all: add OpenBSD (X11) support (#36)

* all: add OpenBSD (X11) support

OpenBSD ships the same X11/Xlib API as Linux, so the existing X11
backend works there with the right cgo include/lib paths
(/usr/X11R6). Rename hotkey_linux.* to hotkey_x11.* because the
_linux filename suffix carries an implicit linux-only build
constraint that a //go:build line cannot widen, then extend the
constraints to "linux || openbsd". Also widen mainthread/os.go so
mainthread.Init/Call are available on OpenBSD.

Adapted from #32 by Simon Dassow (@sdassow).

* ci: add OpenBSD VM job exercising the X11 cgo build

The CGO_ENABLED=0 cross-build only compiles the nocgo stub for
openbsd. Add a vmactions OpenBSD VM that builds and vets with cgo
enabled, validating the X11 backend's openbsd cgo flags (/usr/X11R6)
and link against libX11.

Author: changkun

.github/workflows/hotkey.yml

@@ -99,3 +99,23 @@ jobs:
           export GOARCH=${TARGET#*/}
           echo "Building for $GOOS/$GOARCH"
           CGO_ENABLED=0 go build -v ./...
+
+  # Real OpenBSD run inside a VM. This exercises the X11 cgo build/link path
+  # (libX11 lives under /usr/X11R6 in the OpenBSD base system) that the
+  # CGO_ENABLED=0 cross-build job cannot validate. The hotkey runtime tests
+  # need an X server, so here we compile- and vet-check with cgo enabled.
+  openbsd:
+    name: openbsd (X11, cgo)
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@v4
+      - name: Build and vet on OpenBSD
+        uses: vmactions/openbsd-vm@v1
+        with:
+          usesh: true
+          prepare: |
+            pkg_add -I go
+          run: |
+            go version
+            CGO_ENABLED=1 go build -v ./...
+            CGO_ENABLED=1 go vet ./...

hotkey_linux.c hotkey_x11.chotkey_linux.c renamed to hotkey_x11.c

@@ -4,7 +4,7 @@
 //
 // Written by Changkun Ou <changkun.de>
 
-//go:build linux
+//go:build linux || openbsd
 
 #include <X11/Xlib.h>
 #include <X11/Xutil.h>

hotkey_linux.go hotkey_x11.gohotkey_linux.go renamed to hotkey_x11.go

@@ -4,12 +4,14 @@
 //
 // Written by Changkun Ou <changkun.de>
 
-//go:build linux
+//go:build linux || openbsd
 
 package hotkey
 
 /*
 #cgo LDFLAGS: -lX11
+#cgo openbsd CFLAGS: -I/usr/X11R6/include
+#cgo openbsd LDFLAGS: -L/usr/X11R6/lib -lX11
 
 #include <stdint.h>
 #include <X11/Xlib.h>

hotkey_linux_internal_test.go hotkey_x11_internal_test.gohotkey_linux_internal_test.go renamed to hotkey_x11_internal_test.go

@@ -4,7 +4,7 @@
 //
 // Written by Changkun Ou <changkun.de>
 
-//go:build linux && cgo
+//go:build (linux || openbsd) && cgo
 
 package hotkey
 

hotkey_linux_test.go hotkey_x11_test.gohotkey_linux_test.go renamed to hotkey_x11_test.go

@@ -4,7 +4,7 @@
 //
 // Written by Changkun Ou <changkun.de>
 
-//go:build linux && cgo
+//go:build (linux || openbsd) && cgo
 
 package hotkey_test
 

mainthread/os.go

@@ -4,7 +4,7 @@
 //
 // Written by Changkun Ou <changkun.de>
 
-//go:build windows || linux || (darwin && !cgo)
+//go:build windows || linux || openbsd || (darwin && !cgo)
 
 package mainthread