keyboard: turn down key repeat before going to lock screen

As mentioned here:

    https://twitter.com/wincent/status/1068234903811223552

Going to see if this can cure my lock screen woes. You can turn off key
repeat with:

    defaults write -g KeyRepeat 300000

But you have to log out for it to take effect. I did some reverse
engineering and header-file searching to figure out how:

    /System/Library/PreferencePanes/Keyboard.prefPane/Contents/MacOS/Keyboard

Is forcing the changes to take effect immediately, and discovered some
deprecated (sigh) APIs that hopefully will continue to exist for a
while:

    NXSetKeyRepeatInterval()
    NXKeyRepeatInterval()
    NXOpenEventStatus()

I bundled these up in a `dry` executable (short for "Don't Repeat
Yourself") that can be used to set the key repeat delay in seconds. Not
building or installing this automatically yet so that I can test it.

Calling `dry` from the `karabiner-kill` and `karabiner-boot` scripts,
and also switched to from running on systemWillSleep to screensDidLock,
which allows us to cover both normal screen saver and sleep events with
a single branch.

roles/dotfiles/files/.hammerspoon/karabiner.lua

@@ -19,7 +19,7 @@ return {
   init = (function()
     local watcher = hs.caffeinate.watcher.new(
       function(event)
-        if event == hs.caffeinate.watcher.systemWillSleep then
+        if event == hs.caffeinate.watcher.screensDidLock then
           disable()
         elseif event == hs.caffeinate.watcher.screensDidUnlock then
           enable()

roles/dotfiles/files/.zsh/bin/karabiner-boot

@@ -6,6 +6,10 @@ if [ -z "$UID" ]; then
   UID=$(id -u)
 fi
 
+# In Hammerspoon, $PATH will be too minimal(/usr/bin:/bin:/usr/sbin:/sbin)
+# to find the `dry` executable.
+PATH=$PATH:$HOME/bin
+
 # Depends on /private/etc/sudoers.d/karabiner-sudoers:
 sudo launchctl load /Library/LaunchDaemons/org.pqrs.karabiner.karabiner_grabber.plist
 sudo launchctl load /Library/LaunchDaemons/org.pqrs.karabiner.karabiner_observer.plist
@@ -14,4 +18,9 @@ launchctl enable gui/"$UID"/org.pqrs.karabiner.karabiner_console_user_server
 launchctl bootstrap gui/"$UID" /Library/LaunchAgents/org.pqrs.karabiner.karabiner_console_user_server.plist
 launchctl enable gui/"$UID"/org.pqrs.karabiner.karabiner_console_user_server
 
+# Turn key repeat back on:
+if command -v dry &> /dev/null; then
+  dry 0.033333 > /dev/null
+fi
+
 echo "🐣 Karabiner-Elements bootstrapped"

roles/dotfiles/files/.zsh/bin/karabiner-kill

@@ -6,6 +6,15 @@ if [ -z "$UID" ]; then
   UID=$(id -u)
 fi
 
+# In Hammerspoon, $PATH will be too minimal(/usr/bin:/bin:/usr/sbin:/sbin)
+# to find the `dry` executable.
+PATH=$PATH:$HOME/bin
+
+# For good measure, turn off key repeat:
+if command -v dry &> /dev/null; then
+  dry 300 > /dev/null
+fi
+
 launchctl bootout gui/"$UID" /Library/LaunchAgents/org.pqrs.karabiner.karabiner_console_user_server.plist
 launchctl disable gui/"$UID"/org.pqrs.karabiner.karabiner_console_user_server
 

roles/dotfiles/support/dry/.gitignore

@@ -0,0 +1 @@
+/dry

roles/dotfiles/support/dry/Makefile

@@ -0,0 +1,12 @@
+PREFIX ?= $(HOME)
+CFLAGS := -ansi -pedantic -Wall -Wextra ${CFLAGS}
+
+dry: main.c
+	${CC} ${CFLAGS} \
+		-framework CoreFoundation \
+		-framework CoreServices \
+		-framework IOKit \
+		-o dry main.c
+
+install:
+	install -m755 dry ${PREFIX}/bin

roles/dotfiles/support/dry/main.c

@@ -0,0 +1,36 @@
+/*
+ * dry (Don't Repeat Yourself)
+ *
+ * Usage: `dry 300`
+ *
+ * Sets the key repeat interval without requiring a logout.
+ */
+
+#include <stdio.h>
+#include <stdlib.h>
+#include <IOKit/hidsystem/event_status_driver.h>
+
+int main(int argc, const char * argv[]) {
+    NXEventHandle handle;
+    double interval;
+
+    if (argc != 2) {
+        printf("Expected 1 argument (key repeat in seconds); got %d\n", argc - 1);
+        return EXIT_FAILURE;
+    }
+
+    handle = NXOpenEventStatus();
+    if (!handle) {
+        perror("NXOpenEventStatus");
+        return EXIT_FAILURE;
+    }
+
+    interval = NXKeyRepeatInterval(handle);
+    printf("Old interval: %lf\n", interval);
+
+    sscanf(argv[1], "%lf", &interval);
+    printf("New interval: %lf\n", interval);
+
+    NXSetKeyRepeatInterval(handle, interval);
+    return 0;
+}