widget: Add API to override font options

https://gitlab.gnome.org/GNOME/vte/-/issues/2573

11 files changed, 172 insertions, 34 deletions

diff --git a/meson.build b/meson.build
index dcb2360a..62bfefdf 100644
--- a/meson.build
+++ b/meson.build
@@ -45,6 +45,8 @@ gtk4_req_version          = '4.0.1'
 gtk4_min_req_version      = '4.0'
 gtk4_max_allowed_version  = '4.0'
 
+cairo_req_version         = '1.0'
+cairo_gobject_req_version = '1.0'
 fribidi_req_version       = '1.0.0'
 gio_req_version           = '2.52.0'
 glib_req_version          = '2.52.0'
@@ -617,13 +619,15 @@ endforeach
 
 # Dependencies
 
-gio_dep      = dependency('gio-2.0',    version: '>=' + gio_req_version)
-glib_dep     = dependency('glib-2.0',   version: '>=' + glib_req_version)
-gobject_dep  = dependency('gobject-2.0')
-pango_dep    = dependency('pango',      version: '>=' + pango_req_version)
-pcre2_dep    = dependency('libpcre2-8', version: '>=' + pcre2_req_version)
-pthreads_dep = dependency('threads')
-zlib_dep     = dependency('zlib')
+cairo_dep         = dependency('cairo', version: '>=' + cairo_req_version)
+cairo_gobject_dep = dependency('cairo-gobject', version: '>=' + cairo_gobject_req_version)
+gio_dep           = dependency('gio-2.0',    version: '>=' + gio_req_version)
+glib_dep          = dependency('glib-2.0',   version: '>=' + glib_req_version)
+gobject_dep       = dependency('gobject-2.0')
+pango_dep         = dependency('pango',      version: '>=' + pango_req_version)
+pcre2_dep         = dependency('libpcre2-8', version: '>=' + pcre2_req_version)
+pthreads_dep      = dependency('threads')
+zlib_dep          = dependency('zlib')
 
 if get_option('fribidi')
   fribidi_dep = dependency('fribidi', version: '>=' + fribidi_req_version)
diff --git a/src/drawing-cairo.cc b/src/drawing-cairo.cc
index 0a1cdae1..202444b4 100644
--- a/src/drawing-cairo.cc
+++ b/src/drawing-cairo.cc
@@ -138,6 +138,7 @@ DrawingContext::clear(int x,
 void
 DrawingContext::set_text_font(GtkWidget* widget,
                               PangoFontDescription const* fontdesc,
+                              cairo_font_options_t const* font_options,
                               double cell_width_scale,
                               double cell_height_scale)
 {
@@ -168,11 +169,11 @@ DrawingContext::set_text_font(GtkWidget* widget,
 	bolditalicdesc = pango_font_description_copy (bolddesc);
 	pango_font_description_set_style (bolditalicdesc, PANGO_STYLE_ITALIC);
 
-	m_fonts[VTE_DRAW_NORMAL]  = FontInfo::create_for_widget(widget, fontdesc);
-	m_fonts[VTE_DRAW_BOLD]    = FontInfo::create_for_widget(widget, bolddesc);
-	m_fonts[VTE_DRAW_ITALIC]  = FontInfo::create_for_widget(widget, italicdesc);
+	m_fonts[VTE_DRAW_NORMAL]  = FontInfo::create_for_widget(widget, fontdesc, font_options);
+	m_fonts[VTE_DRAW_BOLD]    = FontInfo::create_for_widget(widget, bolddesc, font_options);
+	m_fonts[VTE_DRAW_ITALIC]  = FontInfo::create_for_widget(widget, italicdesc, font_options);
 	m_fonts[VTE_DRAW_ITALIC | VTE_DRAW_BOLD] =
-                FontInfo::create_for_widget(widget, bolditalicdesc);
+                FontInfo::create_for_widget(widget, bolditalicdesc, font_options);
 	pango_font_description_free (bolddesc);
 	pango_font_description_free (italicdesc);
 	pango_font_description_free (bolditalicdesc);
diff --git a/src/drawing-cairo.hh b/src/drawing-cairo.hh
index 24bf5010..65e2ef8c 100644
--- a/src/drawing-cairo.hh
+++ b/src/drawing-cairo.hh
@@ -77,6 +77,7 @@ public:
         void clear_font_cache();
         void set_text_font(GtkWidget* widget,
                            PangoFontDescription const* fontdesc,
+                           cairo_font_options_t const* font_options,
                            double cell_width_scale,
                            double cell_height_scale);
         void get_text_metrics(int* cell_width,
diff --git a/src/fonts-pangocairo.cc b/src/fonts-pangocairo.cc
index 98f1ab08..0fb23b75 100644
--- a/src/fonts-pangocairo.cc
+++ b/src/fonts-pangocairo.cc
@@ -346,6 +346,7 @@ FontInfo*
 FontInfo::create_for_context(vte::glib::RefPtr<PangoContext> context,
                              PangoFontDescription const* desc,
                              PangoLanguage* language,
+                             cairo_font_options_t const* font_options,
                              guint fontconfig_timestamp)
 {
 	if (!PANGO_IS_CAIRO_FONT_MAP(pango_context_get_font_map(context.get()))) {
@@ -366,35 +367,50 @@ FontInfo::create_for_context(vte::glib::RefPtr<PangoContext> context,
             language != pango_context_get_language(context.get()))
                 pango_context_set_language(context.get(), language);
 
-        // Ensure Pango and cairo are configured to quantize and hint font metrics.
-        // Terminal cells in vte have integer pixel sizes. If Pango is configured to do sub-pixel
-        // glyph advances, a small fractional part might get rounded up to a whole pixel - so the
-        // character spacing will appear too wide. Setting the cairo hint metrics option ensures
-        // that there are integer numbers of pixels both above and below the baseline.
         {
-                auto font_options = vte::take_freeable(cairo_font_options_create());
+                // Make sure our contexts have a font_options set.  We use
+                // this invariant in our context hash and equal functions.
+                auto builtin_font_options = vte::take_freeable(cairo_font_options_create());
+
 #if VTE_GTK == 4
-                cairo_font_options_set_hint_metrics(font_options.get(),
+                // On gtk4, we need to ensure Pango and cairo are configured to quantize
+                // and hint font metrics.  Terminal cells in vte have integer pixel sizes.
+                // If Pango is configured to do sub-pixel glyph advances, a small fractional
+                // part might get rounded up to a whole pixel; so the character spacing will
+                // appear too wide. Setting the cairo hint metrics option ensures that there
+                // are integer numbers of pixels both above and below the baseline.
+                // See issue#2573.
+                cairo_font_options_set_hint_metrics(builtin_font_options.get(),
                                                     CAIRO_HINT_METRICS_ON);
 #endif /* VTE_GTK == 4 */
 
-                if (auto const ctx_font_options =
-                    pango_cairo_context_get_font_options(context.get())) {
+                // Allow using the API to override the built-in hint metrics setting.
+                if (!font_options)
+                        font_options = builtin_font_options.get();
+
+                if (auto const ctx_font_options = pango_cairo_context_get_font_options(context.get())) {
                         auto const merged_font_options =
                                 vte::take_freeable(cairo_font_options_copy(ctx_font_options));
                         cairo_font_options_merge(merged_font_options.get(),
-                                                 font_options.get());
+                                                 font_options);
                         pango_cairo_context_set_font_options(context.get(),
                                                              merged_font_options.get());
                 } else {
-                        // Make sure our contexts have a font_options set.  We use
-                        // this invariant in our context hash and equal functions.
-                        pango_cairo_context_set_font_options(context.get(),
-                                                             font_options.get());
+                        pango_cairo_context_set_font_options(context.get(), font_options);
                 }
 
 #if VTE_GTK == 4
-                pango_context_set_round_glyph_positions (context.get(), true);
+                // If hinting font metrics, also make sure to round glyph positions
+                // to integers.  See issue#2573.
+                if (auto const ctx_font_options = pango_cairo_context_get_font_options(context.get());
+                    ctx_font_options &&
+                    cairo_version() >= CAIRO_VERSION_ENCODE(1, 17, 4)) {
+                        auto const hint_metrics = cairo_font_options_get_hint_metrics(ctx_font_options);
+                        pango_context_set_round_glyph_positions(context.get(),
+                                                                hint_metrics == CAIRO_HINT_METRICS_ON);
+                } else {
+                        pango_context_set_round_glyph_positions(context.get(), false);
+                }
 #endif /* VTE_GTK == 4 */
         }
 
@@ -420,30 +436,32 @@ FontInfo::create_for_context(vte::glib::RefPtr<PangoContext> context,
 FontInfo*
 FontInfo::create_for_screen(GdkScreen* screen,
                             PangoFontDescription const* desc,
-                            PangoLanguage* language)
+                            PangoLanguage* language,
+                            cairo_font_options_t const* font_options)
 {
 	auto settings = gtk_settings_get_for_screen(screen);
 	auto fontconfig_timestamp = guint{};
 	g_object_get (settings, "gtk-fontconfig-timestamp", &fontconfig_timestamp, nullptr);
 	return create_for_context(vte::glib::take_ref(gdk_pango_context_get_for_screen(screen)),
-                                  desc, language, fontconfig_timestamp);
+                                  desc, language, font_options, fontconfig_timestamp);
 }
 #endif /* VTE_GTK */
 
 FontInfo*
 FontInfo::create_for_widget(GtkWidget* widget,
-                            PangoFontDescription const* desc)
+                            PangoFontDescription const* desc,
+                            cairo_font_options_t const* font_options)
 {
 #if VTE_GTK == 3
 	auto screen = gtk_widget_get_screen(widget);
-	return create_for_screen(screen, desc, nullptr);
+	return create_for_screen(screen, desc, nullptr, font_options);
 #elif VTE_GTK == 4
         auto display = gtk_widget_get_display(widget);
         auto settings = gtk_settings_get_for_display(display);
         auto fontconfig_timestamp = guint{};
         g_object_get (settings, "gtk-fontconfig-timestamp", &fontconfig_timestamp, nullptr);
         return create_for_context(vte::glib::take_ref(gtk_widget_create_pango_context(widget)),
-                                  desc, nullptr, fontconfig_timestamp);
+                                  desc, nullptr, font_options, fontconfig_timestamp);
         // FIXMEgtk4: this uses a per-widget context, while the gtk3 code uses a per-screen
         // one. That means there may be a lot less sharing and a lot more FontInfo's around?
 #endif
diff --git a/src/fonts-pangocairo.hh b/src/fonts-pangocairo.hh
index 586e6668..6db0a872 100644
--- a/src/fonts-pangocairo.hh
+++ b/src/fonts-pangocairo.hh
@@ -24,6 +24,7 @@
 #include <pango/pangocairo.h>
 #include <gtk/gtk.h>
 
+#include "cairo-glue.hh"
 #include "pango-glue.hh"
 #include "refptr.hh"
 #include "vteunistr.h"
@@ -268,17 +269,20 @@ private:
         static FontInfo* create_for_context(vte::glib::RefPtr<PangoContext> context,
                                             PangoFontDescription const* desc,
                                             PangoLanguage* language,
+                                            cairo_font_options_t const* font_options,
                                             guint fontconfig_timestamp);
 #if VTE_GTK == 3
         static FontInfo *create_for_screen(GdkScreen* screen,
                                            PangoFontDescription const* desc,
-                                           PangoLanguage* language);
+                                           PangoLanguage* language,
+                                           cairo_font_options_t const* font_options);
 #endif
 
 public:
 
         static FontInfo *create_for_widget(GtkWidget* widget,
-                                           PangoFontDescription const* desc);
+                                           PangoFontDescription const* desc,
+                                           cairo_font_options_t const* font_options);
 
 private:
         static inline GHashTable* s_font_info_for_context{nullptr};
diff --git a/src/meson.build b/src/meson.build
index b3f934a2..7737c04a 100644
--- a/src/meson.build
+++ b/src/meson.build
@@ -274,6 +274,7 @@ libvte_common_sources += gnome.genmarshal(
 )
 
 libvte_common_public_deps = [
+  cairo_dep,
   gio_dep,
   glib_dep,
   gobject_dep,
@@ -281,6 +282,7 @@ libvte_common_public_deps = [
 ]
 
 libvte_common_deps = libvte_common_public_deps + [
+  cairo_gobject_dep,
   fribidi_dep,
   gnutls_dep,
   icu_dep,
diff --git a/src/vte.cc b/src/vte.cc
index 70815088..05c12901 100644
--- a/src/vte.cc
+++ b/src/vte.cc
@@ -7218,6 +7218,7 @@ Terminal::ensure_font()
                                 m_draw.set_text_font(
                                                      m_widget,
                                                      m_unscaled_font_desc.get(),
+                                                     m_font_options.get(),
                                                      m_cell_width_scale,
                                                      m_cell_height_scale);
                                 m_draw.get_text_metrics(
@@ -7228,6 +7229,7 @@ Terminal::ensure_font()
 			m_draw.set_text_font(
                                                  m_widget,
                                                  m_fontdesc.get(),
+                                                 m_font_options.get(),
                                                  m_cell_width_scale,
                                                  m_cell_height_scale);
 			m_draw.get_text_metrics(
@@ -7385,6 +7387,22 @@ Terminal::set_font_scale(gdouble scale)
 }
 
 bool
+Terminal::set_font_options(vte::Freeable<cairo_font_options_t> font_options)
+{
+        if ((m_font_options &&
+             font_options &&
+             cairo_font_options_equal(m_font_options.get(), font_options.get())) ||
+            (!m_font_options &&
+             !font_options))
+                return false;
+
+        m_font_options = std::move(font_options);
+        update_font();
+
+        return true;
+}
+
+bool
 Terminal::set_cell_width_scale(double scale)
 {
         /* FIXME: compare old and new scale in pixel space */
diff --git a/src/vte/vteterminal.h b/src/vte/vteterminal.h
index 90aae937..baaeccf4 100644
--- a/src/vte/vteterminal.h
+++ b/src/vte/vteterminal.h
@@ -23,6 +23,7 @@
 
 #include <glib.h>
 #include <gio/gio.h>
+#include <cairo.h>
 #include <pango/pango.h>
 #include <gtk/gtk.h>
 
@@ -237,6 +238,12 @@ _VTE_PUBLIC
 gdouble vte_terminal_get_font_scale(VteTerminal *terminal) _VTE_CXX_NOEXCEPT _VTE_GNUC_NONNULL(1);
 
 _VTE_PUBLIC
+void vte_terminal_set_font_options(VteTerminal *terminal,
+                                   cairo_font_options_t const* font_options) _VTE_CXX_NOEXCEPT _VTE_GNUC_NONNULL(1);
+_VTE_PUBLIC
+cairo_font_options_t const* vte_terminal_get_font_options(VteTerminal *terminal) _VTE_CXX_NOEXCEPT _VTE_GNUC_NONNULL(1);
+
+_VTE_PUBLIC
 void vte_terminal_set_cell_width_scale(VteTerminal *terminal,
                                        double scale) _VTE_CXX_NOEXCEPT _VTE_GNUC_NONNULL(1);
 _VTE_PUBLIC
diff --git a/src/vtegtk.cc b/src/vtegtk.cc
index cf8ea434..d4eeea4f 100644
--- a/src/vtegtk.cc
+++ b/src/vtegtk.cc
@@ -1,6 +1,6 @@
 /*
  * Copyright (C) 2001-2004,2009,2010 Red Hat, Inc.
- * Copyright © 2008, 2009, 2010, 2015 Christian Persch
+ * Copyright © 2008, 2009, 2010, 2015, 2022, 2023 Christian Persch
  *
  * This library is free software: you can redistribute it and/or modify
  * it under the terms of the GNU Lesser General Public License as published
@@ -62,6 +62,8 @@
 #include "vteptyinternal.hh"
 #include "vteregexinternal.hh"
 
+#include <cairo-gobject.h>
+
 #ifdef WITH_A11Y
 #if VTE_GTK == 3
 #include "vteaccess.h"
@@ -993,6 +995,9 @@ try
                 case PROP_FONT_DESC:
                         g_value_set_boxed (value, vte_terminal_get_font (terminal));
                         break;
+                case PROP_FONT_OPTIONS:
+                        g_value_set_boxed(value, vte_terminal_get_font_options(terminal));
+                        break;
                 case PROP_FONT_SCALE:
                         g_value_set_double (value, vte_terminal_get_font_scale (terminal));
                         break;
@@ -1136,6 +1141,10 @@ try
                 case PROP_FONT_DESC:
                         vte_terminal_set_font (terminal, (PangoFontDescription *)g_value_get_boxed (value));
                         break;
+                case PROP_FONT_OPTIONS:
+                        vte_terminal_set_font_options(terminal,
+                                                      reinterpret_cast<cairo_font_options_t const*>(g_value_get_boxed(value)));
+                        break;
                 case PROP_FONT_SCALE:
                         vte_terminal_set_font_scale (terminal, g_value_get_double (value));
                         break;
@@ -2148,6 +2157,25 @@ vte_terminal_class_init(VteTerminalClass *klass)
 
 
         /**
+         * VteTerminal:font-options:
+         *
+         * The terminal's font options, or %NULL to use the default font options.
+         *
+         * Note that on GTK4, the terminal by default uses font options
+         * with %CAIRO_HINT_METRICS_ON set; to override that, use this
+         * function to set a #cairo_font_options_t that has
+         * %CAIRO_HINT_METRICS_OFF set.
+         *
+         * Since: 0.74
+         */
+        pspecs[PROP_FONT_OPTIONS] =
+                g_param_spec_boxed("font-options", nullptr, nullptr,
+                                   CAIRO_GOBJECT_TYPE_FONT_OPTIONS,
+                                   GParamFlags(G_PARAM_READWRITE |
+                                               G_PARAM_STATIC_STRINGS |
+                                               G_PARAM_EXPLICIT_NOTIFY));
+
+        /**
          * VteTerminal:font-scale:
          *
          * The terminal's font scale.
@@ -5584,6 +5612,57 @@ catch (...)
 }
 
 /**
+ * vte_terminal_get_font_options:
+ * @terminal: a #VteTerminal
+ *
+ * Returns: (nullable): the terminal's font options, or %NULL
+ *
+ * Since: 0.74
+ */
+cairo_font_options_t const*
+vte_terminal_get_font_options(VteTerminal *terminal) noexcept
+try
+{
+        g_return_val_if_fail(VTE_IS_TERMINAL(terminal), nullptr);
+
+        return IMPL(terminal)->get_font_options();
+}
+catch (...)
+{
+        vte::log_exception();
+        return nullptr;
+}
+
+/**
+ * vte_terminal_set_font_options:
+ * @terminal: a #VteTerminal
+ * @font_options: (nullable): the font options, or %NULL
+ *
+ * Sets the terminal's font options to @options.
+ *
+ * Note that on GTK4, the terminal by default uses font options
+ * with %CAIRO_HINT_METRICS_ON set; to override that, use this
+ * function to set a #cairo_font_options_t that has
+ * %CAIRO_HINT_METRICS_OFF set.
+ *
+ * Since: 0.74
+ */
+void
+vte_terminal_set_font_options(VteTerminal *terminal,
+                              cairo_font_options_t const* font_options) noexcept
+try
+{
+        g_return_if_fail(VTE_IS_TERMINAL(terminal));
+
+        if (IMPL(terminal)->set_font_options(vte::take_freeable(font_options ? cairo_font_options_copy(font_options) : nullptr)))
+                g_object_notify_by_pspec(G_OBJECT(terminal), pspecs[PROP_FONT_OPTIONS]);
+}
+catch (...)
+{
+        vte::log_exception();
+}
+
+/**
  * vte_terminal_get_font_scale:
  * @terminal: a #VteTerminal
  *
diff --git a/src/vtegtk.hh b/src/vtegtk.hh
index 778b555a..cca9a188 100644
--- a/src/vtegtk.hh
+++ b/src/vtegtk.hh
@@ -78,6 +78,7 @@ enum {
         PROP_ENABLE_SIXEL,
         PROP_ENCODING,
         PROP_FONT_DESC,
+        PROP_FONT_OPTIONS,
         PROP_FONT_SCALE,
         PROP_HYPERLINK_HOVER_URI,
         PROP_ICON_TITLE,
diff --git a/src/vteinternal.hh b/src/vteinternal.hh
index 88464760..b9f77891 100644
--- a/src/vteinternal.hh
+++ b/src/vteinternal.hh
@@ -617,6 +617,7 @@ public:
 
 	/* Data used when rendering the text which does not require server
 	 * resources and which can be kept after unrealizing. */
+        vte::Freeable<cairo_font_options_t> m_font_options{};
         vte::Freeable<PangoFontDescription> m_api_font_desc{};
         vte::Freeable<PangoFontDescription> m_unscaled_font_desc{};
         vte::Freeable<PangoFontDescription> m_fontdesc{};
@@ -1408,6 +1409,8 @@ public:
                           GError** error);
         bool set_font_desc(vte::Freeable<PangoFontDescription> desc);
         bool update_font_desc();
+        bool set_font_options(vte::Freeable<cairo_font_options_t> font_options);
+        cairo_font_options_t const* get_font_options() const noexcept { return m_font_options.get(); }
         bool set_font_scale(double scale);
         bool set_input_enabled(bool enabled);
         bool set_mouse_autohide(bool autohide);