Make GtkSourceView scheme-style configurable

This commit adds a "color scheme" entry to preferences which controls
the GtkSourceView scheme-style property to allow the user toggle between
different color schemes installed in the system. This is particularly
relevant for syntax highlighting since the default scheme (classic) is
not great in all circumstances such as dark theme usage. In general this
is heavily user preference driven so this commit allows users to select a
scheme they like.

Author: mrpdaemon

data/org.gnome.meld.gschema.xml

@@ -80,6 +80,11 @@
           <summary>Highlight syntax</summary>
           <description>Whether to highlight syntax in comparisons. Because of Meld's own color highlighting, this is off by default.</description>
       </key>
+      <key name="style-scheme" type="s">
+          <default>"classic"</default>
+          <summary>Color scheme to use for syntax highlighting</summary>
+          <description>Used by GtkSourceView to determine colors for syntax highlighting</description>
+      </key>
       <key name="draw-spaces" flags='org.gnome.meld.spacesflags'>
           <default>[]</default>
           <summary>Displayed whitespace</summary>

data/ui/preferences.ui

@@ -457,14 +457,53 @@
                               </packing>
                             </child>
                             <child>
-                              <object class="GtkCheckButton" id="checkbutton_use_syntax_highlighting">
-                                <property name="label" translatable="yes">Use s_yntax highlighting</property>
+                              <object class="GtkHBox" id="hbox11">
                                 <property name="visible">True</property>
-                                <property name="can_focus">True</property>
-                                <property name="receives_default">False</property>
-                                <property name="use_underline">True</property>
-                                <property name="xalign">0</property>
-                                <property name="draw_indicator">True</property>
+                                <property name="can_focus">False</property>
+                                <property name="spacing">6</property>
+                                <child>
+                                  <object class="GtkCheckButton" id="checkbutton_use_syntax_highlighting">
+                                    <property name="label" translatable="yes">Use s_yntax highlighting</property>
+                                    <property name="visible">True</property>
+                                    <property name="can_focus">True</property>
+                                    <property name="receives_default">False</property>
+                                    <property name="use_underline">True</property>
+                                    <property name="xalign">0</property>
+                                    <property name="draw_indicator">True</property>
+                                  </object>
+                                  <packing>
+                                    <property name="expand">False</property>
+                                    <property name="fill">False</property>
+                                    <property name="position">0</property>
+                                  </packing>
+                                </child>
+                                <child>
+                                  <object class="GtkLabel" id="label16">
+                                    <property name="visible">True</property>
+                                    <property name="can_focus">False</property>
+                                    <property name="label" translatable="yes">Color Scheme:</property>
+                                    <attributes>
+                                      <attribute name="weight" value="bold"/>
+                                    </attributes>
+                                  </object>
+                                  <packing>
+                                    <property name="expand">True</property>
+                                    <property name="fill">True</property>
+                                    <property name="padding">8</property>
+                                    <property name="position">1</property>
+                                  </packing>
+                                </child>
+                                <child>
+                                  <object class="GtkComboBox" id="combobox_style_scheme">
+                                    <property name="visible">True</property>
+                                    <property name="can_focus">False</property>
+                                  </object>
+                                  <packing>
+                                    <property name="expand">True</property>
+                                    <property name="fill">True</property>
+                                    <property name="position">2</property>
+                                  </packing>
+                                </child>
                               </object>
                               <packing>
                                 <property name="expand">False</property>

meld/filediff.py

@@ -852,6 +852,9 @@ def load_font(self):
     def on_setting_changed(self, settings, key):
         if key == 'font':
             self.load_font()
+        elif key == 'style-scheme':
+            for i in range(3):
+                self.textview[i].get_buffer().change_style_scheme(meldsettings.style_scheme)
 
     def check_save_modified(self, label=None):
         response = Gtk.ResponseType.OK

meld/meldbuffer.py

@@ -24,7 +24,7 @@
 from gi.repository import GtkSource
 
 from meld.conf import _
-from meld.settings import bind_settings
+from meld.settings import bind_settings,settings
 from meld.util.compat import text_type
 
 
@@ -41,6 +41,12 @@ def __init__(self, filename=None):
         bind_settings(self)
         self.data = MeldBufferData(filename)
         self.user_action_count = 0
+        self.change_style_scheme(settings.get_string('style-scheme'))
+
+    def change_style_scheme(self, scheme):
+        manager = GtkSource.StyleSchemeManager.get_default()
+        style = GtkSource.StyleSchemeManager.get_scheme(manager, scheme)
+        GtkSource.Buffer.set_style_scheme(self, style)
 
     def do_begin_user_action(self, *args):
         self.user_action_count += 1

meld/preferences.py

@@ -240,8 +240,29 @@ def __init__(self, parent):
         self.combo_file_order.bind_to('vc-left-is-local')
         self.combo_merge_order.bind_to('vc-merge-file-order')
 
+        # Fill color schemes
+        liststore = Gtk.ListStore(str)
+        manager = GtkSource.StyleSchemeManager.get_default()
+        scheme_ids = GtkSource.StyleSchemeManager.get_scheme_ids(manager)
+        for scheme in scheme_ids:
+            liststore.append([scheme])
+        self.combobox_style_scheme.set_model(liststore)
+        cell = Gtk.CellRendererText()
+        self.combobox_style_scheme.pack_start(cell, True)
+        self.combobox_style_scheme.add_attribute(cell, 'text',0)
+
+        style_scheme = settings.get_string('style-scheme')
+        for idx,scheme in enumerate(scheme_ids):
+            if scheme == style_scheme:
+                self.combobox_style_scheme.set_active(idx)
+
+        self.combobox_style_scheme.connect("changed", self.on_combobox_style_scheme_changed)
+
         self.widget.show()
 
+    def on_combobox_style_scheme_changed(self, combobox):
+        settings.set_string('style-scheme', combobox.get_model()[combobox.get_active()][0])
+
     def on_checkbutton_wrap_text_toggled(self, button):
         if not self.checkbutton_wrap_text.get_active():
             wrap_mode = Gtk.WrapMode.NONE

meld/settings.py

@@ -55,6 +55,9 @@ def on_setting_changed(self, settings, key):
         elif key in ('use-system-font', 'custom-font'):
             self.font = self._current_font_from_gsetting()
             self.emit('changed', 'font')
+        elif key in ('style-scheme'):
+            self.style_scheme = settings.get_string('style-scheme')
+            self.emit('changed', 'style-scheme')
 
     def _filters_from_gsetting(self, key, filt_type):
         filter_params = settings.get_value(key)