From 8da986ea877b07a5eb117446f410f2a7fc8cd9cb Mon Sep 17 00:00:00 2001 From: bfredl Date: Wed, 13 Sep 2023 13:39:18 +0200 Subject: refactor(grid): change schar_T representation to be more compact Previously, a screen cell would occupy 28+4=32 bytes per cell as we always made space for up to MAX_MCO+1 codepoints in a cell. As an example, even a pretty modest 50*80 screen would consume 50*80*2*32 = 256000, i e a quarter megabyte With the factor of two due to the TUI side buffer, and even more when using msg_grid and/or ext_multigrid. This instead stores a 4-byte union of either: - a valid UTF-8 sequence up to 4 bytes - an escape char which is invalid UTF-8 (0xFF) plus a 24-bit index to a glyph cache This avoids allocating space for huge composed glyphs _upfront_, while still keeping rendering such glyphs reasonably fast (1 hash table lookup + one plain index lookup). If the same large glyphs are using repeatedly on the screen, this is still a net reduction of memory/cache consumption. The only case which really gets worse is if you blast the screen full with crazy emojis and zalgo text and even this case only leads to 4 extra bytes per char. When only <= 4-byte glyphs are used, plus the 4-byte attribute code, i e 8 bytes in total there is a factor of four reduction of memory use. Memory which will be quite hot in cache as the screen buffer is scanned over in win_line() buffer text drawing A slight complication is that the representation depends on host byte order. I've tested this manually by compling and running this in qemu-s390x and it works fine. We might add a qemu based solution to CI at some point. --- src/nvim/api/vim.c | 9 ++++++++- 1 file changed, 8 insertions(+), 1 deletion(-) (limited to 'src/nvim/api/vim.c') diff --git a/src/nvim/api/vim.c b/src/nvim/api/vim.c index 916409b973..0a94b8aafc 100644 --- a/src/nvim/api/vim.c +++ b/src/nvim/api/vim.c @@ -1947,7 +1947,9 @@ Array nvim__inspect_cell(Integer grid, Integer row, Integer col, Arena *arena, E } ret = arena_array(arena, 3); size_t off = g->line_offset[(size_t)row] + (size_t)col; - ADD_C(ret, CSTR_AS_OBJ((char *)g->chars[off])); + char *sc_buf = arena_alloc(arena, MAX_SCHAR_SIZE, false); + schar_get(sc_buf, g->chars[off]); + ADD_C(ret, CSTR_AS_OBJ(sc_buf)); int attr = g->attrs[off]; ADD_C(ret, DICTIONARY_OBJ(hl_get_attr_by_id(attr, true, arena, err))); // will not work first time @@ -1963,6 +1965,11 @@ void nvim__screenshot(String path) ui_call_screenshot(path); } +void nvim__invalidate_glyph_cache(void) +{ + schar_cache_clear_force(); +} + Object nvim__unpack(String str, Error *err) FUNC_API_FAST { -- cgit