Clean up meter_arm logic; add comments

src/c/auxiliary.c

@@ -91,7 +91,7 @@ char * get_tempo_marking(void) {
  * Updates the bpm to the closest tempo marking 
  * @param dir - 1 for higher, -1 for lower
  */
-int change_tempo_marking(int dir) {
+static int change_tempo_marking(int dir) {
     if(dir != 1 && dir != -1) {
         APP_LOG(APP_LOG_LEVEL_ERROR, "invalid direction of %d", dir);
         return -1;

src/c/main.c

@@ -71,7 +71,7 @@ void select_play_click_handler(ClickRecognizerRef recognizer, void *context) {
         metro_timer = NULL;
 
         toggle_colors(false);
-        reset_animation();
+        reset_meter_arm_animation();
     }
 }
 
@@ -129,7 +129,7 @@ void down_tempo_click_handler(ClickRecognizerRef recognizer, void *context) {
 }
 
 void window_load(Window *window) {
-    Layer *window_layer = window_get_root_layer(window);
+    window_layer = window_get_root_layer(window);
     GRect bounds = layer_get_bounds(window_layer);
     int status_bar_h = PBL_IF_RECT_ELSE(16, 24);
 
@@ -239,11 +239,10 @@ void init(void) {
 
 void deinit(void) {
     app_timer_cancel(metro_timer);
-    // Destroy main Window
     prv_save_settings();
-    window_destroy(window);
 
     gpath_destroy(s_meter_path);
+    window_destroy(window);
 }
 
 int main(void) {

src/c/main.h

@@ -7,6 +7,8 @@
 
 Window *window;
 
+Layer *window_layer;
+
 // The actual value of the metronome
 TextLayer *bpm_text_layer,
 // What tempo group the bpm falls under

src/c/meter_arm.c

@@ -7,20 +7,16 @@
 
 static int angle_bounds;
 
-/**
-  * Creating the meter arm
-  */
 // The metronome arm drawn as a polygon
 const GPathInfo METER_ARM_POINTS = {
-    // This is the amount of points
+    // Number of points
     8,
-    // The shape to draw
+    // Position of each point
     (GPoint []) {{-METER_ARM_W - METER_BOX_W, -METER_ARM_H}, {-METER_ARM_W - METER_BOX_W, -METER_ARM_H - METER_BOX_H}, {METER_ARM_W + METER_BOX_W, -METER_ARM_H - METER_BOX_H},
                  {METER_ARM_W + METER_BOX_W, -METER_ARM_H}, {METER_ARM_W, -METER_ARM_H}, {METER_ARM_W, 0}, {-METER_ARM_W, 0}, {-METER_ARM_W, -METER_ARM_H}}
 };
 
 void create_meter_arm(void) {
-    Layer *window_layer = window_get_root_layer(window);
     GRect bounds = layer_get_bounds(window_layer);
     angle_bounds = get_angle_bounds();
 
@@ -41,44 +37,58 @@ void path_layer_update_callback(Layer *layer, GContext *ctx) {
     gpath_draw_filled(ctx, s_meter_path);
 }
 
-int path_angle_add(int angle) {
+/**
+ * Updates the angle by the given amount, circling around
+ * if the angle would end up being greater than 360
+ * @param angle - How much to increase the angle by
+ */
+static int path_angle_add(int angle) {
     return s_path_angle = (s_path_angle + angle) % 360;
 }
 
+/**
+ * Put the meter arm in the original position
+ */
+static void reset_path_angle() {
+    path_angle_add(-angle_bounds - s_path_angle);
+}
+
 int get_angle_bounds(void) {
     int angle = 0;
     float ab = ACTION_BAR_WIDTH;
-    GRect wb = layer_get_bounds(window_get_root_layer(window));
+    GRect wb = layer_get_bounds(window_layer);
 
-    // For square watches
+    /* Gets the ratio of the triangle sides between the horizontal and the meter arm */
+    float hypotenuse = METER_ARM_H + sm_sqrt(sm_powint(METER_BOX_W + METER_ARM_W, 2) + sm_powint(METER_BOX_H, 2));
+    // Meter arm is centered with respect to action bar, so just half that distance
     #ifdef PBL_RECT
-        float temp = (wb.size.w - ab) / (2 * (METER_ARM_H + sm_sqrt(sm_powint(METER_BOX_W + METER_ARM_W, 2) + sm_powint(METER_BOX_H, 2))));
+        float horizontal_leg = (wb.size.w - ab) / 2;
     #else
-    // For round watches
-        float temp = (.5*wb.size.w - ab) / (METER_ARM_H + sm_sqrt(sm_powint(METER_BOX_W + METER_ARM_W, 2) + sm_powint(METER_BOX_H, 2)));
+    // Meter arm is in center of screen, so half the distance of the screen minus the action bar width
+        float horizontal_leg = .5 * wb.size.w - ab - 5;
     #endif
 
-    angle = sm_acosd(temp);
+    angle = sm_acosd(horizontal_leg / hypotenuse);
 
     return 90 - angle;
 }
 
-void reset_animation(void) {
+void reset_meter_arm_animation(void) {
     if(forward_animate) animation_destroy(forward_animate);
     if(backward_animate) animation_destroy(backward_animate);
-    path_angle_add(-angle_bounds - s_path_angle);
+    reset_path_angle();
     layer_mark_dirty(s_path_layer);
 }
 
-void forward_animate_update(Animation *animation, const AnimationProgress progress) {
+static void forward_animate_update(Animation *animation, const AnimationProgress progress) {
     int progress_percent = ((int)progress * 100) / ANIMATION_NORMALIZED_MAX;
     int delta = angle_bounds*2*progress_percent/100 - (s_path_angle+angle_bounds);
 
     path_angle_add(delta);
     layer_mark_dirty(s_path_layer);
 }
 
-void backward_animate_update(Animation *animation, const AnimationProgress progress) {
+static void backward_animate_update(Animation *animation, const AnimationProgress progress) {
     int progress_percent = ((int)progress * 100) / ANIMATION_NORMALIZED_MAX;
     int delta = -angle_bounds*2*progress_percent/100 - (s_path_angle-angle_bounds);
 
@@ -112,7 +122,7 @@ void animate_meter_arm(bool direction, int duration) {
 }
 
 void toggle_meter_arm_visibility() {
-    GRect bounds = layer_get_bounds(window_get_root_layer(window));
+    GRect bounds = layer_get_bounds(window_layer);
     // Centers the text on the round watches, looks weird if off center
     int action_bar_w = ACTION_BAR_WIDTH==30 ? ACTION_BAR_WIDTH : 0,
         bpm_y_pos, tempo_y_pos;

src/c/meter_arm.h

@@ -4,15 +4,15 @@
 #include "main.h"
 #include "SmallMaths.h"
 
-/**
-  * Creating the meter arm
-  */
-const GPathInfo METER_ARM_POINTS;
+extern const GPathInfo METER_ARM_POINTS;
 Layer *s_path_layer;
 GPath *s_meter_path;
 int s_path_angle;
 int meter_color;
 
+/**
+  * Creates the meter arm and sets it to the max angle on the left
+  */
 void create_meter_arm(void);
 
 /**
@@ -21,13 +21,6 @@ void create_meter_arm(void);
  */
 void path_layer_update_callback(Layer *layer, GContext *ctx);
 
-/**
- * Updates the angle by the given amount, circling around
- * if the angle would end up being greater than 360
- * @param angle - How much to increase the angle by
- */
-int path_angle_add(int angle);
-
 /**
  * Return the bounds that the metronome arm can travel
  */
@@ -40,11 +33,9 @@ Animation *forward_animate, *backward_animate;
 AnimationImplementation forward_impl, backward_impl;
 
 /**
- * Animate the meter arm
+ * Turns off the animation, and puts the arm back in its original position
  */
-void reset_animation(void);
-void forward_animate_update(Animation *animation, const AnimationProgress progress);
-void backward_animate_update(Animation *animation, const AnimationProgress progress);
+void reset_meter_arm_animation(void);
 
 /**
  * Sets up and executes the animation in the given direction for the duration