I'm sure that software rendered webgl will be fine unless you're running a 5k monitor. It's just being used as a convenient texture glitter, the primary benefit is bypassing the DOM.

> Why is OpenGL necessary for a text editor?

Why not? Modern desktops are all hardware-accelerated anyway.

Not all graphics hardware is supported by WebKit. For example, Intel 965 chipset doesn't support WebGL.

It looks like Intel hasn't updated the 965 drivers since before Windows 8, seven years ago. The group of people using that chipset is only getting smaller at this point.

Hardware acceleration of rendering is more energy-efficient and less resource intensive than CPU-based software rendering.

The way XRay render text is more compositing than rendering.

They will render text to a bitmap using HTML canvas and then use that as a texture for GPU.

GPU will be compositing those bitmaps, it won't actually be rendering text.

Is it really so? Can OpenGL update only a small part of a framebuffer (for example, when a single letter is typed) or will it rerender the whole text?

Depends on how you render.

I've written a OpenGL engine for a university course that use partial frame updates to reduce the number of redraws per frame.

IIRC the partial rerender variant was about 3 times faster than the full render.

If done in a smart way, of course you can. Similar thing with canvas. If letter/word spacing depends on that character, then you'd probably need to rerender more stuff.

consider how many pixels a 5k monitor has.

try drawing a 5k monitor full of true type fonts in software sometime.

Are 5k monitors that popular? Do they even exist? I think it makes sense to make editor available on maximum number of platforms.

Things like filling rectangles or scrolling have been hardware optimized for years on Windows without using any OpenGL and it works even on ancient graphic cards. So I think it might be a better technology for a text editor.

> Are 5k monitors that popular? Do they even exist?

Yes - for example, Apple has been shipping 5K 27” displays in iMacs for three years now.

Is the iMac popular?

You struggle to find a 5K display outside that one machine that Apple doesn't seem all that fussed about compared to their laptop and iOS offerings.

no need to be aggressive dude, op was just askin'