GUI subsystem: -H=windowsgui + AttachConsole, MB_TOPMOST on test window

drover.exe is now a GUI subsystem binary:
  - Double-click no longer flashes a console window — a clean
    smoke-test message box opens immediately.
  - When run from cmd / PowerShell, AttachConsole reattaches stdout
    and stderr to the parent terminal so '--version', 'check', etc.
    still print as expected.
  - MB_TOPMOST flag added to MessageBox so the window can't be
    obscured by other windows on launch (this was the actual cause
    of "I clicked but nothing happened" reports).

Verified locally: built with GOOS=windows GOARCH=amd64 -H=windowsgui;
running drover-gui.exe --version prints to PowerShell, drover-gui.exe
gui shows the message box on top of the active window.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

.gitea/workflows/build.yml

@@ -92,7 +92,11 @@ jobs:
           SHORT_SHA="${GITHUB_SHA:0:7}"
           BUILD_DATE="$(date -u +%Y-%m-%d)"
           mkdir -p bin
-          go build -trimpath -ldflags="-s -w \
+          # -H=windowsgui = subsystem WINDOWS, double-click no longer
+          # flashes a console window. main.go calls AttachConsole on
+          # startup so CLI invocations from cmd/PowerShell still print
+          # to the parent terminal.
+          go build -trimpath -ldflags="-s -w -H=windowsgui \
             -X main.Version=dev-${SHORT_SHA} \
             -X main.Commit=${SHORT_SHA} \
             -X main.BuildDate=${BUILD_DATE}" \

.gitea/workflows/release.yml

@@ -67,7 +67,11 @@ jobs:
           BUILD_DATE="$(date -u +%Y-%m-%d)"
           SHORT_SHA="${GITHUB_SHA:0:7}"
           mkdir -p dist
-          go build -trimpath -ldflags="-s -w \
+          # -H=windowsgui makes drover.exe a GUI subsystem binary so the
+          # double-click experience doesn't flash a console window. main.go
+          # calls AttachConsole on startup so CLI runs still print to the
+          # parent terminal when launched from cmd/PowerShell.
+          go build -trimpath -ldflags="-s -w -H=windowsgui \
             -X main.Version=${{ steps.version.outputs.version }} \
             -X main.Commit=${SHORT_SHA} \
             -X main.BuildDate=${BUILD_DATE}" \

cmd/drover/console_other.go

@@ -0,0 +1,5 @@
+//go:build !windows
+
+package main
+
+func attachToParentConsole() {}

cmd/drover/console_windows.go

@@ -0,0 +1,46 @@
+//go:build windows
+
+package main
+
+import (
+	"os"
+	"syscall"
+
+	"golang.org/x/sys/windows"
+)
+
+// attachToParentConsole reconnects stdin/stdout/stderr to the console of the
+// process that launched us, if any. It is a no-op when the binary was started
+// from Explorer (double-click) — there is no parent console to attach to.
+//
+// Why we need this: the binary is built with -H=windowsgui, which means
+// Windows treats it as a GUI application and does NOT allocate a console
+// when it starts. That gives a clean double-click experience (no flashing
+// console window). But it also disconnects fmt.Println output when the
+// user runs us from cmd.exe / PowerShell. Calling AttachConsole here
+// re-attaches us to the parent's console so CLI output works as expected.
+func attachToParentConsole() {
+	const ATTACH_PARENT_PROCESS = ^uint32(0) // (DWORD)-1
+
+	kernel32 := windows.NewLazySystemDLL("kernel32.dll")
+	attachConsole := kernel32.NewProc("AttachConsole")
+
+	r, _, _ := attachConsole.Call(uintptr(ATTACH_PARENT_PROCESS))
+	if r == 0 {
+		// AttachConsole failed — most likely there is no parent console
+		// (we were started from Explorer). That's fine: GUI mode is the
+		// default UX and stdout/stderr just go nowhere.
+		return
+	}
+
+	// Re-bind os.Stdout / os.Stderr to the freshly-attached console.
+	if h, err := syscall.GetStdHandle(syscall.STD_OUTPUT_HANDLE); err == nil && h != 0 {
+		os.Stdout = os.NewFile(uintptr(h), "stdout")
+	}
+	if h, err := syscall.GetStdHandle(syscall.STD_ERROR_HANDLE); err == nil && h != 0 {
+		os.Stderr = os.NewFile(uintptr(h), "stderr")
+	}
+	if h, err := syscall.GetStdHandle(syscall.STD_INPUT_HANDLE); err == nil && h != 0 {
+		os.Stdin = os.NewFile(uintptr(h), "stdin")
+	}
+}

cmd/drover/gui_windows.go

@@ -38,8 +38,10 @@ func showTestWindow() {
 	bodyW, _ := windows.UTF16PtrFromString(body)
 	titleW, _ := windows.UTF16PtrFromString(title)
 
-	// MB_OK | MB_ICONINFORMATION | MB_SETFOREGROUND
-	const flags = 0x00000000 | 0x00000040 | 0x00010000
+	// MB_OK | MB_ICONINFORMATION | MB_SETFOREGROUND | MB_TOPMOST
+	// MB_TOPMOST is essential — without it the message box can pop up
+	// behind other windows and the user thinks nothing happened.
+	const flags = 0x00000000 | 0x00000040 | 0x00010000 | 0x00040000
 
 	messageBox.Call(
 		0,

cmd/drover/main.go

@@ -22,6 +22,12 @@ var (
 var configPath string
 
 func main() {
+	// On Windows the binary is linked with -H=windowsgui so a double-click
+	// doesn't flash a console window. When the user runs us from cmd or
+	// PowerShell we still want stdout/stderr to land in their terminal —
+	// AttachConsole(ATTACH_PARENT_PROCESS) wires that up. No-op elsewhere.
+	attachToParentConsole()
+
 	// Inject our build version so the updater package can stamp it on the
 	// User-Agent header it sends to git.okcu.io.
 	updater.SetVersion(Version)