feat(layers): character layer

src/c/character_layer.c

@@ -0,0 +1,67 @@
+#include "character_layer.h"
+
+#define CHARACTER_H 80
+#define CHARACTER_STEP 4
+
+static Layer *s_character_layer;
+static GBitmap *s_character_even;
+static GBitmap *s_character_odd;
+static int s_character_ticks;
+
+static void character_layer_update_proc(Layer *layer, GContext *ctx) {
+  // Get the character bitmap.
+  GBitmap *bitmap;
+  if (s_character_ticks % 2 == 0) {
+    bitmap = s_character_even;
+  } else {
+    bitmap = s_character_odd;
+  }
+
+  // Get the position of character bitmap and align it to bottom.
+  GRect frame = gbitmap_get_bounds(bitmap);
+  GRect frame_inside = layer_get_unobstructed_bounds(layer);
+  grect_align(&frame, &frame_inside, GAlignBottom, true);
+
+  // Move the character.
+  switch (s_character_ticks) {
+    case 1:
+      frame.origin.x += CHARACTER_STEP;  // to right
+      break;
+    case 3:
+      frame.origin.x -= CHARACTER_STEP;  // to left
+      break;
+  }
+
+  // Draw the character.
+  graphics_context_set_compositing_mode(ctx, GCompOpSet);
+  graphics_draw_bitmap_in_rect(ctx, bitmap, frame);
+}
+
+void character_layer_init(Window *window) {
+  s_character_ticks = 0;
+
+  s_character_even = gbitmap_create_with_resource(RESOURCE_ID_CHARACTER_EVEN);
+  s_character_odd = gbitmap_create_with_resource(RESOURCE_ID_CHARACTER_ODD);
+
+  Layer *window_root_layer = window_get_root_layer(window);
+  GRect window_bounds = layer_get_unobstructed_bounds(window_root_layer);
+
+  s_character_layer =
+      layer_create(GRect(0, window_bounds.size.h - CHARACTER_H, window_bounds.size.w, CHARACTER_H));
+  layer_set_update_proc(s_character_layer, character_layer_update_proc);
+
+  layer_add_child(window_root_layer, s_character_layer);
+}
+
+void character_layer_tick(void) {
+  if (++s_character_ticks == 4) {
+    s_character_ticks = 0;
+  }
+  layer_mark_dirty(s_character_layer);
+}
+
+void character_layer_deinit(void) {
+  layer_destroy(s_character_layer);
+  gbitmap_destroy(s_character_even);
+  gbitmap_destroy(s_character_odd);
+}