Home > Articles > Programming > C/C++

This chapter is from the book

Built-in Widget and Dialog Classes

Qt provides a complete set of built-in widgets and common dialogs that cater to most situations. In this section, we present screenshots of almost all of them. A few specialized widgets are deferred until later: We cover main window widgets such as QMenuBar, QToolBar, and QStatusBar in Chapter 3, and we cover layout-related widgets such as QSplitter and QScrollArea in Chapter 6. Most of the built-in widgets and dialogs are used in the examples presented in this book. In the screenshots shown in Figures 2.17 to 2.26, all the widgets are shown using the Plastique style.

02fig17.jpg

Figure 2.17 Qt's button widgets

02fig18.jpg

Figure 2.18 Qt's single-page container widgets

02fig19.jpg

Figure 2.19 Qt's multi-page container widgets

02fig20.jpg

Figure 2.20 Qt's item view widgets

02fig21.jpg

Figure 2.21 Qt's display widgets

02fig22.jpg

Figure 2.22 Qt's input widgets

02fig23.jpg

Figure 2.23 Qt's feedback dialogs

02fig24.jpg

Figure 2.24 Qt's color and font dialogs

02fig25.jpg

Figure 2.25 Qt's file and print dialogs

02fig26.jpg

Figure 2.26 Qt's dialog

Qt provides four kinds of "buttons": QPushButton, QToolButton, QCheckBox, and QRadioButton; they are shown in Figure 2.17. QPushButton and QToolButton are most commonly used to initiate an action when they are clicked, but they can also behave like toggle buttons (click to press down, click to restore). QCheckBox can be used for independent on/off options, whereas QRadioButtons are normally mutually exclusive.

Qt's container widgets are widgets that contain other widgets. They are shown in Figure 2.18 and Figure 2.19. QFrame can also be used on its own to simply draw lines and serves as the base class for many other widget classes, including QToolBox and QLabel.

QTabWidget and QToolBox are multi-page widgets. Each page is a child widget, and the pages are numbered starting from 0. For QTabWidgets, both the shape and the position of the tabs can be set.

The item views, shown in Figure 2.20, are optimized for handling large amounts of data and often use scroll bars. The scroll bar mechanism is implemented in QAbstractScrollArea, a base class for item views and other kinds of scrollable widgets.

The Qt library includes a rich text engine that can be used for displaying and editing formatted text. The engine supports font specifications, text alignments, lists, tables, images, and hyperlinks. Rich text documents can be created pro-grammatically element by element or supplied as HTML-formatted text. The precise HTML tags and CSS properties that the engine supports are documented at http://doc.trolltech.com/4.3/richtext-html-subset.html.

Qt provides a few widgets that are used purely for displaying information; they are shown in Figure 2.21. QLabel is the most important of these, and it can be used for showing plain text, HTML, and images.

QTextBrowser is a read-only QTextEdit subclass that can display formatted text. This class is used in preference to QLabel for large formatted text documents, because unlike QLabel, it automatically provides scroll bars when necessary, and also provides extensive support for keyboard and mouse navigation. Qt Assistant 4.3 uses QTextBrowser to present documentation to the user.

Qt provides several widgets for data entry, as shown in Figure 2.22. QLineEdit can restrict its input using an input mask, a validator, or both. QTextEdit is a QAbstractScrollArea subclass capable of editing large amounts of text. A QTextEdit can be set to edit plain text or rich text. In the latter case, it is able to display all of the elements that Qt's rich text engine supports. Both QLineEdit and QTextEdit are fully integrated with the clipboard.

Qt provides a versatile message box and an error dialog that remembers which messages it has shown—these are shown in Figure 2.23. The progress of time-consuming operations can be indicated using QProgressDialog or using the QProgressBar shown in Figure 2.21. QInputDialog is very convenient when a single line of text or a single number is required from the user.

Qt provides the standard set of common dialogs that make it easy to ask the user to select a color, font, or file, or to print a document. These are shown in Figure 2.24 and Figure 2.25.

On Windows and Mac OS X, Qt uses the native dialogs rather than its own common dialogs when possible. Colors can also be chosen using one of the Qt Solutions color selection widgets, and fonts can be chosen using the built-in QFontComboBox.

Finally, QWizard provides a framework for creating wizards (also called assistants on Mac OS X). Wizards are useful for complex or infrequent tasks that users may find difficult to learn. An example of a wizard is shown in Figure 2.26.

A lot of ready-to-use functionality is provided by the built-in widgets and common dialogs. More specialized requirements can often be satisfied by setting widget properties, or by connecting signals to slots and implementing custom behavior in the slots.

If none of the widgets or common dialogs provided with Qt is suitable, one may be available from Qt Solutions, or from a commercial or non-commercial third party. Qt Solutions provides a number of additional widgets, including various color choosers, a thumbwheel control, pie menus, and a property browser, as well as a copy dialog.

In some situations, it may be desirable to create a custom widget from scratch. Qt makes this straightforward, and custom widgets can access all the same platform-independent drawing functionality as Qt's built-in widgets. Custom widgets can even be integrated with Qt Designer so that they can be used in the same way as Qt's built-in widgets. Chapter 5 explains how to create custom widgets.

InformIT Promotional Mailings & Special Offers

I would like to receive exclusive offers and hear about products from InformIT and its family of brands. I can unsubscribe at any time.

Overview


Pearson Education, Inc., 221 River Street, Hoboken, New Jersey 07030, (Pearson) presents this site to provide information about products and services that can be purchased through this site.

This privacy notice provides an overview of our commitment to privacy and describes how we collect, protect, use and share personal information collected through this site. Please note that other Pearson websites and online products and services have their own separate privacy policies.

Collection and Use of Information


To conduct business and deliver products and services, Pearson collects and uses personal information in several ways in connection with this site, including:

Questions and Inquiries

For inquiries and questions, we collect the inquiry or question, together with name, contact details (email address, phone number and mailing address) and any other additional information voluntarily submitted to us through a Contact Us form or an email. We use this information to address the inquiry and respond to the question.

Online Store

For orders and purchases placed through our online store on this site, we collect order details, name, institution name and address (if applicable), email address, phone number, shipping and billing addresses, credit/debit card information, shipping options and any instructions. We use this information to complete transactions, fulfill orders, communicate with individuals placing orders or visiting the online store, and for related purposes.

Surveys

Pearson may offer opportunities to provide feedback or participate in surveys, including surveys evaluating Pearson products, services or sites. Participation is voluntary. Pearson collects information requested in the survey questions and uses the information to evaluate, support, maintain and improve products, services or sites, develop new products and services, conduct educational research and for other purposes specified in the survey.

Contests and Drawings

Occasionally, we may sponsor a contest or drawing. Participation is optional. Pearson collects name, contact information and other information specified on the entry form for the contest or drawing to conduct the contest or drawing. Pearson may collect additional personal information from the winners of a contest or drawing in order to award the prize and for tax reporting purposes, as required by law.

Newsletters

If you have elected to receive email newsletters or promotional mailings and special offers but want to unsubscribe, simply email information@informit.com.

Service Announcements

On rare occasions it is necessary to send out a strictly service related announcement. For instance, if our service is temporarily suspended for maintenance we might send users an email. Generally, users may not opt-out of these communications, though they can deactivate their account information. However, these communications are not promotional in nature.

Customer Service

We communicate with users on a regular basis to provide requested services and in regard to issues relating to their account we reply via email or phone in accordance with the users' wishes when a user submits their information through our Contact Us form.

Other Collection and Use of Information


Application and System Logs

Pearson automatically collects log data to help ensure the delivery, availability and security of this site. Log data may include technical information about how a user or visitor connected to this site, such as browser type, type of computer/device, operating system, internet service provider and IP address. We use this information for support purposes and to monitor the health of the site, identify problems, improve service, detect unauthorized access and fraudulent activity, prevent and respond to security incidents and appropriately scale computing resources.

Web Analytics

Pearson may use third party web trend analytical services, including Google Analytics, to collect visitor information, such as IP addresses, browser types, referring pages, pages visited and time spent on a particular site. While these analytical services collect and report information on an anonymous basis, they may use cookies to gather web trend information. The information gathered may enable Pearson (but not the third party web trend services) to link information with application and system log data. Pearson uses this information for system administration and to identify problems, improve service, detect unauthorized access and fraudulent activity, prevent and respond to security incidents, appropriately scale computing resources and otherwise support and deliver this site and its services.

Cookies and Related Technologies

This site uses cookies and similar technologies to personalize content, measure traffic patterns, control security, track use and access of information on this site, and provide interest-based messages and advertising. Users can manage and block the use of cookies through their browser. Disabling or blocking certain cookies may limit the functionality of this site.

Do Not Track

This site currently does not respond to Do Not Track signals.

Security


Pearson uses appropriate physical, administrative and technical security measures to protect personal information from unauthorized access, use and disclosure.

Children


This site is not directed to children under the age of 13.

Marketing


Pearson may send or direct marketing communications to users, provided that

  • Pearson will not use personal information collected or processed as a K-12 school service provider for the purpose of directed or targeted advertising.
  • Such marketing is consistent with applicable law and Pearson's legal obligations.
  • Pearson will not knowingly direct or send marketing communications to an individual who has expressed a preference not to receive marketing.
  • Where required by applicable law, express or implied consent to marketing exists and has not been withdrawn.

Pearson may provide personal information to a third party service provider on a restricted basis to provide marketing solely on behalf of Pearson or an affiliate or customer for whom Pearson is a service provider. Marketing preferences may be changed at any time.

Correcting/Updating Personal Information


If a user's personally identifiable information changes (such as your postal address or email address), we provide a way to correct or update that user's personal data provided to us. This can be done on the Account page. If a user no longer desires our service and desires to delete his or her account, please contact us at customer-service@informit.com and we will process the deletion of a user's account.

Choice/Opt-out


Users can always make an informed choice as to whether they should proceed with certain services offered by InformIT. If you choose to remove yourself from our mailing list(s) simply visit the following page and uncheck any communication you no longer want to receive: www.informit.com/u.aspx.

Sale of Personal Information


Pearson does not rent or sell personal information in exchange for any payment of money.

While Pearson does not sell personal information, as defined in Nevada law, Nevada residents may email a request for no sale of their personal information to NevadaDesignatedRequest@pearson.com.

Supplemental Privacy Statement for California Residents


California residents should read our Supplemental privacy statement for California residents in conjunction with this Privacy Notice. The Supplemental privacy statement for California residents explains Pearson's commitment to comply with California law and applies to personal information of California residents collected in connection with this site and the Services.

Sharing and Disclosure


Pearson may disclose personal information, as follows:

  • As required by law.
  • With the consent of the individual (or their parent, if the individual is a minor)
  • In response to a subpoena, court order or legal process, to the extent permitted or required by law
  • To protect the security and safety of individuals, data, assets and systems, consistent with applicable law
  • In connection the sale, joint venture or other transfer of some or all of its company or assets, subject to the provisions of this Privacy Notice
  • To investigate or address actual or suspected fraud or other illegal activities
  • To exercise its legal rights, including enforcement of the Terms of Use for this site or another contract
  • To affiliated Pearson companies and other companies and organizations who perform work for Pearson and are obligated to protect the privacy of personal information consistent with this Privacy Notice
  • To a school, organization, company or government agency, where Pearson collects or processes the personal information in a school setting or on behalf of such organization, company or government agency.

Links


This web site contains links to other sites. Please be aware that we are not responsible for the privacy practices of such other sites. We encourage our users to be aware when they leave our site and to read the privacy statements of each and every web site that collects Personal Information. This privacy statement applies solely to information collected by this web site.

Requests and Contact


Please contact us about this Privacy Notice or if you have any requests or questions relating to the privacy of your personal information.

Changes to this Privacy Notice


We may revise this Privacy Notice through an updated posting. We will identify the effective date of the revision in the posting. Often, updates are made to provide greater clarity or to comply with changes in regulatory requirements. If the updates involve material changes to the collection, protection, use or disclosure of Personal Information, Pearson will provide notice of the change through a conspicuous notice on this site or other appropriate way. Continued use of the site after the effective date of a posted revision evidences acceptance. Please contact us if you have questions or concerns about the Privacy Notice or any objection to any revisions.

Last Update: November 17, 2020