Disentangle and clean the classes of the Audio File Processor (#7069)

## Extract views
Extract the classes `AudioFileProcessorWaveView` and `AudioFileProcessorView` into their own files.

Reformat the new classes by removing unnecessary whitespace and underscores. Add spaces to if-statements.

Cleanup the includes.

## Remove friend relationship
Remove the friend relationship between `AudioFileProcessor` and `AudioFileProcessorView`.

Introduce getters for entities that the view is interested in.

plugins/AudioFileProcessor/AudioFileProcessorWaveView.h

@@ -0,0 +1,181 @@
+/*
+ * AudioFileProcessorWaveView.h - Wave renderer of the AFP
+ *
+ * Copyright (c) 2004-2014 Tobias Doerffel <tobydox/at/users.sourceforge.net>
+ *
+ * This file is part of LMMS - https://lmms.io
+ *
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU General Public
+ * License as published by the Free Software Foundation; either
+ * version 2 of the License, or (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+ * General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public
+ * License along with this program (see COPYING); if not, write to the
+ * Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor,
+ * Boston, MA 02110-1301 USA.
+ *
+ */
+
+#ifndef LMMS_AUDIO_FILE_PROCESSOR_WAVE_VIEW_H
+#define LMMS_AUDIO_FILE_PROCESSOR_WAVE_VIEW_H
+
+
+#include "Knob.h"
+
+
+namespace lmms
+{
+
+class Sample;
+
+namespace gui
+{
+
+class AudioFileProcessorView;
+
+class AudioFileProcessorWaveView : public QWidget
+{
+	Q_OBJECT
+protected:
+	virtual void enterEvent(QEvent* e);
+	virtual void leaveEvent(QEvent* e);
+	virtual void mousePressEvent(QMouseEvent* me);
+	virtual void mouseReleaseEvent(QMouseEvent* me);
+	virtual void mouseMoveEvent(QMouseEvent* me);
+	virtual void wheelEvent(QWheelEvent* we);
+	virtual void paintEvent(QPaintEvent* pe);
+
+
+public:
+	enum class Point
+	{
+		Start,
+		End,
+		Loop
+	} ;
+
+	class knob : public Knob
+	{
+		const AudioFileProcessorWaveView* m_waveView;
+		const Knob* m_relatedKnob;
+
+
+	public:
+		knob(QWidget* parent) :
+			Knob(KnobType::Bright26, parent),
+			m_waveView(0),
+			m_relatedKnob(0)
+		{
+			setFixedSize(37, 47);
+		}
+
+		void setWaveView(const AudioFileProcessorWaveView* wv)
+		{
+			m_waveView = wv;
+		}
+
+		void setRelatedKnob(const Knob* knob)
+		{
+			m_relatedKnob = knob;
+		}
+
+		void slideBy(double v, bool check_bound = true)
+		{
+			slideTo(model()->value() + v, check_bound);
+		}
+
+		void slideTo(double v, bool check_bound = true);
+
+
+	protected:
+		float getValue(const QPoint & p);
+
+
+	private:
+		bool checkBound(double v) const;
+	} ;
+
+
+public slots:
+	void update()
+	{
+		updateGraph();
+		QWidget::update();
+	}
+
+	void isPlaying(lmms::f_cnt_t current_frame);
+
+
+private:
+	static const int s_padding = 2;
+
+	enum class DraggingType
+	{
+		Wave,
+		SampleStart,
+		SampleEnd,
+		SampleLoop
+	} ;
+
+	Sample const* m_sample;
+	QPixmap m_graph;
+	f_cnt_t m_from;
+	f_cnt_t m_to;
+	f_cnt_t m_last_from;
+	f_cnt_t m_last_to;
+	float m_last_amp;
+	knob* m_startKnob;
+	knob* m_endKnob;
+	knob* m_loopKnob;
+	f_cnt_t m_startFrameX;
+	f_cnt_t m_endFrameX;
+	f_cnt_t m_loopFrameX;
+	bool m_isDragging;
+	QPoint m_draggingLastPoint;
+	DraggingType m_draggingType;
+	bool m_reversed;
+	f_cnt_t m_framesPlayed;
+	bool m_animation;
+
+	friend class AudioFileProcessorView;
+
+public:
+	AudioFileProcessorWaveView(QWidget* parent, int w, int h, Sample const* buf);
+	void setKnobs(knob* start, knob* end, knob* loop);
+
+
+	void updateSampleRange();
+private:
+	void zoom(const bool out = false);
+	void slide(int px);
+	void slideSamplePointByPx(Point point, int px);
+	void slideSamplePointByFrames(Point point, f_cnt_t frames, bool slide_to = false);
+	void slideSampleByFrames(f_cnt_t frames);
+
+	void slideSamplePointToFrames(Point point, f_cnt_t frames)
+	{
+		slideSamplePointByFrames(point, frames, true);
+	}
+
+	void updateGraph();
+	void reverse();
+	void updateCursor(QMouseEvent* me = nullptr);
+
+	static bool isCloseTo(int a, int b)
+	{
+		return qAbs(a - b) < 4;
+	}
+
+} ;
+
+} // namespace gui
+
+} // namespace lmms
+
+#endif // LMMS_AUDIO_FILE_PROCESSOR_WAVE_VIEW_H