Use css value for message input placeholder

gajim/data/style/default.css

-.gajim-incoming-nickname {
    color: rgb(164, 0, 0)
    }.gajim-outgoing-nickname {
    color: rgb(52, 101, 164)
    }.gajim-outgoing-message-text {
    color: rgb(85, 87, 83)
    }.gajim-status-message {
    color: rgb(78, 154, 6)
    }.gajim-url {
    color: rgb(32, 74, 135)
    }.gajim-highlight-message {
    color: rgb(255, 128, 128)
    }.gajim-restored-message {
    color: rgb(85, 87, 83)
    }.gajim-roster-disconnected {
    background: rgb(171 ,97 ,97)
    }.gajim-roster-connected {
    background: rgb(173, 195, 198)
    }.gajim-state-composing {
    color: rgb(0, 139, 0)
    }.gajim-state-inactive {
    color: rgb(158, 158, 158)
    }.gajim-state-gone {
    color: rgb(128, 128, 128)
    }.gajim-state-paused {
    color: rgb(0, 0, 205)
    }
\ No newline at end of file
+.gajim-incoming-nickname {
    color: rgb(164, 0, 0)
    }.gajim-outgoing-nickname {
    color: rgb(52, 101, 164)
    }.gajim-outgoing-message-text {
    color: rgb(85, 87, 83)
    }.gajim-status-message {
    color: rgb(78, 154, 6)
    }.gajim-url {
    color: rgb(32, 74, 135)
    }.gajim-highlight-message {
    color: rgb(255, 128, 128)
    }.gajim-restored-message {
    color: rgb(85, 87, 83)
    }.gajim-roster-disconnected {
    background: rgb(171 ,97 ,97)
    }.gajim-roster-connected {
    background: rgb(173, 195, 198)
    }.gajim-state-composing {
    color: rgb(0, 139, 0)
    }.gajim-state-inactive {
    color: rgb(158, 158, 158)
    }.gajim-state-gone {
    color: rgb(128, 128, 128)
    }.gajim-state-paused {
    color: rgb(0, 0, 205)
    }.gajim-message-placeholder {
    color: rgb(195, 195, 192)
    }
\ No newline at end of file

gajim/gtkgui_helpers.py

@@ -54,14 +54,6 @@ if os.name == 'nt':
 log = logging.getLogger('gajim.gtkgui_helpers')
 
 
-class Color:
-    BLACK = Gdk.RGBA(red=0, green=0, blue=0, alpha=1)
-    GREEN = Gdk.RGBA(red=115/255, green=210/255, blue=22/255, alpha=1)
-    RED = Gdk.RGBA(red=204/255, green=0, blue=0, alpha=1)
-    GREY = Gdk.RGBA(red=195/255, green=195/255, blue=192/255, alpha=1)
-    ORANGE = Gdk.RGBA(red=245/255, green=121/255, blue=0/255, alpha=1)
-
-
 def get_pixbuf_from_data(file_data):
     """
     Get image data and returns GdkPixbuf.Pixbuf

gajim/message_textview.py

@@ -24,10 +24,9 @@ from gi.repository import GLib
 from gi.repository import GObject
 from gi.repository import Pango
 
-from gajim import gtkgui_helpers
-
 from gajim.common import app
 from gajim.common.i18n import _
+from gajim.common.const import StyleAttr
 
 from gajim.gtk.util import scroll_to_end
 
@@ -76,9 +75,12 @@ class MessageTextView(Gtk.TextView):
         self.color_tags = []
         self.fonts_tags = []
         self.other_tags = {}
+
+        color = app.css_config.get_value(
+            '.gajim-message-placeholder', StyleAttr.COLOR)
         self.placeholder_tag = buffer_.create_tag('placeholder')
-        self.placeholder_tag.set_property('foreground_rgba',
-                                      gtkgui_helpers.Color.GREY)
+        self.placeholder_tag.set_property('foreground', color)
+
         self.other_tags['bold'] = buffer_.create_tag('bold')
         self.other_tags['bold'].set_property('weight', Pango.Weight.BOLD)
         self.begin_tags['bold'] = '<strong>'