HOMEWORK 2: Building Custom Swing Components

This is an INDIVIDUAL assignment.

Objective

In the last assignment you learned how to put together Swing applications by using existing components. In this assignment, you'll learn how to create your own Swing component from scratch. We'll be building a component to display a photo and any associated annotations. At this stage of the homework, a single PhotoComponent will be displayed as the "content area" of the photo album application. This PhotoComponent you'll write will have to respond to both keyboard and mouse input (using the mouse to simulate a pen), and render appropriate output.

The learning goals for this assignment are:

Experience with the Swing drawing pipeline.
Experience writing a variety of input listeners.
Experience with the Swing component architecture

Description

Don't be intimidated by the length of the homework description! Although long, most of this writeup is here just to provide detail about what I expect from this assignment, as well as some hints about how best to do the implementation.

In this homework, we'll create a custom Swing component that can display a single photo and any annotations associated with that photo. A single one of these PhotoComponents will be displayed at any given time, and will serve as the content area of the photo album application. The basic idea is that this component can display a single photo, and also provide a way to store and render annotations including text and drawn strokes: You can "flip the photo over" to annotate on it using either mouse strokes or text.

There are a number of specific requirements for this assignment:

#1: Basic component architecture.

You should start by creating a new subclass of JComponent, called PhotoComponent or some such. Your new component should have a paintComponent() method in it that will do all the drawing, plus contain whatever state information is associated with the photo. This will likely include a reference to the Image that represents the photo, a boolean indicating whether it is in its "flipped" state or not, plus a representation for any annotations on the photo (described later). It will implement the necessary listeners (and add these listeners) so that it can respond to input events.

#2: Photo display.

Your component will display a single photo, and so your component should render this image in its paintComponent() method whenever it is requested to draw itself. But be sure to realize that the component may be larger or smaller than the photo it displays (because the user may resize the window, for example). Your component should have a size and a preferredSize that are the size of the photo itself, but you probably don't want any minimumSize or maximumSize. When your PhotoComponent is initialized, and before any photo is loaded, you probably want to use some default value for size and preferred size

So that the component looks good in cases where the window is larger than the photo itself, you should render some nice-looking background behind the photo, which will be visible when the photo doesn't cover the entire extend of the component. This can be as simple as a solid color, or some pattern such as graph paper. You'd create this effect by simply doing some drawing in your paintComponent() method before drawing the image.

If the user shrinks the window so that the component cannot display the entire photograph, it should be scrollable so that the user can pan around the image. The easiest way to do this is to simply insert your PhotoComponent into a JScrollPane, and then insert that JScrollPane into the container area in your application. There are settings on JScrollPane that determine whether the scrollbars are always displayed, or just when they are needed (it's fine if the scrollbars are always displayed). Remember that the way JScrollPane works is that it allows its child to be any size it wants, but clips and positions it so that the correct part is shown under the visible region. This is why you want to make sure your component has a size and preferred size. If you reload a photo and change the size, you will probably want to call revalidate() on your PhotoComponent so that the scroll pane "notices" that its size has been updated.

If you want, you might also like to display some graphical "frame" around the picture, such as a while border or "scrapbook corners," although this is not required.

#3: Flipping to annotate.

With physical paper photos, people often flip them over to write notes and other annotations on the back. Your PhotoComponent should support this also. Double-clicking on the photo should cause it to be replaced by a plain white surface of the same size as the photo for annotation. The background of your component should be drawn the same--only the photo should be replaced. When in this mode, you can annotate the photo's "back" via drawn strokes and typed text (see #4 and #5 below). Double-click on the photo back again to flip it over and see the photo again. The current "flip state" of a given photo should be stored in a boolean in your component.

Hint: Your paintComponent method will have two paths through it, depending on the setting of this boolean. In the default path, it will draw the background and then the image. In the flipped path, it will draw the background, draw the white surface, and then draw the annotations (see below)

#4: Support for drawn strokes.

When in the flipped state, and the annotation mode radio button from HW1 is in the DRAWING mode, you should be able to draw onto the photo back using the mouse (if you're using a pen tablet, the pen also produces mouse events and so this sort of implementation will also work nicely on a pen-based computer). What this means is that the user should be able to draw freehand strokes by dragging the mouse on the photo back with the button pressed. The component should show the stroke while it is in the process of being drawn, to give appropriate feedback to the user. Drawing should only occur in the white back-of-photo area, not the background.

Hint: Remember that you'll need to redraw all of these same strokes anytime the Swing repaint pipeline tells you that you need to paint your component. So, the classic way to do this is to add strokes to a display list that contains the things to be rendered, and then in your paint code you simply iterate through the items to be painted, rendering them to the screen.
Hint: Painted strokes will look much better if you use Java2D's anti-aliasing mechanism. Look at the setRenderingHints() method on Graphics2D.

#5: Support for typed text.

When the annotation mode radio button is in the TEXT mode, your component should allow typed text to be entered onto the page.

Here's how text entry should work. First, the user selects the TEXT annotation mode (from Homework 1), then mouses out a rectangular region into which the text will go. This region should have a distinct appearance, such as a yellow post-it note. Next, when the user begins typing, the text should appear in the post-it, starting inside the top left, and fill out to the edge of the box. Once a line of text hits the edge, the system should word-wrap to the next line. If the user types more text than can fit in the post-it vertically, the post-it should expand vertically to accommodate the additional text.

While you don't have to do any especially fancy text processing (no ligatures or custom fonts or anything like that), you should make the basics work correctly. For this assignment, the basics are:

You should implement word wrap. This means that when your typing hits the edge of the post-it you should find the rightmost whitespace in the line, break the line there, and put the remaining word on a new line. If there is no whitespace in the line then you can just break the line at the last character that will fit on the line.
Use reasonable linespacing. Remember: ascent + descent + leading.
It's ok if the user positions post-it notes so that they overlap each other. More recent post-it notes should be drawn over the top of prior content, visibly blocking it.

You do not have to implement more complicated features (although you're welcome to for extra credit). For example, you do not have to implement:

Backspacing over already entered characters.
The ability to put the insertion point into already-entered text and edit it.
The ability to select a span of text.

Hint: While you could perhaps build off the JTextArea component as a way to implement the post-it notes, please do not do that for this assignment. My goal is for you to learn how to do low-level text processing code from scratch. This approach also gives you more control over the text and its appearance.
Hint: While all the word wrapping and repainting stuff may seem difficult, it's possible to architect the code in a way that makes it pretty straightforward. The key is to remember that, like with stokes above, you'll need to keep a data structure containing the text that will be rendered by your component. So one way to architect things is to simply create a new object (called TextRegion perhaps) whenever the user draws the post-it; at a minimum, this object needs to remember the X and width of the post-it, and the set of characters that are associated with it. Whenever characters are typed they are simply added to the string in the current TextRegion object. The job of your paint code, then, is simply to iterate over the list of TextRegions in your display list and draw them to the screen, wrapping as you draw based on the width of the region. In other words, rather than precomputing and saving the positions of every substring, you just figure it out each time when you paint.

#6: Integration with the rest of the application

Once you've implemented and debugged your PhotoComponent, it's time to integrate it into the application you wrote for Homework #1.

Important Note: my recommendation is to not use full-size digital images when testing your application. Images take a lot of memory, and without additional configuration settings when you run Java, your Java Virtual Machine may run out of memory (this will especially be a problem when we start handling multiple photos in the next assignment.) So, to make your life easier, you may want to scale down your photos to 640x480 or some such.

When your application starts up, it should contain no photos, and hence no PhotoComponents.

Selecting Import should prompt the user for a photo file (via the JFileChooser), and create a new PhotoComponent containing the selected photo and display it in the content area.

NOTE that for this assignment, we'll only be dealing with a single photo at a time. So you don't need to worry about being able to select a folder and importing a bunch of photos... it's ok if your program just pops up an error message or ignores any selection that's not a single file. In later homework assignments, we'll build a container component that will display multiple PhotoComponents at the same time.

The currently displayed PhotoComponent should be used in the central content area of your application, should resize properly when the window is resized, etc., as described above. (You don't have to worry about doing fancy stuff like scaling photos.)

Selecting Delete Photo should delete the current PhotoComponent, meaning that the application should just show an empty content area.

Selecting Previous and Next will do nothing, since there's only ever zero or one photos in this version of the homework.

Changing any of the View Modes will do nothing, since we're currently only ever displaying zero or one photos.

Extra Credit

There are a lot of ways to augment this assignment, should you choose to. Some obvious ways are:

More text and graphics processing
- Allow editing of already-entered text, such as insertion or backspace. Up to +4 points, depending on features implemented
- Customizable fonts. Either on a photo-wide basis (+1 point), or for individual spans of text (+3 points).
- Pen sizes and ink color: +2 points.
- Additional drawing tools, such as elipses or rectangles: Up to +4 points, depending on what's implemented.
Fancy features
- Saving and loading of data. PhotoComponents should remember what picture they're displaying as well as the strokes or text on them, between runs of the application. It'd be cool if this happened automatically as strokes or characters are entered, or photos are loaded, so you never have to remember to hit "save." Up to +4 points.
- Scaling photos. Provide a control to let the user scale the displayed photo up or down. +2 points
- Other stuff. If you build in some particularly neat feature, make sure you let us know about it when you turn it in and we'll consider it for possible extra credit.

Deliverable

See here for instructions on how to submit your homework. These instructions will be the same for each assignment.