Support ligature using harfbuzz #1659

Mandarancio · 2023-10-29T19:54:51Z

Support to ligature (#66) rendering using harfbuzz

Guldoman · 2023-10-29T20:36:26Z

As a note, I have a library in the works that's quite a bit smaller than harfbuzz.
It obviously doesn't do as much as harfbuzz (and is simpler to use too), but ligature support is almost 100% complete (basically only Lookup Flags are missing).

Feel free to continue working on this tho, might be a nice comparison point.

jgmdev · 2023-10-29T21:00:39Z

Looking good! I would be interested on integrating this change into Pragtical once it is complete. There is a meson.wrap for harfbuzz that can be easily added for CI builds.

Mandarancio · 2023-10-30T14:02:30Z

Peek.2023-10-30.15-00.mp4

The recording is pretty crappy, but it shows that everything seems to work, I am not sure if I am missing something, maybe someone else could try it and let me know if every is fine?
Otherwise on my side it seems pretty good, everything is working smoothly and I do not see any drop in performances.

Mandarancio · 2023-10-31T14:36:18Z

I added the wrap to harfbuz, now it should work (not 100% sure as I never used wraps or github CI).

meson.build

jgmdev · 2023-11-01T16:48:56Z

Otherwise on my side it seems pretty good, everything is working smoothly and I do not see any drop in performances.

Tested a little bit and it is working pretty nice, the only performance issue I see so far is with font loading. Try ctrl+wheelup or ctrl+wheeldown and you will notice it is slower than before.

Co-authored-by: Jefferson González <jgmdev@gmail.com>

Mandarancio · 2023-11-01T18:27:17Z

Otherwise on my side it seems pretty good, everything is working smoothly and I do not see any drop in performances.

Tested a little bit and it is working pretty nice, the only performance issue I see so far is with font loading. Try ctrl+wheelup or ctrl+wheeldown and you will notice it is slower than before.

First of all thanks for the help with the meson dependencies! Second of all now I slighty changed the way I load the hb fonts and changed the caching parameters. On my machine I can not see any significant difference between the lite-xl/lite-xl and mine, but it could be my configuration. Can you try it now and let me know if it feels better?

jgmdev · 2023-11-01T18:35:56Z

Second of all now I slighty changed the way I load the hb fonts and changed the caching parameters.

I think you forgot to push that change, I only see the meson build options (eagerly waiting for the improvement 😃). Also, I noticed that now fallback fonts are not working. For example I have the following fonts:

NotoSansMono-Medium.ttf
NotoEmoji-Medium.ttf
unifont-15.0.01.ttf

Emojis and other stuff is not rendering because only the first font is been used.

jgmdev · 2023-11-01T19:11:29Z

Just in case this is what I mean with slower font loading:

Non Ligatures:

non-ligatures.mp4

With Ligatures

with-ligatures.mp4

Mandarancio · 2023-11-01T19:59:12Z

Second of all now I slighty changed the way I load the hb fonts and changed the caching parameters.

I think you forgot to push that change, I only see the meson build options (eagerly waiting for the improvement 😃). Also, I noticed that now fallback fonts are not working. For example I have the following fonts:
1. NotoSansMono-Medium.ttf

2. NotoEmoji-Medium.ttf

3. unifont-15.0.01.ttf
Emojis and other stuff is not rendering because only the first font is been used.

You are right! I forgot to push the commit! Ops! I will look into the fallbacks fonts issue (I believe to know the source of the problem and I will look into it).

jgmdev · 2023-11-01T20:30:04Z

You are right! I forgot to push the commit! Ops! I will look into the fallbacks fonts issue (I believe to know the source of the problem and I will look into it).

Whoa now loading performance is much better 🥳, now the only missing issue is restoring font fallbacks support and I would say this is pretty good to go :), would be nice if ligatures could be made optional in the same vain of bold/strike/smooth, etc...

jgmdev · 2023-11-01T21:30:25Z

Was experimenting with GLYPHSET_SIZE and it seems that setting it to #define GLYPHSET_SIZE 8 is enough now with the use of harfbuzz, loading is even faster than originally.

jgmdev · 2023-11-02T05:25:13Z

Playing a bit more with the code and was able to get fallback fonts working again here is the patch:

pragtical/pragtical@ed28c3a

Edit: had to repush removal of debugging artifact

Mandarancio · 2023-11-02T13:43:50Z

Playing a bit more with the code and was able to get fallback fonts working again here is the patch:

pragtical/pragtical@ed28c3a

Edit: had to repush removal of debugging artifact

I also succeeded to add back the fallback fonts support (let me know what do you think about my solution) :)

jgmdev · 2023-11-02T15:27:54Z

I also succeeded to add back the fallback fonts support (let me know what do you think about my solution) :)

Great, this way seems more efficient. And yay it is working:

The other issue is character fallbacks are not working, this is a screenshot of master without an emoji font added to the list of fallbacks:

And this is what I'm getting with the harfbuzz changes:

Also some fonts like Noto Sans Mono Medium seem to have half baked ligature stuff on them which causes wrong rendering with ligatures enabled (notice the extra spacing on the &&):

With ligatures disabled it looks normal:

Maybe making ligatures a toggleable style property as in Bold/Italic/Underline would be useful in such cases.

Mandarancio · 2023-11-02T15:37:20Z

spacing

About the missing characters squares is my fault, I removed the code to draw the empty boxes when debugging my code (I will put it back).
About the wired && ligature I noticed that some fonts (such as Noto) has strange behaviors with it, but is very font dependents, I will look into it and try to understand the source of the problem!

jgmdev · 2023-11-02T17:25:48Z

src/renderer.c

+  hb_buffer_add_utf8(buf, text, -1, 0, -1);
+
+  RenFont * font = fonts[0]; 
+  hb_shape(font->font, buf, NULL, 0);


Question, in case that a fallback font is used for some codepoints not available on main font, shouldn't that portion get shaped also with the fallback font instead of using the main font?

Good question, as it is implemented now, ligatures are supported only for the main font and so the shaping is only applied to the main one, for the fallaback case I am using the fb_codepoint that is computed in src/renderer.c:413 that is then converted if needed to the correct font index using FT_Get_Char_Index at src/renderer.c:181.
I hope the explanation is clear.
It would be possible to shape for all the available fonts but I suspect will be more computational intensive and you could end up with half a ligature of a fallback font and half a normal character form another.
What do you think?

edit: also I am not sure that the mapping between text and glyph would be the same and could be possible that some kind of mapping would be needed between different fonts and the string.

The function shared on pragtical/pragtical@ed28c3a iterates a string giving you the range of a string (thru the char** next out param) and returns the font that has all of its codepoints for rendering:

static RenFont* utf8_iterator( RenFont** fonts, const char* start, const char* end, char** next ) { if (start == end) return NULL; unsigned int codepoint; RenFont* current_font = fonts[0]; bool iterated = false; *next = (char*) start; char* prev_next = *next; while(*next < end) { *next = (char*) utf8_to_codepoint(*next, &codepoint); if (!FT_Get_Char_Index(current_font->face, codepoint)) { if (!iterated) { bool codepoint_found = false; for (short i = 1; i < FONT_FALLBACK_MAX && fonts[i]; ++i) { if (FT_Get_Char_Index(fonts[i]->face, codepoint)) { current_font = fonts[i]; codepoint_found = true; break; } } if (!codepoint_found) return fonts[0]; } else { // set next to the end of previously iterated text range *next = prev_next; return current_font; } } // Allow emojis to be rendered with different fonts, this is needed because // sometimes a single glyph can be queried, which could be on the first // font and also on previously used fallbacks when rendering. if (!iterated && (*next - start) > 3) { return current_font; } prev_next = *next; iterated = true; } return current_font; }

This way you can shape string segments using the assigned font (which is the strategy used on that patch). When tested I didn't notice a performance drop but I didn't benchmark the thing :)

I start to have a look at your commit but I did not finish yet as I am quite busy now. However I am still not 100% sure that is a good idea to support ligatures in fallback fonts, maybe can @Guldoman gives us his opinion?

Mandarancio · 2023-11-02T21:46:33Z

I also succeeded to add back the fallback fonts support (let me know what do you think about my solution) :)

Great, this way seems more efficient. And yay it is working:

The other issue is character fallbacks are not working, this is a screenshot of master without an emoji font added to the list of fallbacks:

And this is what I'm getting with the harfbuzz changes:

Also some fonts like Noto Sans Mono Medium seem to have half baked ligature stuff on them which causes wrong rendering with ligatures enabled (notice the extra spacing on the &&):

With ligatures disabled it looks normal:

Maybe making ligatures a toggleable style property as in Bold/Italic/Underline would be useful in such cases.

Both issues should be solved now! :D

jgmdev · 2023-11-02T22:33:00Z

Both issues should be solved now! :D

Whoa, I can confirm it works now! The fixes to tab size handling code now cause tabs to not be rendered as spaces (notice on the screenshot 2 tabs rendered with the glyph provided by fallback font unifont):

This could be fixed on the lua side by replacing tabs with the amount of spaces set on the document tab size when sending text to renderer but it would perform slower I guess because of all the strings allocations and lookups that would be performed by string.gsub. Or just perform a glyph replacement of tab -> space to the amount of required spaces, maybe by dividing the size_of_tab_set_with_set_tab_size / width_of_single_space, don't know...

You will come up with a better solution :)

Edit:

Also forgot, one have to take into consideration the drawwhitespace plugin.

jgmdev · 2023-11-03T19:35:55Z

Just in case this change fixes the tab issue mentioned above, which I didn't properly look before commenting 😞

diff --git a/src/renderer.c b/src/renderer.c
index bd6bf993..ba3398d3 100644
--- a/src/renderer.c
+++ b/src/renderer.c
@@ -176,14 +176,18 @@ static RenFont* font_group_get_glyph(GlyphSet** set, GlyphMetric** metric, RenFo
   if (!metric) {
     return NULL;
   }
+  bool is_tab = false;
+  if (fb_codepoint == '\t') { is_tab = true; fb_codepoint = '\0'; }
   if (bitmap_index < 0)
     bitmap_index += SUBPIXEL_BITMAPS_CACHED;
   for (int i = 0; i < FONT_FALLBACK_MAX && fonts[i]; ++i) {
     unsigned cp = i == 0 ? codepoint : FT_Get_Char_Index(fonts[i]->face, fb_codepoint);
     *set = font_get_glyphset(fonts[i], cp, bitmap_index);
     *metric = &(*set)->metrics[cp % GLYPHSET_SIZE];
-    if ((*metric)->loaded || fb_codepoint == 0)
+    if ((*metric)->loaded || fb_codepoint == 0) {
+      if (is_tab) (*metric)->xadvance = fonts[i]->tab_advance;
       return fonts[i];
+    }
   }
   if (*metric && !(*metric)->loaded && fb_codepoint > 0xFF && fb_codepoint != 0x25A1)
     return font_group_get_glyph(set, metric, fonts, 0x25A1, 0x25A1, bitmap_index);

Mandarancio · 2023-11-06T13:49:44Z

@jgmdev the colliding codepoint issue between \t and other char (such as & for the Noto sans example) it has been fixed (at least to me look like its working fine). Can you check?

jgmdev · 2023-11-06T16:04:22Z

Can you check?

On a default install when pressing tab with detected indentation and when pressing tab after setting indentation to tabs:

tabs-on-default-install.mp4

Martino Ferrari added 2 commits October 29, 2023 20:44

feat: added dependency to harfbuzz library

faeaae5

feat: added initial support to ligatures

efafbbb

Mandarancio marked this pull request as draft October 29, 2023 19:54

github-actions bot added Category: Build System Category: C Core labels Oct 29, 2023

fix: free hb objects

2bfafc7

Martino Ferrari added 2 commits October 30, 2023 14:14

fix: better constructor and distructor fo hb objects

b5e2203

feat: re-enabled glyset logic with 256 size buffer

85a7513

Martino Ferrari added 2 commits October 30, 2023 17:09

fix: added harfbuzz.wrap

ff81ee4

fix: using harfbuzz wrap

5c90651

Mandarancio closed this Oct 30, 2023

Mandarancio reopened this Oct 30, 2023

fix: removed not used dependencies

b5bcf19

jgmdev mentioned this pull request Nov 1, 2023

Support ligature using harfbuzz lite-xl/lite-xl#1659 pragtical/pragtical#39

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jgmdev reviewed Nov 1, 2023

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meson.build Outdated Show resolved Hide resolved

Mandarancio and others added 2 commits November 1, 2023 19:13

Update meson.build

89108f8

Co-authored-by: Jefferson González <jgmdev@gmail.com>

feat: better loading performances

dd4f27e

jgmdev closed this Nov 1, 2023

jgmdev reopened this Nov 1, 2023

feat: added support for fallback fonts

f599543

fix: restored missing character

40d9a3a

jgmdev reviewed Nov 2, 2023

View reviewed changes

fix: tab spacing could modify metrics of other fonts

509efd8

fix: put back support for space advance

878579d

fix: fixed issue with tab and colliding codepoints

02c1959

Guldoman mentioned this pull request Nov 20, 2023

Add ligatures support via libatures #1671

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Support ligature using harfbuzz #1659

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Support ligature using harfbuzz #1659

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