Since st has no scroll buffer, theoretically it's impossible for st to consume more memory than xterm. If st does eat up more, it should be because of its screen buffer, whose size is decided by the size of its window.
Also, yes, the rendering portion of st is not the fastest. I know it pretty well because I implemented it like an year ago. It has been improved, but it's still kinda hacky due to lack of proper Unicode layout engine (or normalization). And what makes things worse is that existing layout engines(ICU, harfbuzz, etc) are just "sucks" for suckles community, while making a new one is not feasible AFAIK.
I don't understand what you're saying about the three different buffers and if you mean that there's a hidden buffer I don't see in xterm but which is used somewhere else in the stack.
I exclusively use bitmap fonts in terminals and editors for crisp and clear text and cannot get bitmap fonts to work in st config.h anymore.
Since st has no scroll buffer, theoretically it's impossible for st to consume more memory than xterm. If st does eat up more, it should be because of its screen buffer, whose size is decided by the size of its window.
Also, yes, the rendering portion of st is not the fastest. I know it pretty well because I implemented it like an year ago. It has been improved, but it's still kinda hacky due to lack of proper Unicode layout engine (or normalization). And what makes things worse is that existing layout engines(ICU, harfbuzz, etc) are just "sucks" for suckles community, while making a new one is not feasible AFAIK.