config: add scrollback-{up,down}-half key bindings

These new bindings scroll up/down half a page in the
scrollback (instead of the full page scrolled by
‘scrollback-{up,down}’).

Closes #128.

CHANGELOG.md

@@ -64,6 +64,9 @@
   `-W,--window-size-chars` command line option to `foot`. This option
   configures the initial window size in **characters**, and is an
   alternative to **initial-window-size-pixels**.
+* **scrollback-up-half** and **scrollback-down-half** key
+  bindings. They scroll up/down half of a page in the scrollback
+  (https://codeberg.org/dnkl/foot/issues/128).
 
 
 ### Removed

config.c

@@ -56,7 +56,9 @@ static const uint32_t default_bright[] = {
 static const char *const binding_action_map[] = {
     [BIND_ACTION_NONE] = NULL,
     [BIND_ACTION_SCROLLBACK_UP] = "scrollback-up",
+    [BIND_ACTION_SCROLLBACK_UP_HALF] = "scrollback-up-half",
     [BIND_ACTION_SCROLLBACK_DOWN] = "scrollback-down",
+    [BIND_ACTION_SCROLLBACK_DOWN_HALF] = "scrollback-down-half",
     [BIND_ACTION_CLIPBOARD_COPY] = "clipboard-copy",
     [BIND_ACTION_CLIPBOARD_PASTE] = "clipboard-paste",
     [BIND_ACTION_PRIMARY_PASTE] = "primary-paste",

doc/foot.ini.5.scd

@@ -239,10 +239,19 @@ default binding. This can be done by setting _action=none_;
 e.g. *search-start=none*.
 
 *scrollback-up*
-	Scrolls up/back in history. Default: _Shift+Page\_Up_.
+	Scrolls up/back one page in history. Default: _Shift+Page\_Up_.
+
+*scrollback-up-half*
+	Scrolls up/back half of a page in history. Default:
+	_Shift+Page\_Up_.
 
 *scrollback-down*
-	Scroll down/forward in history. Default: _Shift+Page\_Down_.
+	Scroll down/forward one page in history. Default:
+	_Shift+Page\_Down_.
+
+*scrollback-down-half*
+	Scroll down/forward half of a page in history. Default:
+	_Shift+Page\_Down_.
 
 *clipboard-copy*
 	Copies the current selection into the _clipboard_. Default: _Control+Shift+C_.

foot.ini

@@ -58,7 +58,9 @@
 
 [key-bindings]
 # scrollback-up=Shift+Page_Up
+# scrollback-up-half=none
 # scrollback-down=Shift+Page_Down
+# scrollback-down-half=none
 # clipboard-copy=Control+Shift+C
 # clipboard-paste=Control+Shift+V
 # search-start=Control+Shift+R

input.c

@@ -91,10 +91,18 @@ execute_binding(struct seat *seat, struct terminal *term,
         cmd_scrollback_up(term, term->rows);
         return true;
 
+    case BIND_ACTION_SCROLLBACK_UP_HALF:
+        cmd_scrollback_up(term, max(term->rows / 2, 1));
+        return true;
+
     case BIND_ACTION_SCROLLBACK_DOWN:
         cmd_scrollback_down(term, term->rows);
         return true;
 
+    case BIND_ACTION_SCROLLBACK_DOWN_HALF:
+        cmd_scrollback_down(term, max(term->rows / 2, 1));
+        return true;
+
     case BIND_ACTION_CLIPBOARD_COPY:
         selection_to_clipboard(seat, term, serial);
         return true;

wayland.h

@@ -27,7 +27,9 @@ typedef tll(struct key_binding) key_binding_list_t;
 enum bind_action_normal {
     BIND_ACTION_NONE,
     BIND_ACTION_SCROLLBACK_UP,
+    BIND_ACTION_SCROLLBACK_UP_HALF,
     BIND_ACTION_SCROLLBACK_DOWN,
+    BIND_ACTION_SCROLLBACK_DOWN_HALF,
     BIND_ACTION_CLIPBOARD_COPY,
     BIND_ACTION_CLIPBOARD_PASTE,
     BIND_ACTION_PRIMARY_PASTE,