Since 3DViews use IDs like images or clips, we can't skip anymore `lib_link_screen()`
when reading from mem for undo/redo stuff. Else, freeing (unused) screen in `BKE_read_file_from_memfile()`
will lead to using data already freed (since pointers have not been updated when reading that undo step).
There were a few issues to fix here:
* We did not really unpremultiply float image dabs prior to sending them
to the GPU. That made float and byte image result different in texture
painting and undoing could change the result.
* To make textures nicely composited over the mesh, I used decal mode in
OpenGL texture environment for the texture unit. This uses the texture's
alpha channel with a nice over operator.
* Texture creation used to override the alpha setting due to the display
restrictions. Not so anymore, people can now create transparent byte
images.
Also, made alpha zero default for new textures now, since it has such a
nice effect here.
Problem is that setup of stack indices which refer to the same stack
entry can lead to cyclic TexDelegate node pointers, causing an infinite
loop.
Fixing this would take too much time and require recoding large parts of
the texnodes system, which is earmarked for scrapping anyway ... So for
now just disabled muting in texnodes to avoid crashes.
The stored context object was used for creation of shade nodes. A closer look at the
node system showed that the context is not actually used when shader nodes are
added to a shader node tree. Relying on this fact, now a NULL pointer is passed to
nodeAddStaticNode() instead of the stored bContext pointer.
Looks like the issue was caused by a UV map name starting with a lower case
letter (e.g., "color"). Capitalizing the name fixed the problem. Also adjusted
the creation of custom data layers to optimize things a bit.
Removed the previous changes for passing a line style through the Controller, and
revised the BlenderTextureShader to assign the shader node tree of a line style
(if specified) to strokes. This way the assignment of shading nodes can be done
through both the Freestyle GUI and Python scripting.
Changes to ED_node_shader_default() were reverted since the code there was actually
not suitable for setting up the default line style node tree properly.
Now the shader node tree of a line style ID datablock is used to define textures
as well as their mapping and influence.
TODO: Textures alpha channel mapping and influence.
TODO: Blend mode in the Output Line Style shader node.
