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In-Reply-To: <20200110144548.34087-1-mural@ctli.io>
Date: Fri, 10 Jan 2020 18:10:50 +0100
Subject: Re: [gio] app/internal/log: add logger for Windows DebugView
From: "Elias Naur" <mail@eliasnaur.com>
To: "mural" <mural@ctli.io>, <~eliasnaur/gio-patches@lists.sr.ht>
Cc: "mural" <mural@ctli.io>
Message-Id: <BZSA0XKTYNO0.1A2TNG8GE6WTU@toolbox>

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_windo=
ws.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           =3D syscall.NewLazyDLL("kernel32")
> +	outputDebugStringW =3D 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 !=3D syscall.InvalidHandle {

Did you test the change? From my manual testing, syscall.Stderr
is never equal to syscall.InvalidHandle when building with
`-ldflags=3D"-H windowsgui"`.

Regardless, you shouldn't set the logger to os.Stderr here. Just
leave it alone and return early.

> +		out =3D os.Stderr
> +	} else {
> +		out =3D debugView
> +	}
> +	log.SetOutput(out)
> +}
> +
> +func (l *logger) Write(buf []byte) (int, error) {
> +	p, err :=3D syscall.UTF16PtrFromString(string(buf))
> +	if err !=3D nil {
> +		return 0, err
> +	}
> +	outputDebugStringW.Call(uintptr(unsafe.Pointer(p)))
> +	return len(buf), nil
> +}
> --=20
> 2.19.1