Add TXGainField user interface element.

firmware/application/ui_receiver.cpp

@@ -353,4 +353,29 @@ void VGAGainField::on_focus() {
 	}
 }
 
+/* TXGainField **********************************************************/
+
+TXGainField::TXGainField(
+	Point parent_pos
+) : NumberField {
+		parent_pos, 2,
+		{ max2837::tx::gain_db_range.minimum, max2837::tx::gain_db_range.maximum },
+		max2837::tx::gain_db_step,
+		' ',
+	}
+{
+	set_value(receiver_model.tx_gain());
+
+	on_change = [](int32_t v) {
+		receiver_model.set_tx_gain(v);
+	};
+}
+
+void TXGainField::on_focus() {
+	//Widget::on_focus();
+	if( on_show_options ) {
+		on_show_options();
+	}
+}
+
 } /* namespace ui */

firmware/application/ui_receiver.hpp

@@ -330,6 +330,15 @@ public:
 	void on_focus() override;
 };
 
+class TXGainField : public NumberField {
+public:
+	std::function<void(void)> on_show_options;
+
+	TXGainField(Point parent_pos);
+
+	void on_focus() override;
+};
+
 } /* namespace ui */
 
 #endif/*__UI_RECEIVER_H__*/