Add quick scrolling

Not ideal, but better than nothing.

Closes: https://github.com/sayanarijit/xplr/issues/509

docs/en/src/messages.md

@@ -208,8 +208,6 @@ Example:
 
 #### FocusByFileName
 
-**YAML:** `FocusByFileName: string`
-
 Focus on the file by name from the present working directory.
 
 Type: { FocusByFileName = "string" }
@@ -219,6 +217,42 @@ Example:
 - Lua: `{ FocusByFileName = "filename.ext" }`
 - YAML: `FocusByFileName: filename.ext`
 
+#### ScrollUp
+
+Scroll up by terminal height.
+
+Example:
+
+- Lua: `"ScrollUp"`
+- YAML: `ScrollUp`
+
+#### ScrollDown
+
+Scroll down by terminal height.
+
+Example:
+
+- Lua: `"ScrollDown"`
+- YAML: `ScrollDown`
+
+#### ScrollUpHalf
+
+Scroll up by half of terminal height.
+
+Example:
+
+- Lua: `"ScrollUpHalf"`
+- YAML: `ScrollUpHalf`
+
+#### ScrollDownHalf
+
+Scroll down by half of terminal height.
+
+Example:
+
+- Lua: `"ScrollDownHalf"`
+- YAML: `ScrollDownHalf`
+
 #### ChangeDirectory
 
 Change the present working directory ($PWD)

src/app.rs

@@ -406,6 +406,10 @@ impl App {
                 FocusByIndex(i) => self.focus_by_index(i),
                 FocusByIndexFromInput => self.focus_by_index_from_input(),
                 FocusByFileName(n) => self.focus_by_file_name(&n, true),
+                ScrollUp => self.scroll_up(),
+                ScrollDown => self.scroll_down(),
+                ScrollUpHalf => self.scroll_up_half(),
+                ScrollDownHalf => self.scroll_down_half(),
                 ChangeDirectory(dir) => self.change_directory(&dir, true),
                 Enter => self.enter(),
                 Back => self.back(),
@@ -635,7 +639,7 @@ impl App {
         Ok(self)
     }
 
-    fn focus_previous_by_relative_index(mut self, index: usize) -> Result<Self> {
+    pub fn focus_previous_by_relative_index(mut self, index: usize) -> Result<Self> {
         let mut history = self.history.clone();
         if let Some(dir) = self.directory_buffer_mut() {
             if let Some(n) = dir.focused_node() {
@@ -680,7 +684,7 @@ impl App {
         Ok(self)
     }
 
-    fn focus_next_by_relative_index(mut self, index: usize) -> Result<Self> {
+    pub fn focus_next_by_relative_index(mut self, index: usize) -> Result<Self> {
         let mut history = self.history.clone();
         if let Some(dir) = self.directory_buffer_mut() {
             if let Some(n) = dir.focused_node() {
@@ -927,6 +931,26 @@ impl App {
         }
     }
 
+    pub fn scroll_up(mut self) -> Result<Self> {
+        self.msg_out.push_back(MsgOut::ScrollUp);
+        Ok(self)
+    }
+
+    pub fn scroll_down(mut self) -> Result<Self> {
+        self.msg_out.push_back(MsgOut::ScrollDown);
+        Ok(self)
+    }
+
+    pub fn scroll_up_half(mut self) -> Result<Self> {
+        self.msg_out.push_back(MsgOut::ScrollUp);
+        Ok(self)
+    }
+
+    pub fn scroll_down_half(mut self) -> Result<Self> {
+        self.msg_out.push_back(MsgOut::ScrollDownHalf);
+        Ok(self)
+    }
+
     pub fn focus_path(self, path: &str, save_history: bool) -> Result<Self> {
         let mut pathbuf = PathBuf::from(path);
         if pathbuf.is_relative() {

src/init.lua

@@ -1206,6 +1206,30 @@ xplr.config.modes.builtin.default = {
           },
         },
       },
+      ["page-up"] = {
+        help = "scroll up",
+        messages = {
+          "ScrollUp",
+        },
+      },
+      ["page-down"] = {
+        help = "scroll down",
+        messages = {
+          "ScrollDown",
+        },
+      },
+      ["{"] = {
+        help = "scroll up half",
+        messages = {
+          "ScrollUpHalf",
+        },
+      },
+      ["}"] = {
+        help = "scroll down half",
+        messages = {
+          "ScrollDownHalf",
+        },
+      },
     },
     on_number = {
       help = "input",

src/msg/in_/external.rs

@@ -174,9 +174,6 @@ pub enum ExternalMsg {
     /// - YAML: `FocusByIndexFromInput`
     FocusByIndexFromInput,
 
-    ///
-    /// **YAML:** `FocusByFileName: string`
-    ///
     /// Focus on the file by name from the present working directory.
     ///
     /// Type: { FocusByFileName = "string" }
@@ -187,6 +184,38 @@ pub enum ExternalMsg {
     /// - YAML: `FocusByFileName: filename.ext`
     FocusByFileName(String),
 
+    /// Scroll up by terminal height.
+    ///
+    /// Example:
+    ///
+    /// - Lua: `"ScrollUp"`
+    /// - YAML: `ScrollUp`
+    ScrollUp,
+
+    /// Scroll down by terminal height.
+    ///
+    /// Example:
+    ///
+    /// - Lua: `"ScrollDown"`
+    /// - YAML: `ScrollDown`
+    ScrollDown,
+
+    /// Scroll up by half of terminal height.
+    ///
+    /// Example:
+    ///
+    /// - Lua: `"ScrollUpHalf"`
+    /// - YAML: `ScrollUpHalf`
+    ScrollUpHalf,
+
+    /// Scroll down by half of terminal height.
+    ///
+    /// Example:
+    ///
+    /// - Lua: `"ScrollDownHalf"`
+    /// - YAML: `ScrollDownHalf`
+    ScrollDownHalf,
+
     /// Change the present working directory ($PWD)
     ///
     /// Type: { ChangeDirectory = "string" }

src/msg/out/mod.rs

@@ -8,7 +8,6 @@ pub enum MsgOut {
     ExploreParentsAsync,
     Refresh,
     ClearScreen,
-    Quit,
     Debug(String),
     Call(Command),
     CallSilently(Command),
@@ -23,6 +22,11 @@ pub enum MsgOut {
     StartFifo(String),
     StopFifo,
     ToggleFifo(String),
+    ScrollUp,
+    ScrollDown,
+    ScrollUpHalf,
+    ScrollDownHalf,
+    Quit,
     PrintPwdAndQuit,
     PrintFocusPathAndQuit,
     PrintSelectionAndQuit,

src/runner.rs

@@ -316,6 +316,30 @@ impl Runner {
                                 terminal.clear()?;
                             }
 
+                            ScrollUp => {
+                                app = app.focus_previous_by_relative_index(
+                                    terminal.size()?.height as usize,
+                                )?;
+                            }
+
+                            ScrollDown => {
+                                app = app.focus_next_by_relative_index(
+                                    terminal.size()?.height as usize,
+                                )?;
+                            }
+
+                            ScrollUpHalf => {
+                                app = app.focus_next_by_relative_index(
+                                    terminal.size()?.height as usize / 2,
+                                )?;
+                            }
+
+                            ScrollDownHalf => {
+                                app = app.focus_next_by_relative_index(
+                                    terminal.size()?.height as usize / 2,
+                                )?;
+                            }
+
                             ExplorePwdAsync => {
                                 explorer::explore_async(
                                     app.explorer_config.clone(),