Enable the glStringMarker logger when available

glStringMarker is usually only available when running under some
kind of GL debugger, and can be used to insert strings into the
GL command string. Writing logs using it can be useful, since it
lets us correspond GL calls with what happens in compton.

More info about the extension can be found here:

https://www.khronos.org/registry/OpenGL/extensions/GREMEDY/GREMEDY_string_marker.txt

Signed-off-by: Yuxuan Shui <yshuiv7@gmail.com>

src/compton.c

@@ -2953,6 +2953,14 @@ session_init(session_t *ps_old, int argc, char **argv) {
     exit(0);
   }
 
+  if (bkend_use_glx(ps)) {
+    auto glx_logger = glx_string_marker_logger_new();
+    if (glx_logger) {
+      log_info("Enabling gl string marker");
+      log_add_target_tls(glx_logger);
+    }
+  }
+
   // Initialize software optimization
   if (ps->o.sw_opti)
     ps->o.sw_opti = swopti_init(ps);

src/log.c

@@ -8,7 +8,7 @@
 #include <unistd.h>
 
 #ifdef CONFIG_OPENGL
-#include <GL/glx.h>
+#include <opengl.h>
 #endif
 
 #include "compiler.h"
@@ -326,6 +326,10 @@ static const struct log_ops glx_string_marker_logger_ops = {
 };
 
 struct log_target *glx_string_marker_logger_new(void) {
+	if (!glx_hasglext("GL_GREMEDY_string_marker")) {
+		return NULL;
+	}
+
 	void *fnptr = glXGetProcAddress((GLubyte *)"glStringMarkerGREMEDY");
 	if (!fnptr)
 		return NULL;

src/opengl.c

@@ -347,7 +347,7 @@ glx_init(session_t *ps, bool need_render) {
   // Check GL_ARB_texture_non_power_of_two, requires a GLX context and
   // must precede FBConfig fetching
   if (need_render)
-    psglx->has_texture_non_power_of_two = glx_hasglext(ps,
+    psglx->has_texture_non_power_of_two = glx_hasglext(
         "GL_ARB_texture_non_power_of_two");
 
   // Acquire function addresses

src/opengl.h

@@ -119,7 +119,7 @@ glx_hasglxext(session_t *ps, const char *ext) {
  * Check if a GLX extension exists.
  */
 static inline bool
-glx_hasglext(session_t *ps, const char *ext) {
+glx_hasglext(const char *ext) {
   const char *gl_exts = (const char *) glGetString(GL_EXTENSIONS);
   if (!gl_exts) {
     log_error("Failed get GL extension list.");