How to get the display names of multiple monitors with the Win32 API?

Question

I have two monitors connected to my Windows PC -- one is a normal monitor and the other is a projector. Because Windows doesn't consistently assign one or the other as the primary monitor (in part because they aren't always both on when Windows boots), I need to programmatically detect which monitor is which.

The Control Panel shows the names of the monitors as "HP 2159" (the normal monitor) and "PROJECTOR" in the screen where you choose which is the primary monitor. That's the information I want to get in my program.

I can't find the right Win32 API function for this info. I've tried both EnumDisplayDevices and EnumDisplayMontiors. Both just give "DISPLAY1" and "DISPLAY2" as devices names. What should I be using to get the "HP 2159" and "PROJECTOR" info or something analogous?

UPDATE: Here's the Python code I'm using:

>>> import win32api
>>> monitors = win32api.EnumDisplayMonitors()
>>> win32api.GetMonitorInfo(monitors[0][0])
{'Device': '\\\\.\\DISPLAY1', 'Work': (0, 0, 1920, 1080), 'Flags': 1, 'Monitor': (0, 0, 1920, 1080)}
>>> win32api.GetMonitorInfo(monitors[1][0])
{'Device': '\\\\.\\DISPLAY2', 'Work': (1920, 0, 3360, 1080), 'Flags': 0, 'Monitor': (1920, 0, 3360, 1080)}

Post your code. The method I outline in my answer has always worked for me. — Jim Mischel
– Jim Mischel, Commented Mar 29, 2014 at 2:43
@Jim Mischel - see the Python code (accessing the Win32 API via the win32api PyWin library). Maybe it's something wrong with the PyWin implementation of the API? — Ghopper21
– Ghopper21, Commented Apr 1, 2014 at 2:09
Perhaps somebody else can help you with it. I'm not a Python programmer, and I know nothing about PyWin. — Jim Mischel
– Jim Mischel, Commented Apr 1, 2014 at 2:35
It occurs to me that the problem could be that when PyWin calls GetMonitorInfo, it's passing a MonitorInfo structure rather than a MonitorInfoEx. I don't know if that's the actual behavior, but that behavior would explain the results you're seeing. — Jim Mischel
– Jim Mischel, Commented Apr 1, 2014 at 13:38
Although a quick look at the source, bitbucket.org/amauryfa/pywin32-pypy/src/0d23a353509b/win32/src/…, leads me to believe that PyWin is doing the right thing. — Jim Mischel
– Jim Mischel, Commented Apr 1, 2014 at 13:46

Andrew Truckle · Accepted Answer · 2022-06-17 09:11:44Z

7

The EnumDisplayMonitors passes a monitor handle to the MonitorEnumProc callback function. You can pass that handle to GetMonitorInfo, being sure to pass a pointer to a MonitorInfoEx structure and setting the cbSize member accordingly.

Upon return, the szDevice field in the MonitorInfoEx structure will contain the name of the monitor.

edited Jun 17, 2022 at 9:11

Andrew Truckle

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answered Mar 28, 2014 at 23:35

Jim Mischel

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2 Comments

Ghopper21 Over a year ago

Afraid this isn't working for me -- that's what I've already tried, and I get the same "DISPLAY1" and "DISPLAY2" as names.

Adrian McCarthy Over a year ago

This is not a PyWin issue, as you get the same behavior directly from the C API. You can use EnumDisplayDevices to get the monitor names, but the projector for me is just named "Generic PnP Monitor" and yet the control panel applet shows it as PROJECTOR as the OP explains.

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