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Mathematica > Dynamic Interactivity > Custom Interface Construction > Low-Level Interface Control > EventHandler >

BUILT-IN MATHEMATICA SYMBOL

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EventHandler

displays as expr, evaluating

whenever

occurs in connection with expr.

MORE INFORMATION

Standard mouse-related event specifications include:

	"MouseClicked"	mouse clicked without moving
	{"MouseClicked",i}	mouse button i clicked without moving
	"MouseDown"	primary mouse button depressed
	{"MouseDown",i}	mouse button i depressed
	"MouseDragged"	mouse moving with primary button depressed
	{"MouseDragged",i}	mouse moving with button i depressed
	"MouseMoved"	mouse moves in the region defined by expr
	"MouseUp"	primary mouse button released
	{"MouseUp",i}	mouse button i released

For mouse events, EventHandler handles events for which the mouse is within the rectangular region defined by the display of expr.

Standard keyboard-related event specifications include:

	"KeyDown"	any key on the keyboard depressed
	{"KeyDown","x"}	key x depressed
	"ReturnKeyDown"	Return or Enter key depressed
	"EscapeKeyDown"	Esc key depressed
	"LeftArrowKeyDown"	left arrow key depressed
	"RightArrowKeyDown"	right arrow key depressed
	"UpArrowKeyDown"	up arrow key depressed
	"DownArrowKeyDown"	down arrow key depressed

Standard interface events include:

	{"MenuCommand","name"}	menu command with specified name chosen
	"WindowClose"	closing of window requested

If functions like MousePosition or CurrentValue are evaluated in a particular , the values they give are those associated with the event that triggered that .

When EventHandler expressions are nested, events are by default shared by all the expressions, with the innermost expression operating first on a particular event.

The following options can be given:

	PassEventsDown	Automatic	whether to pass events to inner event handlers
	PassEventsUp	True	whether to pass events to outer event handlers

With the default setting PassEventsDown->Automatic, events handled by an EventHandler are not also passed to built-in event handlers in the Mathematica front end.

Basic Examples (2)

Create text that turns red when clicked:

Create text that toggles between red and green when clicked repeatedly:

Create text that turns red when clicked:

Out[1]=

Create text that toggles between red and green when clicked repeatedly:

Out[1]=

Create a graphic that changes color when clicked:

Allow events to pass down to inner event handlers, changing the color as well as position:

Do not pass mouse events to the inner event handler:

By default, nested EventHandler actions are triggered upon the specified action:

By disabling PassEventsUp, prevent the outer EventHandler action from being triggered:

Allow the outer EventHandler action when the Shift key is pressed:

Applications (2)

Automatically fit a line to a set of points:

Piecewise interpolation through a set of points:

Properties & Relations (1)

EventHandler can be used with MousePosition:

Mouseover Button ClickPane LocatorPane CurrentValue Manipulate MousePosition CellEventActions NotebookEventActions FrontEndEventActions ControlActive

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