Blender Git Loki

Removed commented out code

Rebase latest master

Fixed failing assert statement due to recent refactoring in master

Use DrawManager for Image/UV Editor

This project moves the current UV/Image editor drawing to the draw manager. Why would we do this:
**Performance**:

Current implementation would draw each texel per time. Multiple texels could be drawn per pixel what would overwrite the previous result. You can notice this when working with large textures. Repeat image drawing made this visible by drawing for a small period of time and stop drawing the rest. Now the rendering is fast and all repeated images are drawn.

**Alpha drawing**:
Current implementation would draw directly in display space. Giving incorrect results when displaying alpha transparent images.
Old:
{F8780114}

New:
{F8780113}

This addresses {T52680}, {T74709}, {T79518}

The image editor now can show emission only colors.
{F8787296}

**Current Limitations**

Using images that are larger than supported by your GPU are resized (eg larger than 16000x16000 are resized to 8k). This leaves some blurring artifacts. It is a low priority to add support back of displaying individual pixels of huge images. There is a design task {T80113} with more detail.

**Implementation overview**
Introduced an Image Engine in the draw module. this engine is responsible for drawing the texture in the main area of the UV/Image editor. The overlay engine has a edit_uv overlay which is responsible to draw the UV's, shadows and overlays specifically for the UV Image editor. The background + checker pattern is drawn by the overlay_background.

The patch will allow us to share overlays between the 3d viewport and UV/Image editor more easily. In most cases we just need to switch the `pos` with the `u` attribute in the vertex shader.

The project can be activated in the user preferences as experimental features. When support of huge textures is implemented we can switch over.

**Future developments**
* Support huge texture sizes. {T80113}
* Share overlay shaders between 3d view and image editor, makes it possible to render certain overlays in both editors.
* Connect smooth wire to `USER_GPU_FLAG_OVERLAY_SMOOTH_WIRE`.
* Move overlay options to a pop-over and other UI improvements.
* Replace the unavailability shader with the overlay grid.

Maniphest Tasks: T67530

Differential Revision: https://developer.blender.org/D8234

GPU: Extract GPU Base Test case

The draw manager test case initialized ghost, gpu and draw manager. This
change splits the base test case to GPU specific and draw manager
specific test case.

The GPU test base test case will be used for low level GPU tests.

DrawManager: Fixed memory leak in test cases

Memory leak is introduced as test cases reinitializes the GPU stack.
Added a call to GPU_backend_exit to fix this.

In GPU_backend_exit the GPU backend was destroyed but the pointer wasn't
reset for reuse. This patch also clears the pointer to be reused.

DrawManager: Move tests in namespace

Using blender::draw::tests as namespaces.

cleanup: remove debug prints

alembic, compute the frame index from the schema

Cleanup: Refactor USD Exporter, make parameter const

Follow-up of 63dc72c3521, make parameter `const`.

No functional changes.

Cleanup: USD export, refactor mesh instancing

Extract the mesh instancing code from the mesh writing function into a
generic 'mark as instance' function on the abstract USD writer. This will
help in supporting non-mesh instances.

No functional changes.

Cleanup: Refactor `ED_object_parent_set`

Refactor `ED_object_parent_set`:
- Mark parameters `ob` and `par` as `const` so that it's clear the
function doesn't assign any other value to them.
- Rename `pararm` to `is_armature_parent`; I mis-read it as `param` all
the time, and it was very confusing.
- Replace repeated `if-else` statements with `switch` statements.
- Reorder preconditions to have some simple checks first.
- Flip condition on a huge `if`-statement to return early and unindent
the remainder of the function.

This function still requires splitting up into smaller functions, but at
least this is a step forward.

No functional changes.

alembic, cleanup, use the socket API to set the current frame and check
for precreated data

Fix T80238: Crash adding properties to material node-trees

The localized node-tree was freeing the materials ID properties twice.

This matches how animation data behaves, setting to NULL after freeing.

Docs: comment values for DispList.type

Cleanup: rename group to collection for internal instancing flag

Also update old comment.

Cleanup: naming for library link enum

Use 'e' prefix, update comments.

Link/Append: support instancing object data

This patch supports instantiating object data on append/link,
reported as a bug T58304.

This is an option, available when linking/appending,
similar to the existing "Instance Collections" option.

Reviewed by @sybren

Ref D8792

Refactor: move library linking arguments into a parameter struct

Move arguments to BLO_library_link_{begin/named_part/end} into
a single parameter struct, to ensure arguments always match.

This allows is to skip tagging ID's LIB_TAG_DOIT when it's not needed,
previously it was always cleared just in case it was needed.

This also makes it possible to remove BLO_library_link_named_part_ex
which was only used when tagging was needed.

encapsulate AlembicObject's data