XPWidgetDefs API

WIDGET DEFINITIONS

A widget is a call-back driven screen entity like a push-button, window, text entry field, etc.

Use the widget API to create widgets of various classes. You can nest them into trees of widgets to create complex user interfaces.

XPWidgetID

typedef void * XPWidgetID;

A Widget ID is an opaque unique non-zero handle identifying your widget. Use 0 to specify “no widget”. This type is defined as wide enough to hold a pointer. You receive a widget ID when you create a new widget and then use that widget ID to further refer to the widget.

XPWidgetPropertyID

Properties are values attached to instances of your widgets. A property is identified by a 32-bit ID and its value is the width of a pointer.

Each widget instance may have a property or not have it. When you set a property on a widget for the first time, the property is added to the widget; it then stays there for the life of the widget.

Some property IDs are predefined by the widget package; you can make up your own property IDs as well.

NameValueDescription
xpProperty_Refcon"0" A window's refcon is an opaque value used by client code to find other data based on it.
xpProperty_Dragging"1" These properties are used by the utlities to implement dragging.
xpProperty_DragXOff"2"
xpProperty_DragYOff"3"
xpProperty_Hilited"4" Is the widget hilited? (For widgets that support this kind of thing.)
xpProperty_Object"5" Is there a C++ object attached to this widget?
xpProperty_Clip"6" If this property is 1, the widget package will use OpenGL to restrict drawing to the Wiget's exposed rectangle.
xpProperty_Enabled"7" Is this widget enabled (for those that have a disabled state too)?
xpProperty_UserStart"10000" NOTE: Property IDs 1 - 999 are reserved for the widgets library.

NOTE: Property IDs 1000 - 9999 are allocated to the standard widget classes provided with the library.

Properties 1000 - 1099 are for widget class 0, 1100 - 1199 for widget class 1, etc.

XPMouseState_t

When the mouse is clicked or dragged, a pointer to this structure is passed to your widget function.

typedef struct {
     int                       x;
     int                       y;
     // Mouse Button number, left = 0 (right button not yet supported.
     int                       button;
     // Scroll wheel delta (button in this case would be the wheel axis number).
     int                       delta;
} XPMouseState_t;

XPKeyState_t

When a key is pressed, a pointer to this struct is passed to your widget function.

typedef struct {
     // The ASCII key that was pressed.  WARNING: this may be 0 for some non-ASCII key sequences.
     char                      key;
     // The flags.  Make sure to check this if you only want key-downs!
     XPLMKeyFlags              flags;
     // The virtual key code for the key
     char                      vkey;
} XPKeyState_t;

XPWidgetGeometryChange_t

This structure contains the deltas for your widget’s geometry when it changes.

typedef struct {
     int                       dx;
     // +Y = the widget moved up
     int                       dy;
     int                       dwidth;
     int                       dheight;
} XPWidgetGeometryChange_t;

XPDispatchMode

The dispatching modes describe how the widgets library sends out messages. Currently there are three modes:

NameValueDescription
xpMode_Direct"0" The message will only be sent to the target widget.
xpMode_UpChain"1" The message is sent to the target widget, then up the chain of parents until the message is
handled or a parentless widget is reached.
xpMode_Recursive"2" The message is sent to the target widget and then all of its children recursively depth-first.
xpMode_DirectAllCallbacks"3" The message is snet just to the target, but goes to every callback, even if it is handled.
xpMode_Once"4" The message is only sent to the very first handler even if it is not accepted. (This is really only useful for some internal widget library functions.)

XPWidgetClass

typedef int XPWidgetClass;

Widget classes define predefined widget types. A widget class basically specifies from a library the widget function to be used for the widget. Most widgets can be made right from classes.

xpWidgetClass_None

#define xpWidgetClass_None   0

An unspecified widget class. Other widget classes are in XPStandardWidgets.h

WIDGET MESSAGES

XPWidgetMessage

Widgets receive 32-bit messages indicating what action is to be taken or notifications of events. The list of messages may be expanded.

NameValueDescription
xpMsg_None"0" No message, should not be sent.
xpMsg_Create"1" The create message is sent once per widget that is created with your widget function and once
for any widget that has your widget function attached.

Dispatching: Direct

Param 1: 1 if you are being added as a subclass, 0 if the widget is first being created.
xpMsg_Destroy"2" The destroy message is sent once for each message that is destroyed that has your widget function.

Dispatching: Direct for all

Param 1: 1 if being deleted by a recursive delete to the parent, 0 for explicit deletion.
xpMsg_Paint"3" The paint message is sent to your widget to draw itself. The paint message is the bare-bones
message; in response you must draw yourself, draw your children, set up clipping and culling,
check for visibility, etc. If you don't want to do all of this, ignore the paint message and
a draw message (see below) will be sent to you.

Dispatching: Direct
xpMsg_Draw"4" The draw message is sent to your widget when it is time to draw yourself. OpenGL will be set up
to draw in 2-d global screen coordinates, but you should use the XPLM to set up OpenGL state.

Dispatching: Direct
xpMsg_KeyPress"5" The key press message is sent once per key that is pressed. The first parameter is the type of key
code (integer or char) and the second is the code itself. By handling this event, you consume the
key stroke.

Handling this message 'consumes' the keystroke; not handling it passes it to your parent widget.

Dispatching: Up Chain

Param 1: A pointer to an XPKeyState_t structure with the keystroke.
xpMsg_KeyTakeFocus"6" Keyboard focus is being given to you. By handling this message you accept keyboard focus. The
first parameter will be one if a child of yours gave up focus to you, 0 if someone set focus on
you explicitly.

Handling this message accepts focus; not handling refuses focus.

Dispatching: direct

Param 1: 1 if you are gaining focus because your child is giving it up, 0 if someone is explicitly
giving you focus.
xpMsg_KeyLoseFocus"7" Keyboard focus is being taken away from you. The first parameter will be one if you are losing
focus because another widget is taking it, or 0 if someone called the API to make you lose focus
explicitly.

Dispatching: Direct

Param 1: 1 if focus is being taken by another widget, 0 if code requested to remove focus.
xpMsg_MouseDown"8" You receive one mousedown event per click with a mouse-state structure pointed to by parameter 1,
by accepting this you eat the click, otherwise your parent gets it. You will not receive drag and
mouse up messages if you do not accept the down message.

Handling this message consumes the mouse click, not handling it passes it to the next widget.
You can act 'transparent' as a window by never handling moues clicks to certain areas.

Dispatching: Up chain NOTE: Technically this is direct dispatched, but the widgets library will shop
it to each widget until one consumes the click, making it effectively "up chain".

Param 1: A pointer to an XPMouseState_t containing the mouse status.
xpMsg_MouseDrag"9" You receive a series of mouse drag messages (typically one per frame in the sim) as the mouse is
moved once you have accepted a mouse down message. Parameter one points to a mouse-state structure
describing the mouse location. You will continue to receive these until the mouse button is
released.
You may receive multiple mouse state messages with the same mouse position. You will receive mouse
drag events even if the mouse is dragged out of your current or original bounds at the time of the
mouse down.

Dispatching: Direct

Param 1: A pointer to an XPMouseState_t containing the mouse status.
xpMsg_MouseUp"10" The mouseup event is sent once when the mouse button is released after a drag or click. You only
receive this message if you accept the mouseDown message. Parameter one points to a mouse state
structure.

Dispatching: Direct

Param 1: A pointer to an XPMouseState_t containing the mouse status.
xpMsg_Reshape"11" Your geometry or a child's geometry is being changed.

Dispatching: Up chain

Param 1: The widget ID of the original reshaped target.

Param 2: A pointer to a XPWidgetGeometryChange_t struct describing the change.
xpMsg_ExposedChanged"12" Your exposed area has changed.

Dispatching: Direct
xpMsg_AcceptChild"13" A child has been added to you. The child's ID is passed in parameter one.

Dispatching: Direct

Param 1: The Widget ID of the child being added.
xpMsg_LoseChild"14" A child has been removed from to you. The child's ID is passed in parameter one.

Dispatching: Direct

Param 1: The Widget ID of the child being removed.
xpMsg_AcceptParent"15" You now have a new parent, or have no parent. The parent's ID is passed in, or 0 for no parent.

Dispatching: Direct

Param 1: The Widget ID of your parent
xpMsg_Shown"16" You or a child has been shown. Note that this does not include you being shown because your parent
was shown, you were put in a new parent, your root was shown, etc.

Dispatching: Up chain

Param 1: The widget ID of the shown widget.
xpMsg_Hidden"17" You have been hidden. See limitations above.

Dispatching: Up chain

Param 1: The widget ID of the hidden widget.
xpMsg_DescriptorChanged"18" Your descriptor has changed.

Dispatching: Direct
xpMsg_PropertyChanged"19" A property has changed. Param 1 contains the property ID.

Dispatching: Direct

Param 1: The Property ID being changed.

Param 2: The new property value
xpMsg_MouseWheel"20" The mouse wheel has moved.

Return 1 to consume the mouse wheel move, or 0 to pass the message to a parent.
Dispatching: Up chain

Param 1: A pointer to an XPMouseState_t containing the mouse status.
xpMsg_CursorAdjust"21" The cursor is over your widget. If you consume this message, change the XPLMCursorStatus
value to indicate the desired result, with the same rules as in XPLMDisplay.h.

Return 1 to consume this message, 0 to pass it on.

Dispatching: Up chain
Param 1: A pointer to an XPMouseState_t struct containing the mouse status.

Param 2: A pointer to a XPLMCursorStatus - set this to the cursor result you desire.
xpMsg_UserStart"10000" NOTE: Message IDs 1000 - 9999 are allocated to the standard widget classes provided with the library
with 1000 - 1099 for widget class 0, 1100 - 1199 for widget class 1, etc. Message IDs 10,000 and
beyond are for plugin use.

WIDGET CALLBACK FUNCTION

XPWidgetFunc_t

typedef int (* XPWidgetFunc_t)(
                         XPWidgetMessage      inMessage,    
                         XPWidgetID           inWidget,    
                         intptr_t             inParam1,    
                         intptr_t             inParam2);    

This function defines your custom widget’s behavior. It will be called by the widgets library to send messages to your widget. The message and widget ID are passed in, as well as two ptr-width signed parameters whose meaning varies with the message. Return 1 to indicate that you have processed the message, 0 to indicate that you have not. For any message that is not understood, return 0.