From 0bc5b39f1034971917c5331c6e0975f9fe1c6926 Mon Sep 17 00:00:00 2001
From: ShuheiKubota <kubota.shuhei+github@gmail.com>
Date: Sun, 10 Nov 2019 09:48:51 +0900
Subject: [PATCH] add: alpha command

---
 go.sum  |  1 +
 vvin.go | 33 +++++++++++++++++++++++++++++++++
 2 files changed, 34 insertions(+)

diff --git a/go.sum b/go.sum
index ff92e53..e9c5162 100644
--- a/go.sum
+++ b/go.sum
@@ -7,6 +7,7 @@ github.com/shu-go/cliparser v0.0.0-20190822025044-17b54d2ae1aa/go.mod h1:b89EpZS
 github.com/shu-go/clise v0.0.0-20190822023516-79849fb81cfe/go.mod h1:VLiMEzXMBozBLD37i3id3qPflaupus48v/979ipQ43s=
 github.com/shu-go/gli v0.0.0-20191003020935-c6817caa1c0a h1:N7WMOChI8J5Dx22ZNbg4xaogju9gKARbjWmNaLo5irM=
 github.com/shu-go/gli v0.0.0-20191003020935-c6817caa1c0a/go.mod h1:F0pECDJ/7sP7e6/BlCGNScgK3O3dOLo/0d8CeH1Z7Ks=
+github.com/shu-go/gotwant v0.0.0-20190822031422-724391433f13 h1:ny9pVZ7fzuKapDWhfcQwVD5XtO/WUqYDt3BeOgbj+3o=
 github.com/shu-go/gotwant v0.0.0-20190822031422-724391433f13/go.mod h1:UxvcvxZEQUBw6lS9UgXOPh1outjvx2+bvDlEOpCTuGo=
 github.com/shu-go/rog v0.0.0-20190826055139-09f31aeaaebd h1:4HEm7TeZfpMp8mrjUoRt0MxTCvJrakuRn3rSbOSOBqE=
 github.com/shu-go/rog v0.0.0-20190826055139-09f31aeaaebd/go.mod h1:z2vjwV5lUEhVBjFneBZQECuBiel1kmKuU0sVJCwysDY=
diff --git a/vvin.go b/vvin.go
index 27cf2b7..53832ed 100644
--- a/vvin.go
+++ b/vvin.go
@@ -33,6 +33,7 @@ type globalCmd struct {
 	Maximize maxCmd     `cli:"maximize,max"`
 	Restore  restoreCmd `cli:"restore"`
 	Resize   resizeCmd  `cli:"resize,move,mv"`
+	Alpha    alphaCmd   `cli:"alpha"`
 
 	targetHandle syscall.Handle
 
@@ -171,6 +172,28 @@ func (c resizeCmd) Run(g globalCmd) {
 	}
 }
 
+type alphaCmd struct {
+}
+
+func (c alphaCmd) Run(args []string, g globalCmd) error {
+	if len(args) != 1 {
+		return errors.New("an argument is required")
+	}
+
+	alpha := toInt(args[0], 255)
+
+	style, _, _ := getWindowLong.Call(uintptr(g.targetHandle), GWL_EXSTYLE)
+	setWindowLong.Call(uintptr(g.targetHandle), GWL_EXSTYLE, style|WS_EX_LAYERED)
+
+	if alpha == 255 {
+		setWindowLong.Call(uintptr(g.targetHandle), GWL_EXSTYLE, style&^WS_EX_LAYERED)
+	} else {
+		setLayeredWindowAttributes.Call(uintptr(g.targetHandle), 0, uintptr(alpha), LWA_ALPHA)
+	}
+
+	return nil
+}
+
 func main() {
 	app := gli.NewWith(&globalCmd{})
 	app.Name = "vvin"
@@ -193,6 +216,10 @@ var (
 	setWindowPos             = user32.NewProc("SetWindowPos")
 	getWindowRect            = user32.NewProc("GetWindowRect")
 	getSystemMetrics         = user32.NewProc("GetSystemMetrics")
+
+	setLayeredWindowAttributes = user32.NewProc("SetLayeredWindowAttributes")
+	getWindowLong              = user32.NewProc("GetWindowLongW")
+	setWindowLong              = user32.NewProc("SetWindowLongW")
 )
 
 const (
@@ -210,6 +237,12 @@ const (
 	SM_CYVIRTUALSCREEN = 79
 	SM_CXSIZEFRAME     = 32
 	SM_CYSIZEFRAME     = 33
+
+	GWL_EXSTYLE      = 0xFFFFFFEC
+	WS_EX_TOOLWINDOW = 0x00000080
+	WS_EX_LAYERED    = 0x80000
+
+	LWA_ALPHA = 0x2
 )
 
 type (