Use ColorType::InheritParent in more places

cursive-core/src/printer.rs

@@ -340,13 +340,9 @@ impl<'a, 'b> Printer<'a, 'b> {
         let color = style.color;
         let effects = style.effects;
 
-        if let Some(color) = color {
         self.with_color(color, |printer| {
             printer.with_effects(effects, f);
         });
-        } else {
-            self.with_effects(effects, f);
-        }
     }
 
     /// Call the given closure with a modified printer
@@ -496,7 +492,7 @@ impl<'a, 'b> Printer<'a, 'b> {
                     ColorStyle::highlight_inactive()
                 }
             } else {
-                ColorStyle::primary()
+                ColorStyle::inherit_parent()
             },
             f,
         );

cursive-core/src/theme/color_style.rs

@@ -5,7 +5,9 @@ use super::{BaseColor, Color, ColorPair, Palette, PaletteColor};
 /// Represents a color pair role to use when printing something.
 ///
 /// The current theme will assign each role a foreground and background color.
-#[derive(Clone, Copy, Debug, PartialEq, Eq, Hash)]
+///
+/// The `Default` value is to inherit the parent's colors.
+#[derive(Clone, Copy, Debug, PartialEq, Eq, Hash, Default)]
 pub struct ColorStyle {
     /// Color used for the foreground (the text itself).
     pub front: ColorType,
@@ -42,6 +44,11 @@ impl ColorStyle {
         Self::new(ColorType::InheritParent, back)
     }
 
+    /// Uses `ColorType::InheritParent` for both front and background.
+    pub fn inherit_parent() -> Self {
+        Self::new(ColorType::InheritParent, ColorType::InheritParent)
+    }
+
     /// Style set by terminal before entering a Cursive program.
     pub fn terminal_default() -> Self {
         Self::new(Color::TerminalDefault, Color::TerminalDefault)
@@ -92,6 +99,16 @@ impl ColorStyle {
         Self::new(PaletteColor::HighlightText, PaletteColor::HighlightInactive)
     }
 
+    /// Merge the style `b` over style `a`.
+    ///
+    /// This merges the front and back color types of `a` and `b`.
+    pub fn merge(a: Self, b: Self) -> Self {
+        ColorStyle {
+            front: ColorType::merge(a.front, b.front),
+            back: ColorType::merge(a.back, b.back),
+        }
+    }
+
     /// Return the color pair that this style represents.
     pub fn resolve(
         &self,
@@ -107,25 +124,25 @@ impl ColorStyle {
 
 impl From<Color> for ColorStyle {
     fn from(color: Color) -> Self {
-        Self::new(color, PaletteColor::View)
+        Self::front(color)
     }
 }
 
 impl From<BaseColor> for ColorStyle {
     fn from(color: BaseColor) -> Self {
-        Self::new(Color::Dark(color), PaletteColor::View)
+        Self::front(Color::Dark(color))
     }
 }
 
 impl From<PaletteColor> for ColorStyle {
     fn from(color: PaletteColor) -> Self {
-        Self::new(color, PaletteColor::View)
+        Self::front(color)
     }
 }
 
 impl From<ColorType> for ColorStyle {
     fn from(color: ColorType) -> Self {
-        Self::new(color, PaletteColor::View)
+        Self::front(color)
     }
 }
 
@@ -140,6 +157,8 @@ where
 }
 
 /// Either a color from the palette, or a direct color.
+///
+/// The `Default` implementation returns `InheritParent`.
 #[derive(Clone, Copy, Debug, PartialEq, Eq, Hash)]
 pub enum ColorType {
     /// Uses a color from the application palette.
@@ -152,6 +171,12 @@ pub enum ColorType {
     InheritParent,
 }
 
+impl Default for ColorType {
+    fn default() -> Self {
+        ColorType::InheritParent
+    }
+}
+
 impl ColorType {
     /// Given a palette, resolve `self` to a concrete color.
     pub fn resolve(self, palette: &Palette, previous: Color) -> Color {
@@ -161,6 +186,17 @@ impl ColorType {
             ColorType::InheritParent => previous,
         }
     }
+
+    /// Merge the color type `b` over the color type `a`.
+    ///
+    /// This returns `b`, unless `b = ColorType::InheritParent`,
+    /// in which case it returns `a`.
+    pub fn merge(a: ColorType, b: ColorType) -> ColorType {
+        match b {
+            ColorType::InheritParent => a,
+            b => b,
+        }
+    }
 }
 
 impl From<Color> for ColorType {

cursive-core/src/theme/style.rs

@@ -16,7 +16,7 @@ pub struct Style {
     /// Color style to apply.
     ///
     /// `None` to keep using the previous colors.
-    pub color: Option<ColorStyle>,
+    pub color: ColorStyle,
 }
 
 impl Default for Style {
@@ -30,7 +30,7 @@ impl Style {
     pub fn none() -> Self {
         Style {
             effects: EnumSet::new(),
-            color: None,
+            color: ColorStyle::inherit_parent(),
         }
     }
 
@@ -54,7 +54,7 @@ impl From<Effect> for Style {
     fn from(effect: Effect) -> Self {
         Style {
             effects: enum_set!(effect),
-            color: None,
+            color: ColorStyle::inherit_parent(),
         }
     }
 }
@@ -63,7 +63,7 @@ impl From<ColorStyle> for Style {
     fn from(color: ColorStyle) -> Self {
         Style {
             effects: EnumSet::new(),
-            color: Some(color),
+            color,
         }
     }
 }
@@ -91,14 +91,11 @@ impl From<ColorType> for Style {
 /// Will use the last non-`None` color, and will combine all effects.
 impl<'a> FromIterator<&'a Style> for Style {
     fn from_iter<I: IntoIterator<Item = &'a Style>>(iter: I) -> Style {
-        let mut color = None;
+        let mut color = ColorStyle::inherit_parent();
         let mut effects = EnumSet::new();
 
         for style in iter {
-            if style.color.is_some() {
+            color = ColorStyle::merge(color, style.color);
-                color = style.color;
-            }
-
             effects.insert_all(style.effects);
         }