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Date: Sat, 11 Jan 2020 01:42:03 +0800
From: mural <mural@ctli.io>
To: "Elias Naur" <mail@eliasnaur.com>, ~eliasnaur/gio-patches@lists.sr.ht
Subject: Re: [gio] app/internal/log: add logger for Windows DebugView
Content-Type: text/plain

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
> 
>