From ed7c6d687306a69cb31154e9251c6b1d8af62de5 Mon Sep 17 00:00:00 2001
From: Po Lu <luangruo@yahoo.com>
Date: Wed, 5 Jan 2022 12:02:32 +0000
Subject: [PATCH] Enable subpixel antialiasing on the Cairo font driver on
 Haiku

* src/ftcrfont.c (ftcrfont_open): Manually enable subpixel
antialiasing on Haiku.

* src/haiku_support.cc
(get_subpixel_antialiasing): New function declaration.
(be_use_subpixel_antialising):
* src/haiku_support.h (be_use_subpixel_antialising): New
functions.
---
 src/ftcrfont.c       |  4 ++++
 src/haiku_support.cc | 15 +++++++++++++++
 src/haiku_support.h  |  3 +++
 3 files changed, 22 insertions(+)

diff --git a/src/ftcrfont.c b/src/ftcrfont.c
index 337e804b895..558e44d5b91 100644
--- a/src/ftcrfont.c
+++ b/src/ftcrfont.c
@@ -169,6 +169,10 @@ ftcrfont_open (struct frame *f, Lisp_Object entity, int pixel_size)
   cairo_matrix_init_scale (&font_matrix, pixel_size, pixel_size);
   cairo_matrix_init_identity (&ctm);
   cairo_font_options_t *options = cairo_font_options_create ();
+#ifdef USE_BE_CAIRO
+  if (be_use_subpixel_antialiasing ())
+    cairo_font_options_set_antialias (options, CAIRO_ANTIALIAS_SUBPIXEL);
+#endif
   cairo_scaled_font_t *scaled_font
     = cairo_scaled_font_create (font_face, &font_matrix, &ctm, options);
   cairo_font_face_destroy (font_face);
diff --git a/src/haiku_support.cc b/src/haiku_support.cc
index 40f37d577e1..2e9eff40676 100644
--- a/src/haiku_support.cc
+++ b/src/haiku_support.cc
@@ -112,6 +112,10 @@ static BLocker child_frame_lock;
 
 static BLocker movement_locker;
 
+/* This could be a private API, but it's used by (at least) the Qt
+   port, so it's probably here to stay.  */
+extern status_t get_subpixel_antialiasing (bool *);
+
 extern "C"
 {
   extern _Noreturn void emacs_abort (void);
@@ -3043,3 +3047,14 @@ BWindow_is_active (void *window)
   BWindow *w = (BWindow *) window;
   return w->IsActive ();
 }
+
+bool
+be_use_subpixel_antialiasing (void)
+{
+  bool current_subpixel_antialiasing;
+
+  if (get_subpixel_antialiasing (&current_subpixel_antialiasing) != B_OK)
+    return false;
+
+  return current_subpixel_antialiasing;
+}
diff --git a/src/haiku_support.h b/src/haiku_support.h
index 550ebd00505..6a99eb245dc 100644
--- a/src/haiku_support.h
+++ b/src/haiku_support.h
@@ -853,6 +853,9 @@ extern "C"
   extern bool
   BWindow_is_active (void *window);
 
+  extern bool
+  be_use_subpixel_antialiasing (void);
+
 #ifdef __cplusplus
   extern void *
   find_appropriate_view_for_draw (void *vw);
-- 
2.39.2