This appendix shows you how you might interface the graphics library to your window system (say X) if you are not using a widget library. This is mainly of historical interest now.
Some examples are provided below. Note that these are not complete applications: merely code extracts. These examples are targetted towards applications which will not use the Xt Intrinsics and widget libraries: some other X toolkit is assumed (i.e. XView). Please refer to the documentation on the Karma widget library for how to do things the easy way. An entire chapter is devoted to a simple image display tool (this uses Karma widgets and is less then 500 lines long). Unless you are doing something unusual, the following examples are probably not of much interest to you.
These examples are legacy examples which date from the time XView was still heavily used, and life was hard. Use Xt Intrinsics and Karma widgets instead. (Think I'm trying to tell you something?)
A code extract is given below which shows how the image display system is initialised, and X refresh/ resize events are handled. See the documentation on ``Intelligent Arrays'' on how you would create and fill a 2-D iarray.
If you are using the Xt toolkit, the creation, geometry management and event translation is all done within the CanvasWidget, hence the code below may not be relevant to you. The more powerful MultiCanvasWidget supports multiple visual types and the ImageDisplayWidget provides a very featureful and flexible user interface.
/*----------------------------------------------------------*/
/* Image display sample programme: display only */
/*----------------------------------------------------------*/
#include <karma.h>
/* Need to define this if using X. Can use -DX11 as an alternative. Must be
done before including the karma_viewimg.h header. */
#define X11
#include <karma_viewimg.h>
#include <karma_iarray.h>
#include <karma_xc.h>
#include <X11/Xlib.h>
#include <X11/Xutil.h>
#define DEFAULT_COLOURMAP_NAME "Greyscale1"
#define MAX_COLOURS (unsigned int) 200
void setup_window (dpy, window, gc, win_width, win_height, array)
/* This routine will create a viewable image for an X window from an
"Intelligent Array".
The X display must be given by dpy .
The X window must be given by window .
The X Graphics Context must be given by gc .
The window width must be given by win_width .
The window height must be given by win_height .
The Intelligent Array must be given by array .
The routine returns nothing.
*/
Display *display;
Window window;
GC gc;
int win_width;
int win_height;
iarray array;
{
/* Declare variables */
Kdisplay dpy_handle;
ViewableImage vimage;
XWindowAttributes window_attributes;
struct win_scale_type win_scale;
extern KPixCanvas pixcanvas;
extern KWorldCanvas worldcanvas;
extern Kcolourmap cmap;
/* Initialise colourmap */
XGetWindowAttributes (display, win, &window_attributes);
dpy_handle = xc_get_dpy_handle (display, window_attributes.colormap);
cmap = kcmap_va_create (DEFAULT_COLOURMAP_NAME, MAX_COLOURS, TRUE,
dpy_handle, xc_alloc_colours, xc_free_colours,
xc_store_colours, xc_get_location,
KCMAP_ATT_END);
/* Create the pixel canvas */
pixcanvas = kwin_create_x (display, window, gc,
0, 0, win_width, win_height);
/* Create the world canvas */
/* Initialise the win_scale structure */
canvas_init_win_scale (&win_scale, K_WIN_SCALE_MAGIC_NUMBER);
/* Specify colour to use for out of bounds values */
win_scale.min_sat_pixel = BlackPixel (display, DefaultScreen (display));
win_scale.max_sat_pixel = WhitePixel (display, DefaultScreen (display));
win_scale.blank_pixel = BlackPixel (display, DefaultScreen (display));
worldcanvas = canvas_create (pixcanvas, cmap, &win_scale);
/* Create the viewable image from the Intelligent Array */
viewimg_init (worldcanvas);
vimage = viewimg_create_from_iarray (worldcanvas, array, FALSE);
/* Make this viewable image active (or else we see nothing) */
viewimg_make_active (vimage);
} /* End Function setup_window */
void process_refresh (win_width, win_height)
/* This routine will process a refresh/ resize event on an X window and will
refresh the associated pixel canvas.
The window width must be given by win_width .
The window height must be given by win_height .
The routine returns nothing.
*/
int win_width;
int win_height;
{
extern KPixCanvas pixcanvas;
/* Cause the pixel canvas to be refreshed */
kwin_resize (pixcanvas, FALSE, 0, 0, win_width, win_height);
} /* End Function process_refresh */
The following example expands on the previous one by adding mouse tracking (i.e. the position of the pointer is displayed, as well as the value of the image data at that point) and dynamic colourmap control.
/*------------------------------------------------------------------------*/
/* Image display sample programme: mouse tracking and colourmap control */
/*------------------------------------------------------------------------*/
#include <karma.h>
/* Need to define this if using X. Can use -DX11 as an alternative. Must be
done before including the karma_viewimg.h header. */
#define X11
#include <karma_viewimg.h>
#include <karma_iarray.h>
#include <karma_xc.h>
#include <k_event_codes.h>
#include <X11/Xlib.h>
#include <X11/Xutil.h>
#define DEFAULT_COLOURMAP_NAME "Greyscale1"
#define MAX_COLOURS (unsigned int) 200
flag track_canvas_event (/* vimage, x, y, value, event_code, e_info,f_info */);
flag unit_canvas_position_func (/* canvas, x, y, event_code, e_info,f_info */);
void setup_window (dpy, window, gc, win_width, win_height, array)
/* This routine will create a viewable image for an X window from an
"Intelligent Array".
The X display must be given by dpy .
The X window must be given by window .
The X Graphics Context must be given by gc .
The window width must be given by win_width .
The window height must be given by win_height .
The Intelligent Array must be given by array .
The routine returns nothing.
*/
Display *display;
Window window;
GC gc;
int win_width;
int win_height;
iarray array;
{
/* Declare variables */
Kdisplay dpy_handle;
ViewableImage vimage;
XWindowAttributes window_attributes;
KWorldCanvas unit_worldcanvas;
KWorldCanvas image_worldcanvas;
struct win_scale_type win_scale;
extern KPixCanvas pixcanvas;
extern Kcolourmap cmap;
/* Initialise colourmap */
XGetWindowAttributes (display, win, &window_attributes);
dpy_handle = xc_get_dpy_handle (display, window_attributes.colormap);
cmap = kcmap_va_create (DEFAULT_COLOURMAP_NAME, MAX_COLOURS, TRUE,
dpy_handle, xc_alloc_colours, xc_free_colours,
xc_store_colours, xc_get_location,
KCMAP_ATT_END);
/* Create the pixel canvas */
pixcanvas = kwin_create_x (display, window, gc, 0, 0,win_width,win_height);
/* Create the unit world canvas (for colourmap change events) */
/* Initialise the win_scale structure */
canvas_init_win_scale (&win_scale, K_WIN_SCALE_MAGIC_NUMBER);
unit_worldcanvas = canvas_create (image_pixcanvas, image_cmap, &win_scale);
/* Register event handler which allows user to change colourmap */
canvas_register_position_event_func (unit_worldcanvas,
unit_canvas_position_func,
(void *) cmap);
/* Create the image world canvas */
/* Specify colour to use for out of bounds values */
win_scale.min_sat_pixel = BlackPixel (display, DefaultScreen (display));
win_scale.max_sat_pixel = WhitePixel (display, DefaultScreen (display));
win_scale.blank_pixel = BlackPixel (display, DefaultScreen (display));
image_worldcanvas = canvas_create (pixcanvas, cmap, &win_scale);
/* Create the viewable image from the Intelligent Array */
viewimg_init (image_worldcanvas);
vimage = viewimg_create_from_iarray (worldcanvas, array, FALSE);
/* Register event handler which allows user to see image values */
viewimg_register_position_event_func (image_worldcanvas,
track_canvas_event,
(void *) image_worldcanvas);
/* Make this viewable image active (or else we see nothing) */
viewimg_make_active (vimage);
} /* End Function setup_window */
void process_refresh (win_width, win_height)
/* This routine will process a refresh/ resize event on an X window and will
refresh the associated pixel canvas.
The window width must be given by win_width .
The window height must be given by win_height .
The routine returns nothing.
*/
int win_width;
int win_height;
{
extern KPixCanvas pixcanvas;
/* Cause the pixel canvas to be refreshed */
kwin_resize (pixcanvas, FALSE, 0, 0, win_width, win_height);
} /* End Function process_refresh */
void process_x_event (event, x, y)
/* This routine is called whenever a mouse event occurs on the underlying
X window for the pixel canvas. This is the routine that "injects" events
into the Karma image display system.
The event information is given by event .This is given for example only.
The event co-ordinate is given by x and y .
The routine returns nothing.
*/
int event;
int x;
int y;
{
unsigned int event_code;
extern KPixCanvas pixcanvas;
switch (event_action)
{
case MiddleMouseClick:
event_code = K_CANVAS_EVENT_MIDDLE_MOUSE_CLICK;
break;
case MiddleMouseDrag:
event_code = K_CANVAS_EVENT_MIDDLE_MOUSE_DRAG;
break;
case MouseMove:
event_code = K_CANVAS_EVENT_POINTER_MOVE;
break;
default:
return;
}
if ( !kwin_process_position_event (pixcanvas, x, y, TRUE, event_code,
(void *) NULL) )
{
(void) fprintf (stderr, "Paint window event not consumed\n");
}
} /* End Function process_x_event */
flag unit_canvas_position_func (canvas, x, y, event_code, e_info, f_info)
/* This routine is a position event consumer for a world canvas. This routine
will process mouse click and drag events for dynamic colourmap control.
The canvas is given by canvas .
The horizontal world co-ordinate of the event will be given by x .
The vertical world co-ordinate of the event will be given by y .
The arbitrary event code is given by event_code .
The arbitrary event information is pointed to by e_info .
The arbitrary function information pointer is pointed to by f_info .
The routine returns TRUE if the event was consumed, else it return
FALSE indicating that the event is still to be processed.
*/
KWorldCanvas canvas;
double x;
double y;
unsigned int event_code;
void *e_info;
void **f_info;
{
Kcolourmap cmap;
if ( (cmap = (Kcolourmap) *f_info) == NULL )
{
(void) fprintf (stderr, "NULL Kcolourmap\n");
exit (1);
}
if ( (event_code != K_CANVAS_EVENT_MIDDLE_MOUSE_CLICK) &&
(event_code != K_CANVAS_EVENT_MIDDLE_MOUSE_DRAG) ) return (FALSE);
kcmap_modify (cmap, x, y, (void *) NULL);
return (TRUE);
} /* End Function unit_canvas_position_func */
flag track_canvas_event (vimage, x, y, value, event_code, e_info,f_info)
/* This routine is a position event consumer for a viewable image canvas. This
routine will process mouse movement events for a tracking display.
The viewable image is given by vimage .
The horizontal position of the event, relative to the canvas origin,
will be given by x .
The vertical position of the event, relative to the canvas origin,
will be given by y .
The value in the viewable image at the co-ordinates is given by value.
The arbitrary event code is given by event_code .
The arbitrary event information is pointed to by e_info .
The arbitrary function information pointer is pointed to by f_info .
The routine returns TRUE if the event was consumed, else it returns
FALSE indicating that the event is still to be processed.
*/
ViewableImage vimage;
double x;
double y;
double value[2];
unsigned int event_code;
void *e_info;
void **f_info;
{
if (event_code != K_CANVAS_EVENT_POINTER_MOVE) return (FALSE);
(void) fprintf (stderr, "abs: %e ord: %e value: %e\n", x, y, value[0]);
return (TRUE);
} /* End Function track_canvas_event */