut( Qt::CTRL | Qt::Key_V );
+	cutAction->setShortcut(QKeySequence(Qt::CTRL | Qt::Key_X));
+	copyAction->setShortcut(QKeySequence(Qt::CTRL | Qt::Key_C));
+	pasteAction->setShortcut(QKeySequence(Qt::CTRL | Qt::Key_V));
 
 	connect( cutAction, SIGNAL(triggered()), m_editor, SLOT(cutSelectedNotes()));
 	connect( copyAction, SIGNAL(triggered()), m_editor, SLOT(copySelectedNotes()));
@@ -4823,19 +4823,19 @@ PianoRollWindow::PianoRollWindow() :
 
 	auto glueAction = new QAction(embed::getIconPixmap("glue"), tr("Glue"), noteToolsButton);
 	connect(glueAction, SIGNAL(triggered()), m_editor, SLOT(glueNotes()));
-	glueAction->setShortcut( Qt::SHIFT | Qt::Key_G );
+	glueAction->setShortcut(QKeySequence(Qt::SHIFT | Qt::Key_G));
 
 	auto knifeAction = new QAction(embed::getIconPixmap("edit_knife"), tr("Knife"), noteToolsButton);
 	connect(knifeAction, &QAction::triggered, m_editor, &PianoRoll::setKnifeAction);
-	knifeAction->setShortcut( Qt::SHIFT | Qt::Key_K );
+	knifeAction->setShortcut(QKeySequence(Qt::SHIFT | Qt::Key_K));
 
 	auto fillAction = new QAction(embed::getIconPixmap("fill"), tr("Fill"), noteToolsButton);
 	connect(fillAction, &QAction::triggered, [this](){ m_editor->fitNoteLengths(true); });
-	fillAction->setShortcut(Qt::SHIFT | Qt::Key_F);
+	fillAction->setShortcut(QKeySequence(Qt::SHIFT | Qt::Key_F));
 
 	auto cutOverlapsAction = new QAction(embed::getIconPixmap("cut_overlaps"), tr("Cut overlaps"), noteToolsButton);
 	connect(cutOverlapsAction, &QAction::triggered, [this](){ m_editor->fitNoteLengths(false); });
-	cutOverlapsAction->setShortcut(Qt::SHIFT | Qt::Key_C);
+	cutOverlapsAction->setShortcut(QKeySequence(Qt::SHIFT | Qt::Key_C));
 
 	auto minLengthAction = new QAction(embed::getIconPixmap("min_length"), tr("Min length as last"), noteToolsButton);
 	connect(minLengthAction, &QAction::triggered, [this](){ m_editor->constrainNoteLengths(false); });

src/gui/embed.cpp

@@ -37,7 +37,7 @@ QPixmap getIconPixmap(const QString& pixmapName,
 	QString cacheName;
 	if (width > 0 && height > 0)
 	{
-		cacheName = QString("%1_%2_%3").arg(pixmapName, width, height);
+		cacheName = QString("%1_%2_%3").arg(pixmapName).arg(width).arg(height);
 	}
 	else
 	{

src/gui/widgets/FloatModelEditorBase.cpp

@@ -233,7 +233,7 @@ void FloatModelEditorBase::mouseReleaseEvent(QMouseEvent* event)
 }
 
 
-void FloatModelEditorBase::enterEvent(QEvent *event)
+void FloatModelEditorBase::enterEvent(QEnterEvent *event)
 {
 	showTextFloat(700, 2000);
 }

src/gui/widgets/SimpleTextFloat.cpp

@@ -40,7 +40,7 @@ SimpleTextFloat::SimpleTextFloat() :
 	QWidget(getGUI()->mainWindow(), Qt::ToolTip)
 {
 	QHBoxLayout * layout = new QHBoxLayout(this);
-	layout->setMargin(3);
+	layout->setContentsMargins(3, 3, 3, 3);
 	setLayout(layout);
 
 	m_textLabel = new QLabel(this);