[libadwaita] about-window: Warn against copying the header bar hack

[Alexander Mikhaylenko <alexm src gnome org>]

commit e537a007c5808039b7d86ff7b6f21d0e2e11c014
Author: António Fernandes <antoniojpfernandes gmail com>
Date:   Sat Jul 9 21:53:10 2022 +0000

    about-window: Warn against copying the header bar hack

 src/adw-about-window.c            | 1 +
 src/stylesheet/widgets/_misc.scss | 1 +
 2 files changed, 2 insertions(+)
---
diff --git a/src/adw-about-window.c b/src/adw-about-window.c
index 7fa739a7..2fdd2670 100644
--- a/src/adw-about-window.c
+++ b/src/adw-about-window.c
@@ -356,6 +356,7 @@ string_is_not_empty (AdwAboutWindow *self,
   return string && string[0];
 }
 
+/* WARNING: Don't copy into your app. This is a hack which hardcodes pixels. */
 static char *
 get_headerbar_name (AdwAboutWindow *self,
                     double          value)
diff --git a/src/stylesheet/widgets/_misc.scss b/src/stylesheet/widgets/_misc.scss
index 3d35a672..582cdc81 100644
--- a/src/stylesheet/widgets/_misc.scss
+++ b/src/stylesheet/widgets/_misc.scss
@@ -104,6 +104,7 @@ window.about {
   .main-page {
     scrollbar.vertical {
       // Keep in sync with header bar height
+      // WARNING: Don't copy into your app. This is a hack which hardcodes pixels. 
       margin-top: 47px;
       background: none;
       box-shadow: none;