DX.DisplayInfo

A lightweight Delphi library for DPI and display diagnostics on Windows. It exposes per-monitor resolution, effective DPI, physical (raw) DPI, DPI awareness mode and scaling percentage — all without external dependencies.

Two ready-to-run executables are included: a VCL GUI with visual DPI rulers and a CLI for scripting and automation.

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Screenshot

The VCL UI shows DPI awareness mode, theme status, per-monitor resolution and DPI values, and two calibrated rulers that let you verify at a glance whether the physical monitor DPI matches what Windows reports to your application.

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Features

• DPI awareness detection — reads PER_MONITOR_DPI_AWARE, SYSTEM_DPI_AWARE or UNAWARE via shcore.dll (Windows 8.1+), with automatic fallback to IsProcessDPIAware on older systems
• Per-monitor enumeration — iterates all connected monitors and reports device name, resolution, effective DPI, physical (raw) DPI and scaling percentage for each
• Effective vs. physical DPI rulers — visual comparison of what Windows reports to your app vs. the true panel DPI (useful for detecting HiDPI / Retina screens running inside VMs)
• Framework-agnostic core — DX.DisplayInfo.pas has no VCL or FMX dependency; use it in any Delphi project
• VCL diagnostic UI — standalone DisplayInfoUI.exe with live ruler rendering
• CLI tool — DisplayInfoCLI.exe for scripting, CI pipelines or remote diagnostics

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Project Structure

DX.DisplayInfo/
├── src/
│   ├── DX.DisplayInfo.pas          # Core library unit (RTL + WinAPI only)
│   ├── DisplayInfoCLI.dpr/.dproj   # Console application
│   ├── DisplayInfoUI.dpr/.dproj    # VCL GUI application
│   ├── DisplayInfoUI.Main.Form.*   # Main form (VCL)
│   └── DPITest.manifest            # Custom DPI manifest (see note below)
├── build/
│   ├── DelphiBuildDPROJ.ps1        # Universal build script
│   └── Win32/Debug/                # Compiled output
├── docs/
│   └── Screenshot.png
├── DisplayInfo.groupproj           # Project group (CLI + UI)
├── LICENSE
└── README.md

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Application Manifest and DPI Awareness

The VCL UI project includes a hand-crafted manifest file (src/DPITest.manifest) for demonstration purposes. It declares permonitorv2 DPI awareness and the supported Windows OS versions explicitly.

Why the manual manifest?

Delphi support for High DPI evolved gradually across several releases:

Delphi version	VCL DPI support	IDE manifest option
XE7 and earlier	None	None — manual manifest required (tested, both CLI and UI build and run)
XE8	None	Unknown / untested
10.0 Seattle – 10.2 Tokyo	Basic Per-Monitor DPI (from 10.2)	Basic Enable High-DPI checkbox in Project Options
10.3 Rio and later	Full Per-Monitor v2	Complete Application > Manifest page with DPI Awareness dropdown

The IDE manifest page with the full DPI Awareness dropdown (as shown in the screenshot above) was introduced in 10.3 Rio alongside Per-Monitor v2 support in the VCL framework.

In all supported versions, a custom manifest file can still be used instead of the IDE option via Project > Options > Application > Manifest > Use application manifest file, which gives full control over all manifest entries.

The manifest ships with two ready-to-use option blocks:

Option	dpiAwareness value	Effect
1 (active)	permonitorv2 + true/pm fallback	App handles scaling itself — crisp rendering
2 (commented out)	unaware	Windows bitmap-stretches the window — may appear blurry

To switch options, remove the XML comment markers around the desired <application> block, then do a full Clean + Build so the updated manifest is embedded in the executable.

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Getting Started

Prerequisites

• Delphi XE7 or later (tested with XE7 and Delphi 13 / RAD Studio 12)
• Windows 8.1 or later for full per-monitor DPI support (Windows Vista+ for basic DPI awareness; physical DPI is unavailable on older systems)

Build with Delphi IDE

1. Open DisplayInfo.groupproj in the IDE.
2. Right-click the project group → Build All.
3. Compiled executables land in build\Win32\Debug\.

Build from the command line

.\build\DelphiBuildDPROJ.ps1 -ProjectFile src\DisplayInfoCLI.dproj
.\build\DelphiBuildDPROJ.ps1 -ProjectFile src\DisplayInfoUI.dproj

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Using the Library

Add DX.DisplayInfo.pas to your project (no package or BPL required) and call EnsureDpiAwareness at startup.

uses DX.DisplayInfo;

// Set PER_MONITOR_DPI_AWARE before the first window is created
EnsureDpiAwareness;

// Query DPI info for a specific window handle (0 = desktop / primary monitor)
var LInfo := GetDisplayInfo(Self.Handle);

// Enumerate all connected monitors
var LMonitors := GetAllMonitorsInfo;
for var LEntry in LMonitors do
  Writeln(MonitorEntryToText(LEntry));

Key types

Type	Description
TMonitorEntry	Resolution, effective DPI, physical DPI and scaling % for one monitor
TDisplayInfo	System DPI, scaling %, awareness mode and per-monitor DPI for a window
TDpiAwarenessInfo	Awareness enum value, human-readable text and detection source
TMonitorDpiInfo	Effective and raw DPI pair from GetDpiForMonitor

Key routines

Routine	Description
EnsureDpiAwareness	Sets PER_MONITOR_DPI_AWARE (or legacy fallback)
GetDisplayInfo(HWND)	Full DPI diagnostics for a given window
GetAllMonitorsInfo	Array of TMonitorEntry for every connected monitor
MonitorEntryToText	Formatted text block for one monitor
AllMonitorsInfoToText	Formatted text block for all monitors
DisplayInfoToText	Formatted text summary of TDisplayInfo

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CLI Output Example

DPI Awareness:  PER_MONITOR_DPI_AWARE

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Device:          \\.\DISPLAY1
Primary:         Yes
Resolution:      3584 x 2240 px
Effective DPI:   192 x 192  (200%)
Physical DPI:    267 x 270  (105.1 px/cm)

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Understanding Effective vs. Physical DPI

Scenario	Effective DPI	Physical DPI	Rulers
Standard 1080p at 100%	96	96	Equal length
4K display at 200% scaling	192	192	Equal length
Retina screen inside a VM	192	267	Physical ruler is longer
External monitor, scaling > physical	144	110	Effective ruler is longer

The two rulers in the VCL UI make the difference immediately visible without any arithmetic.

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License

MIT License — Copyright © 2026 Olaf Monien. See LICENSE for the full text.