Develop Reference

How to constrain the mouse cursor within the bounds of the window in LibGDX?

This is a widely known issue that can even sometimes appear on even high-budget professional titles, that when you set the window type to "borderless" and you have an extended display your mouse can "slide off-screen" if the mouse is not constrained to the limits of the display the game is running on currently.
I was wondering how LibGDX can tackle this.
Is there some direct way to constraint mouse movement?
Or does one need to do continuous iterative calculations on mouse position or something?

Libgdx offers built-in function for trapping mouse cursor inside window. Function you are looking is Gdx.input.setCursorCatched(true).
Taken from the docs:
void setCursorCatched(boolean catched)
Only viable on the desktop. Will confine the mouse cursor location to the window and hide the mouse cursor. X and y coordinates are still reported as if the mouse was not catched.
Parameters:
catched - whether to catch or not to catch the mouse cursor
Or checkout documentation by yourself here.

LibGDX is built on top of LWJGL, so you should be able to use the Mouse.setGrabbed() method.
More info in the API: http://www.lwjgl.org/javadoc/org/lwjgl/input/Mouse.html#setGrabbed(boolean)
And here's a discussion on what changes when you call Mouse.setGrabbed(): http://lwjgl.org/forum/index.php?topic=5150.0

Suggestion for implementing a drawing program - UML designer

This program will have an infinite canvas (ie as long as the user scrolls, it becomes bigger) with a tiled background image, and you can drag and drop blocks and draw arrows between blocks. Obviously I won't use a layout manager for placing blocks and lines, since they will be absolutely positioned (any link on this, possibily with a snapping feature?). The problem arises with blocks and lines. Basically I'll have two options:
Using a simple layout for each building block. This is the simplest and clearest approach, but does it scale well when you have hundreds of objects? This may not be uncommon, just imagine a database with 50 tables and dozens of relationships
Drawing everything with primitives (rectangles, bitmaps, etc). This seems too complicated (especially things like text padding and alignment) but may be more scalable if you have a large number of objects. Also there won't be any event handler
Please give me some hints based on your experience. I have never drawn with Java before - well I did something rather basic with PHP and on Android. Here is a simple preview
DISCLAIMER
You are not forced to answer this. I am looking for someone who did something like this before, what's the use of writing I can check an open source project? Do you know how difficult it is to understand someone else's code? I'm talking about implementations details here... Moreover, there is no guarantee that he's right. This project is just for study and will be funny, I don't want to sell it or anything and I don't need your authorization to start it.

Measuring and drawing text isn't such a pain, since java has built in classes for doing that. you may want to take a look at the 2D Text Tutorial for more information. In fact, I did some text drawing computations with a different graphics engine which is much more primitive, and in the end it was rather easy (at least for the single-line drawing, for going multiline see the previous link).
For the infinite canvas problem, that's also something I always wanted to be able to do. A quick search here at stackoverflow gives this which sounds nice, althought I'm not sure I like it. What you can do, is use the way GIMP has a scroll area that can extend as you move - catch the click of the middle mouse button for marking the initial intention to move the viewport. Then, when the mouse is dragged (while the button is clicked) move the viewport of the jscrollpane by the offset between the initial click and the current position. If we moved outside the bounds of the canvas, then you should simply enlarge the canvas.
In case you are still afraid of some of the manual drawing, you can actually have a JPanel as your canvas, with a fixed layout. Then you can override it's paint method for drawing the connectors, while having child components (such as buttongs and text areas) for other interaction (and each component may override it's own paint method in case it wants to have a custom-painted rect).
In my last drawing test in java, I made an application for drawing bezier curves (which are basically curves made of several control points). It was a JPanel with overidden paint method that drew the curve itself, and buttons with custom painting placed on the location of the control points. Clicking on the control point actually was clicking on a button, so it was easy to detect the matching control point (since each button had one control point associated with it). This is bad in terms of efficiency (manual hit detection may be faster) but it was easy in terms of programming.
Anyway, This idea can be extended by having one child JPanel for each class rectangle - this will provide easy click detection and custom painting, while the parent will draw the connectors.
So in short - go for nested JPanels with custom drawing, so that you can also place "on-canvas" widgets (and use real swing widgets such as text labels to do some ready drawing) while also having custom drawing (by overriding the paint method of the panels). Note that the con of this method is that some swing look-and-feel's may interfere with your drawing, so may need to mess a bit with that (as far as I remember, the metal and nimbus look-and-feel's were ok, and they are both cross-platform).

How to make a customizable graph

I'm looking to use the java2d API to make a graph in which users can manipulate certain features using their mouse - such as the scale used for an axis or move around the different points plotted on the graph.
So far all I have found is the drawX methods on a Graphics2D object, however there does not seem to be an easy way to capture a user clicking on one of these and moving it so that I can redraw the graph.
Can anyone suggest the best/easiest way to implement this? Just looking for a point in the right direction.

Not reinventing the wheel is always the best way, there are plenty of excellent libraries you can use: http://www.jfree.org/jfreechart/
If you are looking to implement this yourself, you would listen to mouse events on whatever component you're actually using to display your chart (say a JPanel), and then would have to convert between screen and chart coordinates to figure out what you need to change.

Does SWT Canvas Provide Tools For Mouse Move/Click Active Areas?

I'm creating an application with Java and SWT, and have a workspace generated on a Canvas. I need to make certain areas (controls) on the canvas trigger an event when mouseover-ed or clicked. Of course this could be done by listening to the MouseMoveEvent and checking the location of the mouse manually, but I would like to know if SWT provides an easier way to do this.
Thanks

As far as I know, there is no facility to automate this. You will need to register mouse listeners and investigate the x & y coordinates manually.
A different approach might be adding individual Canvas objects onto an enclosing Canvas. This way, you could add listeners to the individual controls. This will, however, use more memory (as the underlying object has a buffer, as well as the control on top) and redrawing will be more CPU intensive.
My personal preference goes to the first technique.

Thanks for the answer, Paul. I finally created an ArrayList of Rectangle objects for each control. Whenever the mousemove event triggers, I loop through each Rectangle and call Rectangle.contains() with the mouse coordinates. This solution turned out to be very organized.
In my case, the control events are homogenous (they all do the same thing), but if anyone has multiple control actions, Rectangle.data can be used to contain a Command object.

Dynamically changing the tooltip of a draw2d figure

We are currently using Eclipse Draw2D/GEF for an information page describing a process in our application. This basically consists of a matrix of large squares, each containing a matrix of smaller squares. We originally had all the squares as GEF objects, but because of the large volume of them being shown, we found that this did not scale very well and the view took a very long time to open. We then changed it so that only the large squares are Figures and we then draw the smaller squares using the graphic in paintFigure.
The problem that we are running into is that we still want the tooltip to change depending on which small square you are hovering over. I tried to do this by adding a mouseMotionListener and setting the tooltip, through setTooltip, depending on where the mouse currently is. The problem is that once the tooltip is displayed, it does not change any more when setTooltip is called.
Does any one know of an alternative way of doing this? Is there a way of getting the viewpart's PopupHelper and using that? Any help would be appreciated.
Thanks

Hmnn.. interesting problem. Since you paint your own Grid within the Figure, I would think that you have two options.
Try posting SWT events to fool Eclipse. I'd try a focus lost followed by a focused gained, to trigger tooltip machinery, at which point you could get the coordinates and display the appropriate contents.
Don't use the Figure#getTooltip strategy at all. Just show your own composite.

To dynamically change the tooltip, you can hold an instance of the tooltip Figure in your parent Figure. In the constructor of the parent Figure, create a new tooltip Figure (e.g. a Label) and use setToolTip() method to set the tooltip Figure to parent Figure.
When data model is changed, the updated tooltip text/icon can be set to the tooltip Figure. Then you just call setToolTip(tooltipFigure) method again.
You can have a method like:
protected Label toolTipLabel;
protected void updateToolTip(String text, Image icon){
toolTipLabel.setText(text);
toolTipLabel.setIcon(icon);
setToolTip(toolTipLabel);
}
The updateToolTip() method can be invoked in parent Figure's conturctor to initialize the tooltip. And this method can be invoked each time after the data model is changed.
I encountered the same problem in my code and solved it with that method. In my code, I invoked the updateToolTip() in the parentFigure.paintFigure() method.