Changes between Initial Version and Version 1 of GraphicsApps

Timestamp:

Jan 26, 2015, 11:50:29 AM (11 years ago)

Author:

davea

Comment:

--

GraphicsApps

@@ +1 @@
+[[PageOutline]]
+
+= Providing graphics for BOINC applications =
+
+A BOINC application may provide graphics (e.g. visualizations) to volunteers.
+These graphics are shown in two contexts:
+
+ * As a screensaver, if selected by the user.
+ * In a window, opened using the Show Graphics button in the BOINC Manager.
+
+Graphics are generated by a 'graphics app' program (separate from the 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
+  (if you use the [#api BOINC graphics API] library this is handled automatically).
+ * 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 [AppVersionNew 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/or 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).
+
+
+== Communication between main and graphics apps ==
+
+The graphics app may want to get information from the main app.
+This can be done using either shared memory or a file.
+
+=== Shared memory ===
+
+Communicating large amounts of data
+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);
+}}}
+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).
+
+{{{
+void* boinc_graphics_get_shmem(char* appname);
+}}}
+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 application-dependent;
+typically it contains numeric information describing the state of the computation.
+
+You may want to include the following items:
+{{{
+struct UC_SHMEM {
+    double update_time;
+    double fraction_done;
+    double cpu_time;
+    BOINC_STATUS status;
+    int countdown;
+};
+}}}
+
+These items should be updated by the main app once per second,
+using [BasicApi#timer 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,
+   so that it exits if the main app exits.
+ fraction_done::
+   The last fraction done reported by the main app.
+ cpu_time::
+   The current CPU time, as returned by '''boinc_worker_thread_cpu_time()'''.
+ status::
+   The BOINC status, as returned by '''boinc_get_status()'''.
+   If the 'suspended' flag is set,
+   the graphics app should stop changing its display,
+   and instead show an "application suspended" message.
+ countdown::
+   See below.
+
+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.
+
+Updating the shared memory structure uses CPU time,
+and it's desirable to avoid this overhead if no graphics app is running.
+
+One way to do this is to include a '''countdown''' field in the shared memory structure, as above.
+ * The graphics sets this to 5 (say) in its '''app_graphics_render()''' function.
+ * The main app decrements this (if positive) once per second.
+ * The main app updates the application-specific data in shared memory
+   only when '''countdown''' is nonzero.
+
+See [ExampleApps the example application] for an example.
+
+=== File ===
+
+Alternatively, you can communicate data from main app to graphics app via a file.
+The BOINC library provides two functions for this purpose.
+The main program can call
+{{{
+int boinc_write_graphics_status(
+    const char* filename, double cpu_time, double elapsed_time,
+    double fraction_done
+);
+}}}
+to write a file containing its status in XML format.
+The graphics app can call
+{{{
+int boinc_parse_graphics_status(
+    const char* filename, double* update_time, double* cpu_time,
+    double* elapsed_time, double* fraction_done, BOINC_STATUS* status
+);
+}}}
+to read and parse this file.
+
+== Creating an icon for graphics 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()