Drawn list widget

The application-drawn list widget (EwDrawnList) allows an application to draw arbitrary graphics to represent each object in the list. It combines list behavior with a drawing area-based widget. Following is an example of a drawn list widget:

An application hooks the displayCallback to draw the items in the list. If the items in the list have different sizes, an application should hook the measureCallback to specify the height of each individual item in the list. If all items have the same height, the itemHeight resource can be used to specify the height in pixels.

The applicationDrawnStates resource allows for the specification of visuals for any of the emphasis states in the list, such as selection emphasis or cursored emphasis. Applications can choose to allow the drawn list to provide these emphasis visuals. In the following code, a list of CgFontStructs is added to a drawn list, and each font name in the list is drawn with the font that it describes.

Object subclass: #DrawnListExample

instanceVariableNames: 'fontStructs'

classVariableNames: "

poolDictionaries: 'CgConstants CwConstants EwConstants'

open

| shell drawnList |

shell := CwTopLevelShell

createApplicationShell: 'shell'

argBlock: [:w | w title: 'Drawn List Example'].

fontStructs := ((CgDisplay default listFonts: '*' maxnames: 100)

collect: [:fontName |

CgDisplay default loadQueryFont: fontName]) asOrderedCollection.

drawnList := shell

createScrolledDrawnList: 'drawnList'

argBlock: [:w | w items: fontStructs].

drawnList

addCallback: XmNdisplayCallback

receiver: self

selector: #display:clientData:callData:

clientData: nil;

addCallback: XmNmeasureCallback

receiver: self

selector: #measure:clientData:callData:

clientData: nil;

addCallback: XmNdestroyCallback

receiver: self

selector: #destroy:clientData:callData:

clientData: nil.

drawnList manageChild.

shell realizeWidget.

display: widget clientData: clientData callData: callData

"Display the fontStruct by drawing its font name in the

upper left-hand corner of the specified rectangle, using

the fontStruct as the font."

| fontStruct |

fontStruct := callData object.

callData gc setFont: fontStruct font.

callData drawable

drawString: callData gc

x: callData x

y: callData y + fontStruct ascent

string: fontStruct name

 

measure: widget clientData: clientData callData: callData

"Measure the fontStruct by querying its height."

| fontStruct |

fontStruct := callData object.

callData height: fontStruct height

 

destroy: widget clientData: clientData callData: callData

"Destroy the fontStruct collection."

fontStructs do: :fontStruct | fontStruct freeFont].