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Console Example

The console example demonstrates how QSA can be used as an interactive scripting console where each command you type is automatically run in the interpreter.

The console example consists of three different widgets. The Input widget is used for writing script code and it is the largest and most important one of these is the input widget. This widget lies in the center of the dialog. The output window widget is found in the uppermost text area it displays output from print commands. It also displays syntax and logic errors. The third widget is the history window, situated in the lowermost text area of the dialog.History displays all of the commands that the user has typed.

The following sections will show an example and description of the console application.

A Line by Line Example

We will start by stepping thought line by line of a simple example where we create a dialog that reads and displays the first and last name that is typed into a line edit. Altough some lines are grouped together, you should try to type them in one by one and press enter between each line. The example below relies strongly on the QSA Input Dialog Framework.

    var dialog = new Dialog;

We start by creating a dialog.

    dialog.exec();

To verify that the dialog actually changes, we will display the dialog before any changes have been made to it. The dialog pops up with only an Ok and Cancel button on it. The function exec() is in the Dialog class. Close the dialog and continue with the steps below.

    dialog.title = "Name reading dialog";
    dialog.okButtonText = "Done"
    dialog.cancelButtonText = "Abort";
    dialog.exec();

The preceding code configures the dialog to fit our needs. We set the title and modify the text on the OK and Cancel buttons. When you type dialog.exec() at the end of the code, the dialog pops up with your changes. When you have confirmed that the changes have taken place, close the dialog.

    var first = new LineEdit;
    first.label = "First name: ";
    dialog.add( first );
    dialog.exec();

This code creates a line edit which we will use to read the first name. We change the label to "First name: " and add it to the dialog. When we call exec(), the dialog will now contain your new line edit. Close the dialog again.

    var last = new LineEdit;
    last.label = "Last name: ";
    dialog.add( last );
    dialog.exec();

We need to add another line edit for typing the last name. Change the label to "Last name: ", and add the line edit to the dialog. Type in dialog.exec() to run the dialog. Type in your first and last name in the respective input fields and press Done.

Finally, we need to add the following code to get the result from the dialog and print it out.

    var fullName = last.text + ", " + first.text;
    print( "Full name is: " + fullName );

Console in Detail

The console example uses an instance of QSInterpreter and the function QSInterpreter::evaluate() to give line by line commands that are interpreted. To have some classes to play with, we make the QSA Input Dialog Framework available to the scripting engine using the function QSInterpreter::addObjectFactory()

The input widget is a QSEditor, which means that all script code is written with syntax highlighting and completion. To get completion on all the classes that an interpreter knows about, we have to tell the editor which interpreter we are using. (In the most common case of using QSEditor, it is handled using QSProject, but in this example we have no project and therefore have to make the binding ourselves). This is done by calling the function QSEditor::setInterpreter(). Without making this binding, the syntax completion would, for example, not be able to tell that the input dialog framework was available in the interpreter.

We have installed an event filter on the QSEditor so that we can provide the line by line interpretation of the script code that we want. If the user presses enter, we perform a syntax check on the source code in the editor using QSInterpreter::checkSyntax(). If it passes, the code is evaluated. The return value from the interpreter (typically the value of the last statement executed) is always displayed in the output window. If you want to write multi-line commands, use Control+Enter to go to the next line without evaluating the code.

Conclusion

The console example shows how QSA can be used as an input form for giving interactive commands. It also shows how QSEditor can be embedded in an arbitrary user interface without the use of QSA Workbench or the project.


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QSA 1.2.2