vb.net barcode printing The Font Panel in Java

Creator Data Matrix 2d barcode in Java The Font Panel

The next special panel we re going to look at is NSFontPanel. Unlike the color panel, the font panel, does not have a matching control that launches it. However, it can be integrated fairly well with the contents of the system s Format menu, as you ll see a little later. What we re going to do here is create an action method that opens the font panel, and another method which updates the text field. Then we ll create a button to let the user invoke this functionality. In the WindowLabAppDelegate.h file, add the following method declaration inside the class s @interface block:

- (IBAction)showFontPanel:(id)sender;

Then switch to the .m file and add the following methods to the @implementation section:

- (IBAction)showFontPanel:(id)sender { NSFontPanel *panel = [NSFontPanel sharedFontPanel]; NSFontManager *manager = [NSFontManager sharedFontManager]; [manager setSelectedFont:[title font] isMultiple:NO]; [panel orderFront:nil]; }

- (void)changeFont:(id)sender { // here, 'sender' is the shared NSFontManager instance NSFont *oldFont = [title font]; NSFont *newFont = [sender convertFont:oldFont]; [title setFont:newFont]; }

This follows the same usage pattern as the color panel. When the user clicks on a font, the font panel uses the responder chain to look for an object that implements the changeFont: action method, and it manages to find it in our app delegate. Here, things are slightly more complicated, because in both of these methods we make use of a shared instance of the NSFontManager class. A running application s notion of the selected or current font is held within this shared instance, which we use first in showFontPanel: to indirectly tell the NSFontPanel which font it should begin displaying, and then again in changeFont: to get the new selected font. We get the new font by passing the old font to the font manager s convertFont: method, which combines characteristics of the old font with the state of the user s selection in the font panel (for example, if the old font is Lucida Grande/Bold/36, and the user selects Times New Roman, leaving the rest alone, the converted font will be Times New Roman/Bold/36). Now, switch back to Interface Builder, where we ll hook things up. First make your window a little taller. Then duplicate the button you ve already got, name the new one Show Font Panel, and Ctrl-drag from it to the app delegate in the main nib window, connecting to the showFontPanel: action method. Save your work, go back to Xcode, and Build & Run. You can now change both the color and the font for the displayed text (see Figure 10 4).

Next, we re going to demonstrate a simple pattern that occurs often in Cocoa development: making a controller class that loads its own nib file, becoming the owner of all the objects in the file. In every application we ve created so far, all the GUI

elements are contained inside the application s single .nib file. This works well enough for simple applications, but it has its limits. For one thing, we only have one instance of each window and each controller in the nib. For another thing, the entire main nib file is loaded at once, when the application is starting up, and the more stuff you have in that nib, the slower and more memory-intensive the startup phase will be. Granted, on modern computers with several gigabytes of RAM, this may not be such a huge problem, but as a programmer it s always good to try to not waste CPU and RAM recklessly. Finally, putting too many top-level objects (windows, controllers, and the like) into a single nib file makes life more difficult for you, the programmer, because it s harder to see which controllers and windows belong together. The solution to both of these problems is to distribute some of your GUI objects into other nib files, and mediate their use with controller classes that load the nibs. This technique is used by many Cocoa applications, which commonly split windows for preferences, documents, tools, and so on into separate nib files. The following sections will demonstrate two different ways of doing this, with increasing complexity.