ui: allow thread arrow customization

The thread prefix appearance is inspired by mutt and has been regarded
by some as too wide and not very aesthetically pleasing. Nevertheless,
it has some technical limitations, like not being able to show if a
thread is folded.

Allow for full customisation of the thread prefix by introducing 14 new
config options.

Dirlist is not affected.

Changelog-added: Thread arrow prefixes are now fully configurable.
Co-authored-by: Robin Jarry <robin@jarry.cc>
Signed-off-by: inwit <inwit@sindominio.net>
Tested-by: Koni Marti <koni.marti@gmail.com>
Acked-by: Robin Jarry <robin@jarry.cc>

2 files changed, 113 insertions, 0 deletions

diff --git a/config/aerc.conf b/config/aerc.conf
index 30c3c7bb..ac2a6847 100644
--- a/config/aerc.conf
+++ b/config/aerc.conf
@@ -335,6 +335,104 @@
 # Default: 50ms
 #client-threads-delay=50ms
 
+#
+# Thread prefix customization:
+
+#
+# Customize the thread prefix appearance by selecting the arrow head.
+#
+# Default: ">"
+#thread-prefix-tip = ">"
+
+#
+# Customize the thread prefix appearance by selecting the arrow indentation.
+#
+# Default: " "
+#thread-prefix-indent = " "
+
+#
+# Customize the thread prefix appearance by selecting the vertical extension of
+# the arrow.
+#
+# Default: "│"
+#thread-prefix-stem = "│"
+
+#
+# Customize the thread prefix appearance by selecting the horizontal extension
+# of the arrow.
+#
+# Default: ""
+#thread-prefix-limb = ""
+
+#
+# Customize the thread prefix appearance by selecting the folded thread
+# indicator.
+#
+# Default: ""
+#thread-prefix-folded = ""
+
+#
+# Customize the thread prefix appearance by selecting the unfolded thread
+# indicator.
+#
+# Default: ""
+#thread-prefix-unfolded = ""
+
+#
+# Customize the thread prefix appearance by selecting the first child connector.
+#
+# Default: ""
+#thread-prefix-first-child = ""
+
+#
+# Customize the thread prefix appearance by selecting the connector used if
+# the message has siblings.
+#
+# Default: "├─"
+#thread-prefix-has-siblings = "├─"
+
+#
+# Customize the thread prefix appearance by selecting the connector used if the
+# message has no parents and no children.
+#
+# Default: ""
+#thread-prefix-lone = ""
+
+#
+# Customize the thread prefix appearance by selecting the connector used if the
+# message has no parents and has children.
+#
+# Default: ""
+#thread-prefix-orphan = ""
+
+#
+# Customize the thread prefix appearance by selecting the connector for the last
+# sibling.
+#
+# Default: "└─"
+#thread-prefix-last-sibling = "└─"
+
+#
+# Customize the reversed thread prefix appearance by selecting the connector for
+# the last sibling.
+#
+# Default: "┌─"
+#thread-prefix-last-sibling-reverse = "┌─"
+
+#
+# Customize the reversed thread prefix appearance by selecting the first child
+# connector.
+#
+# Default: ""
+#thread-prefix-first-child-reverse = ""
+
+#
+# Customize the reversed thread prefix appearance by selecting the connector
+# used if the message has no parents and has children.
+#
+# Default: ""
+#thread-prefix-orphan-reverse = ""
+
 [statusline]
 #
 # Describes the format for the status line. This is a comma separated list of
diff --git a/config/ui.go b/config/ui.go
index 83b45230..9a97d4ef 100644
--- a/config/ui.go
+++ b/config/ui.go
@@ -78,6 +78,21 @@ type UIConfig struct {
 	ReverseThreadOrder bool `ini:"reverse-thread-order"`
 	SortThreadSiblings bool `ini:"sort-thread-siblings"`
 
+	ThreadPrefixTip                string `ini:"thread-prefix-tip" default:">"`
+	ThreadPrefixIndent             string `ini:"thread-prefix-indent" default:" "`
+	ThreadPrefixStem               string `ini:"thread-prefix-stem" default:"│"`
+	ThreadPrefixLimb               string `ini:"thread-prefix-limb" default:""`
+	ThreadPrefixFolded             string `ini:"thread-prefix-folded" default:""`
+	ThreadPrefixUnfolded           string `ini:"thread-prefix-unfolded" default:""`
+	ThreadPrefixFirstChild         string `ini:"thread-prefix-first-child" default:""`
+	ThreadPrefixHasSiblings        string `ini:"thread-prefix-has-siblings" default:"├─"`
+	ThreadPrefixLone               string `ini:"thread-prefix-lone" default:""`
+	ThreadPrefixOrphan             string `ini:"thread-prefix-orphan" default:""`
+	ThreadPrefixLastSibling        string `ini:"thread-prefix-last-sibling" default:"└─"`
+	ThreadPrefixLastSiblingReverse string `ini:"thread-prefix-last-sibling-reverse" default:"┌─"`
+	ThreadPrefixFirstChildReverse  string `ini:"thread-prefix-first-child-reverse" default:""`
+	ThreadPrefixOrphanReverse      string `ini:"thread-prefix-orphan-reverse" default:""`
+
 	// Tab Templates
 	TabTitleAccount  *template.Template `ini:"tab-title-account" default:"{{.Account}}"`
 	TabTitleComposer *template.Template `ini:"tab-title-composer" default:"{{.Subject}}"`