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SYNOPSIS

#include <agar/core.h>
#include <agar/gui.h>

DESCRIPTION

An Agar graphical user interface is described as a tree of widgets (i.e., structures derived from AG_Widget).

A widget object is always attached (via AG_ObjectAttach(3)) to a parent container widget. Some container widgets (such as AG_Box(3) or AG_Window(3)) are designed as general-purpose container widgets. Other widgets (such as AG_FileDlg(3)) will internally create, attach and position a specific set of child widgets to create a complex, easily re-usable dialog (Agar developers are encouraged to create custom widgets using this technique).

The AG_Widget structure is derived from AG_Object(3). Using Agar's Object system, custom widgets are easily implemented (or derived from existing widget classes) as part of user applications. Agar widgets are extensively re-used. The Object system also provides the AG_Event(3) system and the AG_Variable(3) interface which is the basis of widget bindings (see BINDINGS section below).

INHERITANCE HIERARCHY

AG_Object(3)-> AG_Widget.

CLASS OPERATIONS

Object operations specific to the AG_Widget class are defined as follows:

typedef struct ag_widget_class {
	struct ag_object_class _inherit;
	void (*draw)(AG_Widget *w);
	void (*size_request)(AG_Widget *w, AG_SizeReq *req);
	int  (*size_allocate)(AG_Widget *w, const AG_SizeAlloc *alloc);
} AG_WidgetClass;

The draw() operation renders the widget to the display. Throughout the documentation, the draw() operation is referred to as the rendering context, and some functions (such as AG_WidgetBlitSurface()) are not safe to invoke in any other context.

The size_request() option queries the widget for an initial, preferred geometry, without any guarantee that the request will be satisfied. For example, a AG_Label(3) widget might return the expected size in pixels of the rendered label's text.

The size_allocate() function is called whenever the widget has been allocated a new size or position within its parent container. The AG_SizeAlloc parameter specifies the new allocation. It is also safe to assume that when size_allocate is invoked, the w, h, x, y members of the AG_Widget structure are already set to the new allocated position and size.

The size_allocate() routine of a container widget is responsible for positioning and dimensioning of child widgets attached to it (by calling AG_WidgetSizeAlloc() on them -- see SIZING section below). The function should return 0 on success or -1 to flag the widget as "undersize", disabling further calls to draw().

SIZING

void AG_Expand (AG_Widget *widget)

void AG_ExpandHoriz (AG_Widget *widget)

void AG_ExpandVert (AG_Widget *widget)

void AG_WidgetSizeReq (AG_Widget *widget, AG_SizeReq *req)

void AG_WidgetSizeAlloc (AG_Widget *widget, AG_SizeAlloc *alloc)

void AG_WidgetSetPosition (AG_Widget *widget, int x, int y)

void AG_WidgetSetSize (AG_Widget *widget, int w, int h)

void AG_WidgetSetGeometry (AG_Widget *widget, AG_Rect rect)

void AG_WidgetUpdate (AG_Widget *widget)

The AG_Expand() function arranges for the widget to expand, filling all available area in its parent container widget. AG_ExpandHoriz() and AG_ExpandVert() cause the widget to expand to fill available space horizontally or vertically.

Note that most widget constructors recognize AG_FOO_EXPAND, AG_FOO_HFILL and AG_FOO_VFILL option flags. Setting these flags is equivalent to calling AG_Expand(), AG_ExpandHoriz() and AG_ExpandVert(), respectively.

The AG_WidgetSizeReq() function invokes the size_request() operation of the widget and returns its size requisition into req. AG_WidgetSizeAlloc() allocates the given position and geometry of the widget. If the w or h argument is <= 0, the AG_WIDGET_UNDERSIZE flag is set, preventing the widget from subsequent rendering.

AG_WidgetSizeReq() and AG_WidgetSizeAlloc() are meant to be called only from within the size_request() and size_allocate() functions of a container widget implementation, in order to size and position the child widgets attached to the container (if you must set widget geometries explicitely, use either the AG_Fixed(3) container, or create your own container widget).

The AG_SizeReq and AG_SizeAlloc structures are defined as follows:

typedef struct ag_size_req {
	int w, h;			/* Requested geometry in pixels */
} AG_SizeReq;

typedef struct ag_size_alloc {
	int w, h;			/* Allocated geometry in pixels */
	int x, y;			/* Allocated position in pixels */
} AG_SizeAlloc;

AG_WidgetSetPosition() sets the effective position of the widget relative to its parent container. AG_WidgetSetSize() sets the size of the widget in pixels. AG_WidgetSetGeometry() sets both position and size of a widget from the specified AG_Rect. These functions are typically only used in the context of the size_request() and size_allocate() routines of container widgets.

AG_WidgetUpdate() requests an update of the computed coordinates and geometries of all widgets attached to the widget's current window. The widget may or may not be attached to a parent window (the actual update will be performed later, before rendering starts in AG_WindowDraw()). AG_WidgetUpdate() should be called following AG_ObjectAttach(3) or AG_ObjectDetach(3) calls made in event context, or manual modifications of the x, y, w, h fields of the AG_Widget structure.

INPUT STATE

void AG_WidgetEnable (AG_Widget *widget)

void AG_WidgetDisable (AG_Widget *widget)

int AG_WidgetEnabled (AG_Widget *widget)

int AG_WidgetDisabled (AG_Widget *widget)

The "enabled" flag of a widget determines whether the user is allowed to modify whatever data the widget is accessing. The interpretation of this flag is widget-specific. AG_WidgetEnable() sets the flag, AG_WidgetDisable() clears it. These functions will raise the widget-enabled and widget-disabled events accordingly.

The functions AG_WidgetEnabled() and AG_WidgetDisabled() return the current "enabled" state of the widget. The AG_Widget object must be locked when the call is made.

FOCUS STATE

The focus state of widgets enables the reception of specific types of events which are filtered by default. The focus state also affects the behavior and appearance of some widgets. A widget holding focus (in a currently focused window) will receive mouse events mouse-motion(), mouse-button-up(), as well as keyboard events key-up() and key-down() (note that unfocused widgets can be configured to receive those events unfiltered as well using the AG_WIDGET_UNFOCUSED_* options).

void AG_WidgetSetFocusable (AG_Widget *widget, int enable)

int AG_WidgetFocus (AG_Widget *widget)

void AG_WidgetUnfocus (AG_Widget *widget)

int AG_WidgetIsFocused (AG_Widget *widget)

int AG_WidgetIsFocusedInWindow (AG_Widget *widget)

void AG_WidgetForwardFocus (AG_Widget *widget, AG_Widget *widgetToFocus)

AG_WidgetSetFocusable() specifies whether the widget should be allowed to receive focus (1 = accept focus, 0 = reject focus). The default is to reject focus. Further AG_WidgetFocus() calls on a widget rejecting focus will return 0.

The AG_WidgetFocus() function gives focus to the given widget (and all of its parent widgets, up to the parent window if there is one). AG_WidgetFocus() returns 1 on success and 0 if the widget cannot gain focus (i.e., AG_WIDGET_FOCUSABLE is not set). If the widget is already focused, the function is a no-op and returns 1.

AG_WidgetUnfocus() removes the focus state from the given widget and its children (but not the parent window if any).

AG_WidgetIsFocused() returns 1 if the widget is currently holding focus (i.e., the widget has the focus flag set, and its parent window, if any, is focused as well). AG_WidgetIsFocusedInWindow() returns 1 if the widget has the focus flag set (without evaluating the focus state of any parent windows).

AG_WidgetForwardFocus() arranges automatic forwarding of the focus to a specified widget. Whenever AG_WidgetFocus will be invoked on widget, the focus will be given to widgetToFocus instead.

COORDINATES

int AG_WidgetArea (AG_Widget *widget, int x, int y)

int AG_WidgetRelativeArea (AG_Widget *widget, int x, int y)

The AG_WidgetArea() routine tests whether view coordinates x and y lie inside of the widget's allocated space. The AG_WidgetRelativeArea() variant accepts widget coordinates.

BLITTING SURFACES

These functions manage blitting of graphical surfaces. They are designed specifically for use in GUI widgets. The AG_WidgetBlit*() routines must all be invoked from rendering context (i.e., the draw operation of widgets), and may not be used in any other context.

void AG_WidgetBlit (AG_Widget *widget, AG_Surface *src, int x, int y)

int AG_WidgetMapSurface (AG_Widget *widget, AG_Surface *su)

int AG_WidgetMapSurfaceNODUP (AG_Widget *widget, AG_Surface *su)

void AG_WidgetReplaceSurface (AG_Widget *widget, int surface_id, AG_Surface *newSurface)

void AG_WidgetReplaceSurfaceNODUP (AG_Widget *widget, int surface_id, AG_Surface *newSurface)

void AG_WidgetUnmapSurface (AG_Widget *widget, int surface_id)

void AG_WidgetUpdateSurface (AG_Widget *widget, int surface_id)

void AG_WidgetBlitFrom (AG_Widget *dstWidget, AG_Widget *srcWidget, int surface_id, AG_Rect *rs, int x, int y)

void AG_WidgetBlitSurface (AG_Widget *widget, int surface_id, int x, int y)

The AG_WidgetBlit() function performs a software->hardware blit from the surface src to the video display at the given widget coordinates. AG_WidgetBlit() must invoked in rendering context. See AG_Surface(3) for more information on the Agar surface structure.

Software to hardware blits are slow, so the widget system provides an interface to efficiently take advantage of graphics hardware where it is available. AG_WidgetMapSurface() registers the specified AG_Surface(3) with the widget, returning an integer handle to that surface. The surface can be subsequently rendered by calling AG_WidgetBlitSurface() or AG_WidgetBlitFrom() using this handle. The exact manner in which the surface is rendered depends on the Agar driver in use. For OpenGL-based drivers, a matching hardware texture will typically be generated for the surface on the first call to AG_WidgetBlitSurface(), and cached.

By default, mapped surfaces are automatically freed once the widget is destroyed. The AG_WidgetMapSurfaceNODUP() variant sets the "NODUP" flag on the given surface, so the widget system will never attempt to free the surface.

Note that AG_WidgetMapSurface() will never duplicate the surface. The function merely registers the provided surface pointer with the widget structure. The surface pointer must remain valid for the lifetime of the widget (if in doubt, use AG_SurfaceDup(3)).

Under multithreading, AG_WidgetMapSurface() may be invoked from any context, but the returned name is only valid as long as the widget is locked (see AG_ObjectLock(3)).

AG_WidgetReplaceSurface() replaces the contents of a previously-mapped surface with the contents of newSurface. The AG_WidgetReplaceSurfaceNODUP() variant avoids duplicating the surface.

AG_WidgetUnmapSurface() destroys the given surface mapping. It is equivalent to invoking AG_WidgetReplaceSurface() with a NULL surface. The function is safe to use from any context.

It is important to note that in OpenGL mode, AG_WidgetReplaceSurface() and AG_WidgetUnmapSurface() will not immediately delete any previous texture associated with the previous surface. Instead, it will queue the delete operation for future execution from rendering context, as required by thread safety.

The AG_WidgetUpdateSurface() function should be invoked whenever a mapped surface is changed. If hardware surfaces are supported, it will cause an upload of the software surface to the hardware (otherwise it is a no-op).

The AG_WidgetBlitFrom() function renders a previously mapped (possibly hardware) surface from the source widget srcWidget (using source rectangle rs) onto the destination widget dstWidget, at coordinates x, y. This function must be invoked in rendering context.

The AG_WidgetBlitSurface() variant invokes AG_WidgetBlitFrom with the same argument for both srcWidget and dstWidget (and rs set to NULL).

BINDINGS

Agar widgets can be configured to directly access data of specific types. For example, AG_Slider(3) provides a binding called value, which (in the current implementation) supports the standard integer and floating-point types. Connecting value to an integer or floating point variable allows the user to directly set the value of the variable with the need for tedious callback routines. Similarly, AG_Textbox(3) connects to a text buffer. It is also possible to configure function bindings such that the value is evaluated from a provided function every time the variable is retrieved.

Widget bindings are established using the AG_BindFoo(), AG_BindFooFn() and AG_BindFooMp() functions, see AG_Variable(3) for more information.

Bindings are specifically documented in the API reference. Manual pages for standard Agar widgets include a BINDINGS section with a list of bindings supported by each widget, their supported data types and effects.

Since the value of bindings associated with a widget often dictates the way the widget is rendered (e.g., AG_Button(3) is drawn as a pressed button if its state binding is 1), Agar provides a built-in facility to monitor binding values and request a video update whenever the value changes:

CONTROLLING REDRAW

void AG_Redraw (AG_Widget *widget)

void AG_RedrawOnChange (AG_Widget *widget, int refresh_ms, const char *binding_name)

void AG_RedrawOnTick (AG_Widget *widget, int refresh_ms)

The AG_Redraw() function signals that the widget must be redrawn to the video display. It is equivalent to setting the dirty variable of the widget's parent window to 1. If called from rendering context, AG_Redraw() is a no-op.

The AG_RedrawOnChange() function arranges for the widget to be automatically redrawn whenever the value associated with the existing binding binding_name changes. The value of the binding will be checked at the specified interval refresh_ms in milliseconds. If a refresh_ms argument of -1 is passed, the effect of any previous AG_RedrawOnChange() call with the specified binding is disabled.

The AG_RedrawOnTick() function arranges for the widget to be unconditionally redrawn at the specified interval in milliseconds. If a refresh_ms argument of -1 is passed, the effect of any previous AG_RedrawOnTick() call is disabled.

WIDGET QUERIES

AG_Window * AG_ParentWindow (AG_Widget *widget)

AG_Widget * AG_WidgetFind (AG_Display *view, const char *name)

AG_Widget * AG_WidgetFindFocused (AG_Window *win)

AG_Widget * AG_WidgetFindPoint (const char *classMask, int x, int y)

AG_Widget * AG_WidgetFindRect (const char *classMask, int x, int y, int w, int h)

AG_ParentWindow() returns a pointer to the parent AG_Window(3) for the given widget. If the widget is unattached, NULL is returned. The pointer is only valid as long as the widget's parent VFS is locked.

The AG_WidgetFind() function searches for a given widget by name, given an absolute path, and returns a pointer to the widget, or NULL. AG_WidgetFind() works differently from the generic AG_ObjectFind(3) function, in that widgets not effectively attached to the VFS may be included in the search (for example, widgets attached to AG_Notebook(3) tabs).

AG_WidgetFindFocused() recursively searches win for a widget holding focus. Where multiple widgets may be holding focus, widgets found deepest in the tree have priority over their parents. AG_WidgetFindFocused() returns NULL if no widget is focused.

AG_WidgetFindPoint() searches for a widget matching the given class mask enclosing the point specified in display (pixel) coordinates. The AG_WidgetFindRect() variant requires that the widget enclose the specified rectangle.

The pointer returned by AG_WidgetFind*(), should be considered valid only as long as the parent VFS remains locked.

RENDERING CONTROL

void AG_PushClipRect (AG_Widget *widget, AG_Rect r)

void AG_PopClipRect (AG_Widget *widget)

void AG_WidgetDraw (AG_Widget *widget)

void AG_BeginRendering (AG_Driver *drv)

void AG_EndRendering (AG_Driver *drv)

void AG_WidgetHide (AG_Widget *widget)

void AG_WidgetShow (AG_Widget *widget)

void AG_WidgetHideAll (AG_Widget *widget)

void AG_WidgetShowAll (AG_Widget *widget)

int AG_WidgetVisible (AG_Widget *widget)

AG_Surface * AG_WidgetSurface (AG_Widget *widget)

The AG_PushClipRect() function pushes a rectangle (in widget coordinates) onto the stack of clipping rectangles, and AG_PopClipRect() pops the last entry from the clipping rectangle stack. The effective clipping rectangle will be the intersection of all rectangles on this stack. AG_PushClipRect() and AG_PopClipRect() must be invoked in rendering context.

The AG_WidgetDraw() routine renders a widget to the display. It is typically invoked from an event loop routine (such as AG_EventLoop(3)), to recursively draw the hierarchy of visible GUI elements.

In the event loop, AG_WidgetDraw() invocations must be enclosed between calls to AG_BeginRendering() and AG_EndRendering().

The AG_WidgetHide() and AG_WidgetShow() functions toggle the visibility of the specified widget (setting the AG_WIDGET_HIDE flag as appropriate).

The AG_WidgetHideAll() and AG_WidgetShowAll() routines toggle the visibility of the specified widget and its children by setting the AG_WIDGET_VISIBLE flag (which works independently of AG_WIDGET_HIDE). These routines are intended to be used by container widgets (for example, AG_Notebook(3) which needs to show or hide tabbed containers).

AG_WidgetVisible() returns 1 if the widget is currently visible (equivalent to checking the AG_WIDGET_VISIBLE flag).

The AG_WidgetSurface() routine renders the widget to a newly-allocated AG_Surface(3). This surface should be freed after use.

STYLE PROPERTIES

Presentation settings such as fonts and colors are stored as named AG_Variable(3) properties (e.g., "font-size", "color", "color#hover", etc.) Those properties should be set using the following functions:

void AG_SetFont (AG_Widget *widget, const AG_Font *font)

void AG_SetStyle (AG_Widget *widget, const char *which, const char *value)

The AG_SetFont() function sets the widget's default font attributes to match those of the specified font object.

The AG_SetStyle() function sets the specified style attribute to the given value. Accepted attributes are as follows:

font-family	Font face specification ("Courier", "Terminal").
font-size	Font size in points ("10pts") or ratio ("50%").
font-weight	Font weight, either "bold" or "normal".
font-style	Font style, either "italic" or "normal".
color	Main color of the widget. Colors may be specified as unsigned 8-bit components with "rgb(r,g,b[,a])", or floating-point HSV parameters with "hsv(h,s,v[,a])". In either mode, components may be expressed as a ratio to the parent widget's color components by appending a "%".
text-color	Color for rendered text.
line-color	Color for line drawings.
shape-color	Color for polygons and other filled shapes.
border-color	Color for cosmetic borders.

An optional selector may be appended to the attribute names. Accepted selectors include "#disabled", "#hover" and "#selected". Selectors may be interpreted differently on a per-widget basis.

STANDARD WIDGET ACTIONS

User-generated events such as key presses or mouse button events can be tied to actions, such as executing a specified routine or controlling a boolean variable. Registered actions are described by the AG_Action structure.

Where the conditions for execution of an Action are fixed (e.g., a specific mouse button was clicked, or a specific key was pressed), use of AG_ActionOn*() is preferred over low-level event handlers (such as "key-down" or "mouse-button-down"), because it allows keyboard and mouse bindings to be configured by the end-user in a standard way. AG_Menu(3) also provides interfaces for working with widget actions.

AG_Action * AG_ActionFn (AG_Widget *widget, const char *action, void (*fn)(AG_Event *), const char *fnArgs, ...)

AG_Action * AG_ActionSetInt (AG_Widget *widget, const char *action, int *variable, int value)

AG_Action * AG_ActionSetFlag (AG_Widget *widget, const char *action, Uint *variable, Uint bitmask, int value)

AG_Action * AG_ActionToggleInt (AG_Widget *widget, const char *action, int *variable)

AG_Action * AG_ActionToggleFlag (AG_Widget *widget, const char *action, Uint *variable, Uint bitmask)

void AG_ActionOnButtonDown (AG_Widget *widget, int button, const char *action)

void AG_ActionOnButtonUp (AG_Widget *widget, int button, const char *action)

void AG_ActionOnKeyDown (AG_Widget *widget, AG_KeySym sym, AG_KeyMod mod, const char *action)

void AG_ActionOnKeyUp (AG_Widget *widget, AG_KeySym sym, AG_KeyMod mod, const char *action)

void AG_ActionOnKey (AG_Widget *widget, AG_KeySym sym, AG_KeyMod mod, const char *action)

int AG_ExecMouseAction (AG_Widget *widget, AG_ActionEventType type, int button, int x, int y)

int AG_ExecKeyAction (AG_Widget *widget, AG_ActionEventType type, AG_KeySym sym, AG_KeyMod mod)

int AG_ExecAction (AG_Widget *widget, AG_Action *a)

AG_ActionFn() registers a new widget action which is to invoke a callback function fn, with arguments fnArgs. See AG_Event(3) for a description of the fnArgs format.

AG_ActionSetInt() registers a new action which is to set an integer variable to a specified value. Instead of an integer variable, AG_ActionSetFlag() sets the bits specified by bitmask to the specified value (of 1 or 0). The AG_ActionToggleInt() and AG_ActionToggleFlag() variants do not take an explicit value argument, and toggle the current value instead.

AG_ActionOnButtonDown() and AG_ActionOnButtonUp() tie an action to a button press and a button release event, respectively. The button argument specifies the button index (see AG_MouseButton(3)). AG_ActionOnKeyDown() and AG_ActionOnKeyUp() tie an action to a key press and key release event, respectively. The sym argument specifies the key (see AG_KeySym(3)), and mod specifies the modifier keys which must be in effect. To match any key or any modifier state, AG_KEY_ANY or AG_KEYMOD_ANY can be used.

With AG_ActionOnKeyDown() and AG_ActionOnKeyUp(), the action is triggered once immediately on key press or key release. The AG_ActionOnKey() variant ties an action to a key press, but with "key repeat" behavior. The action is triggered immediately once after an initial key press. If the key combination is held longer than the "key delay" (by default 250ms), the event is repeated with the "key repeat" interval (by default 30ms).

If there are currently no event handlers registered for "key-up", "key-down", "mouse-button-up" and "mouse-button-down", the AG_ActionOn*() functions automatically register event handlers which will invoke AG_ExecMouseAction() or AG_ExecKeyAction() as appropriate (see below).

AG_ExecMouseAction() executes any action associated with mouse button events. It is typically invoked from the "mouse-button-down" and "mouse-button-up" event handlers of the widget. Accepted type values are AG_ACTION_ON_BUTTONDOWN and AG_ACTION_ON_BUTTONUP. button is the pressed button index (see AG_MouseButton(3)). x and y is the position of the cursor in the widget's coordinate system.

AG_ExecKeyAction() executes any action associated with keyboard events. It is typically invoked from the "key-down" and "key-up" event handlers of the widget. Accepted type values are AG_ACTION_ON_KEYDOWN and AG_ACTION_ON_KEYUP. sym and mod specify the key index and modifier state (see AG_KeySym(3) and AG_KeyMod(3)).

AG_ExecAction() executes the specified action. AG_ExecAction() is rarely used directly, but it is invoked internally by the AG_ExecFooAction() functions.

EVENTS

The GUI system may send AG_Widget objects the following events:

widget-shown (void)	The widget is now visible. NOTE: Handlers for this event should be set using AG_AddEvent(3) as opposed to AG_SetEvent(3).
widget-hidden (void)	The widget is no longer visible. NOTE: Handlers for this event should be set using AG_AddEvent(3) as opposed to AG_SetEvent(3).
widget-enabled (void)	Input state has been enabled with AG_WidgetEnable(3).
widget-disabled (void)	Input state has been disabled with AG_WidgetDisable(3).
widget-moved (void)	The widget (or one of its parents) has been moved.
widget-gainfocus (void)	The widget now holds focus inside its parent container.
widget-lostfocus (void)	The widget no longer holds focus.
widget-reshape (void)	Widget size has changed and USE_OPENGL is set (and the GL_PROJECTION or GL_MODELVIEW matrices may need to be updated).
widget-overlay (void)	Invoked following the draw() operation; requires USE_OPENGL.
widget-underlay (void)	Invoked prior to the draw() operation; requires USE_OPENGL.
font-changed (void)	The default font associated with the widget has changed. The new font may be accessed via the `font` structure member.

The following events are usually generated by input devices:

mouse-motion (int x, int y, int xRel, int yRel, int buttons)	The widget is receiving mouse motion events, and the cursor has been moved. `x` and `y` are the coordinates of the cursor in the widget's local coordinate system (these coordinates may be negative or exceed the widget's dimensions if the cursor is not in the widget's area). `xRel` and `yRel` represent the displacement relative to the last position of the mouse cursor. The `buttons` argument is a bitmask representing the state of mouse buttons (see AG_MouseButton(3)).
mouse-button-up (int button, int x, int y)	The widget is receiving mouse button release events, and `button` has been released. `x` and `y` are the cursor coordinates in the widget's local coordinate system.
mouse-button-down (int button, int x, int y)	The widget is receiving mouse button events, and `button` has been pressed. `x` and `y` are the cursor coordinates in the widget's local coordinate system.
mouse-over (void)	The cursor has entered or is leaving the widget's allocated area and the AG_WIDGET_USE_MOUSEOVER option is set.
key-down (int key, int mod, Ulong unicode)	The widget is receiving keyboard events and `key` has been pressed. The `mod` argument is a bitmask representing the state of the current key modifiers and `unicode` is the corresponding Unicode character in UCS-4 format (or 0 if there are none). See AG_KeySym(3) for details.
key-up (int key, int mod, Ulong unicode)	The widget is receiving keyboard events and `key` has been released. The `mod` argument is a bitmask representing the state of the current key modifiers and `unicode` is the corresponding Unicode character in UCS-4 format (or 0 if there are none). See AG_KeySym(3) for details.

STRUCTURE DATA

For the AG_Widget object:

Uint flags	Option flags (see FLAGS section below).
int x, y	Pixel coordinates of the widget relative to its parent.
int w, h	Dimensions of the widget in pixels.
AG_Rect2 rView	Absolute view coordinates of the widget (relative to the parent driver device).
*AG_Font font**	Pointer to the effective font associated with the widget (see AG_Font(3)). This setting is read-only (use AG_SetFont() to change).

FLAGS

The flags member of the AG_Widget structure accepts the following flags:

AG_WIDGET_HFILL	Hint to container widgets that in a vertical packing, this widget can expand to fill all remaining space.
AG_WIDGET_VFILL	Hint to container widgets that in a horizontal packing, this widget can expand to fill all remaining space.
AG_WIDGET_HIDE	Disable rendering of this widget.
AG_WIDGET_VISIBLE	This widget and its parent window are both currently visible (read-only).
AG_WIDGET_UNDERSIZE	Disable rendering of this widget because it was determined to have a zero-valued geometry (read-only, set by AG_WidgetSizeAlloc()).
AG_WIDGET_DISABLED	Advise that widget is not accepting user input. The effect of this option is widget-dependent (read-only; see INPUT STATE section). This flag may affect the way the widget is rendered.
AG_WIDGET_MOUSEOVER	A mouse cursor currently intersects the widget's area (read-only; updated internally if the AG_WIDGET_USE_MOUSEOVER flag is set). This flag may affect the way the widget is rendered.
AG_WIDGET_FOCUSABLE	The widget is allowed to grab the focus; normally set by AG_WidgetSetFocusable(). Note that the widget may still become "focused" if child widgets are attached to it and one of them happens to grab focus.
AG_WIDGET_UNFOCUSED_MOTION	Receive mouse-motion events unconditionally (focus is required by default).
AG_WIDGET_UNFOCUSED_BUTTONUP	Receive all mouse-button-up() (mouse button release) events unconditionally.
AG_WIDGET_UNFOCUSED_BUTTONDOWN	Receive all mouse-button-up() (mouse button press) events unconditionally.
AG_WIDGET_UNFOCUSED_KEYDOWN	Receive key-down() (key press) events unconditionally (focus is required by default).
AG_WIDGET_UNFOCUSED_KEYUP	Receive key-up() (key release) events unconditionally (focus is required by default).
AG_WIDGET_CATCH_TAB	When the user presses the TAB key, generate normal key-down() and key-up() events. Without this flag, TAB is used to change the focus to the next widget.
AG_WIDGET_NOSPACING	Advise parent container to disable spacing and padding (per standard box model), for this widget.
AG_WIDGET_USE_TEXT	Allow draw(), size_request() and size_allocate() to use AG_TextRender(3) and AG_TextSize(3). Agar will automatically save/restore the font engine state according to the widget's computed style settings. Enables reception of the "font-changed" event.
AG_WIDGET_USE_OPENGL	Establish a separate OpenGL context for the widget. Before the draw() routine is invoked, Agar will automatically save/restore the GL_PROJECTION, GL_MODELVIEW and GL_TEXTURE matrices along with GL attributes GL_TRANSFORM_BIT, GL_VIEWPORT_BIT and GL_TEXTURE_BIT. Enables reception of "widget-reshape", "widget-overlay" and "widget-underlay" events.
AG_WIDGET_USE_MOUSEOVER	Detect cursor motion over the widget's area; update the AG_WIDGET_MOUSEOVER flag and generate "mouse-over" events accordingly.

HISTORY

The AG_Widget interface first appeared in Agar 1.0. Widget-level variable bindings have been replaced by generic AG_Variable(3) pointers in Agar 1.3.4. The Actions interface first appeared in Agar 1.4. The AG_WIDGET_USE_OPENGL feature first appeared in Agar 1.5.