Add "Visual-Mode" (#192)

* Add "Visual-Mode"

This adds a "visual-mode" file selection feature where a range-selection follows the file-cursor.

Description of usage is added to the docs.

Also, the "normal" and the new "visual-mode-selection" are now preserved
when a `DirList` is reloaded.

Wrap-up of changes:
* Add command `toggle_visual`, mapped to `V`
* Add command `escape`, mapped to `ESCAPE`
* Add style `[visual_mode_selection]` for file entries which are
  "temporarily" selected by visual-mode
* For `JoshutoDirEntry`, the attribute `selected` has been renamed to
  `permanent_selected`, and a second selection-attribute
  `visual_mode_selected` has been added. "Setters" and "getters" have
  been adapted/added accordingly. The former "getter" for the `selecetd`
  attribute still exists and returns `True` for an entry which is
  "permanant selected" _or_ "visual-mode selected". So any higher logic
  which acts on selected files does not need to care about "how" and
  entry is selected.
* Each `JoshutoDirList` has an optional index of the file where
  visual-mode has been entered and re-calculates the "visual-mode
  selecetd" status for each entry any time the cursor-index changes.
* The footer has been extended so it shows a "VIS" marker when the user
  is in visual-mode.

This implementation of visual-mode is a bit different from the ranger
one, where the visual-selection is turned into a "normal selection" when
a command (like `copy-files`) is issued. This implementation keeps
both selections separate until the user toggles back to "normal mode".
Only then the visual-selection is taken over to the "normal selection".
The user also can withdraw the visual-selection with `escape`.

The `escape` command may be used also for other "reset"-actions in the
future.

* fix syntax for Rust stable

* cargo clippy

1 files changed, 30 insertions, 0 deletions

diff --git a/src/history.rs b/src/history.rs
index 42c5b0a..162c3bd 100644
--- a/src/history.rs
+++ b/src/history.rs
@@ -156,6 +156,8 @@ pub fn create_dirlist_with_history(
 ) -> io::Result<JoshutoDirList> {
     let filter_func = options.filter_func();
     let mut contents = read_directory(path, filter_func, options)?;
+
+    // re-use directory size information on reload
     for entry in contents.iter_mut() {
         if entry.metadata.is_dir() {
             if let Some(lst) = history.get(entry.file_path()) {
@@ -164,6 +166,19 @@ pub fn create_dirlist_with_history(
         }
     }
 
+    // preserve selection status of entries on reload
+    if let Some(former_dir_list) = history.get(path) {
+        let former_entries_by_file_name = HashMap::<&str, &JoshutoDirEntry>::from_iter(
+            former_dir_list.contents.iter().map(|e| (e.file_name(), e)),
+        );
+        for entry in contents.iter_mut() {
+            if let Some(former_entry) = former_entries_by_file_name.get(entry.file_name()) {
+                entry.set_permanent_selected(former_entry.is_permanent_selected());
+                entry.set_visual_mode_selected(former_entry.is_visual_mode_selected());
+            }
+        }
+    }
+
     let sort_options = tab_options.sort_options_ref();
     contents.sort_by(|f1, f2| sort_options.compare(f1, f2));
 
@@ -199,6 +214,20 @@ pub fn create_dirlist_with_history(
             None => 0,
         }
     };
+    let visual_mode_anchor_index = match history.get(path) {
+        None => None,
+        Some(dirlist) => {
+            dirlist
+                .get_visual_mode_anchor_index()
+                .map(|old_visual_mode_anchor_index| {
+                    if old_visual_mode_anchor_index < contents_len {
+                        old_visual_mode_anchor_index
+                    } else {
+                        contents_len - 1
+                    }
+                })
+        }
+    };
 
     let metadata = JoshutoMetadata::from(path)?;
     let dirlist = JoshutoDirList::new(
@@ -206,6 +235,7 @@ pub fn create_dirlist_with_history(
         contents,
         index,
         viewport_index,
+        visual_mode_anchor_index,
         metadata,
     );