# DX11 DXGI monitors enumeration does not give full size for Dell P2715Q monitor

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I make DXGI adapters and monitors enumeration. The second monitor connected to my computer is Dell P2715Q, which has 3840*2160 resolution. However, the program reports it as 2560*1440, the second available resolution. Minimal code to reproduce:

#include "stdafx.h"
#include <Windows.h>
#include <stdio.h>
#include <tchar.h>
#include <iostream>
#include <DXGI.h>
#pragma comment(lib, "DXGI.lib")
using namespace std;

int main()
{
IDXGIFactory1* pFactory1;

HRESULT hr = CreateDXGIFactory1(__uuidof(IDXGIFactory1), (void**)(&pFactory1));

if (FAILED(hr))
{
wcout << L"CreateDXGIFactory1 failed. " << endl;
return 0;
}

for (UINT i = 0;; i++)
{

if (hr == DXGI_ERROR_NOT_FOUND)
{
break;
}

if (FAILED(hr))
{
wcout << L"EnumAdapters1 failed. " << endl;
return 0;
}

if (FAILED(hr))
{
wcout << L"GetDesc1 failed. " << endl;
return 0;
}

wcout << L"Adapter: " << desc.Description << endl;

for (UINT j = 0;; j++)
{
IDXGIOutput *pOutput = nullptr;

if (hr == DXGI_ERROR_NOT_FOUND)
{
// no more outputs
break;
}

if (FAILED(hr))
{
wcout << L"EnumOutputs failed. " << endl;
return 0;
}

DXGI_OUTPUT_DESC desc;

hr = pOutput->GetDesc(&desc);

if (FAILED(hr))
{
wcout << L"GetDesc1 failed. " << endl;
return 0;
}

wcout << L"  Output: " << desc.DeviceName <<
L"  (" << desc.DesktopCoordinates.left << L"," << desc.DesktopCoordinates.top << L")-(" <<
(desc.DesktopCoordinates.right - desc.DesktopCoordinates.left) << L"," <<
(desc.DesktopCoordinates.bottom - desc.DesktopCoordinates.top) << L")" << endl;

}
}

return 0;
}

Program output:

Adapter: Intel(R) Iris(TM) Pro Graphics 6200
Output: \\.\DISPLAY1  (0,0)-(1920,1200)
Output: \\.\DISPLAY2  (1920,0)-(2560,1440)

DISPLAY2 is reported with low resolution.

Environment:

Windows 10 x64

Intel(R) Iris(TM) Pro Graphics 6200

DELL P2715Q

What can cause this behavior: DirectX restrictions, video memory, display adapter, driver, monitor? How can I fix this and get full available resolution?

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Posted (edited)

The desktop coordinate are based on the actual resolution your monitor is set, not the physical capabilities. It may also be influenced by the DPI setting ( not sure on this one, DPI management in windows sucks ).

You have to call IDXGIOutput::GetDisplayModeList to obtain the list of supported modes.

EDIT: Confirmed, it is DPI dependent ( https://msdn.microsoft.com/en-us/library/windows/desktop/bb173068(v=vs.85).aspx ) :

DesktopCoordinates

Type: RECT

A RECT structure containing the bounds of the output in desktop coordinates. Desktop coordinates depend on the dots per inch (DPI) of the desktop. For info about writing DPI-aware Win32 apps, see High DPI.

Edited by galop1n

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galop1n, I played with DPI by using SetProcessDpiAwareness API and setting the text size to 100% in Windows Display Settings. This helped to solve the problem, thank you for pointing in right direction.

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I got onto the same problem and that's true it depends on DPI but there is a soluition to this:

		adapterOutput->GetDesc(&desc);
std::wcout << desc.DeviceName << std::endl;

std::cout << "Monitor X: " << desc.DesktopCoordinates.right - desc.DesktopCoordinates.left << std::endl;
std::cout << "Monitor Y: " << desc.DesktopCoordinates.bottom - desc.DesktopCoordinates.top << std::endl;

DEVMODE displayMode{};
displayMode.dmSize = sizeof(DEVMODE);

EnumDisplaySettings(desc.DeviceName, ENUM_CURRENT_SETTINGS, &displayMode);

float proc = (float)displayMode.dmPelsHeight / (desc.DesktopCoordinates.bottom - desc.DesktopCoordinates.top);
std::cout << "DPI percentage: " << proc << "\n";
std::cout << "Screen Start position: " << displayMode.dmPosition.x << " x " << displayMode.dmPosition.y << std::endl;

this is that simple, now you will know is it scaled or not and make proper code changes hope it helps

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Scaling Matrix:
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After Scaling

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