Is it better now? Can a browser locally scroll an image, without restreaming it?
Here is an awesome (slightly outdated) talk about the architecture: https://groups.google.com/a/chromium.org/g/blink-dev/c/AK_rw...
The basic idea is that HTML content is drawn in transparent 'tiles' which are layered on top of one another. When the user scrolls, the tiles don't need to be redrawn, but instead just re-composited at their new positions. GPU's are super fast at that, and even a 15 year old GPU can easily do this for tens of layers at 60 FPS.
On a linux with a remote X server, I think the tiles would all end up on the X server, with only the pretty small 'draw tile number 22 at this location' going across the network. So the answer to your question is 'yes'.
Based on my limited experience, the performance of running Firefox remotely on a local X11 server was very poor, and I assumed that the absence of these types of acceleration were to blame.
I could imagine XRender to work, though, which would at least support blitting most of the pixels up/down in case of scrolling, and would only require pushing new ones over the network for any newly exposed areas.
My guess is the lack of shared memory buffers stops the use of opengl, and whilst it's theoretically possible, it is probably unimplemented because nobody does that in 2025.
But this requires the browser have a special path for remote X and not just use the GPU. Or even just a path for X that lets the X Server do the rendering.
I remember GTK 1 was well optimized for X and you could run GTK applications over slow modem lines quite comfortably. GTK 2 went a different direction entirely and became almost unusable over the Internet. I doubt GTK 3 or 4 are any better now that they're designed for compositors.
And then... Came the internet. People suddenly started running NCSA Mosaic in droves that bogged down the single core server. And those browsers started to push lots of bitmap stuff through the pipe to the terminals. Now that was bad, yes. When Netscape came with its image backgrounds and even heavier process people started moving away to the PC rooms :( Because all scroll content needed to be bitstreamed then.
Ps video content at that time wasn't even a thing yet. That came a bit later with realvideo first.
But there was a time when X terminals were more than sufficient, probably for a decade or so.