How to Get the Current DPI Scaling Setting in Batch Script

@echo off
setlocal enabledelayedexpansion

echo Reading DPI Scaling Setting...
echo ==============================

:: Try AppliedDPI first (Windows 10/11 preferred)
set "dpi="
for /f "tokens=2*" %%A in ('reg query "HKCU\Control Panel\Desktop\WindowMetrics" /v AppliedDPI 2^>nul ^| findstr /i "REG_DWORD"') do set "dpi=%%B"

:: Fallback to LogPixels if AppliedDPI not found
if not defined dpi (
    for /f "tokens=2*" %%A in ('reg query "HKCU\Control Panel\Desktop" /v LogPixels 2^>nul ^| findstr /i "REG_DWORD"') do set "dpi=%%B"
)

if not defined dpi (
    echo [INFO] No DPI override found. System is likely at default 100%% ^(96 DPI^).
    set "dpi=0x60"
)

:: Convert hex to decimal using set /a (handles 0x prefix natively)
set /a "dpi_dec=!dpi!"

:: Calculate the scaling percentage
set /a "scale_pct=(!dpi_dec! * 100) / 96"

echo Raw DPI Value:      !dpi! ^(!dpi_dec! decimal^)
echo Scaling Percentage: !scale_pct!%%

pause

@echo off
setlocal enabledelayedexpansion

echo Retrieving System DPI via Windows API...
echo =========================================
echo.

set "dpi_x="
set "dpi_y="
set "scale="

:: Write the PowerShell script to a temp file to avoid cmd escaping issues
set "ps_script=%TEMP%\get_dpi_%RANDOM%.ps1"

> "!ps_script!" (
    echo Add-Type -TypeDefinition @'
    echo using System;
    echo using System.Runtime.InteropServices;
    echo public class DPIHelper {
    echo     [DllImport^("user32.dll"^)]
    echo     public static extern IntPtr GetDC^(IntPtr hwnd^);
    echo     [DllImport^("gdi32.dll"^)]
    echo     public static extern int GetDeviceCaps^(IntPtr hdc, int nIndex^);
    echo     [DllImport^("user32.dll"^)]
    echo     public static extern int ReleaseDC^(IntPtr hwnd, IntPtr hdc^);
    echo }
    echo '@
    echo $hdc = [DPIHelper]::GetDC^([IntPtr]::Zero^)
    echo $dpiX = [DPIHelper]::GetDeviceCaps^($hdc, 88^)
    echo $dpiY = [DPIHelper]::GetDeviceCaps^($hdc, 90^)
    echo [void][DPIHelper]::ReleaseDC^([IntPtr]::Zero, $hdc^)
    echo $scale = [math]::Round^(^($dpiX / 96^) * 100^)
    echo Write-Output "DpiX=$dpiX"
    echo Write-Output "DpiY=$dpiY"
    echo Write-Output "Scale=$scale"
)

for /f "tokens=1* delims==" %%A in ('powershell -NoProfile -ExecutionPolicy Bypass -File "!ps_script!" 2^>nul') do (
    if "%%A"=="DpiX" set "dpi_x=%%B"
    if "%%A"=="DpiY" set "dpi_y=%%B"
    if "%%A"=="Scale" set "scale=%%B"
)

del "!ps_script!" 2>nul

if not defined dpi_x (
    echo [ERROR] Could not retrieve DPI information via Windows API.
    pause
    exit /b 1
)

echo Primary Display DPI: !dpi_x! x !dpi_y!
echo Scaling Percentage:  !scale!%%

pause

@echo off
setlocal

:: Quick DPI check: try AppliedDPI, fallback to LogPixels, default to 96
set "dpi=96"
for /f "tokens=2*" %%A in ('reg query "HKCU\Control Panel\Desktop\WindowMetrics" /v AppliedDPI 2^>nul ^| findstr /i "REG_DWORD"') do set /a "dpi=%%B"
if %dpi% equ 96 (
    for /f "tokens=2*" %%A in ('reg query "HKCU\Control Panel\Desktop" /v LogPixels 2^>nul ^| findstr /i "REG_DWORD"') do set /a "dpi=%%B"
)

set /a "scale=(%dpi% * 100) / 96"

if %scale% gtr 100 (
    echo [WARNING] Display scaling is at %scale%%%. Some legacy applications may not render correctly.
) else (
    echo [OK] Display scaling is at standard 100%%.
)

pause

@echo off
setlocal

set "app_path=C:\LegacyApp\app.exe"

:: Check scaling
set "dpi=96"
for /f "tokens=2*" %%A in ('reg query "HKCU\Control Panel\Desktop\WindowMetrics" /v AppliedDPI 2^>nul ^| findstr /i "REG_DWORD"') do set /a "dpi=%%A"
if %dpi% equ 96 (
    for /f "tokens=2*" %%A in ('reg query "HKCU\Control Panel\Desktop" /v LogPixels 2^>nul ^| findstr /i "REG_DWORD"') do set /a "dpi=%%B"
)
set /a "scale=(%dpi% * 100) / 96"

if %scale% gtr 100 (
    echo High-DPI detected ^(%scale%%%^). Setting compatibility mode...

    :: Set the application to use "System (Enhanced)" DPI awareness
    set "compat_key=HKCU\Software\Microsoft\Windows NT\CurrentVersion\AppCompatFlags\Layers"
    REG ADD "%compat_key%" /v "%app_path%" /t REG_SZ /d "~ HIGHDPIAWARE" /f >nul

    echo [OK] DPI compatibility override applied for %scale%%% scaling.
)

if not exist "%app_path%" (
    echo [ERROR] Application not found: %app_path%
    pause
    exit /b 1
)

echo Launching application...
start "" "%app_path%"

:: WRONG - Hardcoding 100% scaling assumption
echo Setting window size to 1920x1080 for full HD...

:: WRONG - DpiScalingVer is an internal version flag, not the DPI value
reg query "HKCU\Control Panel\Desktop" /v DpiScalingVer

:: WRONG - findstr /i "AppliedDPI" can match path lines or headers
for /f "tokens=3" %%A in ('reg query "HKCU\...\WindowMetrics" /v AppliedDPI 2^>nul ^| findstr /i "AppliedDPI"') do set "dpi=%%A"