Misc: Add DEBUG_GLX_MARK & Misc

- GLX backend: Add DEBUG_GLX_MARK, to add GL marks around functions with
  glStringMarkerGREMEDY(), and mark frame termination with
  glFrameTerminatorGREMEDY().

- Print output of `compton -h` to stdout. (#110)

- GLX backend: Strip out elements with factor 0 in GLSL blur code.
  Thanks to jrfonseca for guides. (#107)

src/common.h

@@ -317,6 +317,11 @@ typedef void (*f_ReleaseTexImageEXT) (Display *display, GLXDrawable drawable, in
 
 typedef void (*f_CopySubBuffer) (Display *dpy, GLXDrawable drawable, int x, int y, int width, int height);
 
+#ifdef DEBUG_GLX_MARK
+typedef void (*f_StringMarkerGREMEDY) (GLsizei len, const void *string);
+typedef void (*f_FrameTerminatorGREMEDY) (void);
+#endif
+
 /// @brief Wrapper of a GLX FBConfig.
 typedef struct {
   GLXFBConfig cfg;
@@ -688,6 +693,12 @@ typedef struct {
   f_ReleaseTexImageEXT glXReleaseTexImageProc;
   /// Pointer to glXCopySubBufferMESA function.
   f_CopySubBuffer glXCopySubBufferProc;
+#ifdef DEBUG_GLX_MARK
+  /// Pointer to StringMarkerGREMEDY function.
+  f_StringMarkerGREMEDY glStringMarkerGREMEDY;
+  /// Pointer to FrameTerminatorGREMEDY function.
+  f_FrameTerminatorGREMEDY glFrameTerminatorGREMEDY;
+#endif
   /// FBConfig-s for GLX pixmap of different depths.
   glx_fbconfig_t *glx_fbconfigs[OPENGL_MAX_DEPTH + 1];
 #ifdef CONFIG_VSYNC_OPENGL_GLSL
@@ -1803,6 +1814,38 @@ glx_create_program(const GLuint * const shaders, int nshaders);
 #endif
 #endif
 
+/**
+ * Add a OpenGL debugging marker.
+ */
+static inline void
+glx_mark_(session_t *ps, const char *func, XID xid, bool start) {
+#ifdef DEBUG_GLX_MARK
+  if (BKEND_GLX == ps->o.backend && ps->glStringMarkerGREMEDY) {
+    if (!func) func = "(unknown)";
+    const char *postfix = (start ? " (start)": " (end)");
+    char *str = malloc((strlen(func) + 12 + 2
+          + strlen(postfix) + 5) * sizeof(char));
+    strcpy(str, func);
+    sprintf(str + strlen(str), "(%#010lx)%s", xid, postfix);
+    ps->glStringMarkerGREMEDY(strlen(str), str);
+    free(str);
+  }
+#endif
+}
+
+#define glx_mark(ps, xid, start) glx_mark_(ps, __func__, xid, start)
+
+/**
+ * Add a OpenGL debugging marker.
+ */
+static inline void
+glx_mark_frame(session_t *ps) {
+#ifdef DEBUG_GLX_MARK
+  if (BKEND_GLX == ps->o.backend && ps->glFrameTerminatorGREMEDY)
+    ps->glFrameTerminatorGREMEDY();
+#endif
+}
+
 static inline void
 free_texture(session_t *ps, glx_texture_t **pptex) {
 #ifdef CONFIG_VSYNC_OPENGL

src/compton.c

@@ -1402,6 +1402,8 @@ render(session_t *ps, int x, int y, int dx, int dy, int wid, int hei,
 static inline void
 win_paint_win(session_t *ps, win *w, XserverRegion reg_paint,
     const reg_data_t *pcache_reg) {
+  glx_mark(ps, w->id, true);
+
   // Fetch Pixmap
   if (!w->paint.pixmap && ps->has_name_pixmap) {
     set_ignore_next(ps);
@@ -1564,6 +1566,8 @@ win_paint_win(session_t *ps, win *w, XserverRegion reg_paint,
 #endif
     }
   }
+
+  glx_mark(ps, w->id, false);
 }
 
 /**
@@ -1812,6 +1816,7 @@ paint_all(session_t *ps, XserverRegion region, XserverRegion region_real, win *t
     default:
       assert(0);
   }
+  glx_mark_frame(ps);
 
   if (ps->o.vsync_aggressive)
     vsync_wait(ps);
@@ -4050,7 +4055,7 @@ ev_handle(session_t *ps, XEvent *ev) {
  * Print usage text and exit.
  */
 static void
-usage(void) {
+usage(int ret) {
 #define WARNING_DISABLED " (DISABLED AT COMPILE TIME)"
 #define WARNING
   const static char *usage_text =
@@ -4277,11 +4282,12 @@ usage(void) {
     "  Specify window ID to repaint in benchmark mode. If omitted or is 0,\n"
     "  the whole screen is repainted.\n"
     ;
-  fputs(usage_text , stderr);
+  FILE *f = (ret ? stderr: stdout);
+  fputs(usage_text, f);
 #undef WARNING
 #undef WARNING_DISABLED
 
-  exit(1);
+  exit(ret);
 }
 
 /**
@@ -4903,7 +4909,7 @@ get_cfg(session_t *ps, int argc, char *const *argv, bool first_pass) {
       else if ('d' == o)
         ps->o.display = mstrcpy(optarg);
       else if ('?' == o || ':' == o)
-        usage();
+        usage(1);
     }
 
     // Check for abundant positional arguments
@@ -4944,7 +4950,7 @@ get_cfg(session_t *ps, int argc, char *const *argv, bool first_pass) {
 #define P_CASEBOOL(idx, option) case idx: ps->o.option = true; break
       // Short options
       case 'h':
-        usage();
+        usage(0);
         break;
       case 'd':
         break;
@@ -5118,7 +5124,7 @@ get_cfg(session_t *ps, int argc, char *const *argv, bool first_pass) {
         break;
       P_CASEBOOL(303, glx_use_gpushader4);
       default:
-        usage();
+        usage(1);
         break;
 #undef P_CASEBOOL
     }

src/compton.h

@@ -813,7 +813,7 @@ ev_window(session_t *ps, XEvent *ev);
 #endif
 
 static void __attribute__ ((noreturn))
-usage(void);
+usage(int ret);
 
 static bool
 register_cm(session_t *ps);

src/dbus.c

@@ -605,6 +605,20 @@ cdbus_process(session_t *ps, DBusMessage *msg) {
         "org.freedesktop.DBus.Introspectable", "Introspect")) {
     success = cdbus_process_introspect(ps, msg);
   }
+  else if (dbus_message_is_method_call(msg,
+        "org.freedesktop.DBus.Peer", "Ping")) {
+    cdbus_reply(ps, msg, NULL, NULL);
+    success = true;
+  }
+  else if (dbus_message_is_method_call(msg,
+        "org.freedesktop.DBus.Peer", "GetMachineId")) {
+    char *uuid = dbus_get_local_machine_id();
+    if (uuid) {
+      cdbus_reply_string(ps, msg, uuid);
+      dbus_free(uuid);
+      success = true;
+    }
+  }
   else if (dbus_message_is_signal(msg, "org.freedesktop.DBus", "NameAcquired")
       || dbus_message_is_signal(msg, "org.freedesktop.DBus", "NameLost")) {
     success = true;
@@ -1028,6 +1042,12 @@ cdbus_process_introspect(session_t *ps, DBusMessage *msg) {
     "      <arg name='data' direction='out' type='s' />\n"
     "    </method>\n"
     "  </interface>\n"
+    "  <interface name='org.freedesktop.DBus.Peer'>\n"
+    "    <method name='Ping' />\n"
+    "    <method name='GetMachineId'>\n"
+    "      <arg name='machine_uuid' direction='out' type='s' />\n"
+    "    </method>\n"
+    "  </interface>\n"
     "  <interface name='" CDBUS_INTERFACE_NAME "'>\n"
     "    <signal name='win_added'>\n"
     "      <arg name='wid' type='" CDBUS_TYPE_WINDOW_STR "'/>\n"

src/opengl.c

@@ -90,6 +90,13 @@ glx_init(session_t *ps, bool need_render) {
 
   // Acquire function addresses
   if (need_render) {
+#ifdef DEBUG_GLX_MARK
+    ps->glStringMarkerGREMEDY = (f_StringMarkerGREMEDY)
+      glXGetProcAddress((const GLubyte *) "glStringMarkerGREMEDY");
+    ps->glFrameTerminatorGREMEDY = (f_FrameTerminatorGREMEDY)
+      glXGetProcAddress((const GLubyte *) "glFrameTerminatorGREMEDY");
+#endif
+
     ps->glXBindTexImageProc = (f_BindTexImageEXT)
       glXGetProcAddress((const GLubyte *) "glXBindTexImageEXT");
     ps->glXReleaseTexImageProc = (f_ReleaseTexImageEXT)
@@ -249,6 +256,8 @@ glx_init_blur(session_t *ps) {
           if (hei / 2 == i && wid / 2 == j)
             continue;
           double val = XFixedToDouble(ps->o.blur_kern[2 + i * wid + j]);
+          if (0.0 == val)
+            continue;
           sum += val;
           sprintf(pc, shader_add, val, texture_func, j - wid / 2, i - hei / 2);
           pc += strlen(pc);