emacs-gpu

GNU Emacs with a GPU-accelerated display backend.

On macOS it renders with native Apple Metal: text goes through a GPU glyph atlas, images and inline video are textures, and the whole frame is composited by the GPU instead of CoreGraphics. The output is pixel-accurate against the stock Cocoa backend.

OpenGL support for GNU/Linux and Windows is planned but not implemented yet. The drawing logic is already platform-neutral (src/gfxterm.c) behind a small driver interface (src/gfxdrv.h); an OpenGL driver only needs to implement that interface (src/glterm.c is the documented skeleton). Contributions welcome.

Why a GPU backend?

Beyond raw rendering, it enables things the stock backend cannot do:

Inline video playback: AVFoundation decodes straight into Metal textures (zero copies) and the frames are composited inside the buffer, following scrolling and clipped to the window. No xwidgets, no embedded browser.
GPU cursor effects (opt-in): expanding rings, comet trails and friends are drawn as a compositor overlay, without ever touching the buffer content underneath.
A path to cheap visual effects: buffer transitions, smooth scrolling or any future eye candy is one more shader pass over the composited frame, not a rewrite of the display engine.

Text is rasterized once into a GPU glyph atlas and drawn as textured quads; scrolling moves already-rendered pixels with a texture blit.

Status: experimental, under active development.

Note: I am not answering issues for now. Feel free to open them as a public record (they will be read eventually), but do not expect a reply at this stage.

Demos

Inline video playing inside a buffer, decoded by AVFoundation straight into Metal textures (mtl-video-insert):

An animated GIF playing next to font-locked code scrolling, all composited by the GPU:

GPU cursor effects (mtl-animations), here the sonicboom mode:

Building on macOS

Requires Xcode (or the Command Line Tools) and the usual Emacs build dependencies (brew install autoconf automake gnutls texinfo pkg-config).

./autogen.sh

SDK=$(xcrun --sdk macosx --show-sdk-path)
CC="xcrun clang" OBJC="xcrun clang" \
CFLAGS="-isysroot $SDK" CPPFLAGS="-isysroot $SDK" OBJCFLAGS="-isysroot $SDK" \
./configure --with-ns --with-mtl

make -j$(sysctl -n hw.ncpu)

The binary is src/emacs (or install the app bundle from nextstep/).

Enabling the GPU backend

Emacs starts with the regular Cocoa backend; switch a frame to Metal with:

(add-to-list 'load-path "/path/to/emacs-gpu/lisp")
(require 'mtl)
(mtl-enable)

Extras once enabled:

(mtl-video-insert "video.mp4" 480 270 t)  ; inline video, follows scrolling
(mtl-animations t)                        ; GPU cursor effects (experimental)
(mtl-draw-stats)                          ; renderer counters

How it works

redisplay engine (xdisp.c, untouched)
        ↓
src/gfxterm.c   platform-neutral drawing policy
        ↓
src/gfxdrv.h    driver interface (~25 ops)
        ↓
src/mtlterm.m   Metal driver: glyph atlas (CoreText → R8 texture),
                render cycle on a persistent texture, AVFoundation
                video through CVMetalTextureCache

License

GNU General Public License v3 or later, same as GNU Emacs.

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