add QAD::VirtualKeyboard library, vkbd for widgets with JSON-based description

libs/virtual_keyboard/virtual_keyboard_layout_page.h

@@ -0,0 +1,55 @@
+#ifndef virtual_keyboard_layout_page_h
+#define virtual_keyboard_layout_page_h
+
+#include <QToolButton>
+#include <pibase.h>
+
+
+class VirtualKeyboardLayoutPage: public QWidget {
+	Q_OBJECT
+
+public:
+	VirtualKeyboardLayoutPage(QJsonObject root);
+	~VirtualKeyboardLayoutPage();
+
+	bool isValid() const {return !buttons.isEmpty();}
+	QString name() const {return name_;}
+
+	bool isCapital() const {return capital;}
+	void setCapital(bool yes);
+	void setGotoEnabled(bool yes);
+	void setCapitalEnabled(bool yes);
+
+	int buttonColumns() const {return columns;}
+	void setButtonsSize(int h);
+
+	enum Role {
+		rInvalid,
+		rLetter,
+		rBackspace,
+		rReturn,
+		rSpace,
+		rHide,
+		rShift,
+		rGotoPage,
+	};
+
+protected:
+	QToolButton * createButton(QJsonObject jb);
+	Role roleFromText(QString str);
+	Role buttonRole(QToolButton * b) const;
+
+	QVector<QToolButton * > buttons;
+	QString name_;
+	int columns = 0;
+	bool capital = false, capital_enabled = true;
+
+private slots:
+
+signals:
+	void gotoPageRequest(QString);
+	void hideRequest();
+
+};
+
+#endif