Providing graphics for BOINC applications

A BOINC application may provide graphics (e.g. visualizations) to volunteers. These graphics appear in two contexts:

• As a screensaver.
• In a window (opened using the Show Graphics button in the BOINC Manager).

Graphics apps

The most general way of providing graphics involves using a 'graphics app' program (separate from your main application). This graphics app must have the properties that:

• If invoked with --fullscreen, it opens a full-screen borderless window. It must exit on mouse or keyboard input; this is handled automatically by boinc_graphics_loop() if you use the BOINC graphics API library.
• Otherwise it opens a standard window, and may handle mouse/keyboard input.

The logical name of the program must be 'graphics_app'. When you set up your application version directory, use an entry like

<file>
   <physical_name>uppercase_graphics_6.14_windows_intelx86.exe</physical_name>
   <logical_name>graphics_app</logical_name>
</file>

in your version.xml file.

The graphics app is launched by the BOINC Manager and by the screensaver. It may be killed at any time. Multiple instances of the graphics app may run at the same time (e.g. if the user opens a graphics window via the Manager, and then the screensaver runs and launches another instance).

The BOINC graphics API provides cross-platform support for developing graphics apps.

A complete example can be found in boinc/samples/example_app.

The BOINC Graphics API

BOINC supplies a library (libboinc_graphics2.a) that makes it easy to develop graphics apps. To use this library, the graphics app must call

boinc_graphics_loop(int argc, char** argv);

after its initialization. This function executes an event loop, and does not return.

The application must supply the following functions:

void app_graphics_init();

Called once, after the window has been created.

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

This will be called periodically. 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.

void app_graphics_resize(int x, int y);

Called when the window size changes.

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
)

Communicating with the main application

The graphics app may want to get information from the main app. This can be done efficiently using shared memory. The BOINC library supplies the following functions to facilitate this:

void* boinc_graphics_make_shmem(char* appname, int size);
void* boinc_graphics_get_shmem(char* appname);

boinc_graphics_make_shmem() (called from the main app) creates a shared memory segment of the given size. 'appname' should be the name of this application (used to ensure uniqueness of the shared-memory segment name). boinc_graphics_get_shmem() (called from the graphics app) attaches to an existing segment. It must be called AFTER boinc_parse_init_data_file().

The contents of the shared memory segment are up to you. You may want to include the following items:

struct UC_SHMEM {
    double update_time;
    double fraction_done;
    double cpu_time;
    BOINC_STATUS status;
};

This structure should be updated by the main app once per second, using boinc_set_timer_handler(). The items are:

update_time

The current time (dtime()). The graphics app should exit if the current time exceeds this by 5 seconds or so.

fraction_done

The last fraction done reported by the main app.

cpu_time

The current CPU time.

status

The BOINC status. If the 'suspended' flag is set, the graphics app should stop changing its display, and simply display an "application suspended" message.

Keep in mind that multiple instances of the graphics app may run simultaneously; avoid having the graphics app write to the shared memory. If you use shared memory to store a data structure, use a semaphore to synchronize access so that the graphics app doesn't see an inconsistent state.

Creating an icon for your applications

For Windows:

• make Icons (there's a tool for this in Visual Studio), say "boincAppIcon16x16.ico", "boincAppIcon32x32.ico" and "boincAppIcon48x48.ico".
• create a simple resource description file "boincAppIcon.rc" in the same directory as the icon files pointing to the icon filenames, the first entry is the resource name that is later passed to setWinIcon():

  boinca16 ICON boincAppIcon16x16.ico
  boinca32 ICON boincAppIcon32x32.ico
  boinca48 ICON boincAppIcon48x48.ico
  

• compile the resource (I do this on a Visual Studio Command Prompt):

  rc.exe boincAppIcon.rc
  

• when linking the App, add the resulting file boincAppIcon.RES to the objects

• we call setWinIcon("boinca16","boinca48") in app_graphics_init()

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 a JPEG image displayed in 3 dimensions.

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

Displaying a static image

An application can display a pre-existing JPEG file 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.cpp (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.

Using Web graphics

You can also generate graphics using HTML. Note: this works for graphics windows created using the Manager's Show Graphics button; it doesn't provide a screensaver.

In this case your main program supplies a URL that supplies the HTML. This may be an external URL, or it may refer to a web server embedded in your main program (i.e. a URL of the form ​http://localhost:port). Your main program can call

boinc_web_graphics_url(char* url)

to register a URL to be used for graphics; in this case, the BOINC Manager's Show Graphics button will open a Web browser window to this URL.