fix(wm): prevent hidden_hwnds deadlock

I used a parking_lot to detect what I suspected to be the deadlock
resulting in issue #13.

I was pleasantly surprised by the alternative to std::sync::Mutex
provided by parking_lot, especially not having to unlock it to use it,
and of course the excellent and intuitive (even if experimental)
deadlock detector.

I have decided to use parking_lot::Mutex as an almost-drop-in
replacement for std::sync::Mutex, as I expect that this isn't the last
time komorebi will have a deadlocking issue, and I have put the deadlock
detection code which runs in a separate thread behind a
"deadlock_detection" feature.

The actual deadlock itself was solved by scoping the first lock in the
handler for WindowManagerEvent::Hide and then executing any required
operations (some of which, like window.maximize(), may require another
lock on HIDDEN_HWNDS) in a separate scope once the previous lock has
been dropped.

In the future I should look at integrating globals like HIDDEN_HWNDS
into WindowManager in a way that won't lead to double-mutable-borrow
issues.

fix #13

Cargo.lock

@@ -270,10 +270,16 @@ checksum = "975ccf83d8d9d0d84682850a38c8169027be83368805971cc4f238c2b245bc98"
 dependencies = [
  "cfg-if 1.0.0",
  "libc",
- "redox_syscall",
+ "redox_syscall 0.2.10",
  "winapi 0.3.9",
 ]
 
+[[package]]
+name = "fixedbitset"
+version = "0.2.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "37ab347416e802de484e4d03c7316c48f1ecb56574dfd4a46a80f173ce1de04d"
+
 [[package]]
 name = "fs-tail"
 version = "0.1.4"
@@ -423,6 +429,15 @@ dependencies = [
  "libc",
 ]
 
+[[package]]
+name = "instant"
+version = "0.1.10"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "bee0328b1209d157ef001c94dd85b4f8f64139adb0eac2659f4b08382b2f474d"
+dependencies = [
+ "cfg-if 1.0.0",
+]
+
 [[package]]
 name = "iovec"
 version = "0.1.4"
@@ -465,6 +480,7 @@ dependencies = [
  "komorebi-core",
  "lazy_static",
  "nanoid",
+ "parking_lot",
  "paste",
  "serde",
  "serde_json",
@@ -524,6 +540,15 @@ version = "0.2.99"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "a7f823d141fe0a24df1e23b4af4e3c7ba9e5966ec514ea068c93024aa7deb765"
 
+[[package]]
+name = "lock_api"
+version = "0.4.4"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "0382880606dff6d15c9476c416d18690b72742aa7b605bb6dd6ec9030fbf07eb"
+dependencies = [
+ "scopeguard",
+]
+
 [[package]]
 name = "log"
 version = "0.4.14"
@@ -726,12 +751,50 @@ version = "1.3.0"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "2386b4ebe91c2f7f51082d4cefa145d030e33a1842a96b12e4885cc3c01f7a55"
 
+[[package]]
+name = "parking_lot"
+version = "0.11.1"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "6d7744ac029df22dca6284efe4e898991d28e3085c706c972bcd7da4a27a15eb"
+dependencies = [
+ "instant",
+ "lock_api",
+ "parking_lot_core",
+]
+
+[[package]]
+name = "parking_lot_core"
+version = "0.8.3"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "fa7a782938e745763fe6907fc6ba86946d72f49fe7e21de074e08128a99fb018"
+dependencies = [
+ "backtrace",
+ "cfg-if 1.0.0",
+ "instant",
+ "libc",
+ "petgraph",
+ "redox_syscall 0.2.10",
+ "smallvec",
+ "thread-id",
+ "winapi 0.3.9",
+]
+
 [[package]]
 name = "paste"
 version = "1.0.5"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "acbf547ad0c65e31259204bd90935776d1c693cec2f4ff7abb7a1bbbd40dfe58"
 
+[[package]]
+name = "petgraph"
+version = "0.5.1"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "467d164a6de56270bd7c4d070df81d07beace25012d5103ced4e9ff08d6afdb7"
+dependencies = [
+ "fixedbitset",
+ "indexmap",
+]
+
 [[package]]
 name = "pin-project-lite"
 version = "0.2.7"
@@ -894,6 +957,12 @@ dependencies = [
  "rand_core 0.3.1",
 ]
 
+[[package]]
+name = "redox_syscall"
+version = "0.1.57"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "41cc0f7e4d5d4544e8861606a285bb08d3e70712ccc7d2b84d7c0ccfaf4b05ce"
+
 [[package]]
 name = "redox_syscall"
 version = "0.2.10"
@@ -910,7 +979,7 @@ source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "528532f3d801c87aec9def2add9ca802fe569e44a544afe633765267840abe64"
 dependencies = [
  "getrandom",
- "redox_syscall",
+ "redox_syscall 0.2.10",
 ]
 
 [[package]]
@@ -1106,6 +1175,17 @@ dependencies = [
  "unicode-width",
 ]
 
+[[package]]
+name = "thread-id"
+version = "3.3.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "c7fbf4c9d56b320106cd64fd024dadfa0be7cb4706725fc44a7d7ce952d820c1"
+dependencies = [
+ "libc",
+ "redox_syscall 0.1.57",
+ "winapi 0.3.9",
+]
+
 [[package]]
 name = "thread_local"
 version = "1.1.3"