Graphics Performance and High DPI

• Mar 15, 2021
• 5 minutes to read

This document contains information on High DPI support provided by DevExpress controls.

Foreword

The goal of this article is to explain how DevExpress controls help you in developing applications that can run on high DPI devices without loss of quality. To learn the theory on what DPI is and how different Windows versions scale your applications depending on DPI settings, refer to the following links.

• DPI and Device-Independent Pixels - an in-depth article that explains DPI concepts.
• Tutorial: Writing High-DPI Win32 Applications - a tutorial by Microsoft that makes you familiar with key concepts of high DPI desktop applications.
• Writing DPI-Aware Desktop and Win32 Applications - a complete Microsoft guide on writing DPI-aware applications.
• DPI Scaling Level for Displays - an article that describes three different ways to change system display DPI settings in Windows 10.

DPI Awareness

An application can look differently on high DPI devices depending on whether or not this app is DPI-aware.

• Non-DPI-aware applications leave all scaling to the operating system. The OS will render your application under its native 96 DPI (the default 100% DPI value) and then scale it up to the actual device DPI. This keeps your application layout intact at the cost of quality - blurry images, fuzzy captions, thick separator lines and borders, etc. Any desktop Win32 application is non-DPI-aware by default and thus, not adapted for running on high DPI screens.
• DPI-aware applications are not affected by the OS. Such applications render themselves to fit the actual DPI of a screen and provide a much better visual experience. On the downside, you will need to manually implement such DPI awareness - retrieve the current monitor DPI value, listen for DPI changes and respond to these changes by redrawing the application, scaling its content, applying different icon sets, etc.

To activate DPI-awareness for your application, do one of the following:

• Option #1 - Enable the DPI-Aware setting in the Project Settings Page (starting with version 18.1).

• Option #2 - Set the dpiAware parameter to true or the dpiAwareness parameter to system in the application’s manifest file.

  To add a manifest file, right-click the project in Solution Explorer VS window and select “Add New Item” (or press the CTRL+SHIFT+A shortcut). Search for the “Application Manifest File” item, then click “Add”.

  

  XML

  <?xml version="1.0" encoding="utf-8"?>
  <assembly xmlns="urn:schemas-microsoft-com:asm.v1" manifestVersion="1.0" xmlns:asmv3="urn:schemas-microsoft-com:asm.v3" >
      <assemblyIdentity version="1.0.0.0" name="MyApplication.app"/>
      <trustInfo xmlns="urn:schemas-microsoft-com:asm.v2">
          <security>
              <requestedPrivileges xmlns="urn:schemas-microsoft-com:asm.v3">
                  <requestedExecutionLevel level="asInvoker" uiAccess="false" />
              </requestedPrivileges>
          </security>
      </trustInfo>
      <asmv3:application>
          <asmv3:windowsSettings xmlns="http://schemas.microsoft.com/SMI/2005/WindowsSettings">
              <dpiAware>true</dpiAware>
          </asmv3:windowsSettings>
      </asmv3:application>
  </assembly>
  

High DPI Support in DevExpress Controls

DevExpress controls and components are able to recognize and take advantage of high-DPI screens automatically. Enable DPI-aware mode as described above and you will instantly get an application that renders itself correctly on high DPI devices. The following screenshot is a close-up of the Touch-Enabled Hybrid App demo run under 192 DPI.

The figure on the left illustrates the default non-DPI-aware rendering (note the blurry content, increased margins and borders). The right figure shows the same demo with DPI awareness turned on, no custom code added.

To turn DevExpress scaling off, disable the static WindowsFormsSettings.AllowDpiScale setting.

Additional Settings

In addition to this automatic DPI awareness, certain DevExpress controls and components provide features that should be used manually.

• ImageCollection.IsDpiAware - if you have different image sets for each particular DPI value, an ImageCollection that contains these images and has its ImageCollection.IsDpiAware property set to DefaultBoolean.True will pick matching images automatically. This only works when image names reflect their intended DPI values (e.g., “Close.png”, “Close_120DPI.png”, “Close_144DPI.png” and “Close_192DPI.png”).
• BarManagerProperties.ScaleEditors and RibbonProperties.ScaleEditors - these BarAndDockingController properties allow your editors to automatically increase their sizes when the DPI settings change.
• BarManagerProperties.ScaleIcons and RibbonProperties.ScaleIcons - two more BarAndDockingController properties. When set to true, Bar and Ribbon icons will be automatically stretched up if the DPI value increases.

Development Guidelines and Known Issues

The following tips will help you better scale apps across multiple screen resolutions.

• Keep your layout flexible and adaptable to possible changes: use auto-sized (avoid setting MaximumSize) and docked controls. If possible, use the DevExpress Layout Control to arrange UI elements across your form.

  The figure below illustrates scaling impact on the DevExpress SearchControl, when MaximumSize is used (in this example, width was limited to 300 pixels via the control’s MaximumSize property).

  

  This issue arises only when you explicitly limit control size in code. If a control was initially designed with limited size values, it scales correctly at higher DPI settings.

• When the parent form is scaled, child form controls will change size. This will impact applications with custom layout behaviors.
• Design your applications at 96 DPI (100%). Downscaling a form developed at higher DPI values may lead to unexpected issues. If you must create your application at resolution (greater than 96 DPI), you should consult the following KB article for additional guidance.
• When and wherever possible, use vector images for item icons. Vector images scale much better than standard raster images. The following tutorial describes how to draw a valid SVG image: SVG tutorial. Note: Vector icons with animations and external css styles are not supported..
• Use the DPIAwareImageCollection component to supply raster images/icons to DevExpress controls. At high-DPI settings, this collection automatically replaces default images with larger counterparts.
• Enable DirectX hardware acceleration to improve application execution speed on high resolution displays.

• To trace all outdated APIs that are not recommended for use with DirectX-rendered and Per-Monitor DPI-aware applications, call the static WindowsFormsSettings.ForcePaintApiDiagnostics method and set the security level as the first parameter:

  • Throw - unsupported APIs result in exceptions;
  • Trace - unsupported APIs display result in warnings, displayed in Visual Studio’s “Output” window;
  • Disable - ignores unsupported API;
  • Default - acts as “Trace” if DirectX and\or Per-Monitor HiDPI support is enabled; otherwise, as “Disable”.
• Due to a known bug, deploying DPI-aware applications using ClickOnce is not possible if you set DPI awareness mode in the Application Manifest file. Use the Project Settings Page or the static WindowsFormsSettings.SetDPIAware method instead.