GraphicsApiOld

The old BOINC graphics API

DEPRECATED - SEE the BOINC 6 graphics API)

BOINC applications can optionally provide graphics, which are displayed either in an application window or in a full-screen window (when the BOINC screensaver is selected).

You are encouraged to implement graphics using OpenGL. This makes it easy for your application to show graphics on all platforms.

NOTE: if you use this graphics API with the current BOINC API library (changeset 13697 or later) you must explicitly set BOINC_OPTIONS.backwards_compatible_graphics to 0 (false).

Integrated graphics

Graphics can either be integrated in your main application or generated by a separate program. The integrated approach is recommended, and we'll describe it first. In this approach, instead of boinc_init(), an application calls

#if defined(_WIN32) | defined(__APPLE__)
    retval = boinc_init_graphics(worker);
#else
    retval = boinc_init_graphics_lib(worker, argv[0]);
#endif

where worker() is the main function of your application. Your application must supply rendering and input-handling functions (see below).

These functions creates a worker thread that runs the main application function. The original thread becomes the graphics thread, which handles GUI events and does rendering.

On Unix, your graphics code must be put in a separate shared library (.so) file. This is because Unix hosts may not have the needed libraries (OpenGL, GLUT, X11). If an application is linked dynamically to these libraries, it will fail on startup if the libraries are not present. On the other hand, if an application is linked statically to these libraries, graphics will be done very inefficiently on most hosts.

The shared library must have the same name as the executable followed by '.so'. It must be linked with libboinc_graphics_impl.a, with your rendering and input-handling functions, and (dynamically) with glut and opengl. You must bundle the main program and the shared library together as a multi-file application version. Unix/Linux applications that use graphics should compile all files with -D_REENTRANT, since graphics uses multiple threads.

The BOINC example application uses this technique, and shows the Makefile command that are needed to produce the shared library on Unix.

Rendering and input-handling functions

Programs that use integrated graphics must supply the following functions:

void app_graphics_render(int xs, ys, double time_of_day);

This will be called periodically in the graphics thread. It should generate the current graphic. xs and ys are the X and Y sizes of the window, and time_of_day is the relative time in seconds. Applications that don't do graphics must also supply a dummy app_graphics_render() to link with the API.

void app_graphics_init();

This is called in the graphics thread when a window is created. It must make any calls needed to initialize graphics in the window.

void app_graphics_resize(int x, int y);

Called when the window size changes.

void app_graphics_reread_prefs();

This is called, in the graphics thread, whenever the user's project preferences change. It can call

boinc_parse_init_data_file();
boinc_get_init_data(APP_INIT_DATA&);

to get the new preferences.

The application must supply the following input-handling functions:

void boinc_app_mouse_move(
    int x, int y,       // new coords of cursor
    int left,          // whether left mouse button is down
    int middle,
    int right
);

void boinc_app_mouse_button(
    int x, int y,       // coords of cursor
    int which,          // which button (0/1/2)
    int is_down        // true iff button is now down
);

void boinc_app_key_press(
    int, int            // system-specific key encodings
)

void boinc_app_key_release(
    int, int            // system-specific key encodings
)

Limiting frame rate

The following global variables control frame rate:

boinc_max_fps is an upper bound on the number of frames per second (default 30).

boinc_max_gfx_cpu_frac is an upper bound on the fraction of CPU time used for graphics (default 0.5).

Support classes

Several graphics-related classes were developed for SETI@home. They may be of general utility.

REDUCED_ARRAY Represents a two-dimensional array of data, which is reduced to a smaller dimension by averaging or taking extrema. Includes member functions for drawing the reduced data as a 3D graph in several ways (lines, rectangles, connected surface). PROGRESS and PROGRESS_2D Represent progress bars, depicted in 3 or 2 dimensions. RIBBON_GRAPH Represents of 3D graph of a function of 1 variable. MOVING_TEXT_PANEL Represents a flanged 3D panel, moving cyclically in 3 dimensions, on which text is displayed. STARFIELD Represents a set of randomly-generated stars that move forwards or backwards in 3 dimensions. TEXTURE_DESC Represents an image (JPEG, Targa, BMP, PNG, or RGB``) displayed in 3 dimensions.

The file api/txf_util.C has support functions from drawing nice-looking 3D text.

Static graphics

An application can display a pre-existing image file (JPEG, GIFF, BMP or Targa) as its graphic. This is the simplest approach since you don't need to develop any code. You must include the image file with each workunit. To do this, link the application with api/static_graphics.C (edit this file to use your filename). You can change the image over time, but you must change the (physical, not logical) name of the file each time.

Graphics in a separate program

In this approach, an application bundles a 'main program' and a 'graphics program'. The main program executes the graphics program, and kills it when done. The main and graphics programs typically communicate using shared memory; you can use the functions in boinc/lib/shmem.C for this.

The main program should initialize using

int boinc_init_options_graphics(BOINC_OPTIONS&, WORKER_FUNC_PTR worker);

The graphics application can be implemented using the BOINC framework, in which case it must initialize with

int boinc_init_options_graphics(BOINC_OPTIONS&, NULL);

and supply rendering and input-handling functions.

Either the graphics or the main program can handle graphics messages from the core client. It's easiest to have the graphics program handle them; if the main program handles them, it must convey them to the graphics program.