By all means Patrice,
You're free (and encouraged!) to experiment in whatever way you're most interested, and if such results are aesthetically satisfactory (black border-less and with all the peripheral scan colors intact, in this particular case) then we can use them as optional rendering modes for particular scene content.
However most of the GLSL coolest effects with translucency (like e.g. glass surface specular reflection, or refraction, or diffraction, etc.) are implemented not against simple 2D billboard backgrounds but within a 3D world enclosed in a skybox, skysphere, or at least skydome. OpenGL simple stock transparency isn't used at all. Instead, multiple render passes are run into all sorts of buffers (depth, stencil, lighting, etc.) and their final swap on the screen is deferred till the final PP step. Then all the buffers are sampled against the existing scene geometry and its attributes (including emulated translucency), and decisions are taken as to what objects should be seen directly, and which of them should be rendered first to be "seen" through other "translucent" surfaces and in what order, and how these surfaces should distort and fake reflection/refraction of other objects' 3D and planar geometry including the background.
In other words, the shaders should be immediately aware not only of scene geometry but also of the enclosing background. OTOH there would be no background in the scene at all from OpenGL's standpoint if it has been taken out of the scene and placed in parallel, but still alien, unreachable and incommunicado worlds of GDI+ drawing and DirectX compositing.
I am going to introduce sky boxes and probably sky domes in OR a.s.a.p. after FBO because proper rendering of advanced GLSL 3D effects is impossible against flat 2D backgrounds of our current wallpaper type.
