mutter/src/compositor
Daniel van Vugt e5542c3210 shaped-texture: Use the REPLACE combine function on opaque areas
We were setting the pipeline colour to all white (1.0, 1.0, 1.0, 1.0)
and so the default layer combine function multiplied each pixel
(R, G, B, A) by all ones. Obviously multiplying by one four times per
pixel is a waste of effort so we remove the colour setting *and* set
the layer combine function to a trivial shader that will ignore whatever
the current pipeline colour is set to. So now we do **zero** multiplies
per pixel.

On an i7-7700 at UHD 3840x2160 this results in 5% faster render times
and 10% lower power usage (says intel_gpu_top). The benefit is probably
much higher for virtual machines though, as they're no longer being
asked to do CPU-based math on every pixel of a window.

https://gitlab.gnome.org/GNOME/mutter/-/merge_requests/1331
2020-06-27 10:20:11 +00:00
..
2019-06-20 18:25:04 +02:00
2019-08-19 08:44:58 +00:00
2018-11-06 17:17:36 +01:00
2019-01-04 09:32:58 -02:00

Intro
=====

In general, the compositor splits the window from the contents of
the window from the shape of the window. In other words, a window
has contents, and the contents of the window have a shape. This is
represented by the actor hierarchy:

 +--------------------------------------+
 | MetaWindowActor                      |
 | +----------------------------------+ |
 | | MetaSurfaceActor                 | |
 | | +------------------------------+ | |
 | | | MetaShapedTexture            | | |
 | | |                              | | |
 | | |                              | | |
 | | |                              | | |
 | | |                              | | |
 | | +------------------------------+ | |
 | +----------------------------------+ |
 +--------------------------------------+

Surfaces may also contain subsurfaces. The MetaWindowActor and
MetaSurfaceActor subclasses that will be created depend on the client
type, and the display server type.

## Subsurfaces

Additionally, there is also the case of subsurfaces: surfaces that
are child of other surfaces. That is also represented in the actor
hierarchy by having one or many MetaSurfaceActors (the subsurfaces)
added as children of a parent MetaSurfaceActor. There are no limits
to how many subsurfaces a surface may have. With subsurfaces, the
actor hierarchy looks like this:

 MetaWindowActor
  ↳ MetaSurfaceActor (surface)
     ↳ MetaShapedTexture
     ↳ MetaSurfaceActor (subsurface)
        ↳ MetaShapedTexture
        ↳ MetaSurfaceActor (sub-subsurface)
           ↳ MetaShapedTexture
     ↳ MetaSurfaceActor (subsurface)
        ↳ MetaShapedTexture

In this example, the main surface has 2 subsurfaces. One of these
subsurfaces contains a subsurface as well.

All MetaWindowActors contain at least one MetaSurfaceActor, and all
MetaSurfaceActors contain a MetaShapedTexture.

## Client and compositor

MetaWindowActor and its subclasses represent the client window's
type. A X11 client will have a MetaWindowActorX11 representing it,
and a Wayland client will have a MetaWindowActorWayland.

On the compositor side, the surface where the contents of the window
are drawn into are represented by MetaSurfaceActor subclasses. On a
Wayland session, windows are backed by a MetaSurfaceActorWayland
surface, whereas on X11 sessions, by MetaSurfaceActorX11.

XWayland windows are X11 client windows (MetaWindowActorX11) backed
by Wayland surfaces (MetaWindowActorWayland).


Env Vars
========

MUTTER_DISABLE_MIPMAPS - set to disable use of mipmaped windows.