C ha p ter 16 G U I - B a S e D D e S K t O p a p p LI C a t I O N D e V e LO p M e N t in C#

Drawing QR in C# C ha p ter 16 G U I - B a S e D D e S K t O p a p p LI C a t I O N D e V e LO p M e N t

edit line only supports a single line of text. Other than that, both are very similar. Let s see both in situ: Shoes.app do stack do edit_line edit_box :width => 100, height => 100 end end If you run this app, you ll be able to work with a single line of text in the edit_line element and multiple lines in the edit_box element. There s little more to it at this stage. You can position them just as you can any other elements, using top, left, width, and height, though in case they re both in a stack. In the next section, we will look at how to interact with them, such as retrieving any text entered. Other elements include the progress meter, list box, check box, and radio box, as well as non-native controls like video boxes and star shapes. These are all standard elements you ll find in any desktop development toolkit or library. We re not going to explore them in this section, as most of them are quite generic and are not useful for our examples, but others require that we understand how to interact with the controls through events and attributes, which I m going to cover in the next section. Some of these other elements will therefore be introduced later.

We ve already looked at one sort of event in Shoes so far. When a button is clicked, for example, the code in the associated code block is run. This is a click event with a callback. For example: Shoes.app do button("Press me") do alert Time.now end end This was the first Shoes example in this chapter. A button is presented that, when clicked, brings up an alert dialog box showing the current time. In this section, we re going to dig deeper and look at different types of events and how to use methods associated with different element types. The code shown in the previous button example was concise, but not particularly dynamic. It would be a lot more interesting if we could associate the button element with a

variable that we could then call methods on in order to do various things. Luckily, we can do just that! Shoes.app do @button = button("Press me") @button.click { alert Time.now } end Functionally, this is equivalent to the first example, but instead of defining a button on the fly and then having no handle back to it, we ve assigned the button to the @button variable. The click method is then used to associate the on click action with the button.

Note Instance variables are commonly used in Shoes applications as they will remain in scope throughout the whole application. This is particularly worth keeping in mind considering the large number of blocks and anonymous methods used throughout most Shoes applications.

While buttons offer the click method for defining click handlers, all elements offer a core set of common methods. For example, you can change the positioning of an element on the fly: Shoes.app do @button = button("Press me") @button.click { @button.move(rand, rand) } end Arguably, this could be the simplest game you could build with Shoes! When you click the button, the button is moved to a random position within the window, ready for you to click again. This is done with the move method, and by using rand (which supplies, by default, a floating point number between 0 and 1) for the x and y coordinates, the button is moved to a random place within the application window. There s a collection of methods you can use on any element in this way. To show and hide an element, you can use the show and hide methods. To retrieve the left, top, height, and width attributes of an element, you can use the respective left, top, height, and width methods. These methods work on all elements. Other types of elements present different methods that can be used. For example, let s flesh out an example using an edit box: Shoes.app :height => 500, :width => 500 do stack do para "Type:" @e = edit_box :width => 0.9, :height => 300 @chars = para "0 characters"