mousePressed

MousePressed is a name used for a callback function in several graphical programming environments. It denotes the moment a mouse button is pressed and is commonly used to trigger actions in response to user input.

In Processing (Java), developers define a function void mousePressed() { ... }. This function is invoked automatically when any mouse button is pressed while the program is running. Inside it, the programmer can check the mouseButton variable to determine which button was pressed (LEFT, RIGHT, or CENTER). The environment also provides a boolean mousePressed that reflects whether the mouse button is currently held down, allowing state tracking between frames.

In p5.js (JavaScript), the pattern is similar: function mousePressed() { ... } is called on a press event. The global mouseIsPressed flag indicates whether the mouse button is currently pressed, and mouseButton can be used to distinguish buttons. These callbacks are part of a broader set of mouse-related events, including mouseReleased and mouseDragged, which support more complex interactions.

Common usage of mousePressed includes initiating actions such as selecting objects, starting a drag operation, firing a project, or toggling interface elements. The function provides a convenient entry point that responds to user input without needing explicit event listeners in every context.

Differences across environments exist. While Processing uses a dedicated mousePressed callback and a separate mousePressed state, p5.js often organizes input through similar callbacks complemented by a global state variable. Other libraries may implement mouse press handling as part of a broader MouseListener or event object model.

See also: mouseReleased, mouseClicked, mouseDragged.