Allow to remove account folder with Delete or Backspace keystroke

[MathiusD]

When you have a large number of accounts/folder to monitor, it's quite useful to enable deletion with a keystroke on the keyboard instead of clicking a button, so this PR is made for that.

[Abestanis]

I think this is a good idea, I just have an alternative proposal for the QTreeViewWithKeyEvents class.

Also, should we make the keyboard shortcut more discoverable? We could add a tooltip to the delete button that mentions the keyboard shortcuts.

[Abestanis]

How about we just use the Qt event system instead of building our own, that way we can avoid some casts and manually storing listeners.

Suggested change

	typedef void ( * TreeViewKeyPressedEvent)(void * handle, QKeyEvent * event);
	/**
	* A QTreeView that allow to define listener of keyEvent received
	*/
	class QTreeViewWithKeyEvents : public QTreeView {
	Q_OBJECT
	public:
	explicit QTreeViewWithKeyEvents(QWidget *parent = NULL);
	public slots:
	void onKeyPressed(void * handleUsed, TreeViewKeyPressedEvent callback);
	protected:
	void keyPressEvent(QKeyEvent * event) override;
	private:
	TreeViewKeyPressedEvent mCallback;
	void * mHandle;
	};
	/**
	* A QTreeView that allow to define listener of keyEvent received.
	*/
	class QTreeViewWithKeyEvents : public QTreeView {
	Q_OBJECT
	public:
	explicit QTreeViewWithKeyEvents(QWidget* parent = nullptr);
	signals:
	void onKeyPressed(QKeyEvent* event);
	protected:
	void keyPressEvent(QKeyEvent* event) override;
	};

with

void QTreeViewWithKeyEvents::keyPressEvent( QKeyEvent *event )
{
    emit onKeyPressed(event);
    QTreeView::keyPressEvent(event);
}

and

connect(treeAccounts, &QTreeViewWithKeyEvents::onKeyPressed, this, &DialogSettings::onKeyPressedOnTreeAccount);

[gyunaev]

Looks fine with me. I mean, those are rare operations, hardly worthy optimizing, but as you wish :)

[MathiusD]

I think this is a good idea, I just have an alternative proposal for the QTreeViewWithKeyEvents class.

Also, should we make the keyboard shortcut more discoverable? We could add a tooltip to the delete button that mentions the keyboard shortcuts.

Yes i can had a tooltip in another PR !

How about we just use the Qt event system instead of building our own, that way we can avoid some casts and manually storing listeners.

Yes, i have search if such signal exist in qt component and because i doesn't exist i have had own listener and i admit i've don't think to reuse signal system, i can follow your recommandation in another PR (Because it's already merged) !