Make PluginView::isResizable a virtual (#7541)

Remove the member `PluginView::m_isResizable` and it's associated method `setResizable`. Turn `isResizable` into a virtual method.

The reasoning is that whether or not an effect can be resized depends on its implementation. Therefore does not make sense to have a method like `setResizable`. If the underlying implementation does not support resizing then it would not make sense to call `setResizable(true)`. So `isResizable` now describes the underlying ability of a plugin to resize. It's then up to the clients of that method to decide how to treat the result of `isResizable`, i.e. if they want to make use of the ability to resize or not.

include/PluginView.h

@@ -41,11 +41,7 @@ class LMMS_EXPORT PluginView : public QWidget, public ModelView
 	{
 	}
 
-	void setResizable(bool resizable) { m_isResizable = resizable; }
-	bool isResizable() { return m_isResizable; }
-
-private:
-	bool m_isResizable = false;
+	virtual bool isResizable() const { return false; }
 };
 
 } // namespace lmms::gui

plugins/SlicerT/SlicerTView.cpp

@@ -55,7 +55,6 @@ SlicerTView::SlicerTView(SlicerT* instrument, QWidget* parent)
 
 	setMaximumSize(QSize(10000, 10000));
 	setMinimumSize(QSize(516, 400));
-	setResizable(true);
 
 	m_wf = new SlicerTWaveform(248, 128, instrument, this);
 	m_wf->move(0, s_topBarHeight);

plugins/SlicerT/SlicerTView.h

@@ -78,6 +78,8 @@ public slots:
 	void resizeEvent(QResizeEvent* event) override;
 
 private:
+	bool isResizable() const override { return true; }
+
 	SlicerT* m_slicerTParent;
 
 	Knob* m_noteThresholdKnob;