[vte] font: pangocairo: Use PangoFontMetrics to measure the font

[Christian Persch <chpe src gnome org>]

commit ce347e7022f0e7422c0a4410d51d7caa534b22ce
Author: Christian Persch <chpe src gnome org>
Date:   Mon Feb 1 21:54:32 2021 +0100

    font: pangocairo: Use PangoFontMetrics to measure the font
    
    Based on a patch by Arthur Huillet.
    
    Fixes: https://gitlab.gnome.org/GNOME/vte/-/issues/163

 src/fonts-pangocairo.cc | 72 ++++++++++++++++++++++++++++++-------------------
 src/fonts-pangocairo.hh |  2 +-
 src/pango-glue.hh       |  4 +++
 3 files changed, 49 insertions(+), 29 deletions(-)
---
diff --git a/src/fonts-pangocairo.cc b/src/fonts-pangocairo.cc
index 16f3edd6..52847af5 100644
--- a/src/fonts-pangocairo.cc
+++ b/src/fonts-pangocairo.cc
@@ -179,8 +179,8 @@ FontInfo::measure_font()
          * leading to unreadable, overlapping characters.
          * https://gitlab.gnome.org/GNOME/vte/issues/138
          */
-        int max_width{1};
-        int max_height{1};
+        auto max_width = 1;
+        auto max_height = 1;
         for (char c = 0x21; c < 0x7f; ++c) {
                 pango_layout_set_text(m_layout.get(), &c, 1);
                 pango_layout_get_extents(m_layout.get(), nullptr, &logical);
@@ -208,10 +208,6 @@ FontInfo::measure_font()
        if (m_ascent == 0) {
                m_ascent = PANGO_PIXELS_CEIL(pango_layout_get_baseline(m_layout.get()));
        }
-
-       _vte_debug_print (VTE_DEBUG_MISC,
-                         "vtepangocairo: %p font metrics = %dx%d (%d)\n",
-                         (void*)this, m_width, m_height, m_ascent);
 }
 
 FontInfo::FontInfo(PangoContext *context)
@@ -229,7 +225,33 @@ FontInfo::FontInfo(PangoContext *context)
         // FIXME!!!
        m_string = g_string_sized_new(VTE_UTF8_BPC+1);
 
+#if PANGO_VERSION_CHECK(1, 44, 0)
+        auto need_measure = true;
+        if (auto metrics = vte::take_freeable
+            (pango_context_get_metrics(context,
+                                       nullptr /* use font from context */,
+                                       nullptr /* use language from context */))) {
+                _vte_debug_print(VTE_DEBUG_PANGOCAIRO, "Using pango metrics\n");
+
+               /* Use provided metrics if possible */
+               m_ascent = PANGO_PIXELS_CEIL(pango_font_metrics_get_ascent(metrics.get()));
+               m_height = PANGO_PIXELS_CEIL(pango_font_metrics_get_height(metrics.get()));
+               /* XXX can we trust this one, since we are monospace-only ?*/
+               m_width = PANGO_PIXELS_CEIL(pango_font_metrics_get_approximate_char_width(metrics.get()));
+
+               if (m_ascent && m_height && m_width)
+                        need_measure = false;
+       }
+
+        if (need_measure)
+                measure_font();
+#else
        measure_font();
+#endif /* pango >= 1.44 */
+
+       _vte_debug_print (VTE_DEBUG_PANGOCAIRO | VTE_DEBUG_MISC,
+                         "vtepangocairo: %p font metrics = %dx%d (%d)\n",
+                         (void*)this, m_width, m_height, m_ascent);
 
        g_hash_table_insert(s_font_info_for_context,
                             pango_layout_get_context(m_layout.get()),
@@ -307,27 +329,6 @@ context_equal (PangoContext *a,
            && vte_pango_context_get_fontconfig_timestamp (a) == vte_pango_context_get_fontconfig_timestamp 
(b);
 }
 
-// FIXMEchpe return vte::base::RefPtr<FontInfo>
-/* assumes ownership/reference of context */
-FontInfo*
-FontInfo::find_for_context(vte::glib::RefPtr<PangoContext>& context)
-{
-       if (G_UNLIKELY (s_font_info_for_context == nullptr))
-               s_font_info_for_context = g_hash_table_new((GHashFunc) context_hash, (GEqualFunc) 
context_equal);
-
-       auto info = reinterpret_cast<FontInfo*>(g_hash_table_lookup(s_font_info_for_context, context.get()));
-       if (G_LIKELY(info)) {
-               _vte_debug_print (VTE_DEBUG_PANGOCAIRO,
-                                 "vtepangocairo: %p found font_info in cache\n",
-                                 info);
-               info = info->ref();
-       } else {
-                info = new FontInfo{context.release()};
-       }
-
-       return info;
-}
-
 /* assumes ownership/reference of context */
 FontInfo*
 FontInfo::create_for_context(vte::glib::RefPtr<PangoContext> context,
@@ -362,7 +363,22 @@ FontInfo::create_for_context(vte::glib::RefPtr<PangoContext> context,
                 cairo_font_options_destroy (font_options);
         }
 
-       return find_for_context(context);
+       if (G_UNLIKELY(s_font_info_for_context == nullptr))
+               s_font_info_for_context = g_hash_table_new((GHashFunc) context_hash, (GEqualFunc) 
context_equal);
+
+       auto info = reinterpret_cast<FontInfo*>(g_hash_table_lookup(s_font_info_for_context, context.get()));
+       if (G_LIKELY(info)) {
+               _vte_debug_print (VTE_DEBUG_PANGOCAIRO,
+                                 "vtepangocairo: %p found FontInfo in cache\n",
+                                 info);
+               info = info->ref();
+       } else {
+               _vte_debug_print (VTE_DEBUG_PANGOCAIRO,
+                                 "vtepangocairo: FontInfo not in cache\n");
+                info = new FontInfo{context.get()};
+        }
+
+       return info;
 }
 
 FontInfo*
diff --git a/src/fonts-pangocairo.hh b/src/fonts-pangocairo.hh
index d85b68d8..c7aac75c 100644
--- a/src/fonts-pangocairo.hh
+++ b/src/fonts-pangocairo.hh
@@ -24,6 +24,7 @@
 #include <pango/pangocairo.h>
 #include <gtk/gtk.h>
 
+#include "pango-glue.hh"
 #include "refptr.hh"
 #include "vteunistr.h"
 
@@ -264,7 +265,6 @@ private:
        int m_coverage_count[4]{0, 0, 0, 0};
 #endif
 
-        static FontInfo* find_for_context(vte::glib::RefPtr<PangoContext>& context);
         static FontInfo* create_for_context(vte::glib::RefPtr<PangoContext> context,
                                             PangoFontDescription const* desc,
                                             PangoLanguage* language,
diff --git a/src/pango-glue.hh b/src/pango-glue.hh
index e5a29df0..f793c1ea 100644
--- a/src/pango-glue.hh
+++ b/src/pango-glue.hh
@@ -26,4 +26,8 @@ namespace vte {
 VTE_DECLARE_FREEABLE(PangoAttrList, pango_attr_list_unref);
 VTE_DECLARE_FREEABLE(PangoFontDescription, pango_font_description_free);
 
+#if PANGO_VERSION_CHECK(1, 44, 0)
+VTE_DECLARE_FREEABLE(PangoFontMetrics, pango_font_metrics_unref);
+#endif
+
 } // namespace vte