fix warns, simplify, begin watcher

src/device/dialog.rs

@@ -1,4 +1,4 @@
-use crate::{*, browse::*, device::*, menu::*};
+use crate::{*, device::*};
 
 /// Various possible dialog modes.
 ///
@@ -127,3 +127,19 @@ impl Dialog {
     /// FIXME: implement
     pub fn browser_target (&self) -> Option<&BrowseTarget> { todo!() }
 }
+
+/// Increment a wrapping counter.
+pub const fn wrap_inc (index: usize, count: usize) -> usize {
+    if count > 0 { (index + 1) % count } else { 0 }
+}
+
+/// Decrement a wrapping counter.
+pub const fn wrap_dec (index: usize, count: usize) -> usize {
+    if count > 0 {
+        let a = index.overflowing_sub(1).0;
+        let b = count.saturating_sub(1);
+        if a < b { a } else { b }
+    } else {
+        0
+    }
+}