Simple .NET/ASP.NET PDF document editor web control SDK

ometimes users need a helping hand. With Qt you can give them the instruction they re looking for in a variety of ways: wizards, tooltips, status bar messages, and pointers to product documentation, to name a few. When considering how to add help-related features to your application, keep in mind that there s much more to it than simply responding to the F1 key (the de facto mechanism for displaying the application s help window). Assistance is most effective when it s an integral yet nonintrusive part of your entire application. By using a good design that clearly reflects both what users are currently doing and where in the process they are, you can dramatically reduce the need for help. Some of the tools and principles include providing wizards for complex settings, avoiding or clearly indicating different working modes such as insert and overwrite, and alerting users when they re about to do something that can destroy a lot of information. Providing lots and lots of help does not make it easy to use an application; too much help can just make it hard to find the information that the user is looking for. What you need to achieve is an easy-to-use whole: a combination of relevant help and a clear design. This is what makes using your application a joy.

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If we compile and run with our all-new error checking added, we see the following output:

Arthur Arthur Arthur Arthur Arthur Arthur is is is is is is at at at at at at (0,0) and is pointing at angle 0.00 radians. (0,10) and is pointing at angle 0.00 radians. (0,10) and is pointing at angle 0.00 radians. (0,-15) and is pointing at angle 0.00 radians. (0,-15) and is pointing at angle 0.00 radians. (0,-18.5355339059327) and is pointing at angle 0.00 radians.

Hmmm; that s not very good. Rotate has indeed failed, but we ve carried on driving the turtle up and down that line because we didn t do anything with the return value.

Let s take a look at how the Login pane realizes this functionality. The Login pane, along with many of the others, is actually implemented on the master page. This makes sense because you should be able to log in from anywhere. If you view the page Default.master in the ASP .NET designer, you ll see something like Figure 7-13.

One of the most common ways to add some additional guidance to the user is to provide tooltips, which are little signs containing information (see Figure 9-1). They appear when you hover the mouse pointer over a control for a short period of time.

Let s look at where we call Rotate and see what we can do with that error (see Example 6-7).

// Run the turtle for the specified duration public void RunFor(double duration) { // ... // // // if The motors are running in opposite directions, so we don't move, we just rotate about the center of the rig ((LeftMotorState == MotorState.Running && RightMotorState == MotorState.Reversed) || (LeftMotorState == MotorState.Reversed && RightMotorState == MotorState.Running))

{

All widgets can be assigned a tooltip using the setTooltip(const QString&) method, which accepts a string that can either be plain text or formatted using HTML. To demonstrate tooltips, I have put together a QDialog class with a number of widgets. Listing 9-1 presents the constructor used to set up the widgets and layouts (refer to Figure 9-1 to see the result). Listing 9-1. The dialog constructor ToolTipDialog::ToolTipDialog() : QDialog() { QGroupBox *groupBox = new QGroupBox( tr("Group") ); QGridLayout *gbLayout = new QGridLayout( groupBox ); QCheckBox *checkBox = new QCheckBox( tr("Check!") ); QLabel *label = new QLabel( tr("label") ); QPushButton *pushButton = new QPushButton( tr("Push me!") ); gbLayout->addWidget( checkBox, 0, 0 ); gbLayout->addWidget( label, 0, 1 ); gbLayout->addWidget( pushButton, 1, 0, 1, 2 ); QGridLayout *dlgLayout = new QGridLayout( this ); dlgLayout->addWidget( groupBox, 0, 0 ); ... } In Listing 9-2 the tooltips for the checkbox and group box are set. The checkbox gets a single line, while the group box text is divided into three lines using the standard line break \n. The group box tooltip shows when you hover the mouse pointer around and between the widgets contained in the group box. If you hover over the label, checkbox, or push button, their respective tooltips are shown. Listing 9-2. Setting simple tooltip texts checkBox->setToolTip( tr("This is a simple tool tip for the check box.") ); groupBox->setToolTip( tr("This is a group box tool tip.\n" "Notice that it appears between " "and around the contained widgets.\n" "It is also spanning several lines.") );

}

}

if (!Rotate(duration)) { // It failed, so what now } return;

It is simple enough to check to see if it failed, but what are we actually going to do about it Is there any action we can take Not surprisingly, the answer is no we know no more about the needs of our caller than we did when we were discussing the other options. So we are going to have to pass the error on up. Example 6-8 shows an implementation of Run that does that.