glwdrawingarea - Man Page
GLwDrawingArea(3X) 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 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
Page 1
GLwDrawingArea(3X) GLwDrawingArea(3X)
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 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.
Page 2
GLwDrawingArea(3X) GLwDrawingArea(3X)
___________________________________________________________________________
| 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 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).
Page 3
GLwDrawingArea(3X) GLwDrawingArea(3X)
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 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.
Page 4
GLwDrawingArea(3X) GLwDrawingArea(3X)
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 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
Page 5
GLwDrawingArea(3X) GLwDrawingArea(3X)
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:
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.
Page 6
GLwDrawingArea(3X) GLwDrawingArea(3X)
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.
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.
Page 7
GLwDrawingArea(3X) GLwDrawingArea(3X)
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 Escape.
Motif programmers may also create a GLwMDrawingArea widget with the Motif
style GLwCreateMDrawingArea.
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);
Page 8
GLwDrawingArea(3X) GLwDrawingArea(3X)
/* 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)
{
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 9