Example: a primitive extended widget

Two example extended widgets are provided in the next two sections. The first, below, is a subclass of CwExtendedPrimitive, and the second, on page Example: a composite extended widget, is a subclass of CwExtendedComposite. The prefix 'Cew' is used to differentiate these new widgets from basic widgets. For simplicity, the examples do not include robust error-checking, nor does each widget provide a complete set of resources.

The CewEntryField widget, shown below, has a label on the left and a text box on the right. It allows a user to enter text into its text box, and it invokes a valueChanged callback if a new value is present when the user either hits the tab key or clicks on a different widget.

The extended widget is implemented using a CwForm as the primary widget with CwLabel and CwText children. A losingFocus callback on the CwText enables the widget to test entered data, and possibly call any registered valueChanged callbacks.

CwExtendedPrimitive subclass: #CewEntryField

instanceVariableNames: 'label value valueChangedCallback labelWidget textWidget '

classVariableNames: ''

poolDictionaries: ''

createPrimaryWidget: theName parent: parent argBlock: argBlock

"Private - Create and answer the basic widget that is the root of the

widget hierarchy for the receiver's widget system."

^self parent

createForm: theName, 'Form'

argBlock: argBlock

createWidgetSystem

"Private - Create the children of the receiver's primary widget which form the

widget hierarchy."

| pw |

pw := self primaryWidget.

self labelWidget:

(pw

createLabel: pw name , 'Label'

argBlock: [:w | w labelString: self label])

manageChild.

self textWidget:

(pw

createText: pw name , 'Text'

argBlock: [:w |

w

borderWidth: 1;

value: self value])

manageChild.

self textWidget

addCallback: XmNlosingFocusCallback

receiver: self

selector: #losingFocus:clientData:callData:

clientData: nil.

"Add form attachments for the two children."

self labelWidget

setValuesBlock: [:w |

w

topAttachment: XmATTACHFORM;

leftAttachment: XmATTACHFORM;

rightAttachment: XmATTACHNONE;

bottomAttachment: XmATTACHFORM].

self textWidget

setValuesBlock: [:w |

w

topAttachment: XmATTACHFORM;

leftAttachment: XmATTACHWIDGET;

leftWidget: self labelWidget;

rightAttachment: XmATTACHFORM;

bottomAttachment: XmATTACHFORM].

initializeResources

"Private - Set the default extended widget resource values. This is sent

during create with isCreated set to false. All extended resource

variables should be initialized to default values here."

label := String new.

value := String new.

initializeAfterCreate

"Private - Perform any widget-specific post-create initialization."

self primaryWidget

horizontalSpacing: 4;

verticalSpacing: 4;

borderWidth: 1.

"Resources that involve the children of the primary widget have to be set

after the children are created."

self labelWidget labelString: label.

self textWidget value: value.

label

"Answer the value of the label resource.

Resource type: String

Default setting: ''

Resource access: CSG

Description:

Specifies the string for the CewEntryField's label.

This label is to the left of the CewEntryField's text box."

^label

label: resourceValue

"Set the value of the label resource to resourceValue.

Resource type: String

Default setting: ''

Resource access: CSG

Description:

Specifies the string for the CewEntryField's label.

This label is to the left of the CewEntryField's text box."

label := resourceValue.

self isCreated

ifTrue: [labelWidget labelString: resourceValue]

value

"Answer the value of the value resource.

Resource type: String

Default setting: '

Resource access: CSG

Description:

Specifies the string for the CewEntryField's value.

This value is displayed in the CewEntryField's text box if

set using the #value: message, or if a valid string followed

by a tab key is entered by the user.

Note that while the user is typing, the string displayed in the

text box might not be the same as the CewEntryField's value."

^value

value: resourceValue

"Set the value of the value resource to resourceValue.

Resource type: String

Default setting: '

Resource access: CSG

Description:

Specifies the string for the CewEntryField's value.

This value is displayed in the CewEntryField's text box if

set using the #value: message, or if a valid string followed

by a tab key is entered by the user.

Note that while the user is typing, the string displayed in the

text box might not be the same as the CewEntryField's value."

value := resourceValue.

self isCreated

ifTrue: [textWidget value: resourceValue]

valueChangedCallback

"Private - Answer the value of valueChangedCallback."

valueChangedCallback isNil

ifTrue: [self valueChangedCallback: OrderedCollection new].

^valueChangedCallback

valueChangedCallback: resourceValue

"Set the value of the XmNvalueChangedCallback resource to resourceValue.

Resource type: OrderedCollection of CwCallbackRec

Default setting: OrderedCollection new

Resource access: C

Callback reason: XmCRVALUECHANGED

Calldata structure: CwValueCallbackData

Description:

Specifies the list of callbacks that is called when the value

of the CewEntryField has changed. The reason sent by the

callback is XmCRVALUECHANGED. The structure returned

by this callback is CwValueCallbackData."

valueChangedCallback := resourceValue.

labelWidget

"Private - Answer the value of labelWidget."

^labelWidget

labelWidget: aCwLabel

"Private - Set the value of labelWidget to aCwLabel."

labelWidget := aCwLabel.

textWidget

"Private - Answer the value of textWidget."

^textWidget

textWidget: aCwText

"Private - Set the value of textWidget to aCwText."

textWidget := aCwText.

losingFocus: widget clientData: clientData callData: callData

"Private - Process a losing focus callback for the primary widget."

| newValue |

newValue := self textWidget value.

"If the new value is different, invoke the entryField widget's

valueChanged callback."

self value = newValue

ifTrue: [

self

value: newValue;

callCallbacks: XmNvalueChangedCallback

callData: (CwValueCallbackData new value: newValue)].

Using the CewEntryField primitive extended widget

The following code creates a CewEntryField instance, sets its name and label resources inside the create argBlock, and hooks a valueChanged callback to it. The new widget is shown in the diagram at the beginning of this section, on page Example: a primitive extended widget.

| shell entryField |

shell := CwTopLevelShell

createApplicationShell: 'CewEntryField Test'

argBlock: nil.

entryField := CewEntryField

createManagedWidget: 'entryField'

parent: shell

argBlock: [:w |

w

label: 'Name :';

value: 'Your name here'].

entryField

addCallback: XmNvalueChangedCallback

receiver: self

selector: #valueChanged:clientData:callData:

clientData: nil.

shell realizeWidget.

valueChanged: widget clientData: clientData callData: callData

"Display the new value on the transcript."

Transcript cr; show: 'Value changed to: ' , callData value printString.

The CewEntryField class can be subclassed to provide a slightly different extended widget by simply overriding one method, as in the following class definition for CewNumericEntryField:

CewEntryField subclass: #CewNumericEntryField

instanceVariableNames: ''

classVariableNames: ''

poolDictionaries: ''

losingFocus: widget clientData: clientData callData: callData

"Private - Process a losing focus callback for the primary widget."

| newValue |

newValue := self textWidget value.

"Verify that the new value string represents a number.

If it doesn't, reset the text widget and return."

(newValue notEmpty and: [newValue conform: [:c | c isDigit]])

ifFalse: [^self value: value].

"If the new value is different, invoke the entryField widget's

valueChanged callback."

self value = newValue

ifTrue: [

self

value: newValue;

callCallbacks: XmNvalueChangedCallback

callData: (CwValueCallbackData new value: newValue)]