Time Left Face: Visualize progress in any time interval (#217)

* time left face: initial commit, fully functional

* time left face: typos

* time left face: correct even more typos in documentation

---------

Co-authored-by: joeycastillo <joeycastillo@utexas.edu>

movement/watch_faces/complication/time_left_face.h

@@ -0,0 +1,89 @@
+/*
+ * MIT License
+ *
+ * Copyright (c) 2022 Andreas Nebinger, based on the work of Joey Castillo
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy
+ * of this software and associated documentation files (the "Software"), to deal
+ * in the Software without restriction, including without limitation the rights
+ * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+ * copies of the Software, and to permit persons to whom the Software is
+ * furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in all
+ * copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+ * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+ * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+ * SOFTWARE.
+ */
+
+#ifndef TIME_LEFT_FACE_H_
+#define TIME_LEFT_FACE_H_
+
+#include "movement.h"
+
+/*
+ * The Time Left Face helps you to visualize how far you have proceeded in a certain
+ * time span. Much like the Day One Face, you can set your beginning date. In addition
+ * to that, you also set your target or destination date. You can then use the face
+ * to display your progress in different ways.
+ * 
+ * Usage:
+ * 
+ * - Long pressing of the light button starts the settings mode:
+ *   - First, you set the beginning date (indicated by a 'b' in the upper right corner).
+ *   - Start by setting the year (indicated by the letter 'YR'). Use the alarm button
+ *     to cycle the value. Short pressing the light button brings you to the next
+ *     settings page.
+ *   - Set the values in this order:
+ *     a. beginning date (indicated by a 'b'): year - month - day
+ *     b. destination date (indicated by a 'd'): year - month - day
+ *   - After cycling through all settings pages, the face resumes to display mode.
+ * 
+ * - In display mode, use the alarm button (short press) to cycle through these four
+ *   types of display:
+ *   a. number of days left ('DL') until the destination date is reached.
+ *   b. remaining days expressed as percentage of total time span. The value is shown
+ *      with two decimals, using the colon as decimal point.
+ *   c. number of days passed ('DA') since the beginning date.
+ *   d. number of days passed expressed as percentage of total time span. (Two decimal
+ *      points.)
+ *
+ * What is this for?
+ *
+ * You can use this watch face to be reminded of any kind of progess between a set
+ * start and end date. The brave among us can use it as a kind of memento mori
+ * visualization. Set your date of birth and look up the average life expectancy of
+ * your age cohort based on publicly available mortality tables. Then, set the
+ * statistically expected day of death as the target date and you will be able to
+ * see how much of your time has passed and how much is still to come.
+ * 
+ */
+
+typedef struct {
+    uint8_t current_page;
+    uint16_t current_year;
+    movement_birthdate_t birth_date;
+    movement_birthdate_t birth_date_when_activated;
+    movement_birthdate_t target_date;
+} time_left_state_t;
+
+void time_left_face_setup(movement_settings_t *settings, uint8_t watch_face_index, void ** context_ptr);
+void time_left_face_activate(movement_settings_t *settings, void *context);
+bool time_left_face_loop(movement_event_t event, movement_settings_t *settings, void *context);
+void time_left_face_resign(movement_settings_t *settings, void *context);
+
+#define time_left_face ((const watch_face_t){ \
+    time_left_face_setup, \
+    time_left_face_activate, \
+    time_left_face_loop, \
+    time_left_face_resign, \
+    NULL, \
+})
+
+#endif // TIME_LEFT_FACE_H_