Improve readability of text floats

Improve the readability of text floats by removing the hard coded pixel
font size. The widget is now composed of three QLabels which are used to
display the title, text and pixmap. Remove the methods paintEvent and
updateSize because the widget is now updated automatically whenever the
QLabels change state.

Merge both versions of TextFloat::displayMessage because one of them was
only called by the other.

The default constructor of TextFloat now delegates to the "full"
constructor. The latter is private because it is only used from within
displayMessage.

The methods setTitle, setText and setPixmap show/hide their
corresponding labels depending on whether there is text or a pixmap to
show.

Adjust the class Fader so that the text float is shown to the right of
the fader. Otherwise the new implementation would have covered the fader
while it is being moved.

include/TextFloat.h

@@ -27,10 +27,11 @@
 #define TEXT_FLOAT_H
 
 #include <QWidget>
-#include <QPixmap>
 
 #include "lmms_export.h"
 
+class QLabel;
+
 namespace lmms::gui
 {
 
@@ -47,11 +48,6 @@ public:
 
 	void setVisibilityTimeOut( int _msecs );
 
-
-	static TextFloat * displayMessage( const QString & _msg,
-						int _timeout = 2000,
-						QWidget * _parent = nullptr,
-						int _add_y_margin = 0 );
 	static TextFloat * displayMessage( const QString & _title,
 						const QString & _msg,
 						const QPixmap & _pixmap =
@@ -66,16 +62,15 @@ public:
 
 
 protected:
-	void paintEvent( QPaintEvent * _me ) override;
 	void mousePressEvent( QMouseEvent * _me ) override;
 
 
 private:
-	void updateSize();
+	TextFloat(const QString & _title, const QString & _text, const QPixmap & _pixmap);
 
-	QString m_title;
-	QString m_text;
-	QPixmap m_pixmap;
+	QLabel * m_pixmapLabel;
+	QLabel * m_titleLabel;
+	QLabel * m_textLabel;
 
 };