Agar 1.7 Manual



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


AG_Widget is the base class for user interface elements in Agar. Widgets are organized in an ordered virtual filesystem of AG_Object(3) elements. The parent of a widget is referred to as its Container. Container widgets include: AG_Box(3), AG_Fixed(3), AG_Pane(3), AG_Scrollview(3), AG_Titlebar(3) and AG_Window(3) itself.

Widgets are attached to their containers with AG_ObjectAttach(3) and detached with AG_ObjectDetach(3). Unattached widgets can be freed using AG_ObjectDestroy(3). Agar handles garbage collection of windows (and attached widgets) internally. Attempting to destroy an active AG_Window(3) or a widget which is still attached to a parent is an error (which would trigger a fatal assertion in debug mode).

Unless renamed with AG_ObjectSetName(3), widget instances are given a generic name (e.g., "button0"). AG_ObjectFind(3) can be used to get a pointer to a widget by pathname (e.g., "box0/button0").

The AG_Variable(3) table of AG_Object is used to store bindings data, style properties and general user data. The AG_Event(3) table of AG_Object maps widget events (such as "button-pushed") to one or more event handlers (as registered by AG_SetEvent(3) or AG_AddEvent(3)).


AG_Object(3)-> AG_Widget.


Agar widget classes are described by the following structure:
typedef struct ag_widget_class {
	struct ag_object_class _inherit;

	void (*draw)(void *obj);
	void (*size_request)(void *obj, AG_SizeReq *req);
	int  (*size_allocate)(void *obj, const AG_SizeAlloc *alloc);

	void (*mouse_button_down)(void *obj, AG_MouseButton btn,
	                          int x, int y);
	void (*mouse_button_up)(void *obj, AG_MouseButton btn,
	                        int x, int y);
	void (*mouse_motion)(void *obj, int x, int y, int dx, int dy);

	void (*key_down)(void *obj, AG_KeySym ksym, AG_KeyMod kmod,
	                 AG_Char ch);
	void (*key_up)(void *obj, AG_KeySym ksym, AG_KeyMod kmod,
	               AG_Char ch);

	void (*touch)(void *obj, void *inputDevice,
	              const AG_DriverEvent *event);
	void (*ctrl)(void *obj, void *inputDevice,
	             const AG_DriverEvent *event);
	void (*joy)(void *obj, void *inputDevice,
	            const AG_DriverEvent *event);
} AG_WidgetClass;

The draw() method renders the widget to the graphics display (using GL, AG_WidgetPrimitives(3) or other methods). The code under draw() is referred to as rendering context. Widget primitives and operations such as AG_WidgetBlitSurface() must be called only from rendering context.

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

size_allocate() is called once the widget has been successfully allocated a new size or position within its parent (as described by the w, h, x and y members of the AG_SizeAlloc argument). Container widgets allocate the position and size of their children in size_allocate().

size_allocate() should return 0 on success and -1 if the allocation is not satisfactory for draw() to work at all (in which case the UNDERSIZE flag will be set and draw() will not run).

The mouse_button_down() method is invoked if the user presses a button while the cursor is located at coordinates x, y inside the widget's local coordinates system.

The mouse_button_up() method is invoked if the user releases a mouse button while the cursor is located at coordinates x, y relative to the widget's local coordinates system. The cursor must intersect the widget (or the widget hold an AG_WIDGET_UNFOCUSED_BUTTONUP grab).

The mouse_motion() method is invoked if the user moves the cursor to coordinates x, y in the widget's local coordinate system. The widget must hold focus (or hold an AG_WIDGET_UNFOCUSED_MOTION grab). The dx and dy arguments provide the displacement (in px) relative to the last mouse motion event.

The key_down() and key_up() methods are invoked whenever the user presses or releases a key on the keyboard. The widget must hold focus (or a AG_WIDGET_UNFOCUSED_KEYDOWN/ AG_WIDGET_UNFOCUSED_KEYUP grab).


void AG_ExpandHoriz (AG_Widget *obj)

void AG_ExpandVert (AG_Widget *obj)

void AG_Expand (AG_Widget *obj)

void AG_WidgetSizeReq (AG_Widget *obj, AG_SizeReq *req)

void AG_WidgetSizeAlloc (AG_Widget *obj, AG_SizeAlloc *alloc)

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

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

void AG_WidgetSetGeometry (AG_Widget *obj, AG_Rect rect)

void AG_WidgetUpdate (AG_Widget *obj)

void AG_WidgetUpdateCoords (AG_Widget *obj, int x, int y)

The AG_WIDGET_HFILL flag hints to vertically-packing containers that this widget wants to fill any remaining space along the horizontal axis. AG_WIDGET_VFILL flag hints to horizontally-packing containers that this widget wants to fill any remaining space along the horizontal axis.

The AG_ExpandHoriz() and AG_ExpandVert() functions set AG_WIDGET_HFILL and AG_WIDGET_VFILL, respectively. AG_Expand() is equivalent to calling both AG_ExpandHoriz() and AG_ExpandVert().

AG_WidgetSizeReq() 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.

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 external modifications to the x, y, w, h fields of the AG_Widget structure.

AG_WidgetUpdateCoords() is called internally to update the cached absolute display coordinates (the rView rectangle) of wid and its descendents based on their current relative coordinates (the x, y, w, h members). The widget and its parent VFS must be locked.


void AG_SetStyle (AG_Widget *obj, const char *attr, const char *value)

void AG_SetStyleF (AG_Widget *obj, const char *attr, const char *fmt, ...)

void AG_SetFontFamily (AG_Widget *obj, const char *family)

void AG_SetFontSize (AG_Widget *obj, const char *size)

void AG_SetFontWeight (AG_Widget *obj, const char *weight)

void AG_SetFontStyle (AG_Widget *obj, const char *style)

void AG_SetFontStretch (AG_Widget *obj, const char *stretch)

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

void AG_SetMargin (AG_Widget *obj, const char *margin)

void AG_SetPadding (AG_Widget *obj, const char *padding)

void AG_Set<Color> (AG_Widget *obj, const char *color)

void AG_Set<Color>Disabled (AG_Widget *obj, const char *color)

void AG_Set<Color>Focused (AG_Widget *obj, const char *color)

void AG_Set<Color>Hover (AG_Widget *obj, const char *color)

AG_SetStyle() sets the style attribute attr to the given value.

See AG_StyleSheet(3) for the list of available attributes.

The following routines are shorthand forms for AG_SetStyle().

AG_SetFontFamily() sets the "font-family" attribute, which can be either a font name or the name of a file located in one of the directories in the PATH_FONTS of AG_Config(3).

AG_SetFontSize() sets the "font-size" attribute, which may contain the suffix "%" (relative size to the parent widget's font), the suffix "pt" (explicit size in vector-font points) or the suffix "px" (explicit size in bitmap-font pixels).

Font sizes should normally be given in "%" so that the zoom function can work as expected (Agar's zoom works simply by increasing or decreasing the "font-size" of the target window).

AG_SetFontWeight() sets the "font-weight" attribute, which can be one of "Thin", "ExtraLight", "Light", "Regular" (default), "SemiBold", "Bold", "ExtraBold", "Black" or "!parent".

AG_SetFontStyle() sets the "font-style" attribute, which be one of "Normal" / "Regular", "Oblique", "Italic" or "!parent".

AG_SetFontStretch() sets the "font-stretch" attribute, which can be one of "Normal" / "Regular", "UltraCondensed", "Condensed", "SemiCondensed", "SemiExpanded", "Expanded" or "UltraExpanded".

AG_SetFont() sets (inherits) font style attributes "font-family", "font-weight" and "font-stretch" from those of the given font.

AG_SetMargin() sets the margin area around the widget. The argument can be of the form "<HORIZ> <VERT>" to set horizontal and vertical spacing in pixels, respectively. A single argument sets both horizontal and vertical spacings to the same value.

AG_SetPadding() sets the padding inside the widget area. The argument can be of the form "<TOP> <RIGHT> <BOTTOM> <LEFT>" to set each padding in pixels. A single argument sets all paddings to the same value.

The following routines set color attributes. For the list of accepted formats for specifying colors, see AG_Color(3).

AG_SetColor() sets the foreground primary ("color"). AG_SetBgColor() sets the background primary ("background-color"). AG_SetTextColor() sets the color for text and vector icons ("text-color"). AG_SetLineColor() sets the color for lines and filled shapes ("line-color"). AG_SetHighColor() sets the shading color for top and left 3D-style edges ("high-color"). AG_SetLowColor() sets the shading color for bottom and right 3D-style edges ("low-color"). AG_SetSelColor() sets the primary for indicating active selections ("selection-color").

The following routines set state-dependent color attributes AG_Set<Color>Disabled() sets the given color for the widget "#disabled" state. AG_Set<Color>Focused() sets the given color for the "#focused" state. AG_Set<Color>Hover() sets the given color for the "#hover" state.


void AG_WidgetEnable (AG_Widget *obj)

void AG_WidgetDisable (AG_Widget *obj)

int AG_WidgetEnabled (AG_Widget *obj)

int AG_WidgetDisabled (AG_Widget *obj)

void AG_PushDisabledState (AG_Widget *obj)

void AG_PopDisabledState (AG_Widget *obj)

A widget in DISABLED state will not accept user input other than that required for navigation (i.e., scrolling). AG_WidgetEnable() clears the DISABLED state and AG_WidgetDisable() sets it. These functions will raise the widget-enabled and widget-disabled events accordingly.

AG_WidgetEnabled() and AG_WidgetDisabled() return the current state.

AG_PushDisabledState() arranges for widgets subsequently attached to a container widget obj to start in DISABLED state. The AG_WIDGET_DISABLED flag will be set on attach (without raising "widget-disabled").


Focus enables reception of input events that would be filtered out by default. The focused widget (in the currently focused window) will receive "mouse-motion", "mouse-button-up", "key-up" and "key-down" events.

int AG_WidgetSetFocusable (AG_Widget *obj, int enable)

int AG_WidgetFocus (AG_Widget *obj)

void AG_WidgetUnfocus (AG_Widget *obj)

int AG_WidgetIsFocused (const AG_Widget *obj)

int AG_WidgetIsFocusedInWindow (const AG_Widget *obj)

void AG_WidgetForwardFocus (AG_Widget *obj, AG_Widget *widgetToFocus)

AG_WidgetSetFocusable() clears or sets the AG_WIDGET_FOCUSABLE flag and returns the previous setting (0 = Not focusable, 1 = Focusable).

AG_WidgetFocus() focuses the specified widget and all of its parent widgets including the parent AG_Window(3). Returns 1 on success and 0 if the widget is not accepting focus.

AG_WidgetUnfocus() removes the focus state from the given widget and its children, recursively.

AG_WidgetIsFocused() returns 1 if the widget is both focused in relation to its parent window, and the parent window itself is focused. AG_WidgetIsFocusedInWindow() returns 1 if the widget is focused regardless of the focus state of its parent.

AG_WidgetForwardFocus() arranges automatic forwarding of the focus to a specified widget. Whenever obj gains focus, Agar will arrange for the focus to be transferred automatically to widgetToFocus.


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

int AG_WidgetRelativeArea (AG_Widget *obj, 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.


These routines allow graphical surfaces to be managed (mapped in hardware or software) and transferred efficiently. They must be called from rendering context (i.e., the draw() operation of AG_Widget) only.

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

int AG_WidgetMapSurface (AG_Widget *obj, AG_Surface *su)

int AG_WidgetMapSurfaceNODUP (AG_Widget *obj, AG_Surface *su)

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

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

void AG_WidgetUnmapSurface (AG_Widget *obj, int surface_id)

void AG_WidgetUpdateSurface (AG_Widget *obj, int surface_id)

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

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

The AG_WidgetBlit() function performs a software->hardware block image transfer ("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 AG_Widget system provides a way to manage hardware surfaces (i.e., textures) and take advantage the texture capabilities 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 is typically generated on the initial call to AG_WidgetBlitSurface() and kept in cache for later use.

By default, mapped surfaces are freed when the widget is destroyed. AG_WidgetMapSurfaceNODUP() sets the "NODUP" flag on the given surface such that the widget system will never attempt to free the surface.

Note that AG_WidgetMapSurface() will not duplicate the surface. Instead, it will register the given surface pointer to be managed by the AG_Widget system. The surface pointer must remain valid for the lifetime of the widget (if in doubt, you can always use AG_SurfaceDup(3) to map a duplicate of the surface instead).

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

AG_WidgetUnmapSurface() destroys the given surface mapping. It is equivalent to invoking AG_WidgetReplaceSurface() with a NULL surface.

In OpenGL mode, AG_WidgetReplaceSurface() and AG_WidgetUnmapSurface() do not operate on textures immediately. GL texture delete operations are queued to be performed at the end of the current event-processing cycle.

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 obj, 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 obj (and rs set to NULL).


Widget states can be bound to memory locations containing data in a supported format. For example, the "state" binding of AG_Button(3) can be tied to an integer (or bits in an integer), such that the user pressing the button directly manipulates the integer value in memory.

Bindings are documented under the heading BINDINGS section of the widget's manual page. For instance, AG_Slider(3) mentions "value" bindings to integers. Therefore, to control a byte of memory, one might use:
static Uint8 myByte = 0;

AG_Slider *slider = AG_SliderNew(window, AG_SLIDER_HORIZ, 0);
AG_BindUint8(slider, "value", &myByte);

Or alternatively, using a shorthand constructor:
AG_SliderNewUint8(window, AG_SLIDER_HORIZ, 0, &myByte, NULL, NULL);

This method is not limited to primitive data types. For example, AG_Textbox(3) can bind to a fixed-size memory buffer containing a C string in ASCII, UTF-8 or other supported encoding.

The AG_Bind<Type>() family of functions bind widget states to memory data. The AG_Bind<Type>Mp() variants accept a pointer to a mutex which will be acquired prior to accessing the data.

Since the state of a widget can influence its appearance (e.g., AG_Button(3) is drawn as a pressed button if its "state" is 1), it may be necessary to monitor the value and redraw when it changes. AG_RedrawOnChange() arranges for this to occur automatically (see below).


void AG_Redraw (AG_Widget *obj)

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

int AG_RedrawOnTick (AG_Widget *obj, int refresh_ms)

The AG_Redraw() call signals that the widget must be redrawn to the display. It is equivalent to setting the dirty flag on the parent window. If called from rendering context, AG_Redraw() is a no-op.

AG_RedrawOnChange() 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.

AG_RedrawOnTick() enables or disables auto-refresh. Auto-refresh forces the widget to be redrawn unconditionally every refresh_ms milliseconds. If the refresh_ms argument is -1, auto-refresh is disabled. The AG_RedrawOnTick() function returns the previous setting in ms (or -1 if auto-refresh was not set).


AG_Window * AG_ParentWindow (AG_Widget *widget)

AG_Widget * AG_WidgetFindFocused (AG_Window *win)

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

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

AG_ParentWindow() returns a pointer to the parent AG_Window(3) for the given widget instance. The pointer is valid only as long as the parent VFS remains locked. If the widget is not attached, NULL is returned.

AG_WidgetFindFocused() returns the top-most focused widget under win.

AG_WidgetFindPoint() searches for the top-most widget which contains the point at display coordinates x, y.

AG_WidgetFindRect() searches for the top-most widget which encloses the rectangle described by display coordinates x, y, w, h completely.

Both AG_WidgetFindPoint() and AG_WidgetFindRect() will only match widgets that are instances of className. The pattern "AG_Widget:*" would match any class. For details on the class-membership test, see: AG_OfClass(3).

Under threads, the object pointer returned by AG_WidgetFindFocused(), AG_WidgetFindPoint() and AG_WidgetFindRect() is valid only for as long as the parent VFS is locked.


void AG_PushClipRect (AG_Widget *obj, const AG_Rect *r)

void AG_PushClipRectInner (AG_Widget *obj, const AG_Rect *r)

void AG_PopClipRect (AG_Widget *obj)

void AG_PushBlendingMode (AG_Widget *obj, AG_AlphaFn src, AG_AlphaFn dst)

void AG_PopBlendingMode (AG_Widget *obj)

void AG_WidgetDraw (AG_Widget *obj)

void AG_BeginRendering (AG_Driver *drv)

void AG_EndRendering (AG_Driver *drv)

void AG_WidgetHide (AG_Widget *obj)

void AG_WidgetShow (AG_Widget *obj)

void AG_WidgetHideAll (AG_Widget *obj)

void AG_WidgetShowAll (AG_Widget *obj)

int AG_WidgetVisible (AG_Widget *obj)

AG_Surface * AG_WidgetSurface (AG_Widget *obj)

The AG_PushClipRect() function pushes a rectangle (in widget-relative 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. Both functions must be invoked in rendering context.

The AG_PushClipRectInner() variant of AG_PushClipRect() offsets the width and height of the rectangle by -2px.

AG_PushBlendingMode() selects the source and destination functions for further pixel blending operations. It also pushes the current state onto the stack of alpha blending modes. Setting src to AG_ALPHA_ZERO and dst to AG_ALPHA_ONE (the default) effectively disables blending. Setting src to AG_ALPHA_SRC and dst to AG_ALPHA_ONE_MINUS_SRC is the most common case. See AG_AlphaFn(3) for the list of possible alpha blending modes. AG_PopBlendingMode() pops the the last entry off of the stack of alpha blending modes. Both functions must be invoked from rendering context.

The AG_WidgetDraw() routine renders a widget to the display. It is invoked from either the event loop routine (such as AG_EventLoop(3)) or from the draw() operation of a widget. Container widgets must call AG_WidgetDraw() explicitely in order to render their children.

In an 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.


User-generated events such as key presses or mouse button events can be connected to high-level actions such as executing a specified routine or controlling a boolean. The high-level actions of a widget are described by an array of AG_Action structures.

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 *obj, const char *action, void (*fn)(AG_Event *), const char *fnArgs, ...)

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

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

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

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

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

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

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

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

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

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

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

int AG_ExecAction (AG_Widget *obj, 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.


The GUI system may send AG_Widget objects the following events:
font-changed (void)
The active font family, size or style attributes have changed. The new font may be accessed by the font pointer of AG_Widget.
padding-changed (void)
The padding attribute has changed.
palette-changed (void)
At least one entry in the color palette of the widget has changed.
widget-shown (void)
The widget is now visible. User-defined handlers must be appended with AG_AddEvent(3) (as opposed to replaced by AG_SetEvent(3)) since the base class needs its own "widget-shown" handler.
widget-hidden (void)
The widget is no longer visible. User-defined handlers must be appended with AG_AddEvent(3) (as opposed to replaced by AG_SetEvent(3)) since the base class needs its own "widget-hidden" handler.
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-gainfocus (void)
The widget now holds focus inside its parent container.
widget-lostfocus (void)
The widget no longer holds focus.
widget-reshape (void)
The widget was resized and USE_OPENGL is set. The handler is expected to update the GL_PROJECTION or GL_MODELVIEW matrices.
widget-overlay (void)
Invoked following the draw() operation; requires USE_OPENGL.
widget-underlay (void)
Invoked prior to the draw() operation; requires USE_OPENGL.

The following events are usually generated by input devices.

DEPRECATED: As of Agar 1.7.0 the events described below have been superceded by the input device methods of AG_WidgetClass. If a method is defined then the method is called and no event is generated.
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 ch)
The widget is receiving keyboard events and key has been pressed. mod is a bitmask representing the state of the current key modifiers. If non-zero, ch is the matching UCS-4 (or ASCII) character.
key-up (int key, int mod, Ulong ch)
The widget is receiving keyboard events and key has been released. mod is a bitmask representing the state of the current key modifiers. If non-zero, ch is the matching UCS-4 (or ASCII) character.


For the AG_Widget object:
Uint flags Option flags (see FLAGS section below).
int x, y Location of the upper-left pixel (relative to the parent widget). Read-only (set by container).
int w, h Size in pixels. Read-only (set by container).
AG_Rect r Cached rectangle at 0,0. Read-only.
AG_Rect2 rView Cached position & size in display coordinates. Read-only with one exception: before calling AG_WidgetDraw(3) to render a child widget, a container widget may temporarily override its rView in order to render it at a given offset.
AG_Rect2 rSens Rectangle of sensitivity to mouse events (in display coordinates). Scrolling containers such as AG_Scrollview(3) may adjust this rectangle for partially-visible widgets along its edges.
AG_WidgetPalette pal Color palette: a 4 x 8 (or AG_WIDGET_NSTATES by AG_WIDGET_NCOLORS) array of AG_Color(3). Entries are set by the current AG_StyleSheet(3). Read-only (use AG_SetStyle() to modify) with one exception: before calling AG_WidgetDraw(3) to render a child widget, a container widget may temporarily override and restore its palette entries.
AG_Font *font Current font associated with the widget (see AG_Font(3)). Read-only (use AG_SetStyle() or the AG_SetFont*() family of functions to modify).
AG_ActionVec *actions Dynamic array of AG_Action structures describing high-level actions (see WIDGET ACTIONS).


The flags member of the AG_Widget structure accepts the following flags:
AG_WIDGET_HFILLFill any remaining (horizontal) space (hint to vertically-packing containers).
AG_WIDGET_VFILLFill any remaining (vertical) space (hint to horizontal-packing containers).
AG_WIDGET_HIDEDisable rendering of this widget.
AG_WIDGET_VISIBLEThis widget and its parent window are both currently visible (read-only).
AG_WIDGET_UNDERSIZEDisable rendering of this widget because it is too small to draw (read-only).
AG_WIDGET_DISABLE_ON_ATTACHMake attached widgets start in DISABLED state (without raising "widget-disabled").
AG_WIDGET_DISABLEDAdvise that widget is not accepting user input. This state influences color and styling. The effect of this option is widget-dependent (read-only; see INPUT STATE section).
AG_WIDGET_MOUSEOVERA mouse cursor currently intersects the widget's area (read-only; updated internally if the AG_WIDGET_USE_MOUSEOVER flag is set). This state influences color and styling.
AG_WIDGET_FOCUSABLEThe widget is allowed to grab the focus.
AG_WIDGET_UNFOCUSED_MOTIONReceive "mouse-motion" events unconditionally (focus is required by default).
AG_WIDGET_UNFOCUSED_BUTTONUPReceive all mouse-button-up() (mouse button release) events unconditionally.
AG_WIDGET_UNFOCUSED_BUTTONDOWNReceive all mouse-button-up() (mouse button press) events unconditionally.
AG_WIDGET_UNFOCUSED_KEYDOWNReceive key-down() (key press) events unconditionally (focus is required by default).
AG_WIDGET_UNFOCUSED_KEYUPReceive key-up() (key release) events unconditionally (focus is required by default).
AG_WIDGET_CATCH_TABWhen 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_NOSPACINGAdvise parent container to disable spacing and padding (per standard box model), for this widget.
AG_WIDGET_USE_TEXTAllow 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_OPENGLEstablish 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_MOUSEOVERDetect cursor motion over the widget's area; update the AG_WIDGET_MOUSEOVER flag and generate "mouse-over" events accordingly.


AG_Cursor(3), AG_KeyMod(3), AG_KeySym(3), AG_Rect(3), AG_StyleSheet(3), AG_Surface(3), AG_Variable(3), AG_WidgetPrimitives(3), AG_Window(3)


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. Actions were introduced in Agar 1.4.0. AG_WIDGET_USE_OPENGL first appeared in Agar 1.5, replacing AG_GLView(3). Agar 1.6.0 first made the actions, pal and rSens structure members public. The AG_SetStyleF(), AG_PushBlendingMode() and AG_PopBlendingMode() functions appeared in Agar 1.6.0. The "font-changed" and "palette-changed" events appeared in Agar 1.6.0. AG_PushDisabledState(), AG_PopDisabledState(), the AG_WIDGET_DISABLE_ON_ATTACH flag and the "padding-changed" event appeared in Agar 1.7.0.

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