windows console fix

doc/thirdparty.txt

@@ -20,3 +20,8 @@ The licenses are included, and the authorship comments are left intact.
   https://github.com/getlantern/systray (commit:2c0986d) Apache 2.0
 
   removed golog dependency
+
+- fixconsole
+  https://github.com/apenwarr/fixconsole (commit:5a9f648) Apache 2.0
+
+  removed `w32` dependency

doc/todo.txt

@@ -1,6 +1,3 @@
 - feedlist keyboard navigation is flaky in "unread" section
-- windows cli mode not working
-  incorporate changes from:
-  https://github.com/apenwarr/fixconsole/blob/master/fixconsole_windows.go
 - make feed settings available in all filter modes
 - show `mark as read` in `all feeds` filter (along with numbers)

src/platform/fixconsole_default.go

@@ -0,0 +1,14 @@
+// +build !windows
+
+package platform
+
+// On non-windows platforms, we don't need to do anything. The console
+// starts off attached already, if it exists.
+
+func AttachConsole() error {
+	return nil
+}
+
+func FixConsoleIfNeeded() error {
+	return nil
+}

src/platform/fixconsole_windows.go

@@ -0,0 +1,131 @@
+package platform
+
+import (
+	"fmt"
+	"golang.org/x/sys/windows"
+	"os"
+	"syscall"
+)
+
+func AttachConsole() error {
+	const ATTACH_PARENT_PROCESS = ^uintptr(0)
+	proc := syscall.MustLoadDLL("kernel32.dll").MustFindProc("AttachConsole")
+	r1, _, err := proc.Call(ATTACH_PARENT_PROCESS)
+	if r1 == 0 {
+		errno, ok := err.(syscall.Errno)
+		if ok && errno == windows.ERROR_INVALID_HANDLE {
+			// console handle doesn't exist; not a real
+			// error, but the console handle will be
+			// invalid.
+			return nil
+		}
+		return err
+	} else {
+		return nil
+	}
+}
+
+var oldStdin, oldStdout, oldStderr *os.File
+
+// Windows console output is a mess.
+//
+// If you compile as "-H windows", then if you launch your program without
+// a console, Windows forcibly creates one to use as your stdin/stdout, which
+// is silly for a GUI app, so we can't do that.
+//
+// If you compile as "-H windowsgui", then it doesn't create a console for
+// your app... but also doesn't provide a working stdin/stdout/stderr even if
+// you *did* launch from the console.  However, you can use AttachConsole()
+// to get a handle to your parent process's console, if any, and then
+// os.NewFile() to turn that handle into a fd usable as stdout/stderr.
+//
+// However, then you have the problem that if you redirect stdout or stderr
+// from the shell, you end up ignoring the redirection by forcing it to the
+// console.
+//
+// To fix *that*, we have to detect whether there was a pre-existing stdout
+// or not. We can check GetStdHandle(), which returns 0 for "should be
+// console" and nonzero for "already pointing at a file."
+//
+// Be careful though!  As soon as you run AttachConsole(), it resets *all*
+// the GetStdHandle() handles to point them at the console instead, thus
+// throwing away the original file redirects.  So we have to GetStdHandle()
+// *before* AttachConsole().
+//
+// For some reason, powershell redirections provide a valid file handle, but
+// writing to that handle doesn't write to the file.  I haven't found a way
+// to work around that.  (Windows 10.0.17763.379)
+//
+// Net result is as follows.
+// Before:
+//    SHELL            NON-REDIRECTED     REDIRECTED
+//    explorer.exe     no console         n/a
+//    cmd.exe          broken             works
+//    powershell       broken             broken
+//    WSL bash         broken             works
+// After
+//    SHELL            NON-REDIRECTED     REDIRECTED
+//    explorer.exe     no console         n/a
+//    cmd.exe          works              works
+//    powershell       works              broken
+//    WSL bash         works              works
+//
+// We don't seem to make anything worse, at least.
+func FixConsoleIfNeeded() error {
+	// Retain the original console objects, to prevent Go from automatically
+	// closing their file descriptors when they get garbage collected.
+	// You never want to close file descriptors 0, 1, and 2.
+	oldStdin, oldStdout, oldStderr = os.Stdin, os.Stdout, os.Stderr
+
+	stdin, _ := syscall.GetStdHandle(syscall.STD_INPUT_HANDLE)
+	stdout, _ := syscall.GetStdHandle(syscall.STD_OUTPUT_HANDLE)
+	stderr, _ := syscall.GetStdHandle(syscall.STD_ERROR_HANDLE)
+
+	var invalid syscall.Handle
+	con := invalid
+
+	if stdin == invalid || stdout == invalid || stderr == invalid {
+		err := AttachConsole()
+		if err != nil {
+			return fmt.Errorf("attachconsole: %v", err)
+		}
+
+		if stdin == invalid {
+			stdin, _ = syscall.GetStdHandle(syscall.STD_INPUT_HANDLE)
+		}
+		if stdout == invalid {
+			stdout, _ = syscall.GetStdHandle(syscall.STD_OUTPUT_HANDLE)
+			con = stdout
+		}
+		if stderr == invalid {
+			stderr, _ = syscall.GetStdHandle(syscall.STD_ERROR_HANDLE)
+			con = stderr
+		}
+	}
+
+	if con != invalid {
+		// Make sure the console is configured to convert
+		// \n to \r\n, like Go programs expect.
+		h := windows.Handle(con)
+		var st uint32
+		err := windows.GetConsoleMode(h, &st)
+		if err != nil {
+			return fmt.Errorf("GetConsoleMode: %v", err)
+		}
+		err = windows.SetConsoleMode(h, st&^windows.DISABLE_NEWLINE_AUTO_RETURN)
+		if err != nil {
+			return fmt.Errorf("SetConsoleMode: %v", err)
+		}
+	}
+
+	if stdin != invalid {
+		os.Stdin = os.NewFile(uintptr(stdin), "stdin")
+	}
+	if stdout != invalid {
+		os.Stdout = os.NewFile(uintptr(stdout), "stdout")
+	}
+	if stderr != invalid {
+		os.Stderr = os.NewFile(uintptr(stderr), "stderr")
+	}
+	return nil
+}