Examples: OpenGL3: Saving/restoring the Enable state, better than nothing (#347)

examples/opengl3_example/imgui_impl_glfw_gl3.cpp

@@ -37,6 +37,10 @@ void ImGui_ImplGlfwGL3_RenderDrawLists(ImDrawData* draw_data)
     glGetIntegerv(GL_ARRAY_BUFFER_BINDING, &last_array_buffer);
     glGetIntegerv(GL_ELEMENT_ARRAY_BUFFER_BINDING, &last_element_array_buffer);
     glGetIntegerv(GL_VERTEX_ARRAY_BINDING, &last_vertex_array);
+	GLboolean last_enable_blend = glIsEnabled(GL_BLEND);
+	GLboolean last_enable_cull_face = glIsEnabled(GL_CULL_FACE);
+	GLboolean last_enable_depth_test = glIsEnabled(GL_DEPTH_TEST);
+	GLboolean last_enable_scissor_test = glIsEnabled(GL_SCISSOR_TEST);
 
     // Setup render state: alpha-blending enabled, no face culling, no depth testing, scissor enabled
     glEnable(GL_BLEND);
@@ -98,7 +102,10 @@ void ImGui_ImplGlfwGL3_RenderDrawLists(ImDrawData* draw_data)
     glBindBuffer(GL_ARRAY_BUFFER, last_array_buffer);
     glBindBuffer(GL_ELEMENT_ARRAY_BUFFER, last_element_array_buffer);
     glBindVertexArray(last_vertex_array);
-    glDisable(GL_SCISSOR_TEST);
+	if (last_enable_blend) glEnable(GL_BLEND); else glDisable(GL_BLEND);
+	if (last_enable_cull_face) glEnable(GL_CULL_FACE); else glDisable(GL_CULL_FACE);
+	if (last_enable_depth_test) glEnable(GL_DEPTH_TEST); else glDisable(GL_DEPTH_TEST);
+	if (last_enable_scissor_test) glEnable(GL_SCISSOR_TEST); else glDisable(GL_SCISSOR_TEST);
 }
 
 static const char* ImGui_ImplGlfwGL3_GetClipboardText()