Better Text Rendering for cairo / lua #1501

simotek · 2023-04-12T00:46:22Z

Description

Introduction

I have attempted to resolve #900 by creating a new lua binding specifically for doing font rendering in Cairo using Freetype and Harfbuzz, fontconfig is also used to locate the correct fonts. I have chosen to follow the approach of the imlib2_helper binding and not expose functions from the headers of each of these libraries but rather provide simple functions that "internally" use each of these libraries.

At the time of creating this PR I have no fixed thoughts on the API other then it works for my use case and tries to balance the simple act of rendering an English string while also allowing complex options such as RTL text as requested in #75 as well as being able to center and right align text #940 and #1017. So your thoughts on the API topic would be much appreciated, once the API is finalized I will add appropriate documentation. currently this is the last major step for be before being able to move to a lua only config.

Current API Description (Happy to make changes here)

Loading a font from a file is a slow enough operation that we probably don't want to do it multiple times so I separated loading fonts and freeing memory at close into separate functions.

/* font is a string containing the name of the font to load */
/* this will be matched on a best effort basis and FontConfig will fall back to a similar font if the specified font isn't found */
FontData * cairo_text_hp_load_font(const char *font, int font_size);
void cairo_text_hp_destroy_font(FontData *font);

The next set of functions cover the "Simple" English use cases, I could have added a parameter for alignment but I was trying to keep the common Left case as simple as possible.

void cairo_text_hp_simple_show(cairo_t *cr, int x, int y, const char *text, FontData *font);
void cairo_text_hp_simple_show_center(cairo_t *cr, int x, int y, const char *text, FontData *font);
void cairo_text_hp_simple_show_right(cairo_t *cr, int x, int y, const char *text, FontData *font);

The next function is the "catch all" with the main implementation and allows tweeking of the internalization options such as text direction in Harfbuzz for people looking to use non latin languages.

/* 
 * Direction calls hb_direction_from_string example values are LTR and RTL
 *   https://harfbuzz.github.io/harfbuzz-hb-common.html#hb-direction-from-string
 * Script is an ISO 15924 4 character string, "Zyyy" can be used for "Common" and "Zinh"
 *  for "Inherited". 
 *  https://harfbuzz.github.io/harfbuzz-hb-common.html#hb-script-from-string
 * Language is a BCP 47 language tag. eg "en" or "en-US"
 */
void cairo_text_hp_intl_show(cairo_t *cr, int x, int y, cairo_text_alignment_t alignment, const char *text, 
                                                    FontData *font,  const char *direction, const char *script, const char *language);

Finally when doing layouting sometimes its useful to know how wide the final string will be so the following find the text width, again there is a simple latin version and an internationalized version. In the future I'll also provide a Height function which will be important for supporting vertical text.

int cairo_text_hp_simple_text_width(const char *text, FontData *font);
int cairo_text_hp_intl_text_width(const char *text, FontData *font, const char *direction, const char *script, const char *language);

Screenshot

In the following screenshot the "Cairo" text is using Cairo's built in basic text rendering, the "Conky" text is using Conky's standard text rendering and the "Freetype" strings are using this new API with Freetype and Harfbuzz rendering the text in Cairo. All these cases are just using the default settings as found on openSUSE Tumbleweed.

Add empty files and various build options for the lua text bindings Adds requirements for Fontconfig, Freetype and Harfbuzz

netlify · 2023-04-12T00:46:29Z

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I thought I already removed this and squashed the commit

brndnmtthws

Looks great overall, just need to add documentation to https://github.com/brndnmtthws/conky/blob/main/doc/lua.yaml for the new functions.

.github/workflows/build-and-test-linux.yaml

lua/libcairo_text_helper.h

simotek · 2023-04-17T05:09:03Z

Thanks for the feedback, i'll update the docs and finish of implementing the Top to Bottom features then finish up a couple of configs to use them before sending through some updates. But its good to know i'm heading in the right direction.

moceap · 2023-07-04T00:31:27Z

After trying this patches, bug #75 still exist!

simotek · 2023-07-06T02:32:39Z

After trying this patches, bug #75 still exist!

Yes that is currently to be expected, the WIP patch just had the LTR support so I could get feedback on the API, RTL is almost there I just need to finish writing the tests.

Also this change only works with the lua API, however it is the first step in my project to add a toolkit to make using the lua API much simpler. Although that is further from completion.

simotek · 2023-07-20T06:03:00Z

@moceap Can you confirm that the following screenshot looks ok, it should be the days of the week.

I'll probably do just a little more testing of my actual real world usecases before sending through an updated pull request

simotek · 2023-07-20T06:23:17Z

This one uses Noto Sans Arabic instead.

moceap · 2023-08-09T14:15:17Z

No it's not OK.

Letters in Arabic should be connected:

You write:

الإثنين
يوم الثلاثاء
الأربعاء
يوم الخميس
جمعة
السبت
الأحد

Look at them here in the browser, they are connected.

simotek · 2023-08-10T12:18:50Z

No it's not OK.

Letters in Arabic should be connected:

You write:

الإثنين يوم الثلاثاء الأربعاء يوم الخميس جمعة السبت الأحد

Look at them here in the browser, they are connected.

Thanks for the confirmation, that's what I thought i'll have to have a closer look at whats going wrong, the left to right seems to be ok.

Caellian

Never used HarfBuzz, but from what I picked up googling it, the way you're using it seems fine.

lua/libcairo_text_helper.h

moceap · 2023-12-04T02:33:40Z

@simotek Take a look https://github.com/HOST-Oman/libraqm, It may fast the process.

simotek · 2023-12-08T00:31:30Z

@simotek Take a look https://github.com/HOST-Oman/libraqm, It may fast the process.

One thing I noticed at https://github.com/HOST-Oman/libraqm/blob/9d7ca9d59dba38e777bdcd096870776dab5e6e66/src/raqm.c#L1793C1-L1793C48 is that for the RTL case they seem to have hardcoded a -1 into the calculation for character position, So I might have to have a play with that later.

It seemed like hardcoding a -1 into the width of each character would solve the issue but I didn't want to just do it without seeing it documented, but the fact this other codebase is suggests its probably the right solution

Add empty files and various build options for the lua text bindings Adds requirements for Fontconfig, Freetype and Harfbuzz

This should go into its own PR but right now I need it for my system to work.

This replaces the old approach of using a series of function declarations.

For some reason RTL positioning is wrong, it seems somewhat based on font size 1/10th font size seems to get closer to correct so run with that for now, i'll continue investigating a proper fix.

…thws#2047

- reset cmdline_to_pid pathstream each iteration to avoid stale paths - parse /proc/[pid]/stat by skipping comm field so spaces are supported - prevent pid_thread_list writes from overflowing small buffers - add Linux tests for cmdline_to_pid, pid_time, and pid_thread_list safety

Normalize Darwin process CPU times to centiseconds using mach_timebase_info rather than assuming nanoseconds, and avoid reusing aggregate tick totals across updates. Align total CPU normalization with expected per-core vs aggregate behavior and guard zero deltas. Add helper module for Darwin top calculations and unit tests covering sample reset, delta init, and timebase conversion. Fixes brndnmtthws#2276.

Ensure fallback language assignment when Lua callers omit "language". Applies to both cairo_text_hp_show and cairo_text_hp_text_size to prevent uninitialized hb_language_t usage.

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simotek and others added 3 commits April 11, 2023 21:35

lua text: Supporting infra

2a0db1d

Add empty files and various build options for the lua text bindings Adds requirements for Fontconfig, Freetype and Harfbuzz

lua text: initial implementation.

79b81a6

Add the ability to center and right align text.

24706e8

github-actions bot added appimage related to AppImage changes gh-actions suggest changing GitHub actions sources PR modifies project sources labels Apr 12, 2023

lua text: Remove test code

d5d20e8

I thought I already removed this and squashed the commit

simotek mentioned this pull request Apr 12, 2023

Significantly Expanding Polycore. philer/polycore#12

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brndnmtthws requested changes Apr 15, 2023

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simotek and others added 9 commits February 14, 2024 10:19

lua text: Supporting infra

b625e93

Add empty files and various build options for the lua text bindings Adds requirements for Fontconfig, Freetype and Harfbuzz

lua text: initial implementation.

4077ad5

Commit the WIP so I can merge it

00b2ec0

Fix for brndnmtthws#1698

5036cc4

This should go into its own PR but right now I need it for my system to work.

Fix comment hb-unicode.h should be hb-common.h

488b450

Swap to using optional parameters

b0063e5

This replaces the old approach of using a series of function declarations.

Add Hack for RTL positioning

945ce1f

For some reason RTL positioning is wrong, it seems somewhat based on font size 1/10th font size seems to get closer to correct so run with that for now, i'll continue investigating a proper fix.

Remove Top to Bottom Fixme's they are fixed

dc7c0e0

Merge branch 'lua-text-helper2' into lua-text-helper3

ca1be94

brndnmtthws and others added 11 commits January 8, 2026 08:09

chore: only run CI for macos-latest

4dfa1e3

Fix mouse button events for owned windows with XInput2; Fixes brndnmt…

2357947

…thws#2047

fix: ignore non-pid entries in cmdline_to_pid

3112f20

fix(proc): harden /proc helpers

6a19868

fix: parse proc stat without suppressed length modifiers

ddebf25

test(proc): stabilize pid_environ lookup

e48231e

test(proc): tolerate vmrss drift

172fca4

test(proc): freeze child for vm status

1a79566

fix(lua): initialize default harfbuzz language

d71fdcf

Ensure fallback language assignment when Lua callers omit "language". Applies to both cairo_text_hp_show and cairo_text_hp_text_size to prevent uninitialized hb_language_t usage.

github-actions bot added cpu related to CPU stats or system process reporting tests related to project tests 3rdparty suggests changes to 3rd party dependencies display: x11 related to X11 backend display: wayland related to Wayland backend os: macos related to MacOS labels Jan 8, 2026

brndnmtthws approved these changes Jan 8, 2026

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simotek and others added 4 commits January 8, 2026 08:16

Attempt to fix workflows by adding freetype dep

d84e83a

Probably actually need freetype6

f6391c7

Try again, I don't understand Ubuntu

a5d9e78

Merge branch 'main' into simotek-lua-text-helper3

42e3ca7

github-actions bot removed cpu related to CPU stats or system process reporting tests related to project tests 3rdparty suggests changes to 3rd party dependencies display: x11 related to X11 backend display: wayland related to Wayland backend os: macos related to MacOS labels Jan 8, 2026

brndnmtthws merged commit 4f82924 into brndnmtthws:main Jan 8, 2026
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Better Text Rendering for cairo / lua #1501

Better Text Rendering for cairo / lua #1501

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simotek commented Apr 12, 2023 • edited Loading Uh oh! There was an error while loading. Please reload this page.

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Description

Introduction

Current API Description (Happy to make changes here)

Screenshot

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simotek commented Apr 17, 2023

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