Apply relevant msglist styles in order

Allow styles to be layered over a base style. The list of styles to
apply is layered over the base style in order, such that if the layer
does not differ from the base it is not used. The order that these
styles are applied in is, from first to last:

msglist_default
msglist_unread
msglist_read    (exclusive with unread, so technically the same level)
msglist_flagged
msglist_deleted
msglist_marked

So, msglist_marked style dominates.

This fixes an issue where the msglist_deleted style was not being applied.

2 files changed, 57 insertions, 2 deletions

diff --git a/config/config.go b/config/config.go
index 3ae26c12..bb83579c 100644
--- a/config/config.go
+++ b/config/config.go
@@ -699,3 +699,12 @@ func (uiConfig UIConfig) GetStyle(so StyleObject) tcell.Style {
 func (uiConfig UIConfig) GetStyleSelected(so StyleObject) tcell.Style {
 	return uiConfig.style.Selected(so)
 }
+
+func (uiConfig UIConfig) GetComposedStyle(base StyleObject,
+	styles []StyleObject) tcell.Style {
+	return uiConfig.style.Compose(base, styles)
+}
+
+func (uiConfig UIConfig) GetComposedStyleSelected(base StyleObject, styles []StyleObject) tcell.Style {
+	return uiConfig.style.ComposeSelected(base, styles)
+}
diff --git a/config/style.go b/config/style.go
index caf9e4f0..af7241de 100644
--- a/config/style.go
+++ b/config/style.go
@@ -31,9 +31,9 @@ const (
 	STYLE_MSGLIST_DEFAULT
 	STYLE_MSGLIST_UNREAD
 	STYLE_MSGLIST_READ
+	STYLE_MSGLIST_FLAGGED
 	STYLE_MSGLIST_DELETED
 	STYLE_MSGLIST_MARKED
-	STYLE_MSGLIST_FLAGGED
 
 	STYLE_DIRLIST_DEFAULT
 
@@ -67,9 +67,9 @@ var StyleNames = map[string]StyleObject{
 	"msglist_default": STYLE_MSGLIST_DEFAULT,
 	"msglist_unread":  STYLE_MSGLIST_UNREAD,
 	"msglist_read":    STYLE_MSGLIST_READ,
+	"msglist_flagged": STYLE_MSGLIST_FLAGGED,
 	"msglist_deleted": STYLE_MSGLIST_DELETED,
 	"msglist_marked":  STYLE_MSGLIST_MARKED,
-	"msglist_flagged": STYLE_MSGLIST_FLAGGED,
 
 	"dirlist_default": STYLE_DIRLIST_DEFAULT,
 
@@ -180,6 +180,31 @@ func (s *Style) Set(attr, val string) error {
 	return nil
 }
 
+func (s Style) composeWith(styles []*Style) Style {
+	newStyle := s
+	for _, st := range styles {
+		if st.Fg != s.Fg {
+			newStyle.Fg = st.Fg
+		}
+		if st.Bg != s.Bg {
+			newStyle.Bg = st.Bg
+		}
+		if st.Bold != s.Bold {
+			newStyle.Bold = st.Bold
+		}
+		if st.Blink != s.Blink {
+			newStyle.Blink = st.Blink
+		}
+		if st.Underline != s.Underline {
+			newStyle.Underline = st.Underline
+		}
+		if st.Reverse != s.Reverse {
+			newStyle.Reverse = st.Reverse
+		}
+	}
+	return newStyle
+}
+
 type StyleSet struct {
 	objects  map[StyleObject]*Style
 	selected map[StyleObject]*Style
@@ -213,6 +238,27 @@ func (ss StyleSet) Selected(so StyleObject) tcell.Style {
 	return ss.selected[so].Get()
 }
 
+func (ss StyleSet) Compose(so StyleObject, sos []StyleObject) tcell.Style {
+	base := *ss.objects[so]
+	styles := make([]*Style, len(sos))
+	for i, so := range sos {
+		styles[i] = ss.objects[so]
+	}
+
+	return base.composeWith(styles).Get()
+}
+
+func (ss StyleSet) ComposeSelected(so StyleObject,
+	sos []StyleObject) tcell.Style {
+	base := *ss.selected[so]
+	styles := make([]*Style, len(sos))
+	for i, so := range sos {
+		styles[i] = ss.selected[so]
+	}
+
+	return base.composeWith(styles).Get()
+}
+
 func findStyleSet(stylesetName string, stylesetsDir []string) (string, error) {
 	for _, dir := range stylesetsDir {
 		stylesetPath, err := homedir.Expand(path.Join(dir, stylesetName))