diff --git a/kmplot/calculator.cpp b/kmplot/calculator.cpp
--- a/kmplot/calculator.cpp
+++ b/kmplot/calculator.cpp
@@ -42,9 +42,8 @@
 	QWidget * widget = new QWidget( this );
 	setWindowTitle( i18n("Calculator") );
 
-	QVBoxLayout *layout = new QVBoxLayout( widget );
-	layout->setMargin( 0 );
-	
+	QVBoxLayout *layout = new QVBoxLayout( this );
+
 	m_display = new KTextEdit( widget );
 	QSizePolicy displaySizePolicy = m_display->sizePolicy();
 	displaySizePolicy.setVerticalStretch( 10 );
diff --git a/kmplot/equationeditor.cpp b/kmplot/equationeditor.cpp
--- a/kmplot/equationeditor.cpp
+++ b/kmplot/equationeditor.cpp
@@ -40,7 +40,9 @@
 	setWindowTitle(i18n("Equation Editor"));
 	QDialogButtonBox *buttonBox = new QDialogButtonBox(QDialogButtonBox::Close);
 	connect(buttonBox, &QDialogButtonBox::rejected, this, &EquationEditor::reject);
-	m_widget->layout()->addWidget(buttonBox);
+	QVBoxLayout *dialogLayout = new QVBoxLayout (this);
+	dialogLayout->addWidget (m_widget);
+	dialogLayout->addWidget (buttonBox);
 
 	connect(m_widget->edit, &EquationEdit::returnPressed, this, &EquationEditor::accept);
 }
diff --git a/kmplot/functiontools.cpp b/kmplot/functiontools.cpp
--- a/kmplot/functiontools.cpp
+++ b/kmplot/functiontools.cpp
@@ -45,10 +45,9 @@
 
 	QDialogButtonBox *buttonBox = new QDialogButtonBox(QDialogButtonBox::Close);
 	connect(buttonBox, &QDialogButtonBox::rejected, this, &FunctionTools::reject);
-	m_widget->layout()->addWidget(buttonBox);
-	
-	// Adjust margins
-	m_widget->layout()->setMargin( 0 );
+	QVBoxLayout *dialogLayout = new QVBoxLayout (this);
+	dialogLayout->addWidget (m_widget);
+	dialogLayout->addWidget (buttonBox);
 	
 	init( CalculateArea );
 	
diff --git a/kmplot/kconstanteditor.cpp b/kmplot/kconstanteditor.cpp
--- a/kmplot/kconstanteditor.cpp
+++ b/kmplot/kconstanteditor.cpp
@@ -57,7 +57,9 @@
 
 	QDialogButtonBox *buttonBox = new QDialogButtonBox(QDialogButtonBox::Close);
 	connect(buttonBox, &QDialogButtonBox::rejected, this, &KConstantEditor::reject);
-	m_widget->gridLayout->addWidget(buttonBox, 4, 1, 1, 1);
+	QVBoxLayout *dialogLayout = new QVBoxLayout (this);
+	dialogLayout->addWidget(m_widget);
+	dialogLayout->addWidget(buttonBox);
 
 	m_widget->cmdNew->setIcon( QIcon::fromTheme("document-new") );
 	m_widget->cmdDelete->setIcon( QIcon::fromTheme("edit-delete") );
diff --git a/kmplot/kgradientdialog.cpp b/kmplot/kgradientdialog.cpp
--- a/kmplot/kgradientdialog.cpp
+++ b/kmplot/kgradientdialog.cpp
@@ -392,7 +392,7 @@
 	connect(buttonBox, &QDialogButtonBox::rejected, this, &KGradientDialog::reject);
 
 	//BEGIN layout widgets
-	QVBoxLayout * layout = new QVBoxLayout( widget );
+	QVBoxLayout * layout = new QVBoxLayout( this );
 	layout->setMargin( 0 );
 	
 	m_gradient->setFixedHeight( 24 );
diff --git a/kmplot/ksliderwindow.cpp b/kmplot/ksliderwindow.cpp
--- a/kmplot/ksliderwindow.cpp
+++ b/kmplot/ksliderwindow.cpp
@@ -95,14 +95,12 @@
 	setModal( false );
 	QWidget * widget = new QWidget( this );
 	setWindowTitle( i18n("Sliders") );
-	QVBoxLayout *layout = new QVBoxLayout( widget );
-	setLayout(layout);
+
+	QVBoxLayout *layout = new QVBoxLayout( this );
 	layout->addWidget(widget);
 
 	Q_ASSERT( SLIDER_COUNT == 4 ); // safety check, in case SLIDER_COUNT is increased but not this code
-	
-	layout->setMargin( 0 );
-	
+
 	for ( int i = 0; i < SLIDER_COUNT; ++i )
 	{
 		m_sliders[i] = new SliderWidget( widget, i );
diff --git a/kmplot/parameteranimator.cpp b/kmplot/parameteranimator.cpp
--- a/kmplot/parameteranimator.cpp
+++ b/kmplot/parameteranimator.cpp
@@ -64,7 +64,10 @@
 	setWindowTitle( i18n("Parameter Animator") );
 	QDialogButtonBox *buttonBox = new QDialogButtonBox(QDialogButtonBox::Close);
 	connect(buttonBox, &QDialogButtonBox::rejected, this, &ParameterAnimator::reject);
-	m_widget->layout()->addWidget(buttonBox);
+
+	QVBoxLayout *dialogLayout = new QVBoxLayout( this );
+	dialogLayout->addWidget(m_widget);
+	dialogLayout->addWidget(buttonBox);
 
 	m_mode = Paused;
 	m_currentValue = 0;