Accessibility (sometimes abbreviated as a11y) is the practice of making applications usable by people with disabilities, including those who are sight, hearing, or motor impaired. ArcGIS Maps SDK for .NET leverages the W3C Accessibility Standards to ensure the applications and experiences you create are usable by a wide range of audiences.
Basic content accessibility guidelines are defined by the Web Content Accessibility Guidelines (WCAG), which provide a set of recommendations for making content more accessible. These guidelines are organized around four principles:
- Perceivable: Information and user interface components must be presentable to users in ways they can perceive. This includes guidelines for text alternatives, time-based media, adaptable content, and distinguishable elements.
- Operable: User interface components and navigation must be operable. This includes guidelines for keyboard accessibility, enough time to read and use content, seizures and physical reactions, navigable content, and input modalities.
- Understandable: Information and the operation of user interface must be understandable. This includes guidelines for readable text, predictable web pages, and input assistance.
- Robust: Content must be robust enough that it can be interpreted reliably by a wide variety of user agents, including assistive technologies.
Accessibility in ArcGIS Maps SDK for .NET
While originally created for web apps, the principles defined in the Web Content Accessibility Guidelines (WCAG) have also been adapted for native apps. See Guidance on Applying WCAG 2 to Non-Web Information and Communications Technology for details about applying these criteria in non-Web apps.
Where applicable, ArcGIS Maps SDK for .NET supports key accessibility features that allow developers to create apps that are available to a broader audience. While ArcGIS Maps SDK for .NET is created with accessibility in mind, it relies on the application, platform, and operating system to provide additional accessibility support. As an ArcGIS Maps SDK for .NET developer, you can build accessibility into your apps by addressing concerns such as:
- Providing text alternatives for non-text content
- Ensuring sufficient color contrast
- Making all functionality available from a keyboard
- Providing clear and consistent navigation
- Allowing users to customize their experience
- Giving all controls and objects accessible names and descriptions
Color and contrast
Color contrast can be expressed as a ratio between the luminance (brightness) of colors values. For context, the highest contrast ratio is 21:1, which is the contrast between black and white, while the contrast between light gray and white is 1.5:1. The higher the contrast ratio, the more distinguishable the text is from its background. For someone who is visually impaired, color contrast can be the difference between a site that is clear and legible, and one that is completely unusable. Many types of visual impairment, as well as color blindness, can make it difficult to read text with low color contrast.
When designing apps with color in mind, consider the following:
- Use sufficient color contrast to ensure text is readable against its background. The WCAG 2.1 recommends a contrast ratio of at least 4.5:1 for normal text and 3:1 for large text.
- Use color in conjunction with other visual cues (like text labels or patterns) to convey information, as some users may have difficulty distinguishing colors. Do not rely solely on color to convey meaning.
- Use color palettes that are friendly to colorblind users. Tools like Color Brewer can help you select appropriate color schemes.
- Ensure that interactive elements, such as buttons and links, have sufficient contrast against their backgrounds to be easily identifiable.
For tips on using color effectively for creating accessible maps, see Accessibility essentials for GIS and mapping in the ArcGIS Blogs.
Keyboard and focus
Keyboard accessibility for UI controls in your app gives users who are visually impaired, have motor disabilities, or do not have full use of their hands, the ability to effectively interact with your app. To ensure that users with vision or mobility issues can use your app, make sure all interactive elements in your application can be accessed and operated using a keyboard. This includes:
- Providing a logical tab order for navigating through interactive elements
- Using focus indicators to show which element is currently selected
- Allowing users to navigate through content using the arrow keys
- Ensuring that all functionality is available via keyboard shortcuts or commands
By using .NET features like semantic properties and keyboard accelerators, you can ensure that your UI is logically ordered and accessible for those who need to rely on keyboard navigation.
The keyboard navigation for geoview controls in ArcGIS Maps SDK for .NET is described in the following topics:
Resources
- ArcGIS Maps SDK for .NET Accessibility Conformance Report: Outlines ArcGIS Maps SDK for .NET conformance to accessibility standards
- W3C Accessibility Standards: W3C's accessibility standards overview
- Windows Accessibility: Microsoft Windows accessibility documentation
- Accessibility - Calcite Design System: Overview of best practices when designing for accessibility
- Accessibility essentials for GIS and mapping: Blog article with tips for creating accessible maps
- Esri Accessibility: Esri's approach to accessibility
- Esri Legal Accessibility: Esri's legal accessibility statement