Change RENDERDOC_HOOK_EGL to a runtime option on an env var

* Environment variables are not user-friendly, but I don't want to promote this
  to a capture option since it's so niche.
* In future perhaps  it will be feasible to support selecting an arbitrary API
  to capture, or even capturing multiple APIs simultaneously - though with GLES-
  on-GL that will be quite difficult.

renderdoc/driver/gl/egl_hooks.cpp

@@ -551,9 +551,28 @@ static void EGLHooked(void *handle)
   });
 }
 
+#if ENABLED(RDOC_WIN32)
+bool ShouldHookEGL()
+{
+  const char *toggle = Process::GetEnvVariable("RENDERDOC_HOOK_EGL");
+
+  // if the var is set to 0, then don't hook EGL
+  if(toggle && toggle[0] == '0')
+    return false;
+
+  return true;
+}
+#endif
+
 void EGLHook::RegisterHooks()
 {
-#if ENABLED(RENDERDOC_HOOK_EGL)
+#if ENABLED(RDOC_WIN32)
+  if(!ShouldHookEGL())
+  {
+    RDCLOG("EGL hooks disabled - if GLES emulator is in use, underlying API will be captured");
+    return;
+  }
+#endif
 
   RDCLOG("Registering EGL hooks");
 
@@ -591,10 +610,4 @@ void EGLHook::RegisterHooks()
       FunctionHook("egl" STRINGIZE(func), (void **)&EGL.func, (void *)&CONCAT(egl, func)));
   EGL_HOOKED_SYMBOLS(EGL_REGISTER)
 #undef EGL_REGISTER
-
-#else
-
-  RDCLOG("EGL hooks disabled - if GLES emulator is in use, underlying API will be captured");
-
-#endif
 }

renderdoc/driver/gl/gl_common.h

@@ -49,9 +49,9 @@ DECLARE_REFLECTION_ENUM(RDCGLenum);
 #define RENDERDOC_SUPPORT_GL
 #define RENDERDOC_SUPPORT_GLES
 
-// disable this option to disallow hooking EGL on windows. This means that the underlying GL or D3D
-// calls will be captured instead.
-#define RENDERDOC_HOOK_EGL OPTION_ON
+// checks a runtime opt-out option to disallow hooking EGL on windows. This means that the
+// underlying GL or D3D calls will be captured instead.
+bool ShouldHookEGL();
 
 #else
 

renderdoc/driver/gl/gl_hooks.cpp

@@ -185,11 +185,14 @@ void GLHook::RegisterHooks()
 
   ForEachSupported(RegisterFunc);
 
-#if ENABLED(RDOC_WIN32) && defined(RENDERDOC_SUPPORT_GLES)
-  // on windows where hooking is per-library, we also need to register these hooks for any GLES2/3
-  // wrapper library, when GLES support is enabled.
-  libraryName = "libGLESv2.dll";
+#if ENABLED(RDOC_WIN32)
+  if(ShouldHookEGL())
+  {
+    // on windows where hooking is per-library, we also need to register these hooks for any GLES2/3
+    // wrapper library, when GLES support is enabled.
+    libraryName = "libGLESv2.dll";
 
-  ForEachSupported(RegisterFunc);
+    ForEachSupported(RegisterFunc);
+  }
 #endif
 }