Get the title of the current active Window/Document in Mac OS X

In Objective-C, the short answer, using a little Cocoa and mostly the Carbon Accessibility API is:

// Get the process ID of the frontmost application.
NSRunningApplication* app = [[NSWorkspace sharedWorkspace]
                              frontmostApplication];
pid_t pid = [app processIdentifier];

// See if we have accessibility permissions, and if not, prompt the user to
// visit System Preferences.
NSDictionary *options = @{(id)kAXTrustedCheckOptionPrompt: @YES};
Boolean appHasPermission = AXIsProcessTrustedWithOptions(
                             (__bridge CFDictionaryRef)options);
if (!appHasPermission) {
   return; // we don't have accessibility permissions

// Get the accessibility element corresponding to the frontmost application.
AXUIElementRef appElem = AXUIElementCreateApplication(pid);
if (!appElem) {
  return;
}

// Get the accessibility element corresponding to the frontmost window
// of the frontmost application.
AXUIElementRef window = NULL;
if (AXUIElementCopyAttributeValue(appElem, 
      kAXFocusedWindowAttribute, (CFTypeRef*)&window) != kAXErrorSuccess) {
  CFRelease(appElem);
  return;
}

// Finally, get the title of the frontmost window.
CFStringRef title = NULL;
AXError result = AXUIElementCopyAttributeValue(window, kAXTitleAttribute,
                   (CFTypeRef*)&title);

// At this point, we don't need window and appElem anymore.
CFRelease(window);
CFRelease(appElem);

if (result != kAXErrorSuccess) {
  // Failed to get the window title.
  return;
}

// Success! Now, do something with the title, e.g. copy it somewhere.

// Once we're done with the title, release it.
CFRelease(title);

Alternatively, it may be simpler to use the CGWindow API, as alluded to in this StackOverflow answer.

refered to https://stackoverflow.com/a/23451568/11185460

package main

/*
#cgo CFLAGS: -x objective-c
#cgo LDFLAGS: -framework Cocoa
#import <Cocoa/Cocoa.h>

int
GetFrontMostAppPid(void){
    NSRunningApplication* app = [[NSWorkspace sharedWorkspace]
                                  frontmostApplication];
    pid_t pid = [app processIdentifier];
    return pid;
}

CFStringRef
GetAppTitle(pid_t pid) {
    CFStringRef title = NULL;
    // Get the process ID of the frontmost application.
    //  NSRunningApplication* app = [[NSWorkspace sharedWorkspace]
    //                                frontmostApplication];
    //  pid_t pid = [app processIdentifier];

    // See if we have accessibility permissions, and if not, prompt the user to
    // visit System Preferences.
    NSDictionary *options = @{(id)kAXTrustedCheckOptionPrompt: @YES};
    Boolean appHasPermission = AXIsProcessTrustedWithOptions(
                                 (__bridge CFDictionaryRef)options);
    if (!appHasPermission) {
       return title; // we don't have accessibility permissions
    }
    // Get the accessibility element corresponding to the frontmost application.
    AXUIElementRef appElem = AXUIElementCreateApplication(pid);
    if (!appElem) {
      return title;
    }

    // Get the accessibility element corresponding to the frontmost window
    // of the frontmost application.
    AXUIElementRef window = NULL;
    if (AXUIElementCopyAttributeValue(appElem,
          kAXFocusedWindowAttribute, (CFTypeRef*)&window) != kAXErrorSuccess) {
      CFRelease(appElem);
      return title;
    }

    // Finally, get the title of the frontmost window.
    AXError result = AXUIElementCopyAttributeValue(window, kAXTitleAttribute,
                       (CFTypeRef*)&title);

    // At this point, we don't need window and appElem anymore.
    CFRelease(window);
    CFRelease(appElem);

    if (result != kAXErrorSuccess) {
      // Failed to get the window title.
      return title;
    }

    // Success! Now, do something with the title, e.g. copy it somewhere.

    // Once we're done with the title, release it.
    CFRelease(title);

    return title;
}
static inline CFIndex cfstring_utf8_length(CFStringRef str, CFIndex *need) {
  CFIndex n, usedBufLen;
  CFRange rng = CFRangeMake(0, CFStringGetLength(str));
  return CFStringGetBytes(str, rng, kCFStringEncodingUTF8, 0, 0, NULL, 0, need);
}
*/
import "C"
import (
    "github.com/shirou/gopsutil/v3/process"
    "reflect"
    "unsafe"
)

//import "github.com/shirou/gopsutil/v3/process"
func cfstringGo(cfs C.CFStringRef) string {
    var usedBufLen C.CFIndex
    n := C.cfstring_utf8_length(cfs, &usedBufLen)
    if n <= 0 {
        return ""
    }
    rng := C.CFRange{location: C.CFIndex(0), length: n}
    buf := make([]byte, int(usedBufLen))

    bufp := unsafe.Pointer(&buf[0])
    C.CFStringGetBytes(cfs, rng, C.kCFStringEncodingUTF8, 0, 0, (*C.UInt8)(bufp), C.CFIndex(len(buf)), &usedBufLen)

    sh := &reflect.StringHeader{
        Data: uintptr(bufp),
        Len:  int(usedBufLen),
    }
    return *(*string)(unsafe.Pointer(sh))
}

func main() {
    pid := C.GetFrontMostAppPid()

    ps, _ := process.NewProcess(int32(pid))
    title_ref := C.CFStringRef(C.GetAppTitle(pid))

    println(pid) // pid
    println(ps.Name()) // process name
    println(cfstringGo(title_ref)) // active window title
}

I then found this property wont change after it is called.
By this, only after we implement NSWorkspaceDidActivateApplicationNotification, we can monitor the change of activity window. But I didn’t find any solution which can implement NSWorkspaceDidActivateApplicationNotification in golang.

A workaround method is compile one go program and call it by another go program. I then try full Objective-C code in here

To get the active application:

➜ osascript -e 'tell application "System Events" to tell (first process whose frontmost is true) to return name'

To get the active window’s title:

➜ osascript -e 'tell application "System Events" to tell (first process whose frontmost is true) to return name of window 1'

And to get both (to avoid a race condition where the user changes windows between the two calls):

➜ osascript -e 'tell application "System Events" to tell (first process whose frontmost is true) to return {name, name of window 1}'

Source: https://forum.keyboardmaestro.com/t/how-do-i-get-the-name-of-the-frontmost-window/2711/2