How to tell if game is running in fullscreen and borderless window

I have a simple AutoHotkey script that will force this mode for me. The script removes the window border and title bar of any window, and moves the window so that it fills the screen:

^!f::
WinGetTitle, currentWindow, A
IfWinExist %currentWindow%
{
    WinSet, Style, ^0xC00000 ; toggle title bar
    WinMove, , , 0, 0, 1920, 1080
}
return

The hotkey this creates is Control+Alt+f. It applies changes to whatever window has focus. If you wanted to use this script, all you'd need to do is:

1. Install AutoHotkey
2. Copy the script to a text file and name it something like MaxFull.ahk
3. Right click on your new script and use Run as Administrator.
   

Note that you'll need to have your game in windowed mode, set to your desktop's resolution. Also change "1920, 1080" to whatever your resolution is. Press the hotkey and bam! Maximized Fullscreen goodness. It even toggles back and forth if you press the hotkey again.

While the hotkey works on many games that I've played, some games are stubborn and don't want the window border removed. In that case, I have another hotkey that is a bit more forceful.

^!g::
WinGetTitle, currentWindow, A
IfWinExist %currentWindow%
{
   WinSet, Style, -0xC00000 ; hide title bar
   WinSet, Style, -0x800000 ; hide thin-line border
   WinSet, Style, -0x400000 ; hide dialog frame
   WinSet, Style, -0x40000 ; hide thickframe/sizebox
   WinMove, , , 0, 0, 1920, 1080
}   
return

Simply append this to the previous script to enable the hotkey Control+Alt+g.

Update: Some games also use a 0x40000 "ThickFrame" style, which the script wasn't removing until now. See the AutoHotkey documentation for a list of styles that can be removed.

To answer your question: no. Not a "good" way. Borderless mode, or Fullscreen Windowed mode as you call it, will fun the game as "fullscreen", though as a borderless window application. said window is not re-sizable. An adequate solution would be to open a completely black picture to have underneath a regularly windowed game, and set the resolution on said game lower. You will have the border from the game, and you'll have to open a picture every time you wanna game though (plus, it's another thing to have to keep in front of your browser and such after browsing something). Personally, I have yet to play a game that allows resizing of the rendered area in the game window at all, much less re-sizable borderless windows.