[PATCH v3] emacs: make faces readable on dark backgrounds.

[Matt Armstrong]

The notmuch-tag-flagged, notmuch-search-flagged-face and
notmuch-crypto-part-header faces defaulted to "blue", which is nearly
unreadable when a dark background is in use.  This is addressed by using
"LightBlue1" for dark backgrounds.

As a side effect, these faces are now no-op definitions for grayscale or
mono displays.
---
 emacs/notmuch-crypto.el | 7 ++++++-
 emacs/notmuch-tag.el    | 7 ++++++-
 emacs/notmuch.el        | 6 +++++-
 3 files changed, 17 insertions(+), 3 deletions(-)

diff --git a/emacs/notmuch-crypto.el b/emacs/notmuch-crypto.el
index e376aa8..68a7e9f 100644
--- a/emacs/notmuch-crypto.el
+++ b/emacs/notmuch-crypto.el
@@ -42,7 +42,12 @@ mode."
   :group 'notmuch-crypto)
 
 (defface notmuch-crypto-part-header
-  '((t (:foreground "blue")))
+  '((((class color)
+      (background dark))
+     (:foreground "LightBlue1"))
+    (((class color)
+      (background light))
+     (:foreground "blue")))
   "Face used for crypto parts headers."
   :group 'notmuch-crypto
   :group 'notmuch-faces)
diff --git a/emacs/notmuch-tag.el b/emacs/notmuch-tag.el
index 1b2ce5c..09d182d 100644
--- a/emacs/notmuch-tag.el
+++ b/emacs/notmuch-tag.el
@@ -115,7 +115,12 @@ Used in the default value of `notmuch-tag-formats`."
   :group 'notmuch-faces)
 
 (defface notmuch-tag-flagged
-  '((t :foreground "blue"))
+  '((((class color)
+      (background dark))
+     (:foreground "LightBlue1"))
+    (((class color)
+      (background light))
+     (:foreground "blue")))
   "Face used for the flagged tag.
 
 Used in the default value of `notmuch-tag-formats`."
diff --git a/emacs/notmuch.el b/emacs/notmuch.el
index 2fc72b7..c0e9e1d 100644
--- a/emacs/notmuch.el
+++ b/emacs/notmuch.el
@@ -313,7 +313,11 @@ there will be called at other points of notmuch execution."
   :group 'notmuch-faces)
 
 (defface notmuch-search-flagged-face
-  '((t
+  '((((class color)
+      (background dark))
+     (:foreground "LightBlue1"))
+    (((class color)
+      (background light))
      (:foreground "blue")))
   "Face used in search mode face for flagged threads.
 
-- 
2.8.0.rc3.226.g39d4020