XmDrawingArea(3)

NAME
XmDrawingArea — The DrawingArea widget class

SYNOPSIS

#include <Xm/DrawingA.h>

DESCRIPTION

DrawingArea is an empty widget that is easily adaptable to a variety of purposes. It does no drawing and defines no behavior except for invoking callbacks. Callbacks notify the application when graphics need to be drawn (exposure events or widget resize) and when the widget receives input from the keyboard or mouse.

Applications are responsible for defining appearance and behavior as needed in response to DrawingArea callbacks.

DrawingArea is also a composite widget and subclass of XmManager that supports minimal geometry management for multiple widget or gadget children.

DrawingArea uses the XmNinitialFocus resource of XmManager to define whether or not DrawingArea will receive focus when it is traversed to, even if it has traversable children. If XmNinitialFocus is NULL, DrawingArea receives focus only if it does not have any traversable children. If XmNinitialFocus is not NULL, then DrawingArea receives focus when traversed to. In the latter case, the application first needs to be able to realize that the DrawingArea will receive focus, then, as appropriate, needs to either call the XmProcessTraversal function for the desired child, or to navigate across the private DrawingArea graphics objects.

The following resources are not currently used by the DrawingArea widget: XmNshadowThickness, XmNtopShadowPixmap, XmNbottomShadowPixmap, XmNtopShadowColor, and XmNbottomShadowColor

  Data Transfer Behavior

DrawingArea has no widget class conversion or destination procedure. Subclasses and the XmNconvertCallback procedures are responsible for any conversion of selections. Subclasses and the XmNdestinationCallback procedures are responsible for any data transfers to the widget.

  Classes

DrawingArea inherits behavior and resources from the Core, Composite, Constraint, and XmManager classes.

The class pointer is xmDrawingAreaWidgetClass.

The class name is XmDrawingArea.

  New Resources

The following table defines a set of widget resources used by the programmer to specify data. The programmer can also set the resource values for the inherited classes to set attributes for this widget. To reference a resource by name or by class in a .Xdefaults file, remove the XmN or XmC prefix and use the remaining letters. To specify one of the defined values for a resource in a .Xdefaults file, remove the Xm prefix and use the remaining letters (in either lowercase or uppercase, but include any underscores between words). The codes in the access column indicate if the given resource can be set at creation time (C), set by using XtSetValues (S), retrieved by using XtGetValues (G), or is not applicable (N/A).

XmNconvertCallback
    Specifies a list of callbacks called when the DrawingArea is asked to convert a selection. The type of the structure whose address is passed to these callbacks is XmConvertCallbackStruct. The reason is XmCR_OK.

XmNdestinationCallback
    Specifies a list of callbacks called when the DrawingArea is the destination of a transfer operation. The type of the structure whose address is passed to these callbacks is XmDestinationCallbackStruct. The reason is XmCR_OK.

XmNexposeCallback
    Specifies the list of callbacks that is called when DrawingArea receives an exposure event. The callback reason is XmCR_EXPOSE. The callback structure also includes the exposure event.

    The default bit gravity for Manager windows is NorthWestGravity. This may cause the XmNexposeCallback procedures not to be invoked when the DrawingArea window is made smaller.

XmNinputCallback
    Specifies the list of callbacks that is called when the DrawingArea receives a keyboard or mouse event (key or button, up or down). The callback reason is XmCR_INPUT. The callback structure also includes the input event.

XmNmarginHeight
    Specifies the minimum spacing in pixels between the top or bottom edge of DrawingArea and any child widget.

XmNmarginWidth
    Specifies the minimum spacing in pixels between the left or right edge of DrawingArea and any child widget.

XmNresizeCallback
    Specifies the list of callbacks that is called when the DrawingArea is resized. The callback reason is XmCR_RESIZE.

XmNresizePolicy
    Controls the policy for resizing DrawingArea widgets. Possible values include XmRESIZE_NONE (fixed size), XmRESIZE_ANY (shrink or grow as needed), and XmRESIZE_GROW (grow only).

  Inherited Resources

DrawingArea inherits behavior and resources from the following superclasses. For a complete description of each resource, refer to the reference page for that superclass.

  Callback Information

A pointer to the following structure is passed to the XmNexposeCallback, XmNinputCallback, and XmNresizeCallback procedures:

typedef struct
{
        int reason;
        XEvent * event;
        Window window;
} XmDrawingAreaCallbackStruct;

reason
    Indicates why the callback was invoked.

event
    Points to the XEvent that triggered the callback. This is NULL for the XmNresizeCallback.

window
    Is set to the widget window.

A pointer to the following structure is passed to the XmNconvertCallback procedures:

typedef struct
{
        int reason;
        XEvent *event;
        Atom selection;
        Atom target;
        XtPointer source_data;
        XtPointer location_data;
        int flags;
        XtPointer parm;
        int parm_format;
        unsigned long parm_length;
        int status;
        XtPointer value;
        Atom type;
        int format;
        unsigned long length;
} XmConvertCallbackStruct;

reason
    Indicates why the callback was invoked.

event
    Points to the XEvent that triggered the callback. It can be NULL.

selection
    Indicates the selection for which conversion is being requested. Possible values are CLIPBOARD, PRIMARY, SECONDARY, and _MOTIF_DROP.

target
    Indicates the conversion target.

source_data
    Contains information about the selection source. When the selection is _MOTIF_DROP, source_data is the DragContext. Otherwise, it is NULL.

location_data
    Contains information about the location of data to be converted. If the value is NULL, the data to be transferred consists of the widget's current selection.

flags
    Indicates the status of the conversion. Following are the possible values:

    XmCONVERTING_NONE
        This flag is currently unused.

    XmCONVERTING_PARTIAL
        The target widget was able to be converted, but some data was lost.

    XmCONVERTING_SAME
        The conversion target is the source of the data to be transferred.

    XmCONVERTING_TRANSACT
        This flag is currently unused.

parm
    Contains parameter data for this target. If no parameter data exists, the value is NULL.

    When selection is CLIPBOARD and target is _MOTIF_CLIPBOARD_TARGETS or _MOTIF_DEFERRED_CLIPBOARD_TARGETS, the value is the requested operation (XmCOPY, XmMOVE, or XmLINK).

parm_format
    Specifies whether the data in parm should be viewed as a list of char, short, or long quantities. Possible values are 0 (when parm is NULL), 8 (when the data in parm should be viewed as a list of chars), 16 (when the data in parm should be viewed as a list of shorts), or 32 (when the data in parm should be viewed as a list of longs). Note that parm_format symbolizes a data type, not the number of bits in each list element. For example, on some machines, a parm_format of 32 means that the data in parm should be viewed as a list of 64-bit quantities, not 32-bit quantities.

parm_length
    Specifies the number of elements of data in parm, where each element has the size specified by parm_format. When parm is NULL, the value is 0.

status
    An IN/OUT member that specifies the status of the conversion. The initial value is XmCONVERT_DEFAULT. The callback procedure can set this member to one of the following values:

    XmCONVERT_DEFAULT
        This value means that the widget class conversion procedure, if any, is called after the callback procedures return. If the widget class conversion procedure produces any data, it overwrites the data provided by the callback procedures in the value member.

    XmCONVERT_MERGE
        This value means that the widget class conversion procedure, if any, is called after the callback procedures return. If the widget class conversion procedure produces any data, it appends its data to the data provided by the callback procedures in the value member. This value is intended for use with targets that result in lists of data, such as TARGETS.

    XmCONVERT_DONE
        This value means that the callback procedure has successfully finished the conversion. The widget class conversion procedure, if any, is not called after the callback procedures return.

    XmCONVERT_REFUSE
        This value means that the callback procedure has terminated the conversion process without completing the requested conversion. The widget class conversion procedure, if any, is not called after the callback procedures return.

value
    An IN/OUT parameter that contains any data that the callback procedure produces as a result of the conversion. The initial value is NULL. If the callback procedure sets this member, it must ensure that the type, format, and length members correspond to the data in value. The callback procedure is responsible for allocating, but not for freeing, memory when it sets this member.

type
    An IN/OUT parameter that indicates the type of the data in the value member. The initial value is INTEGER.

format
    An IN/OUT parameter that specifies whether the data in value should be viewed as a list of char, short, or long quantities. The initial value is 8. The callback procedure can set this member to 8 (for a list of char), 16 (for a list of short), or 32 (for a list of long).

length
    An IN/OUT member that specifies the number of elements of data in value, where each element has the size symbolized by format. The initial value is 0.

A pointer to the following callback structure is passed to the XmNdestinationCallback procedures:

typedef struct
{
        int reason;
        XEvent *event;
        Atom selection;
        XtEnum operation;
        int flags;
        XtPointer transfer_id;
        XtPointer destination_data;
        XtPointer location_data;
        Time time;
} XmDestinationCallbackStruct;

reason
    Indicates why the callback was invoked.

event
    Points to the XEvent that triggered the callback. It can be NULL.

selection
    Indicates the selection for which data transfer is being requested. Possible values are CLIPBOARD, PRIMARY, SECONDARY, and _MOTIF_DROP.

operation
    Indicates the type of transfer operation requested.

    •   When the selection is PRIMARY, possible values are XmMOVE, XmCOPY, and XmLINK.

    •   When the selection is SECONDARY or CLIPBOARD, possible values are XmCOPY and XmLINK.

    •   When the selection is _MOTIF_DROP, possible values are XmMOVE, XmCOPY, XmLINK, and XmOTHER. A value of XmOTHER means that the callback procedure must get further information from the XmDropProcCallbackStruct in the destination_data member.

flags
    Indicates whether or not the destination widget is also the source of the data to be transferred. Following are the possible values:

    XmCONVERTING_NONE
        The destination widget is not the source of the data to be transferred.

    XmCONVERTING_SAME
        The destination widget is the source of the data to be transferred.

transfer_id
    Serves as a unique ID to identify the transfer transaction.

destination_data
    Contains information about the destination. When the selection is _MOTIF_DROP, the callback procedures are called by the drop site's XmNdropProc, and destination_data is a pointer to the XmDropProcCallbackStruct passed to the XmNdropProc procedure. When the selection is SECONDARY, destination_data is an Atom representing a target recommmended by the selection owner for use in converting the selection. Otherwise, destination_data is NULL.

location_data
    Contains information about the location where data is to be transferred. The value is always NULL when the selection is SECONDARY or CLIPBOARD. If the value is NULL, the data is to be inserted at the widget's cursor position. location_data is only valid for the duration of a transfer. Once XmTransferDone procedures start to be called, location_data will no longer be stable.

time
    Indicates the time when the transfer operation began.

  Translations

XmDrawingArea inherits translations from XmManager. Before calling the XmManager actions, all events in the inherited translations except <BtnMotion>, <EnterWindow>, <LeaveWindow>, <FocusIn>, and <FocusOut> also call the DrawingAreaInput() action.

XmDrawingArea has the following additional translations. The following key names are listed in the X standard key event translation table syntax. This format is the one used by Motif to specify the widget actions corresponding to a given key. A brief overview of the format is provided under VirtualBindings(3). For a complete description of the format, please refer to the X Toolkit Instrinsics Documentation.

<BtnDown>:
    DrawingAreaInput()

<BtnUp>:
    DrawingAreaInput()

<KeyDown>:
    DrawingAreaInput() ManagerGadgetKeyInput()

<KeyUp>:
    DrawingAreaInput()

  Action Routines

The XmDrawingArea action routines are

DrawingAreaInput():
    Unless the event takes place in a gadget, calls the callbacks for XmNinputCallback

ManagerGadgetKeyInput():
    Causes the current gadget to process a keyboard event

  Additional Behavior

The XmDrawingArea widget has the following additional behavior:

<Expose>:
    Calls the callbacks for XmNexposeCallback

<Widget Resize>:
    Calls the callbacks for XmNresizeCallback

  Virtual Bindings

The bindings for virtual keys are vendor specific. For information about bindings for virtual buttons and keys, see VirtualBindings(3).

RELATED

Composite(3), Constraint(3), Core(3), XmCreateDrawingArea(3), and XmManager(3).