GLwDrawingArea(3X) UNIX System V GLwDrawingArea(3X)
NAME
GLwDrawingArea, GLwMDrawingArea - OpenGL drawing widgets.
SYNOPSIS
#include <GL/GLwDrawA.h>
ld ... -lGLw -l<anywidgetlibrary> -lGL -lXext -lX11 -lXm
-lXt -lm
#include <GL/GLwMDrawA.h>
ld ... -lGLw -lGL -lXext -lX11 -lXm -lXt -lm
DESCRIPTION
GLwDrawingArea and GLwMDrawingArea are widgets suitable for
OpenGL drawing. They provide a window with the appropriate
visual and colormaps needed for OpenGL, based on supplied
parameters. GLwDrawingArea and GLwMDrawingArea also provide
callbacks for redraw, resize, input, and initialization.
GLwDrawingArea is not a part of any widget set, but depends
only on Xt. GLwDrawingArea can be used with any widget set.
GLwMDrawingArea is identical to GLwDrawingArea except that
it is a subclass of the Motif widget class XmPrimitive and
has resources and defaults suitable for use with Motif. For
example, GLwMDrawingArea provides the default Motif
background and foreground colors for resources, and deals
better with keyboard traversal. Although the GLwDrawingArea
widget can be used in a Motif program, it is recommended
that GLwMDrawingArea be used instead.
Since both GLwDrawingArea and GLwMDrawingArea widgets behave
almost identically, the remainder of this manual page will
refer only to GLwDrawingArea, except when the behaviors
differ. Unless explicitly stated, all statements about
GLwDrawingArea also apply to GLwMDrawingArea.
Among the information provided when creating a
GLwDrawingArea is information necessary to determine the
visual. This may be provided in three ways, all of them
through resources. A specific visualInfo structure may be
passed in. (This visualInfo must have been obtained
elsewhere; it is the application designer's responsibility
to make sure that it is compatible with the OpenGL rendering
done by the application). Alternatively, an attribute list
may be provided. This attribute list is formatted
identically to that used for direct open GL programming.
Finally, each attribute can be specified as an individual
resource. The latter method is the simplest, and is the
only method that works from resource files.
In addition to allocating the visual, the GLwDrawingArea
Page 1 (printed 4/30/98)
GLwDrawingArea(3X) UNIX System V GLwDrawingArea(3X)
will also allocate the colormap unless one is provided by
the application. (If one is provided it is the application
writer's responsibility to guarantee compatibility between
the colormap and the visual). If an application creates
multiple GLwDrawingAreas with the same visual, the same
colormap will be used. (However the colormap will not be
shared among separate applications).
Creating the widget does not actually create the window
until it is realized, and consequently, the application
should not perform any OpenGL operations to the window
immediately after creation. Instead the application must
wait until after it has realized the window. Alternatively,
the ginit callback may be used to indicate when the window
has been created. Upon receiving this callback, the
application can perform all OpenGL initialization for the
window, and can subsequently perform other operations on it.
The initialization is discussed in more detail below.
Applications select which GLwDrawingArea they are accessing
using either glXMakeCurrent or the convenience function
GLwDrawingAreaMakeCurrent which uses a widget instead of a
display and window. If there is only one GLwDrawingArea
this need only be called once, however if there is more than
one GLwDrawingArea it should be called at the start of each
callback. Callbacks in this case include not only callbacks
provided by the widget itself, but any other callback that
leads to GL activity such as a timeout or a workproc.
If an application is using double buffering, it may call
GLwDrawingAreaSwapBuffers instead of glXSwapBuffers. This
allows the use of the widget instead of the display and
window.
GLwDrawingArea Classes
GLwDrawingArea inherits behavior and resources from the Core
class.
The class pointer is GLwDrawingAreaWidgetClass.
The class name is GLwDrawingArea.
GLwMDrawingArea Classes
GLwMDrawingArea inherits behavior and resources from the
XmPrimitive and Core classes.
The class pointer is glwMDrawingAreaWidgetClass.
The class name is GLwMDrawingArea.
New Resources
The following tables define 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
Page 2 (printed 4/30/98)
GLwDrawingArea(3X) UNIX System V GLwDrawingArea(3X)
or by class in a .Xdefaults file, remove the GLwN or GLwC
prefix and use the remaining letters. There are two tables
included. The first table includes resources that
correspond directly to the attributes used by
glXChooseVisual. As with glXChooseVisual, all Boolean
resources default to FALSE and all integer resources default
to 0, except redSize, greenSize and blueSize which default
to 1. These resources can all be set only at creation time,
and are used to determine the visual. If either the
GLwNattribList or GLwNvisualInfo resource is set, these
resources are ignored. The specific meaning of these
resources is discussed in the glXChooseVisual manual page
and will not be discussed here.
__________________________________________________________________________
| Name | Class | Type | OpenGL attribute |
|___________________|____________________|_________|______________________|
| GLwNbufferSize | GLwCBufferSize | int | GLX_BUFFER_SIZE |
|___________________|____________________|_________|______________________|
| GLwNlevel | GLwCLevel | int | GLX_LEVEL |
|___________________|____________________|_________|______________________|
| GLwNrgba | GLwCRgba | Boolean| GLX_RGBA |
|___________________|____________________|_________|______________________|
| GLwNdoublebuffer | GLwCDoublebuffer | Boolean| GLX_DOUBLEBUFFER |
|___________________|____________________|_________|______________________|
| GLwNstereo | GLwCStereo | Boolean| GLX_STEREO |
|___________________|____________________|_________|______________________|
| GLwNauxBuffers | GLwCAuxBuffers | Boolean| GLX_AUX_BUFFERS |
|___________________|____________________|_________|______________________|
| GLwNredSize | GLwCColorSize | int | GLX_RED_SIZE |
|___________________|____________________|_________|______________________|
| GLwNgreenSize | GLwCColorSize | int | GLX_GREEN_SIZE |
|___________________|____________________|_________|______________________|
| GLwNblueSize | GLwCColorSize | int | GLX_BLUE_SIZE |
|___________________|____________________|_________|______________________|
| GLwNalphaSize | GLwCAlphaSize | int | GLX_ALPHA_SIZE |
|___________________|____________________|_________|______________________|
| GLwNdepthSize | GLwCDepthSize | int | GLX_DEPTH_SIZE |
|___________________|____________________|_________|______________________|
| GLwNstencilSize | GLwCStencilSize | int | GLX_STENCIL_SIZE |
|___________________|____________________|_________|______________________|
| GLwNaccumRedSize | GLwCAccumColorSize| int | GLX_ACCUM_RED_SIZE |
|___________________|____________________|_________|______________________|
| GLwNaccumGreenSize| GLwCAccumColorSize| int | GLX_ACCUM_GREEN_SIZE|
|___________________|____________________|_________|______________________|
| GLwNaccumBlueSize | GLwCAccumColorSize| int | GLX_ACCUM_BLUE_SIZE |
|___________________|____________________|_________|______________________|
| GLwNaccumAlphaSize| GLwCAccumAlphaSize| int | GLX_ACCUM_ALPHA_SIZE|
|___________________|____________________|_________|______________________|
The following table lists other resources of the
Page 3 (printed 4/30/98)
GLwDrawingArea(3X) UNIX System V GLwDrawingArea(3X)
GLwDrawingArea widget. each of these will be described
subsequently. 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).
Name Class Type Def Acc
_____________________________________________________________________________
GLwNallocateBackground GLwCAllocateColors Boolean F CG
GLwNallocateOtherColors GLwCAllocateColors Boolean F CG
GLwNattribList GLwCAttribList int * NULL CG
GLwNexposeCallback GLwCCallback XtCallbackList NULL C
GLwNginitCallback GLwCCallback XtCallbackList NULL C
GLwNinputCallback GLwCCallback XtCallbackList NULL C
GLwNinstallBackground GLwCInstallBackground Boolean T CG
GLwNinstallColormap GLwCInstallColormap Boolean T CG
GLwNresizeCallback GLwCCallback XtCallbackList NULL C
GLwNvisualInfo GLwCVisualInfo XVisualInfo* NULL CG
GLwNallocateBackground
If TRUE, the background pixel and pixmap will be
allocated if appropriate using the newly calculated
colormap and visual. If FALSE, they will retain values
calculated using the parent's colormap and visual.
Applications which wish to have X clear their
background for them will usually set this to TRUE.
Applications clearing their own background will often
set this to FALSE, although they may set this to TRUE
if they query the background for their own use. One
reason to leave this resource FALSE is that if color
index mode is in use this avoid using up a pixel from
the newly allocated colormap. Also, on hardware that
supports only one colormap, the application may need to
do more careful color allocation to avoid flashing
between the openGL colormap and the default X colormap.
(Note that because of the way Xt works, the background
colors are originally calculated using the default
colormap; if this resource is set they can be
recalculated correctly. If a colormap was explicitly
supplied to the widget rather than being dynamically
calculated, these resources are always calculated using
that colormap.)
GLwNallocateOtherColors
This is similar to GLwNallocateBackground, but
allocates other colors normally allocated by widgets.
Although the GLwDrawingArea and GLwMDrawingArea widget
do not make use of these colors the application may
choose to query them. For the non-Motif GLwDrawingArea
widget there are no other colors allocated, so this
resource is a no-op. For the Motif GLwMDrawingArea are
Page 4 (printed 4/30/98)
GLwDrawingArea(3X) UNIX System V GLwDrawingArea(3X)
widget, the XmPrimitive resources XmNforeground,
XmNhighlightColor, and XmNhighlightPixmap are
calculated.
GLwNattribList
Contains the list of attributes suitable for a call to
glXChooseVisual. If this resource is NULL, it is
calculated based on the attribute resources. If it is
not NULL, the attribute resources are ignored.
GLwNexposeCallback
Specifies the list of callbacks that is called when the
widget receives an exposure event. The callback reason
is GLwCR_EXPOSE. The callback structure also includes
the exposure event. The application will generally
want to redraw the scene.
GLwNginitCallback
Specifies the list of callbacks that is called when the
widget is first realized. Since no OpenGL operations
can be done before the widget is realized, this
callback can be used to perform any appropriate OpenGL
initialization such as creating a context. The
callback reason is GLwCR_GINIT.
GLwNinputCallback
Specifies the list of callbacks that is called when the
widget receives a keyboard or mouse event. By default,
the input callback is called on each key press and key
release, on each mouse button press and release, and
whenever the mouse is moved while a button is pressed.
However this can be changed by providing a different
translation table. The callback structure also includes
the input event. The callback reason is GLwCR_INPUT.
The input callback is provided as a programming
convenience, as it provides a convenient way to catch
all input events. However, a more modular program can
often be obtained by providing specific actions and
translations in the application rather than using a
single catch all callback. Use of explicit
translations can also provide for more customizability.
GLwNinstallBackground
If set to TRUE, the background is installed on the
window. If set to FALSE, the window has no background.
This resource has no effect unless
GLwNallocateBackground is also TRUE.
GLwNinstallColormap
If set to TRUE, the widget will call
XSetWMColormapWindows to tell the window manager to
Page 5 (printed 4/30/98)
GLwDrawingArea(3X) UNIX System V GLwDrawingArea(3X)
install the colormap when the window's shell has focus.
If set to FALSE, this will not be called. For
applications with multiple GLwDrawingAreas sharing a
single colormap, it is most efficient to set this
resource to TRUE for exactly one GLwDrawingArea with
each colormap. If an application needs additional
control over the order of colormaps, this resource can
be set to FALSE, with the application calling
XSetWMColormapWindows explicitly.
GLwNresizeCallback
Specifies the list of callbacks that is called when the
GLwDrawingArea is resized. The callback reason is
GLwCR_RESIZE.
GLwNvisualInfo
Contains a pointer to the window's visual info
structure. If NULL, the visualInfo is calculated at
widget creation time based on the GLwNattributeList
resource (which is itself calculated from the various
resources). If GLwNvisualInfo is not NULL the
GLwNattributList and the attribute resources are
ignored.
Inherited Resources
Both GLwDrawingArea and GLwMDrawingArea inherit behavior and
resources from the core superclass. Other than the
behavior of the colormap and background resources described
previously, all defaults are the same as for core.
In addition, the Motif version GLwMDrawingArea also inherits
from XmPrimitive. The behavior of the color resources has
been described previously. The TraversalOn resource is
disabled for this widget, but if keyboard input is required
it should be enabled. (Also, the application should call
XmProcessTraversal(widget, XmTRAVERSE_CURRENT) whenever
mouse button 1 is clicked in the widget. This is similar to
the requirements of the Motif Drawing area.) Because Motif
gets confused by having multiple visuals in one top level
shell, XmNhighlightOnEnter has been disabled, and
XmNhighlightThickness has been set to 0.
Callback Information
A pointer to the following structure is passed to each
callback:
Page 6 (printed 4/30/98)
GLwDrawingArea(3X) UNIX System V GLwDrawingArea(3X)
typedef struct
{
int reason;
XEvent * event;
Dimensionwidth, height;
} GLwDrawingAreaCallbackStruct;
reason Indicates why the callback was invoked. Appropriate
values are stated in the above resource descriptions.
For Motif programmers, the values GLwCR_EXPOSE,
GLwCR_RESIZE, and GLwCR_INPUT are equal to
XmCR_EXPOSE, XmCR_RESIZE, and XmCR_INPUT
respectively. GLwCR_GINIT does not have a Motif
equivalent.
event Points to the XEvent that triggered the callback.
This is NULL for GLwNginitCallback and
GLwNresizeCallback.
width and height
Are set to the width and height of the window.
Translations
GLwDrawingArea has the translations listed below.
<KeyDown>: glwInput()
<KeyUp>: glwInput()
<BtnDown>: glwInput()
<BtnUp>: glwInput()
<BtnMotion>: glwInput()
GLwMDrawingArea has the following additional translation:
<Key>osfHelp: PrimitiveHelp()
An application wishing to catch other events than these
defaults can do so by installing a different translation
table.
Action Routines
The GLwDrawingArea has the following action routine:
glwInput():
Called whenever one of the above translations specifies
that input has occurred. Its sole purpose is to call
the input callback.
Page 7 (printed 4/30/98)
GLwDrawingArea(3X) UNIX System V GLwDrawingArea(3X)
INITIALIZATION
When the widget is initially created (e.g. through
XtCreateWidget(3X)) the associated window is not actually
created. Instead, window creation is delayed until the
widget is realized. However, glXchooseVisual is called
immediately, so information based on its results is
available.
Between the time the widget is created and it is realized,
the following apply:
o No OpenGL operations can be done to the window
o No resize callbacks are generated.
o The normal window is available (XtWindow returns NULL).
o GLwDrawingAreaMakeCurrent (and glXMakeCurrent) should
not be called.
When the widget is realized, the following actions take
place:
o The window is created.
o The ginit callback is called. The user may use this
callback to perform any needed OpenGL initialization to
the window.
NOTES
When using the input callback to receive keyboard input, the
keycode in the event must be converted to a KeySym. Use
XLookupKeysym(3X) or XLookupString(3X) to do the conversion.
Keyboard input can also be dealt using translations, in
which case no such conversion is required.
Motif programmers should keep in mind that OSF uses virtual
bindings and replaces some of the key bindings. As a common
example, if the ESC key is to be used to exit the program
(as it often is in GL programs), the translation should
specify <key>osfCancel instead of <key>Escape.
Motif programmers may also create a GLwMDrawingArea widget
with the Motif style GLwCreateMDrawingArea.
Page 8 (printed 4/30/98)
GLwDrawingArea(3X) UNIX System V GLwDrawingArea(3X)
EXAMPLE
Here are some code fragments that create a GLwDrawingArea
widget, and manage the appropriate callbacks.
#include <X11/GLW/GLwDrawingArea.h>
static GLXContext glx_context; /* assume only one context */
. . .
main()
{
Arg args[10];
int n;
Widget parent;/* The parent of the gl widget */
Widget glw;/* The GLwDrawingArea widget */
. . .
/* Create the widget using RGB mode. This can also be set
* in an X Defaults file
*/
n = 0;
XtSetArg(args[n], GLwNrgba, TRUE); n++;
glw = XtCreateManagedWidget("glw", GLwDrawingAreaWidgetClass,
parent, args, n);
XtAddCallback(glw, GLwNexposeCallback, exposeCB, 0);
XtAddCallback(glw, GLwNresizeCallback, resizeCB, 0);
XtAddCallback(glw, GLwNginitCallback, ginitCB, 0);
/* Also add input callback if needed */
. . .
}
static void
exposeCB(Widget w, XtPointer client_data,
(GLwDrawingAreaCallbackStruct *)call_data)
{
GLwDrawingAreaMakeCurrent (w, glx_context);
/* redraw the display */
}
static void
resizeCB(Widget w, XtPointer client_data,
(GLwDrawingAreaCallbackStruct *)call_data)
{
GLwDrawingAreaMakeCurrent (w, glx_context);
/* perform any resize actions */
}
static void
ginitCB(Widget w, XtPointer client_data,
(GLwDrawingAreaCallbackStruct *)call_data)
{
Page 9 (printed 4/30/98)
GLwDrawingArea(3X) UNIX System V GLwDrawingArea(3X)
Arg args[1];
XVisualInfo *vi;
XtSetArg(args[0], GLwNvisualInfo, &vi);
XtGetValues(w, args, 1);
/* create a visual context */
glx_context = glXCreateContext(XtDisplay(w), vi, 0, GL_FALSE);
GLwDrawingAreaMakeCurrent (w, glx_context);
/* Perform any necessary graphics initialization.*/
}
The Motif program need only differ by including
GLwMDrawingArea.h instead of GLwDrawingArea.h and by
creating a widget of type GLwMDrawingAreaWidgetClass instead
of GLwDrawingAreaWidgetClass. As an alternative, the Motif
program could use GLwCreateMDraw(3X) instead.
WARNINGS
If a GLwDrawingArea widget is created as a child of an
already realized widget, the GLwDrawingArea widget will be
created immediately, without giving the user an opportunity
to add the ginit callback. In such a case, initialization
should be done immediately after creating the widget rather
than by using the callback.
If the non-Motif GLwDrawingArea widget is used in a Motif
program and keyboard traversal is attempted, the behavior is
undefined if the user traverses into the GLwDrawingArea
widget.
SEE ALSO
glXChooseVisual, GLwDrawingAreaMakeCurrent, glXMakeCurrent,
GLwDrawingAreaSwapBuffers GLwCreateMDraw, Core(3X),
XmPrimitive(3X), VirtualBindings(3X), Gflush(3G),
XSetWMColormapWindows(3X11) and the OpenGL spec.
Page 10 (printed 4/30/98)
