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NSButton

Inherits From:
NSControl : NSView : NSResponder : NSObject

Conforms To:
NSCoding (from NSResponder)
NSObject (from NSObject)

Declared In:
AppKit/NSButton.h

Class Description

NSButton is a subclass of NSControl that intercepts mouse-down events and sends an action message to a target object when it's clicked or pressed.

By virtue of its NSButtonCell, NSButton is an NSControl and displays its state depending on the configuration of the NSButtonCell. The NSButton can have two or three states. If it has two, they are on and off. If it has three, they are on, off, and mixed. A mixed state is useful for a checkbox or radio button that reflects the status of a feature. For example, suppose you have a checkbox that makes the selected text bold. If all the selected text is bold, it's on. If none of the selected text is bold, it's off. If the text has a combination of bold and plain text, it's mixed. Now suppose you click the checkbox. If you turn it on, all the text becomes bold. If you turn it off, all the text becomes plain. If you select the mixed state, the text remains as it is.

By default, a button has two states. You can allow the third state with the method setAllowsMixedState:. To set the button's state directly, use setState:. To cycle through all available states, use setNextState. Note that the state is used as the value, so NSControl methods like setIntValue: actually set the state.

The NSButton can send its action continuously and display highlighting in several different ways. What's more, an NSButton can have a key equivalent that's eligible for triggering whenever the NSButton's NSPanel or NSWindow is the key window.

NSButton and NSMatrix both provide a control view, which is needed to display an NSButtonCell object. However, while NSMatrix requires you to access the NSButtonCells directly, most of NSButton's methods are "covers" for identically declared methods in NSButtonCell. (In other words, the implementation of the NSButton method invokes the corresponding NSButtonCell method for you, allowing you to be unconcerned with the NSButtonCell's existence.) The only NSButtonCell methods that don't have covers relate to the font used to display the key equivalent, and to specific methods for highlighting or showing the NSButton's state (these last are usually set together with NSButton's setButtonType: method).

Creating a Subclass of NSButton

Override the designated initializer (NSView's initWithFrame: method) if you create a subclass of NSButton that performs its own initialization. If you want to use a custom NSButtonCell subclass with your subclass of NSButton, you have to override the setCellClass: method, as described in "Creating New NSControls" in the NSControl class specification.

See the NSButtonCell class specification for more on NSButton's behavior.


Method Types

Setting the button type
- setButtonType:
Setting the state
- allowsMixedState
- setAllowsMixedState:
- setNextState
- setState:
- state
Setting the repeat interval
- getPeriodicDelay:interval:
- setPeriodicDelay:interval:
Setting the titles
- alternateTitle
- attributedAlternateTitle
- attributedTitle
- setAlternateTitle:
- setAttributedAlternateTitle:
- setAttributedTitle:
- setTitle:
- setTitleWithMnemonic:
- title
Setting the images
- alternateImage
- image
- imagePosition
- setAlternateImage:
- setImage:
- setImagePosition:
Modifying graphic attributes
- bezelStyle
- isBordered
- isTransparent
- setBordered:
- setBezelStyle:
- setTransparent:
Displaying
- highlight:
Setting the key equivalent
- keyEquivalent
- keyEquivalentModifierMask
- setKeyEquivalent:
- setKeyEquivalentModifierMask:
Handling events and action messages
- performClick:
- performKeyEquivalent:

Instance Methods

allowsMixedState

- (BOOL)allowsMixedState

Returns YES if the button has three states: on, off, and mixed. Returns NO if the button has two states: on and off.

See also: - setAllowsMixedState:, - setNextState


alternateImage

- (NSImage *)alternateImage

Returns the image that appears on the button when it's in its alternate state, or nil if there is no alternate image. Note that some button types don't display an alternate image. Buttons don't display images by default.

See also: - image, - imagePosition, - keyEquivalent, - setButtonType:


alternateTitle

- (NSString *)alternateTitle

Returns the string that appears on the button when it's in its alternate state, or the empty string if the button doesn't display an alternate title. Note that some button types don't display an alternate title. By default, a button's alternate title is "Button".

See also: - attributedAlternateTitle, - setButtonType:, - title


attributedAlternateTitle

- (NSAttributedString *)attributedAlternateTitle

Returns the string that appears on the button when it's in its alternate state as an NSAttributedString, or an empty attributed string if the button doesn't display an alternate title. Note that some button types don't display an alternate title. By default, a button's alternate title is "Button".

See also: - setButtonType:, - attributedTitle


attributedTitle

- (NSAttributedString *)attributedTitle

Returns the string that appears on the button when it's in its normal state as an NSAttributedString, or an empty attributed string if the button doesn't display a title. A button's title is always displayed if the button doesn't use its alternate contents for highlighting or displaying the alternate state. By default, a button's title is "Button".

See also: - attributedAlternateTitle, - setButtonType:


bezelStyle

- (NSBezelStyle)bezelStyle

Returns the appearance of the button's border. See setBezelStyle: for the list of the possible values.


getPeriodicDelay:interval:

- (void)getPeriodicDelay:(float *)delay interval:(float *)interval

Returns by reference the delay and interval periods for a continuous button. delay is the amount of time (in seconds) that the button will pause before starting to periodically send action messages to the target object. interval is the amount of time (also in seconds) between those messages.

Default delay and interval values are taken from a user's defaults (60 seconds maximum for each); if the user hasn't specified default values, delay defaults to 0.4 seconds and interval defaults to 0.075 seconds.

See also: - isContinuous (NSControl)


highlight:

- (void)highlight:(BOOL)flag

Highlights (or unhighlights) the button according to flag. Highlighting may involve the button appearing "pushed in" to the screen, displaying its alternate title or image, or causing the button to appear to be "lit." If the current state of the button matches flag, no action is taken.

See also: - setButtonType:


image

- (NSImage *)image

Returns the image that appears on the button when it's in its normal state, or nil if there is no such image. This image is always displayed on a button that doesn't change its contents when highlighting or showing its alternate state. Buttons don't display images by default.

See also: - alternateImage, - setButtonType:


imagePosition

- (NSCellImagePosition)imagePosition

Returns the position of the button's image relative to its title. The return value is one of the following (these are defined in NSCell.h):
Return Value Meaning
NSNoImage The button doesn't display an image (this is the default)
NSImageOnly The button displays an image, but not a title
NSImageLeft The image is to the left of the title
NSImageRight The image is to the right of the title
NSImageBelow The image is below the title
NSImageAbove The image is above the title
NSImageOverlaps The image overlaps the title

If the title is above, below, or overlapping the image, or if there is no image, the text is horizontally centered within the button.

See also: - setButtonType:, - setImage:, - setTitle:


isBordered

- (BOOL)isBordered

Returns YES if the button has a border, NO otherwise. A button's border isn't the single line of most other controls' borders; instead, it's a raised bezel. By default, buttons are bordered.


isTransparent

- (BOOL)isTransparent

Returns YES if the button is transparent, NO otherwise. A transparent button never draws itself, but it receives mouse-down events and tracks the mouse properly.


keyEquivalent

- (NSString *)keyEquivalent

Returns the key-equivalent character of the button, or the empty string if one hasn't been defined. Buttons don't have a default key equivalent.

See also: - keyEquivalentFont (NSButtonCell), - performKeyEquivalent:


keyEquivalentModifierMask

- (unsigned int)keyEquivalentModifierMask

Returns the mask indicating the modifier keys that are applied to the button's key equivalent. Mask bits are defined in NSEvent.h; only NSControlKeyMask, NSAlternateKeyMask, and NSCommandKeyMask bits are relevant in button key-equivalent modifier masks.

See also: - keyEquivalent


performClick:

- (void)performClick:(id)sender

Simulates the user's clicking the button with the mouse. This method essentially highlights the button, sends the button's action message to the target object, and then unhighlights the button. If an exception is raised while the target object is processing the action message, the button is unhighlighted before the exception is propagated out of performClick:.

See also: - performKeyEquivalent:


performKeyEquivalent:

- (BOOL)performKeyEquivalent:(NSEvent *)anEvent

If the character in anEvent matches the button's key equivalent, and the modifier flags in anEvent match the key-equivalent modifier mask, performKeyEquivalent: simulates the user clicking the button by sending performClick: to self, and returns YES. Otherwise, performKeyEquivalent: does nothing and returns NO. performKeyEquivalent: also returns NO in the event that the button is blocked by a modal panel or the button is disabled.

See also: - keyEquivalentModifierMask


setAllowsMixedState:

- (void)setAllowsMixedState:(BOOL)flag

If flag is YES, the button has three states: on, off, and mixed. If flag is NO, the button has two states: on and off.

See also: - allowsMixedState, - setNextState


setAlternateImage:

- (void)setAlternateImage:(NSImage *)image

Sets the image that appears on the button when it's in its alternate state to image and, if necessary, redraws the contents of the button. Note that some button types don't display an alternate image.

See also: - setImage:, - setButtonType:


setAlternateTitle:

- (void)setAlternateTitle:(NSString *)aString

Sets the string that appears on the button when it's in its alternate state to aString. Note that some button types don't display an alternate title.

See also: - setTitle:, - setTitleWithMnemonic:, - setButtonType:, - setFont: (NSButtonCell)


setAttributedAlternateTitle:

- (void)setAttributedAlternateTitle:(NSAttributedString *)aString

Sets the string that appears on the button when it's in its alternate state to the attributed string aString. Note that some button types don't display an alternate title.

See also: - setAttributedTitle:, - setButtonType:, - setFont: (NSButtonCell)


setAttributedTitle:

- (void)setAttributedTitle:(NSAttributedString *)aString

Sets the string that appears on the button when it's in its normal state to the attributed string aString and redraws the button. The title is always shown on buttons that don't use their alternate contents when highlighting or displaying their alternate state.

See also: - setAttributedAlternateTitle:, - setButtonType:, - setFont: (NSButtonCell)


setBezelStyle:

- (void)setBezelStyle:(NSBezelStyle)bezelStyle

Sets the appearance of the border, if the button has one. bezelStyle must be one of the following:

Bezel Style Description
NSNeXTBezelStyle A rectangular button with a 2 pixel border. It looks like OPENSTEP 4.2 button and is available for backwards compatibility only.
NSPushButtonBezelStyle A rounded rectangle button, designed for text.
NSSmallIconButtonBezelStyle A rectangular button with a 2 pixel border, designed for icons.
NSMediumIconButtonBezelStyle A rectangular button with a 3 pixel border, designed for icons.
NSLargeIconButtonBezelStyle A rectangular button with a 4 pixel border, designed for icons.

The button uses shading to look like it's sticking out or pushed in. You can set the shading with setGradientType:.

If the button is not bordered, the bezel style is ignored.

See also: - bezelStyle


setBordered:

- (void)setBordered:(BOOL)flag

Sets whether the button has a bezeled border. If flag is YES, the button displays a border; if NO, the button doesn't display a border. A button's border is not the single line or most other controls' borders; instead, it's a raised bezel. This method redraws the button if setBordered: causes the bordered state to change.


setButtonType:

- (void)setButtonType:(NSButtonType)aType

Sets how the button highlights while pressed and how it shows its state. setButtonType: redisplays the button before returning.

The types available are for the most common button types, which are also accessible in Interface Builder. You can configure different behavior with NSButtonCell's setHighlightsBy: and setShowsStateBy: methods.

aType can be one of eight constants:

Button Type Description
NSMomentaryLight While the button is held down it's shown as "lit." This type of button is best for simply triggering actions, as it doesn't show its state; it always displays its normal image or title. This option is called "Momentary Light" in Interface Builder's Button Inspector. This is the default button type.
NSMomentaryPushButton While the button is held down it's shown as "lit," and also "pushed in" to the screen if the button is bordered. This type of button is best for simply triggering actions, as it doesn't show its state; it always displays its normal image or title. This option is called "Momentary Push" in Interface Builder's Button Inspector.
NSMomentaryChangeButton While the button is held down, the alternate image and alternate title are displayed. The normal image or title are displayed when the button isn't pressed. This option is called "Momentary Change" in Interface Builder's Button Inspector.
NSPushOnPushOffButton The first click both highlights and causes the button to be "pushed in" if the button is bordered. A second click returns it to its normal state. This option is called "Push On/Push Off" in Interface Builder's Button Inspector.
NSOnOffButton The first click highlights the button. A second click returns it to the normal (unhighlighted) state. This option is called "On/Off" in Interface Builder's Button Inspector.
NSToggleButton The first click highlights the button, while a second click returns it to its normal state. Highlighting is performed by changing to the alternate title or image and showing the button as "pushed in" if the button is bordered. This option is called "Toggle" in Interface Builder's Button Inspector.
NSSwitchButton This is a variant of NSToggleButton that has no border, with the default image set to "NSSwitch," and the alternate image set to "NSHighlightedSwitch" (these are system bitmaps). This type of button is available as a separate palette item in Interface Builder.
NSRadioButton Like NSSwitchButton, but the default image is set to "NSRadioButton" and the alternate image is set to "NSHighlightedRadioButton" (these are system bitmaps). This type of button is available as a separate palette item in Interface Builder.

See also: - setAlternateImage:, - setButtonType: (NSButtonCell), - setImage:


setImage:

- (void)setImage:(NSImage *)image

Sets the button's image to anImage, and redraws the button. A button's image is displayed when the button is in its normal state, or all the time for a button that doesn't change its contents when highlighting or displaying its alternate state.

See also: - setImagePosition:, - setAlternateImage:, - setButtonType:


setImagePosition:

- (void)setImagePosition:(NSCellImagePosition)aPosition

Sets the position of the button's image relative to its title. See the imagePosition method description for a listing of possible values for aPosition.


setKeyEquivalent:

- (void)setKeyEquivalent:(NSString *)charCode

Sets the key equivalent character of the button, and redraws the button's interior if it displays a key equivalent instead of an image. The key equivalent isn't displayed if the image position is set to NSNoImage, NSImageOnly or NSImageOverlaps; that is, the button must display both its title and its "image" (the key equivalent in this case), and they must not overlap.

To display a key equivalent on a button, set the image and alternate image to nil, then set the key equivalent, then set the image position.

See also: - performKeyEquivalent:, - setAlternateImage:, - setImage:, - setImagePosition:, - setKeyEquivalentFont: (NSButtonCell)


setKeyEquivalentModifierMask:

- (void)setKeyEquivalentModifierMask:(unsigned int)mask

Sets the mask indicating the modifier keys to be applied to the button's key equivalent. Mask bits are defined in NSEvent.h; only NSControlKeyMask, NSAlternateKeyMask, and NSCommandKeyMask bits are relevant in button key-equivalent modifier masks.

See also: - setKeyEquivalent:


setNextState

- (void)setNextState

Sets the button to its next state. If the button has three states, it cycles through them in this order: on, off, mixed, on, and so forth. If the button has two states, it toggles between them.

See also: - allowsMixedState, - setAllowsMixedState:


setPeriodicDelay:interval:

- (void)setPeriodicDelay:(float)delay interval:(float)interval

Sets the message delay and interval for the button. These two values are used if the button is configured (by a setContinuous: message) to continuously send the action message to the target object while tracking the mouse. delay is the amount of time (in seconds) that a continuous button will pause before starting to periodically send action messages to the target object. interval is the amount of time (also in seconds) between those messages.

The maximum value allowed for both delay and interval is 60.0 seconds; if a larger value is supplied, it's ignored and 60.0 seconds is used.

See also: - setContinuous: (NSControl)


setState:

- (void)setState:(int)value

Sets the button's state to value and, if necessary, redraws the button.

The button can have two or three states. If it has two, value can be 0 for off (the normal or unpressed state) and 1 for on (the alternate or pressed state). If it has three, value can be 1 for on (the feature is in effect everywhere), 0 for off (the feature is in effect nowhere), or -1 for mixed (the feature is in effect somewhere).

To check whether the button uses the mixed state, use the method allowsMixedState:.


setTitle:

- (void)setTitle:(NSString *)aString

Sets the title displayed by the button when in its normal state to aString and, if necessary, redraws the button's contents. This title is always shown on buttons that don't use their alternate contents when highlighting or displaying their alternate state.

See also: - setAlternateTitle:, - setButtonType:, - setTitleWithMnemonic:, - setFont: (NSButtonCell)


setTitleWithMnemonic:

- (void)setTitleWithMnemonic:(NSString *)aString

Sets the title of a button with a character underlined to denote an access key (Windows only). Use an ampersand character to mark the character (the one following the ampersand) to be underlined. For example, the following message causes the "c" in "Receive" to be underlined:

[aButton setTitleWithMnemonic:NSLocalizedString(@"Re&ceive")];

See also: - setAlternateTitle:, - setButtonType:, - setTitle:, - setFont: (NSButtonCell)


setTransparent:

- (void)setTransparent:(BOOL)flag

Sets whether the button is transparent, and redraws the button if necessary. A transparent button tracks the mouse and sends its action, but doesn't draw. A transparent button is useful for sensitizing an area on the screen so that an action gets sent to a target when the area receives a mouse click.


state

- (int)state

Returns the button's state. The button can have two or three states. If it has two, it returns 0 for off (the normal or unpressed state) and 1 for on (the alternate or pressed state). If it has three, it returns 1 for on (the feature is in effect everywhere), 0 for off (the feature is in effect nowhere), or -1 for mixed (the feature is in effect somewhere).

To check whether the button uses the mixed state, use the method allowsMixedState:.


title

- (NSString *)title

Returns the title displayed on the button when it's in its normal state (this title is always displayed if the button doesn't use its alternate contents for highlighting or displaying the alternate state). Returns the empty string if the button doesn't display a title. By default, a button's title is "Button".

See also: - alternateTitle, - setButtonType:, - setTitle:, - setTitleWithMnemonic:



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