Keyboard improvements (#240)

- Renamed various keyboard functions so it's easier to differentiate hardware versus software keyboard functionality
- Created `Tactility/lvgl/Keyboard.h` as a proxy  for the internal `Gui` service.
- Implemented `tt_lvgl_keyboard.h` in `TactilityC`.

TactilityC/Include/tt_lvgl_keyboard.h

@@ -0,0 +1,63 @@
+#pragma once
+
+#include <lvgl.h>
+
+#ifdef __cplusplus
+extern "C" {
+#endif
+
+/**
+ * Show the on-screen keyboard.
+ * @param[in] textarea the textarea to focus the input for
+ */
+void tt_lvgl_software_keyboard_show(lv_obj_t* textarea);
+
+/**
+ * Hide the on-screen keyboard.
+ * Has no effect when the keyboard is not visible.
+ */
+void tt_lvgl_software_keyboard_hide();
+
+/**
+ * The on-screen keyboard is only shown when both of these conditions are true:
+ *  - there is no hardware keyboard
+ *  - TT_CONFIG_FORCE_ONSCREEN_KEYBOARD is set to true in tactility_config.h
+ * @return if we should show a on-screen keyboard for text input inside our apps
+ */
+bool tt_lvgl_software_keyboard_is_enabled();
+
+/**
+ * Activate the keypad for a widget group.
+ * @param group
+ */
+void tt_lvgl_software_keyboard_activate(lv_group_t* group);
+
+/**
+ * Deactivate the keypad for the current widget group (if any).
+ * You don't have to call this after calling _activate() because widget
+ * cleanup automatically removes itself from the group it belongs to.
+ */
+void tt_lvgl_software_keyboard_deactivate();
+
+/**
+ * @return true if LVGL is configured with a keypad
+ */
+bool tt_lvgl_hardware_keyboard_is_available();
+
+/**
+ * Set the keypad.
+ * @param device the keypad device
+ */
+void tt_lvgl_hardware_keyboard_set_indev(lv_indev_t* device);
+
+/**
+ * Glue code for the on-screen keyboard and the hardware keyboard:
+ *  - Attach automatic hide/show parameters for the on-screen keyboard.
+ *  - Registers the textarea to the default lv_group_t for hardware keyboards.
+ * @param[in] textarea
+ */
+void tt_lvgl_keyboard_add_textarea(lv_obj_t* textarea);
+
+#ifdef __cplusplus
+}
+#endif