I spend a large portion of the day studding the base actor class (5600+ lines
of code, wow :)), and more specifically, the rendering.
And one thing drew my attention - the shader compiling/binding/linking part.
I spend about an hour looking for that, first in the actor, than in cogl, even
in the backend until I finally found it in well...the shader files.
I know it might looks obvious, but it is not to obvious in practice, because
traditionally that phase is handled by OpenGL API and compiling/binding/linking
itself does not have anything to do with the shaders themselves. Even more so,
the bind_shader function in Clutter right now is composed entirely of cogl
calls. My guess is that the function is not in the cogl code simply because it
has to be exposed without the need of cogl to be included, and that is
perfectly reasonable (though it could be exposed through Actor like
clutter_actor_set_shader_param )...
...But my main point is - do we really need clutter_shader_bind to be exposed
at all. Its very very low level function (much like glBlend or glStencilFunc or
whatever) and makes sense only to graphic programmers (not the casual Clutter
users) and only in the actual drawing context, not in the top level scene
creation/management stage. Because of this it is not obvious that the function
must be called at all, and even if the user does know, there is no way of
telling when it is to be called (after or before setting the params? or calling
actor_show? or actor_set_shader?) Even what actor does it effect is not clear
from the statement itself.
In the end, from end user perspective , actor_set_shader should be enough: Its
sets some "property" on my actor, that changes the way it looks. Just like
set_size or set_position.
.
I can image how annoying this kind of mails for the team are, neither bug
report nor feature request, and how terribly wrong I can be, but I decided to
share my thoughts after all :)
I`ll be happy to hear your comments, 10x.
MihailNaydenov
PS In the test-shader example, is it really necessary to call
clutter_actor_set_shader (<actor>, NULL), which destroys the previously set
shader, before setting a new one? Looking at the set_shader code, its seams not
only unnecessary, but even faster if you call it the second time because it
skips the creation of the params hashtable.
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