ASP.NET PDF Viewer using C#, VB/NET

Figure 6-5. A log from the EventWidget Listing 6-11 offers the closeEvent handler as an example. The enterEvent, leaveEvent, showEvent, hideEvent, and paintEvent handlers all simply log the name of the event. The show, hide, and paint events have their own event object types. The QShowEvent and QHideEvent classes add nothing to the QEvent class. The QPaintEvent does add a lot of information (you will look more closely at this event later in this chapter). Listing 6-11. A simple event handling method void EventWidget::closeEvent( QCloseEvent * event ) { emit gotEvent( tr("closeEvent") ); }

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Setting this to BottomLeft means the tag will appear over the bottom-left corner of the element to which the menu is attached You can also use other values in this field: Absolute, Center, TopLeft, BottomRight, and TopRight Finally, a floating behavior gets associated with the pop-up menu, allowing it to float on the page To assign this behavior to this element, you tag it with its handle The next part that is necessary is to connect this menu to the anchor tag You achieve this using the <hyperlink> tag, which is associated with the element called hoverLink As you can see in the HTML, this is the word Microsoft; if you hover over the word, you will get the menu Now that you have a control associated with this element, it is straightforward to implement a pop-up on it.

Some developers have a stylistic objection to field or variable names that include information about the type, and would argue that entriesList View is unnecessarily verbose. However, it s quite common in UI applications to have several different objects all representing the same thing at different layers we ve put the underlying model in a field called entries, we have the binding source representing that model to the data binding system, which we ve called entriesSource, and we have a control displaying the information, called entriesListView. Clearly these objects can t all be called entries. We could call the control entries View, but that sounds less like an individual control and more like a description of the whole form we re building right now. So entriesList View feels right because it seems to be a minimally descriptive and unique name. We would not recommend just slapping the type name on the end of your control names out of habit, of course. Choosing identifier names requires thought (and that goes for all identifiers, not just those in Windows Forms apps). You should aim for the shortest possible name that will make it easy to understand the code when you return to it six months after you wrote it. If that happens to be a name that includes the type name, that s fine, as long as you thought about it first.

Finally, ListView supports multiple-item selection, but we want to have only one item selected at a time. Since multiple selection is the default, we need to set the MultiSelect property to false. Next, we ll add a TextBox so that the user can edit entry titles and a corresponding Label so that the user can see what the TextBox is for. These controls are found in the Common Controls section of the toolbar. We ll set the Text property of the Label to &Title: the ampersand denotes an access key so that the user can press Alt-T to put the focus into the text box. Access keys make user interfaces much easier to use from the keyboard.

When you give a Label an access key, it puts the focus into whichever control is next in the tab order. By default, the tab order will be the order in which you added the controls to the form. But you can change this by selecting the View menu s Tab Order item (which is present only when a Windows Forms design view has the focus). When you enable Tab Order mode, you can click on the controls one after another, and the order in which you click will define the tab order. Therefore, your life will be marginally easier if you add each Label control just before you add the associated TextBox control because you won t then need to go back and redo the tab order.

The events dealing with keyboard activity are keyPressEvent and keyReleaseEvent. They both look similar, so only keyPressEvent is shown in Listing 6-12. Because most modern environments support auto-repeating keys, you might get several keyPressEvents before you see the