[gtk+/wip/matthiasc/font-variations: 1/2] Some initial support for font variations

[Matthias Clasen <matthiasc src gnome org>]

commit efc405a22bde1e0830c6ed48d3f88aa0bc645e98
Author: Matthias Clasen <mclasen redhat com>
Date:   Fri Sep 15 22:38:08 2017 -0400

    Some initial support for font variations
    
    Make the font chooser show sliders for axes of
    variable fonts.

 gtk/gtkfontchooserwidget.c     |  225 ++++++++++++++++++++++++++++++++++++++++
 gtk/ui/gtkfontchooserwidget.ui |   22 +++-
 2 files changed, 242 insertions(+), 5 deletions(-)
---
diff --git a/gtk/gtkfontchooserwidget.c b/gtk/gtkfontchooserwidget.c
index d8a8f3a..268740c 100644
--- a/gtk/gtkfontchooserwidget.c
+++ b/gtk/gtkfontchooserwidget.c
@@ -51,6 +51,13 @@
 #include "gtksettings.h"
 #include "gtkdialog.h"
 
+#include <pango/pangofc-font.h>
+#include <hb.h>
+#include <hb-ot.h>
+#include <hb-ft.h>
+#include <freetype/ftmm.h>
+#include <freetype/ftsnames.h>
+
 /**
  * SECTION:gtkfontchooserwidget
  * @Short_description: A widget for selecting fonts
@@ -98,6 +105,8 @@ struct _GtkFontChooserWidgetPrivate
   GtkWidget *size_spin;
   GtkWidget *size_slider;
 
+  GtkWidget *font_grid;
+
   PangoFontMap         *font_map;
 
   PangoFontDescription *font_desc;
@@ -108,6 +117,9 @@ struct _GtkFontChooserWidgetPrivate
   GDestroyNotify    filter_data_destroy;
 
   guint last_fontconfig_timestamp;
+
+  GHashTable *axes;
+  gboolean updating_variations;
 };
 
 /* Keep in line with GtkTreeStore defined in gtkfontchooserwidget.ui */
@@ -170,6 +182,43 @@ static void     gtk_font_chooser_widget_cell_data_func         (GtkTreeViewColum
                                                                GtkTreeIter       *iter,
                                                                gpointer           user_data);
 
+typedef struct {
+  guint32 tag;
+  GtkAdjustment *adjustment;
+  GtkWidget *label;
+  GtkWidget *scale;
+  GtkWidget *spin;
+  GtkWidget *fontchooser;
+} Axis;
+
+static guint
+axis_hash (gconstpointer v)
+{
+  const Axis *a = v;
+
+  return a->tag;
+}
+
+static gboolean
+axis_equal (gconstpointer v1, gconstpointer v2)
+{
+  const Axis *a1 = v1;
+  const Axis *a2 = v2;
+
+  return a1->tag == a2->tag;
+}
+
+static void
+axis_free (gpointer v)
+{
+  Axis *a = v;
+
+  gtk_widget_destroy (a->label);
+  gtk_widget_destroy (a->scale);
+  gtk_widget_destroy (a->spin);
+  g_free (a);
+}
+
 static void gtk_font_chooser_widget_iface_init (GtkFontChooserIface *iface);
 
 G_DEFINE_TYPE_WITH_CODE (GtkFontChooserWidget, gtk_font_chooser_widget, GTK_TYPE_WIDGET,
@@ -659,6 +708,7 @@ gtk_font_chooser_widget_class_init (GtkFontChooserWidgetClass *klass)
   gtk_widget_class_bind_template_child_private (widget_class, GtkFontChooserWidget, size_spin);
   gtk_widget_class_bind_template_child_private (widget_class, GtkFontChooserWidget, size_slider);
   gtk_widget_class_bind_template_child_private (widget_class, GtkFontChooserWidget, grid);
+  gtk_widget_class_bind_template_child_private (widget_class, GtkFontChooserWidget, font_grid);
 
   gtk_widget_class_bind_template_callback (widget_class, text_changed_cb);
   gtk_widget_class_bind_template_callback (widget_class, stop_search_cb);
@@ -687,6 +737,8 @@ gtk_font_chooser_widget_init (GtkFontChooserWidget *fontchooser)
 
   gtk_widget_init_template (GTK_WIDGET (fontchooser));
 
+  priv->axes = g_hash_table_new_full (axis_hash, axis_equal, NULL, axis_free);
+
   /* Default preview string  */
   priv->preview_text = g_strdup (pango_language_get_sample_string (NULL));
   priv->show_preview_entry = TRUE;
@@ -1035,6 +1087,8 @@ gtk_font_chooser_widget_finalize (GObject *object)
 
   g_clear_object (&priv->font_map);
 
+  g_hash_table_unref (priv->axes);
+
   G_OBJECT_CLASS (gtk_font_chooser_widget_parent_class)->finalize (object);
 }
 
@@ -1235,6 +1289,175 @@ gtk_font_chooser_widget_ensure_selection (GtkFontChooserWidget *fontchooser)
     }
 }
 
+
+#define FixedToFloat(f) (((float)(f))/65536.0)
+
+static void
+add_font_variations (GtkFontChooserWidget *fontchooser,
+                     GString              *s)
+{
+  GHashTableIter iter;
+  Axis *axis;
+  char *sep = "";
+  char buf[G_ASCII_DTOSTR_BUF_SIZE];
+
+  g_hash_table_iter_init (&iter, fontchooser->priv->axes);
+  while (g_hash_table_iter_next (&iter, (gpointer *)NULL, (gpointer *)&axis))
+    {
+      char tag[5];
+      double value;
+
+      tag[0] = (axis->tag >> 24) & 0xff;
+      tag[1] = (axis->tag >> 16) & 0xff;
+      tag[2] = (axis->tag >> 8) & 0xff;
+      tag[3] = (axis->tag >> 0) & 0xff;
+      tag[4] = '\0';
+      value = gtk_adjustment_get_value (axis->adjustment);
+      g_string_append_printf (s, "%s%s=%s", sep, tag, g_ascii_dtostr (buf, sizeof(buf), value));
+      sep = ",";
+    }
+}
+
+static void
+adjustment_changed (GtkAdjustment *adjustment,
+                    Axis          *axis)
+{
+  GtkFontChooserWidget *fontchooser = GTK_FONT_CHOOSER_WIDGET (axis->fontchooser);
+  GtkFontChooserWidgetPrivate *priv = fontchooser->priv;
+  PangoFontDescription *font_desc;
+  GString *s;
+
+  priv->updating_variations = TRUE;
+
+  s = g_string_new ("");
+  add_font_variations (fontchooser, s);
+
+  font_desc = pango_font_description_new ();
+  pango_font_description_set_variations (font_desc, s->str);
+  pango_font_description_set_variations (font_desc, s->str);
+  gtk_font_chooser_widget_take_font_desc (fontchooser, font_desc);
+
+  g_string_free (s, TRUE);
+
+  priv->updating_variations = FALSE;
+}
+
+static gboolean
+should_show_axis (FT_Var_Axis *ax)
+{
+  /* FIXME use FT_Get_Var_Axis_Flags */
+  if (ax->tag == FT_MAKE_TAG ('o', 'p', 's', 'z'))
+    return FALSE;
+
+  return TRUE;
+}
+
+struct {
+  guint32 tag;
+  const char *name;
+} axis_names[] = {
+  { FT_MAKE_TAG ('w', 'd', 't', 'h'), N_("Width") },
+  { FT_MAKE_TAG ('w', 'g', 'h', 't'), N_("Weight") },
+  { FT_MAKE_TAG ('i', 't', 'a', 'l'), N_("Italic") },
+  { FT_MAKE_TAG ('s', 'l', 'n', 't'), N_("Slant") },
+  { FT_MAKE_TAG ('o', 'p', 's', 'z'), N_("Optical Size") },
+};
+
+static void
+add_axis (GtkFontChooserWidget *fontchooser,
+          FT_Var_Axis          *ax,
+          FT_Fixed              value,
+          int                   i)
+{
+  GtkFontChooserWidgetPrivate *priv = fontchooser->priv;
+  Axis *axis;
+  const char *name;
+
+  axis = g_new (Axis, 1);
+  axis->tag = ax->tag;
+  axis->fontchooser = GTK_WIDGET (fontchooser);
+
+  name = ax->name;
+  for (i = 0; i < G_N_ELEMENTS (axis_names); i++)
+    {
+      if (axis_names[i].tag == ax->tag)
+        {
+          name = _(axis_names[i].name);
+          break;
+        }
+    }
+  axis->label = gtk_label_new (name);
+  gtk_widget_set_halign (axis->label, GTK_ALIGN_START);
+  gtk_widget_set_valign (axis->label, GTK_ALIGN_BASELINE);
+  gtk_grid_attach (GTK_GRID (priv->font_grid), axis->label, 0, 4 + i, 1, 1);
+  axis->adjustment = gtk_adjustment_new ((double)FixedToFloat(value),
+                                         (double)FixedToFloat(ax->minimum),
+                                         (double)FixedToFloat(ax->maximum),
+                                         1.0, 10.0, 0.0);
+  axis->scale = gtk_scale_new (GTK_ORIENTATION_HORIZONTAL, axis->adjustment);
+  gtk_scale_add_mark (GTK_SCALE (axis->scale), (double)FixedToFloat(ax->def), GTK_POS_TOP, NULL);
+  gtk_widget_set_valign (axis->scale, GTK_ALIGN_BASELINE);
+  gtk_widget_set_hexpand (axis->scale, TRUE);
+  gtk_widget_set_size_request (axis->scale, 100, -1);
+  gtk_scale_set_draw_value (GTK_SCALE (axis->scale), FALSE);
+  gtk_grid_attach (GTK_GRID (priv->font_grid), axis->scale, 1, 4 + i, 1, 1);
+  axis->spin = gtk_spin_button_new (axis->adjustment, 0, 0);
+  g_signal_connect (axis->spin, "output", G_CALLBACK (output_cb), fontchooser);
+  gtk_widget_set_valign (axis->spin, GTK_ALIGN_BASELINE);
+  gtk_grid_attach (GTK_GRID (priv->font_grid), axis->spin, 2, 4 + i, 1, 1);
+
+  g_hash_table_add (priv->axes, axis);
+
+  adjustment_changed (axis->adjustment, axis);
+  g_signal_connect (axis->adjustment, "value-changed", G_CALLBACK (adjustment_changed), axis);
+}
+
+static void
+gtk_font_chooser_widget_update_font_variations (GtkFontChooserWidget *fontchooser)
+{
+  GtkFontChooserWidgetPrivate *priv = fontchooser->priv;
+  PangoFont *pango_font;
+  FT_Face ft_face;
+  FT_MM_Var *ft_mm_var;
+  FT_Error ret;
+
+  if (priv->updating_variations)
+    return;
+
+  g_hash_table_remove_all (priv->axes);
+
+  pango_font = pango_context_load_font (gtk_widget_get_pango_context (GTK_WIDGET (fontchooser)),
+                                        priv->font_desc);
+  ft_face = pango_fc_font_lock_face (PANGO_FC_FONT (pango_font));
+  ret = FT_Get_MM_Var (ft_face, &ft_mm_var);
+  if (ret == 0)
+    {
+      int i;
+      int pos;
+      FT_Fixed *coords;
+
+      coords = g_new (FT_Fixed, ft_mm_var->num_axis);
+      ret = FT_Get_Var_Design_Coordinates (ft_face, ft_mm_var->num_axis, coords);
+      if (ret == 0)
+        {
+          pos = 0;
+          for (i = 0; i < ft_mm_var->num_axis; i++)
+            {
+              if (should_show_axis (&ft_mm_var->axis[i]))
+                {
+                  add_axis (fontchooser, &ft_mm_var->axis[i], coords[i], pos);
+                  pos++;
+                }
+            }
+        }
+      g_free (coords);
+      free (ft_mm_var);
+    }
+
+  pango_fc_font_unlock_face (PANGO_FC_FONT (pango_font));
+  g_object_unref (pango_font);
+}
+
 static void
 gtk_font_chooser_widget_merge_font_desc (GtkFontChooserWidget       *fontchooser,
                                          const PangoFontDescription *font_desc,
@@ -1280,6 +1503,8 @@ gtk_font_chooser_widget_merge_font_desc (GtkFontChooserWidget       *fontchooser
     }
 
   gtk_font_chooser_widget_update_preview_attributes (fontchooser);
+  if (iter)
+    gtk_font_chooser_widget_update_font_variations (fontchooser);
 
   g_object_notify (G_OBJECT (fontchooser), "font");
   g_object_notify (G_OBJECT (fontchooser), "font-desc");
diff --git a/gtk/ui/gtkfontchooserwidget.ui b/gtk/ui/gtkfontchooserwidget.ui
index 7bf0fc9..abf0d87 100644
--- a/gtk/ui/gtkfontchooserwidget.ui
+++ b/gtk/ui/gtkfontchooserwidget.ui
@@ -61,7 +61,7 @@
           <object class="GtkStack" id="list_stack">
             <property name="visible">1</property>
             <child>
-              <object class="GtkGrid">
+              <object class="GtkGrid" id="font_grid">
                 <property name="visible">1</property>
                 <property name="row-spacing">6</property>
                 <property name="column-spacing">6</property>
@@ -108,7 +108,7 @@
                   <packing>
                     <property name="left-attach">0</property>
                     <property name="top-attach">1</property>
-                    <property name="width">2</property>
+                    <property name="width">3</property>
                   </packing>
                 </child>
                 <child>
@@ -121,7 +121,19 @@
                   <packing>
                     <property name="left-attach">0</property>
                     <property name="top-attach">2</property>
-                    <property name="width">2</property>
+                    <property name="width">3</property>
+                  </packing>
+                </child>
+                <child>
+                  <object class="GtkLabel">
+                    <property name="visible">1</property>
+                    <property name="label" translatable="yes">Size</property>
+                    <property name="xalign">0</property>
+                    <property name="valign">baseline</property>
+                  </object>
+                  <packing>
+                    <property name="left-attach">0</property>
+                    <property name="top-attach">3</property>
                   </packing>
                 </child>
                 <child>
@@ -135,7 +147,7 @@
                     <signal name="scroll-event" handler="resize_by_scroll_cb" swapped="no"/>
                   </object>
                   <packing>
-                    <property name="left-attach">0</property>
+                    <property name="left-attach">1</property>
                     <property name="top-attach">3</property>
                   </packing>
                 </child>
@@ -147,7 +159,7 @@
                     <signal name="output" handler="output_cb"/>
                   </object>
                   <packing>
-                    <property name="left-attach">1</property>
+                    <property name="left-attach">2</property>
                     <property name="top-attach">3</property>
                   </packing>
                 </child>