Tab theme configurable (#317)

Text style for tabs can be configured within
`theme.toml` with the dotted keys `tab.active` and `tab.inactive`.

The default style is the same as the former hard-coded style.

`theme.toml` has been restructured and comments have been
added to give a short documentation on each style item.

The documentation (`theme.toml.md`) has been enhanced, and
the excerpt of `theme.toml` with additional comments has
been removed from there.

That way it should be easier for devs to keep docs and the default
`theme.toml` in sync, and easier for users when the detail comments
can be found in the configuration file itself.

The conversion from `AppStyle` to `tui::style::Style` is now provided as
a function of `AppStyle` and a `From`-implementation for `Style` to
avoid having the same factory code repeating all over.

1 files changed, 44 insertions, 6 deletions

diff --git a/config/theme.toml b/config/theme.toml
index 840d2b0..c26502f 100644
--- a/config/theme.toml
+++ b/config/theme.toml
@@ -1,7 +1,24 @@
+##########################################
+## Tabs
+##########################################
+
+# Inactive tabs
+[tabs.inactive]
+
+# Active tabs
+[tabs.active]
+invert=true
+
+##########################################
+## File List - Selections
+##########################################
+
+# Selected files (standard selection)
 [selection]
 fg = "light_yellow"
 bold = true
 
+# Files selected in current visual mode
 [visual_mode_selection]
 fg = "light_red"
 bold = true
@@ -10,28 +27,49 @@ bold = true
 prefix = "  "
 size = 2
 
-[executable]
-fg = "light_green"
-bold = true
+##########################################
+## File List - System File Types
+##########################################
 
+# Basic style, used for regular files (and also device files and FIFOs)
 [regular]
 fg = "white"
 
+# For directories
 [directory]
 fg = "light_blue"
 bold = true
 
+# For symbolic links
 [link]
 fg = "cyan"
 bold = true
 
+# For socket files
+[socket]
+fg = "light_magenta"
+bold = true
+
+##########################################
+## File List - Exceptional Files
+##########################################
+
+# Files marked as executable
+[executable]
+fg = "light_green"
+bold = true
+
+# Invalid symbolic links (pointing to non-existing target)
 [link_invalid]
 fg = "red"
 bold = true
 
-[socket]
-fg = "light_magenta"
-bold = true
+##########################################
+## File list - Override style by extension
+##########################################
+# This sections allows to override the basic 
+# style with a specific style for the file's
+# extension.
 
 [ext]