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UI Automation TextPattern Overview

  • Artigo

Observação

Esta documentação destina.Os desenvolvedores do NET Framework que desejam usar o gerenciado UI Automation classes definidas na System.Windows.Automation namespace.As informações mais recentes sobre UI Automation, consulte API de automação do Windows: Automação da interface do usuário.

This overview describes how to use Microsoft UI Automation to expose the textual content, including format and style attributes, of text controls in UI Automation-supported platforms. Esses controles incluem, mas não limitados a, o Microsoft .NET Framework TextBox e RichTextBox , bem como seus Win32 equivalentes.

Exposing the textual content of a control is accomplished through the use of the TextPattern control pattern, which represents the contents of a text container as a text stream. Por sua vez, TextPattern requer o suporte a TextPatternRange classe para expor o formato e o estilo de atributos. TextPatternRangesuporta TextPattern por representando contíguas ou múltiplos disjunção distribuições de texto em um recipiente de texto com uma coleção de Start e End pontos de extremidade. TextPatternRangeoferece suporte a funcionalidade de seleção, comparação, recuperação e passagem.

Observação

The TextPattern classes do not provide a means to insert or modify text.No entanto, dependendo do controle, isso pode ser feito pelo UI Automation ValuePattern ou por meio de entrada de teclado direto.See the ValuePattern Insert Text Sample for an example.

The functionality described in this overview is vital to assistive technology vendors and their end users. Assistive technologies can use UI Automation to gather complete text formatting information for the user and provide programmatic navigation and selection of text by TextUnit (character, word, line, or paragraph).

Este tópico contém as seguintes seções.

  • TextPattern de automação da interface do usuário vs.Text Services Framework
  • Control Types
  • TextPattern Client API's
  • TextPattern Provider API's
  • Security
  • Performance
  • TextPattern Terminology
  • Tópicos relacionados

TextPattern de automação da interface do usuário vs.Text Services Framework

Text Services Framework (TSF) is a simple and scalable system framework that enables natural language services and advanced text input on the desktop and within applications. In addition to providing interfaces for applications to expose their text store it also supports metadata for that text store.

However, TSF was designed for applications that need to inject input into context-aware scenarios whereas TextPattern is a read-only solution (with the limited workaround noted above) meant to provide optimized access to a text store for screen-readers and Braille devices.

In short, accessible technologies that require read-only access to a text store can use TextPattern, but will need the more complex functionality of TSF for context-aware input.

Control Types

Text

The Text control is the basic element representing a piece of text on the screen.

A standalone text control can be used as a label or static text on a form. Text controls can also be contained within the structure of a ListItem, TreeItem or DataItem.

Observação

Text controls might not appear in the content view of the UI Automation tree (see Visão geral da árvore de automação de interface do usuário).This is because text controls are often displayed through the Name property of another control.For instance, the text that is used to label an Edit control is exposed through the Name property of the Edit control.Because the Edit control is in the content view of the UI Automation tree, it is not necessary for the text element itself to be in that view of the UI Automation tree.The only text that shows up in the content view is text that is not redundant information.This enables any assistive technology to quickly filter only on the pieces of information that their users need.

Edit

Edit controls enable a user to view and edit a single line of text.

Observação

The single line of text may wrap in certain layout scenarios.

Document

Document controls let a user navigate and obtain information from multiple pages of text.

TextPattern Client API's

System.Windows.Automation.TextPattern Class

The entry point for the Microsoft UI Automation text model.

This class also contains the two TextPattern event listeners, TextSelectionChangedEvent and TextChangedEvent.

System.Windows.Automation.Text.TextPatternRange Class

The representation of a span of text within a text container that supports TextPattern.

UI Automation clients should be careful about the current validity of a text range created using TextPatternRange. If the original text in the text control is completely replaced by new text, the current text range becomes invalid. However, the text range may still have some viability if only part of the original text is changed and the underlying text control is managing its text "pointer" with anchors (or endpoints) rather than with absolute character positioning.

Clients can listen for a TextChangedEvent for notification of any changes to the textual content they are working with.

System.Windows.Automation.AutomationTextAttribute Class

Used to identify the formatting attributes of a text range.

TextPattern Provider API's

UI elements or controls that support TextPattern by implementing the ITextProvider and ITextRangeProvider interfaces, either natively or through Microsoft UI Automation proxies, are capable of exposing detailed attribute information for any text they contain in addition to providing robust navigational capabilities.

A TextPattern provider does not have to support all text attributes if the control lacks support for any particular attributes.

A TextPattern provider must support the GetSelection and Select functions if the control supports text selection or placement of the text cursor (or system caret) within the text area. If the control does not support this functionality then it does not need to support either of these methods. However, the control must expose the type of text selection it supports by implementing the SupportedTextSelection property.

A TextPattern provider must always support the TextUnit constants Character and Document as well as any other TextUnit constants it is capable of supporting.

Observação

O provedor pode ignorar o suporte para uma determinada TextUnit por adiar para a próxima maior TextUnit suportados na seguinte ordem: Character, Format, Word, Line, Paragraph, Page, and Document.

ITextProvider Interface

Exposes methods, properties and attributes that support TextPattern in client applications (see ITextProvider).

ITextRangeProvider Interface

Represents a span of text in a text provider (see ITextRangeProvider).

System.Windows.Automation.TextPatternIdentifiers Class

Contains values that are used as identifiers for text providers (see TextPatternIdentifiers).

Security

The UI Automation architecture was designed with security in mind (see Visão geral de segurança da automação de interface do usuário). However, the TextPattern classes described in this overview require some specific security considerations.

  • Microsoft UI Automation text providers supply read-only interfaces and do not provide the ability to change the existing text in a control.

  • UI Automation clients can only use Microsoft UI Automation if they are fully "trusted". An example of this would be the protected Logon Desktop, where only known and trusted applications can run.

  • Os desenvolvedores de provedor de automação da interface do usuários deve estar ciente de que todas as informações que eles optarem expor em seus controles por meio de Microsoft UI Automation é essencialmente pública e totalmente acessíveis por outro código. Microsoft UI Automationnão faz nenhum esforço para determinar a confiabilidade de qualquer o cliente de automação da interface do usuário e, portanto, o provedor de automação da interface do usuário não devem expor protegidas conteúdas textuais informações confidenciais (como campos de senha).

  • Uma das alterações mais significativas na segurança de Windows Vista é amplamente conhecido como "seguro de entrada" que engloba tecnologias como, por exemplo, com menos privilégios (ou limitado) contas de usuário (LUA) e o isolamento de nível de privilégio de interface do usuário (UIPI).

    • UIPI impede que um programa de controle e/ou monitoramento outra mais "privilegiado" Essa entrada do usuário de spoof de ataques de programa, impedindo que a mensagem em janela de processo cruzado.

    • LUA sets limits on the privileges of applications being run by users in the Administrators group. Applications won't necessarily have administrator privileges, but will instead run with the least privileges necessary. As a consequence, there may be some restrictions enforced in LUA scenarios. Most notably string truncation (including TextPattern strings), where it may be necessary to limit the size of strings being retrieved from administrator-level applications so they aren't forced to allocate memory to the point of disabling the application.

Performance

Because TextPattern relies on cross-process calls for most of its functionality, it does not provide a caching mechanism to improve performance when processing content. This is unlike other control patterns in Microsoft UI Automation that can be accessed using the GetCachedPattern or TryGetCachedPattern methods.

One tactic for improving performance is by making sure UI Automation clients attempt to retrieve moderately-sized blocks of text using GetText. For example, GetText(1) calls will incur cross-process hits for each character whereas one GetText(-1) call will incur one cross-process hit, but can have high latency depending on the size of the text provider.

TextPattern Terminology

  • Attribute
    A formatting characteristic of a text range (for example, IsItalicAttribute or FontNameAttribute).

  • Degenerate Range
    A degenerate range is an empty or zero-character text range. For the purposes of the TextPattern control pattern, the text insertion point (or system caret) is considered a degenerate range. Se nenhum texto for selecionado, GetSelection retornaria um intervalo de degenerate no ponto de inserção de texto e RangeFromPoint retornaria um intervalo de degenerate como ponto de extremidade inicial. RangeFromChilde GetVisibleRanges pode retornar intervalos degenerate quando o provedor de texto não pode localizar qualquer intervalo de texto que correspondam a determinada condição. Este intervalo de degenerate pode ser usado como um ponto de extremidade inicial no provedor de caixa de texto. FindTexte FindAttribute retornar uma referência nula (Nothing na Microsoft Visual Basic .NET) para evitar confusão com um intervalo de descobertas em vez de um intervalo de degenerate.

  • Embedded Object
    There are two types of embedded objects in the UI Automation text model. They consist of text-based content elements such as hyperlinks or tables, and control elements such as images and buttons. For more detailed information, see Access Embedded Objects Using UI Automation.

  • Ponto de extremidade
    The absolute Start or End point of a text range within a text container.

The following illustrates a set of start and end points.

TextPatternRangeEndpoints (início e fim).

  • TextRange
    A representation of a span of text, with start and end points, in a text container including all associated attributes and functionality.

  • TextUnit
    A pre-defined unit of text (character, word, line, or paragraph) used for navigating through logical segments of a text range.

Consulte também

Tarefas

Use Caching in UI Automation

Support Control Patterns in a UI Automation Provider

Conceitos

Padrões de Controle para Clientes de Automação de IU

Visão Geral de Padrões de Controle de Automação de Interface de Usuário

Visão geral da árvore de automação de interface do usuário

Mapeamento de Padrão de Controles para Clientes de Automação de IU

Outros recursos

Text Services Framework