Signed-off-by: mural <mural@ctli.io>
---
 app/internal/log/log_windows.go | 41 +++++++++++++++++++++++++++++++++
 1 file changed, 41 insertions(+)
 create mode 100644 app/internal/log/log_windows.go

diff --git a/app/internal/log/log_windows.go b/app/internal/log/log_windows.go
new file mode 100644
index 0000000..2019bcd
--- /dev/null
+++ b/app/internal/log/log_windows.go
@@ -0,0 +1,41 @@
+// SPDX-License-Identifier: Unlicense OR MIT
+
+package log
+
+import (
+	"io"
+	"log"
+	"os"
+	"syscall"
+	"unsafe"
+)
+
+type logger struct{}
+
+var (
+	kernel32           = syscall.NewLazyDLL("kernel32")
+	outputDebugStringW = kernel32.NewProc("OutputDebugStringW")
+	debugView          *logger
+)
+
+func init() {
+	// Windows DebugView already includes timestamps.
+	log.SetFlags(log.Flags() &^ log.LstdFlags)
+
+	var out io.Writer
+	if syscall.Stderr != syscall.InvalidHandle {
+		out = os.Stderr
+	} else {
+		out = debugView
+	}
+	log.SetOutput(out)
+}
+
+func (l *logger) Write(buf []byte) (int, error) {
+	p, err := syscall.UTF16PtrFromString(string(buf))
+	if err != nil {
+		return 0, err
+	}
+	outputDebugStringW.Call(uintptr(unsafe.Pointer(p)))
+	return len(buf), nil
+}
-- 
2.19.1

On Fri Jan 10, 2020 at 22:45, mural wrote:
> Signed-off-by: mural <mural@ctli.io>
> ---
>  app/internal/log/log_windows.go | 41 +++++++++++++++++++++++++++++++++
>  1 file changed, 41 insertions(+)
>  create mode 100644 app/internal/log/log_windows.go
>
> diff --git a/app/internal/log/log_windows.go b/app/internal/log/log_windows.go
> new file mode 100644
> index 0000000..2019bcd
> --- /dev/null
> +++ b/app/internal/log/log_windows.go
> @@ -0,0 +1,41 @@
> +// SPDX-License-Identifier: Unlicense OR MIT
> +
> +package log
> +
> +import (
> +	"io"
> +	"log"
> +	"os"
> +	"syscall"
> +	"unsafe"
> +)
> +
> +type logger struct{}
> +
> +var (
> +	kernel32           = syscall.NewLazyDLL("kernel32")
> +	outputDebugStringW = kernel32.NewProc("OutputDebugStringW")
> +	debugView          *logger
> +)
> +
> +func init() {
> +	// Windows DebugView already includes timestamps.
> +	log.SetFlags(log.Flags() &^ log.LstdFlags)
> +
> +	var out io.Writer
> +	if syscall.Stderr != syscall.InvalidHandle {

Did you test the change? From my manual testing, syscall.Stderr
is never equal to syscall.InvalidHandle when building with
`-ldflags="-H windowsgui"`.

Regardless, you shouldn't set the logger to os.Stderr here. Just
leave it alone and return early.

> +		out = os.Stderr
> +	} else {
> +		out = debugView
> +	}
> +	log.SetOutput(out)
> +}
> +
> +func (l *logger) Write(buf []byte) (int, error) {
> +	p, err := syscall.UTF16PtrFromString(string(buf))
> +	if err != nil {
> +		return 0, err
> +	}
> +	outputDebugStringW.Call(uintptr(unsafe.Pointer(p)))
> +	return len(buf), nil
> +}
> -- 
> 2.19.1

It's strange that I was struggling with git-send-email and
still couldn't figure out how to make it work on macOS before going to bed. 
I thought no emails were sent successfully. (I managed to use the web interface of sr.ht before this one)

On Sat, Jan 11, 2020, at 1:10 AM, Elias Naur wrote:
> On Fri Jan 10, 2020 at 22:45, mural wrote:
> > Signed-off-by: mural <mural@ctli.io>
> > ---
> >  app/internal/log/log_windows.go | 41 +++++++++++++++++++++++++++++++++
> >  1 file changed, 41 insertions(+)
> >  create mode 100644 app/internal/log/log_windows.go
> >
> > diff --git a/app/internal/log/log_windows.go b/app/internal/log/log_windows.go
> > new file mode 100644
> > index 0000000..2019bcd
> > --- /dev/null
> > +++ b/app/internal/log/log_windows.go
> > @@ -0,0 +1,41 @@
> > +// SPDX-License-Identifier: Unlicense OR MIT
> > +
> > +package log
> > +
> > +import (
> > +	"io"
> > +	"log"
> > +	"os"
> > +	"syscall"
> > +	"unsafe"
> > +)
> > +
> > +type logger struct{}
> > +
> > +var (
> > +	kernel32           = syscall.NewLazyDLL("kernel32")
> > +	outputDebugStringW = kernel32.NewProc("OutputDebugStringW")
> > +	debugView          *logger
> > +)
> > +
> > +func init() {
> > +	// Windows DebugView already includes timestamps.
> > +	log.SetFlags(log.Flags() &^ log.LstdFlags)
> > +
> > +	var out io.Writer
> > +	if syscall.Stderr != syscall.InvalidHandle {
> 
> Did you test the change? From my manual testing, syscall.Stderr
No. I don't have a Windows dev environment at the moment.
I will find one at my home or wait until next weekday at the workspace.

It looks that this approach does not work.

> is never equal to syscall.InvalidHandle when building with
> `-ldflags="-H windowsgui"`.
> 
> Regardless, you shouldn't set the logger to os.Stderr here. Just
> leave it alone and return early.
Ah, understood.
I will revise the patch tomorrow.

> 
> > +		out = os.Stderr
> > +	} else {
> > +		out = debugView
> > +	}
> > +	log.SetOutput(out)
> > +}
> > +
> > +func (l *logger) Write(buf []byte) (int, error) {
> > +	p, err := syscall.UTF16PtrFromString(string(buf))
> > +	if err != nil {
> > +		return 0, err
> > +	}
> > +	outputDebugStringW.Call(uintptr(unsafe.Pointer(p)))
> > +	return len(buf), nil
> > +}
> > -- 
> > 2.19.1
> 
>

Signed-off-by: mural <mural@ctli.io>
---
According to
https://docs.microsoft.com/en-us/windows/console/getstdhandle,
GetStdHandle would return NULL if there is no associated standard handles.
So we chack 0 as well.

 app/internal/log/log_windows.go | 34 +++++++++++++++++++++++++++++++++
 1 file changed, 34 insertions(+)
 create mode 100644 app/internal/log/log_windows.go

diff --git a/app/internal/log/log_windows.go b/app/internal/log/log_windows.go
new file mode 100644
index 0000000..0642919
--- /dev/null
+++ b/app/internal/log/log_windows.go
@@ -0,0 +1,34 @@
+// SPDX-License-Identifier: Unlicense OR MIT
+
+package log
+
+import (
+	"log"
+	"syscall"
+	"unsafe"
+)
+
+type logger struct{}
+
+var (
+	kernel32           = syscall.NewLazyDLL("kernel32")
+	outputDebugStringW = kernel32.NewProc("OutputDebugStringW")
+	debugView          *logger
+)
+
+func init() {
+	// Windows DebugView already includes timestamps.
+	if syscall.Stderr == 0 || syscall.Stderr == syscall.InvalidHandle {
+		log.SetFlags(log.Flags() &^ log.LstdFlags)
+		log.SetOutput(debugView)
+	}
+}
+
+func (l *logger) Write(buf []byte) (int, error) {
+	p, err := syscall.UTF16PtrFromString(string(buf))
+	if err != nil {
+		return 0, err
+	}
+	outputDebugStringW.Call(uintptr(unsafe.Pointer(p)))
+	return len(buf), nil
+}
-- 
2.24.1

On Mon Jan 13, 2020 at 7:43 PM, mural wrote:
> Signed-off-by: mural <mural@ctli.io>
> ---
> According to
> https://docs.microsoft.com/en-us/windows/console/getstdhandle,
> GetStdHandle would return NULL if there is no associated standard
> handles.
> So we chack 0 as well.
>
> 
> app/internal/log/log_windows.go | 34 +++++++++++++++++++++++++++++++++
> 1 file changed, 34 insertions(+)
> create mode 100644 app/internal/log/log_windows.go
>
> 
> diff --git a/app/internal/log/log_windows.go
> b/app/internal/log/log_windows.go
> new file mode 100644
> index 0000000..0642919
> --- /dev/null
> +++ b/app/internal/log/log_windows.go
> @@ -0,0 +1,34 @@
> + // Windows DebugView already includes timestamps.
> + if syscall.Stderr == 0 || syscall.Stderr == syscall.InvalidHandle {

Your commit message implies that 0 is returned for unattached I/O. If
so, please remove the InvalidHandle check which will only confuse future
readers.

Signed-off-by: mural <mural@ctli.io>
---
Please take a look.

 app/internal/log/log_windows.go | 34 +++++++++++++++++++++++++++++++++
 1 file changed, 34 insertions(+)
 create mode 100644 app/internal/log/log_windows.go

diff --git a/app/internal/log/log_windows.go b/app/internal/log/log_windows.go
new file mode 100644
index 0000000..13c5fe4
--- /dev/null
+++ b/app/internal/log/log_windows.go
@@ -0,0 +1,34 @@
+// SPDX-License-Identifier: Unlicense OR MIT
+
+package log
+
+import (
+	"log"
+	"syscall"
+	"unsafe"
+)
+
+type logger struct{}
+
+var (
+	kernel32           = syscall.NewLazyDLL("kernel32")
+	outputDebugStringW = kernel32.NewProc("OutputDebugStringW")
+	debugView          *logger
+)
+
+func init() {
+	// Windows DebugView already includes timestamps.
+	if syscall.Stderr == 0 {
+		log.SetFlags(log.Flags() &^ log.LstdFlags)
+		log.SetOutput(debugView)
+	}
+}
+
+func (l *logger) Write(buf []byte) (int, error) {
+	p, err := syscall.UTF16PtrFromString(string(buf))
+	if err != nil {
+		return 0, err
+	}
+	outputDebugStringW.Call(uintptr(unsafe.Pointer(p)))
+	return len(buf), nil
+}
-- 
2.24.1

Thanks, applied.