[gtk+] Adwaita: add some comments in the GtkScale related scss

[Lapo Calamandrei <lapo src gnome org>]

commit c6dcc6ee62fbe6eb7af2efba81cdd44772cd43b7
Author: Lapo Calamandrei <calamandrei gmail com>
Date:   Tue Mar 15 16:12:40 2016 +0100

    Adwaita: add some comments in the GtkScale related scss

 gtk/theme/Adwaita/_common.scss |    7 +++++++
 1 files changed, 7 insertions(+), 0 deletions(-)
---
diff --git a/gtk/theme/Adwaita/_common.scss b/gtk/theme/Adwaita/_common.scss
index b558d18..1b2149c 100644
--- a/gtk/theme/Adwaita/_common.scss
+++ b/gtk/theme/Adwaita/_common.scss
@@ -2710,15 +2710,18 @@ scale {
   min-width: 10px;
   padding: 12px;
 
+  // those are inside the trough node, I need them to show their own border over the trough one, so negative 
margin
   fill,
   highlight { margin: -1px; }
 
+  // the slider is inside the trough, so to have make it bigger there's a negative margin
   slider {
     min-height: 18px;
     min-width: 18px;
     margin: -9px;
   }
 
+  // click-and-hold the slider to activate
   &.fine-tune {
     &.horizontal {
       padding-top: 9px;
@@ -2732,6 +2735,7 @@ scale {
       min-width: 16px;
     }
 
+    // to make the trough grow in fine-tune mode
     slider { margin: -6px; }
 
     fill,
@@ -2885,6 +2889,8 @@ scale {
           %#{$marks_infix}-#{$dir_infix},
           contents#{$nth_child} > trough > slider {
             &#{$state} {
+              // an asymmetric slider asset is used here, so the margins are uneven, the smaller
+              // margin is set on the point side.
               margin: -10px;
               $_scale_asset: 'assets/slider-#{$dir_infix}-#{$marks_infix}#{$state_infix}#{$suffix}';
               border-style: none;
@@ -2931,6 +2937,7 @@ scale {
 
           @at-root %#{$marks_infix}-#{$dir_infix}-fine-tune,
           &.fine-tune contents#{$nth_child} > trough > slider {
+            // bigger negative margins to make the trough grow here as well
             margin: -7px;
 
             @if $dir_class == 'horizontal' {