add gl::fence

CMakeLists.txt

@@ -108,6 +108,7 @@ set(SOURCES
 "gl/cubemap.cpp"
 "gl/glsl_common.cpp"
 "gl/buffer.cpp"
+"gl/fence.cpp"
 
 "imgui/imgui.cpp"
 "imgui/imgui_demo.cpp"

gl/fence.cpp

@@ -0,0 +1,18 @@
+#include "fence.h"
+
+gl::fence::fence()
+{
+    sync = glFenceSync(GL_SYNC_GPU_COMMANDS_COMPLETE, 0);
+}
+
+gl::fence::~fence()
+{
+    glDeleteSync(sync);
+}
+
+bool gl::fence::is_signalled()
+{
+    GLint val;
+    glGetSynciv(sync, GL_SYNC_STATUS, 1, &val);
+    return val == GL_SIGNALED;
+}

gl/fence.h

@@ -0,0 +1,15 @@
+#include "object.h"
+
+namespace gl
+{
+    class fence
+    {
+        GLsync sync;
+
+    public:
+        fence();
+        ~fence();
+
+        bool is_signalled();
+    };
+}