I want to create a tool with Go that lets me resize multiple windows on my screen. As an example lets assume that I want to find my Firefox window and my Atom (text editor) window and place them, so that they take up exactly half of my screen (FF left, Atom right).
So far I realized, that I need to use the Windows API for that. I created a method that gives me all handles and the titles of all windows, but I'm struggling with geometry information. I understand that the api call GetWindowRect
will help, but how can I get the information out of a pointer to a rect?
Follow up question 1: what other information can I get about the windows? Follow up question 2: How do I resize the window so that it takes exactly half my screen size? I guess, I need another call to get the monitor dimensions.
What I have so far is the code below. The main program finds all handles and displays those containing 'Atom' in the title. The windows package contains the code accessing the windows API.
My current result is that I get 2 handles for atom (why not just 1?). I guess, I have to learn more about the Windows API, too. Are there good summaries to understand the basics?
main.go:
package main
import (
"resizer/windows"
"fmt"
"log"
"strings"
)
func main() {
const title = "Atom"
m := windows.GetAllWindows()
fmt.Printf("Map of windows:
")
for handle := range m {
if strings.Contains(m[handle].Title(), title) {
fmt.Printf("'%v'
", m[handle])
}
}
}
windows.go:
package windows
import (
"fmt"
"log"
"syscall"
"unsafe"
)
var (
user32 = syscall.MustLoadDLL("user32.dll")
procEnumWindows = user32.MustFindProc("EnumWindows")
procGetWindowTextW = user32.MustFindProc("GetWindowTextW")
)
// Window represents any Window that is opened in the Windows OS
type Window struct {
handle syscall.Handle
title string
}
// Title returns the title of the window
func (w Window) Title() string {
return w.title
}
// GetAllWindows finds all currently opened windows
func GetAllWindows() map[syscall.Handle]Window {
m := make(map[syscall.Handle]Window)
cb := syscall.NewCallback(func(h syscall.Handle, p uintptr) uintptr {
bytes := make([]uint16, 200)
_, err := GetWindowText(h, &bytes[0], int32(len(bytes)))
title := "||| no title found |||"
if err == nil {
title = syscall.UTF16ToString(bytes)
}
m[h] = Window{h, title}
return 1 // continue enumeration
})
EnumWindows(cb, 0)
return m
}
// EnumWindows loops through all windows and calls a callback function on each
func EnumWindows(enumFunc uintptr, lparam uintptr) (err error) {
r1, _, e1 := syscall.Syscall(procEnumWindows.Addr(), 2, uintptr(enumFunc), uintptr(lparam), 0)
if r1 == 0 {
if e1 != 0 {
err = error(e1)
} else {
err = syscall.EINVAL
}
}
return
}
// GetWindowText gets the title of a Window given by a certain handle
func GetWindowText(hwnd syscall.Handle, str *uint16, maxCount int32) (len int32, err error) {
r0, _, e1 := syscall.Syscall(procGetWindowTextW.Addr(), 3, uintptr(hwnd), uintptr(unsafe.Pointer(str)), uintptr(maxCount))
len = int32(r0)
if len == 0 {
if e1 != 0 {
err = error(e1)
} else {
err = syscall.EINVAL
}
}
return
}