wezterm: add ClearScrollback key assignment

Bound to CMD-K and CTRL+SHIFT-K by default.  This also functions
while the output is filling up (eg: `find /` and hit the key binding
to keep pruning the scrollback).

closes: https://github.com/wez/wezterm/issues/194

docs/changelog.markdown

@@ -19,6 +19,7 @@ brief notes about them may accumulate here.
   followed an example from the docs; migrate instead to using eg:
   `action=wezterm.action{ActivateTab=i-1}` to pass the integer argument.
 * Windows: now also available with a setup.exe installer
+* Added `ClearScrollback` key assignment to clear the scrollback.  This is bound to CMD-K and CTRL-SHIFT-K by default.
 
 ### 20200517-122836-92c201c6
 

docs/config/keys.markdown

@@ -62,6 +62,8 @@ The default key bindings are:
 | `SUPER`          | `r`    | `ReloadConfiguration` |
 | `CTRL+SHIFT`     | `R`    | `ReloadConfiguration` |
 | `SUPER`          | `h`    | `HideApplication` (macOS only) |
+| `SUPER`          | `k`    | `ClearScrollback` |
+| `CTRL+SHIFT`     | `K`    | `ClearScrollback` |
 
 ## Default Mouse Assignments
 
@@ -538,6 +540,19 @@ return {
 }
 ```
 
+## ClearScrollback
+
+Clears the lines that have scrolled off the top of the viewport, resetting
+the scrollbar thumb to the full height of the window.
+
+```lua
+return {
+  keys = {
+    {key="K", mods="CTRL|SHIFT", action="ClearScrollback"}
+  }
+}
+```
+
 ## ReloadConfiguration
 
 Explicitly reload the configuration.

src/frontend/gui/termwindow.rs

@@ -1469,6 +1469,11 @@ impl TermWindow {
                     window.invalidate();
                 }
             }
+            ClearScrollback => {
+                tab.erase_scrollback();
+                let window = self.window.as_ref().unwrap();
+                window.invalidate();
+            }
         };
         Ok(())
     }

src/keyassignment.rs

@@ -97,6 +97,7 @@ pub enum KeyAssignment {
     SpawnCommandInNewTab(SpawnCommand),
     SpawnCommandInNewWindow(SpawnCommand),
     ShowLauncher,
+    ClearScrollback,
 
     SelectTextAtMouseCursor(SelectionMode),
     ExtendSelectionToMouseCursor(Option<SelectionMode>),
@@ -158,6 +159,8 @@ impl InputMap {
             [KeyModifiers::SUPER, KeyCode::Char('n'), SpawnWindow],
             [ctrl_shift, KeyCode::Char('M'), Hide],
             [ctrl_shift, KeyCode::Char('N'), SpawnWindow],
+            [KeyModifiers::SUPER, KeyCode::Char('k'), ClearScrollback],
+            [ctrl_shift, KeyCode::Char('K'), ClearScrollback],
             // Font size manipulation
             [KeyModifiers::CTRL, KeyCode::Char('-'), DecreaseFontSize],
             [KeyModifiers::CTRL, KeyCode::Char('0'), ResetFontSize],

src/localtab.rs

@@ -91,6 +91,10 @@ impl Tab for LocalTab {
         self.domain_id
     }
 
+    fn erase_scrollback(&self) {
+        self.terminal.borrow_mut().erase_scrollback();
+    }
+
     fn is_mouse_grabbed(&self) -> bool {
         self.terminal.borrow().is_mouse_grabbed()
     }

src/mux/tab.rs

@@ -59,6 +59,8 @@ pub trait Tab: Downcast {
     fn palette(&self) -> ColorPalette;
     fn domain_id(&self) -> DomainId;
 
+    fn erase_scrollback(&self) {}
+
     /// Returns true if the terminal has grabbed the mouse and wants to
     /// give the embedded application a chance to process events.
     /// In practice this controls whether the gui will perform local

term/src/terminalstate.rs

@@ -487,6 +487,10 @@ impl TerminalState {
         }
     }
 
+    pub fn erase_scrollback(&mut self) {
+        self.screen_mut().erase_scrollback();
+    }
+
     pub fn is_mouse_grabbed(&self) -> bool {
         self.sgr_mouse
     }