For example, a button press when the mouse is over an icon can select it, so the icon can be moved to a different location on screen. The mousePressed variable is true if any mouse button is pressed and false if no mouse button is pressed. The variable mouseButton is LEFT, CENTER, or RIGHT depending on the mouse button most recently pressed.
This means that that program mostly sits idle, waiting for events sent by the X server, and then acts upon these events. An event may say 'The user pressed the 1st button mouse in spot (x,y)', or 'The window you control needs to be redrawn'.

This tutorial is the Interactivity chapter from Processing: A Programming Handbook for Visual Designers and Artists, Second Edition, published by MIT Press. © 2014 MIT Press. If you see any errors or have comments, please let us know.

Casey Reas and Ben Fry

Access the Startup Menu by holding down the Ctrl and Alt keys and pressing the Delete key. At the next screen, click on Task Manager. Click on the Startup tab, placing the cursor over X-Mouse Button Control and clicking the Disable button in the lower right corner. Click here to see my video screen capture showing how I set up XMouseButtonControl. In this tutorial I will use LED Edit’s auto layout creator to create a 64 X 64 LED layout which is equally distributed through out all the ports which means each port have 512 LED’s or pixels. Click on “Project Config” in the top menu bar and select “Auto Layout” from the list.The Auto layout window will appear.

The screen forms a bridge between our bodies and the realm of circuits and electricity inside computers. We control elements on screen through a variety of devices such as touch pads, trackballs, and joysticks, but the keyboard and mouse remain the most common input devices for desktop computers. The computer mouse dates back to the late 1960s, when Douglas Engelbart presented the device as an element of the oN-Line System (NLS), one of the first computer systems with a video display. The mouse concept was further developed at the Xerox Palo Alto Research Center (PARC), but its introduction with the Apple Macintosh in 1984 was the catalyst for its current ubiquity. The design of the mouse has gone through many revisions in the last forty years, but its function has remained the same. In Engelbart’s original patent application in 1970 he referred to the mouse as an “X-Y position indicator,” and this still accurately, but dryly, defines its contemporary use.

The physical mouse object is used to control the position of the cursor on screen and to select interface elements. The cursor position is read by computer programs as two numbers, the x-coordinate and the y-coordinate. These numbers can be used to control attributes of elements on screen. If these coordinates are collected and analyzed, they can be used to extract higher-level information such as the speed and direction of the mouse. This data can in turn be used for gesture and pattern recognition.

Keyboards are typically used to input characters for composing documents, email, and instant messages, but the keyboard has potential for use beyond its original intent. The migration of the keyboard from typewriter to computer expanded its function to enable launching software, moving through the menus of software applications, and navigating 3D environments in games. When writing your own software, you have the freedom to use the keyboard data any way you wish. For example, basic information such as the speed and rhythm of the fingers can be determined by the rate at which keys are pressed. This information could control the speed of an event or the quality of motion. It’s also possible to ignore the characters printed on the keyboard itself and use the location of each key relative to the keyboard grid as a numeric position.

The modern computer keyboard is a direct descendant of the typewriter. The position of the keys on an English-language keyboard is inherited from early typewriters. This layout is called QWERTY because of the order of the top row of letter keys. This more than one-hundred-year-old mechanical legacy still affects how we write software today.

Mouse Data

The Processing variables mouseX and mouseY (note the capital X and Y) store the x-coordinate and y-coordinate of the cursor relative to the origin in the upper-left corner of the display window. To see the actual values produced while moving the mouse, run this program to print the values to the console:

When a program starts, the mouseX and mouseY values are 0. If the cursor moves into the display window, the values are set to the current position of the cursor. If the cursor is at the left, the mouseX value is 0 and the value increases as the cursor moves to the right. If the cursor is at the top, the mouseY value is 0 and the value increases as the cursor moves down. If mouseX and mouseY are used in programs without a draw() or if noLoop() is run in setup(), the values will always be 0.

The mouse position is most commonly used to control the location of visual elements on screen. More interesting relations are created when the visual elements relate differently to the mouse values, rather than simply mimicking the current position. Adding and subtracting values from the mouse position creates relationships that remain constant, while multiplying and dividing these values creates changing visual relationships between the mouse position and the elements on the screen. In the first of the following examples, the circle is directly mapped to the cursor, in the second, numbers are added and subtracted from the cursor position to create offsets, and in the third, multiplication and division are used to scale the offsets.

To invert the value of the mouse, subtract the mouseX value from the width of the window and subtract the mouseY value from the height of the screen.

The Processing variables pmouseX and pmouseY store the mouse values from the previous frame. If the mouse does not move, the values will be the same, but if the mouse is moving quickly there can be large differences between the values. To see the difference, run the following program and alternate moving the mouse slowly and quickly. Watch the values print to the console.

Draw a line from the previous mouse position to the current position to show the changing position in one frame and reveal the speed and direction of the mouse. When the mouse is not moving, a point is drawn, but quick mouse movements create long lines.

Use the mouseX and mouseY variables with an if structure to allow the cursor to select regions of the screen. The following examples demonstrate the cursor making a selection between different areas of the display window. The first divides the screen into halves, and the second divides the screen into thirds.

Use the logical operator && with an if structure to select a rectangular region of the screen. As demonstrated in the following example, when a relational expression is made to test each edge of a rectangle (left, right, top, bottom) and these are concatenated with a logical AND, the entire relational expression is true only when the cursor is inside the rectangle.

This code asks, “Is the cursor to the right of the left edge and is the cursor to the left of the right edge and is the cursor beyond the top edge and is the cursor above the bottom?” The code for the next example asks a set of similar questions and combines them with the keyword else to determine which one of the defined areas contains the cursor.

Mouse buttons

Computer mice and other related input devices typically have between one and three buttons; Processing can detect when these buttons are pressed with the mousePressed and mouseButton variables. Used with the button status, the cursor position enables the mouse to perform different actions. For example, a button press when the mouse is over an icon can select it, so the icon can be moved to a different location on screen. The mousePressed variable is true if any mouse button is pressed and false if no mouse button is pressed. The variable mouseButton is LEFT, CENTER, or RIGHT depending on

X Mouse Button Control Tutorial