Use HdxCompositor instead of glDrawPixels.
Right now we are using glDrawPixels to push the rendered image onto the OpenGL viewport. The standard way of doing this is using the HdxCompositor class (bonus, GlDrawPixels won't work in our Maya plugin, while HdxCompositor will). Also, HdxCompositor lets you set up the depth of each pixel, which helps using the render delegate in cases where it has to draw over (under) an already existing UI or mixing the rendered results with other elements.
Suggest by Pal Mezai from Luma.