performable: prefix (#4345)

closes #4328
closes #3970

makes this possible now
```
keybind = performable:ctrl+c=copy_to_clipboard # copy if theres a selection else send sigint
keybind = ctrl+v=paste_from_clipboard
```

src/Surface.zig

@@ -1156,7 +1156,6 @@ pub fn updateConfig(
     }
 
     // If we are in the middle of a key sequence, clear it.
-    self.keyboard.bindings = null;
     self.endKeySequence(.drop, .free);
 
     // Before sending any other config changes, we give the renderer a new font
@@ -1853,9 +1852,6 @@ fn maybeHandleBinding(
         if (self.keyboard.bindings != null and
             !event.key.modifier())
         {
-            // Reset to the root set
-            self.keyboard.bindings = null;
-
             // Encode everything up to this point
             self.endKeySequence(.flush, .retain);
         }
@@ -1941,10 +1937,21 @@ fn maybeHandleBinding(
         return .closed;
     }
 
+    // If we have the performable flag and the action was not performed,
+    // then we act as though a binding didn't exist.
+    if (leaf.flags.performable and !performed) {
+        // If we're in a sequence, we treat this as if we pressed a key
+        // that doesn't exist in the sequence. Reset our sequence and flush
+        // any queued events.
+        self.endKeySequence(.flush, .retain);
+
+        return null;
+    }
+
     // If we consume this event, then we are done. If we don't consume
     // it, we processed the action but we still want to process our
     // encodings, too.
-    if (performed and consumed) {
+    if (consumed) {
         // If we had queued events, we deinit them since we consumed
         self.endKeySequence(.drop, .retain);
 
@@ -1986,6 +1993,10 @@ fn endKeySequence(
         );
     };
 
+    // No matter what we clear our current binding set. This restores
+    // the set we look at to the root set.
+    self.keyboard.bindings = null;
+
     if (self.keyboard.queued.items.len > 0) {
         switch (action) {
             .flush => for (self.keyboard.queued.items) |write_req| {
@@ -3889,7 +3900,11 @@ pub fn performBindingAction(self: *Surface, action: input.Binding.Action) !bool
                     log.err("error setting clipboard string err={}", .{err});
                     return true;
                 };
+
+                return true;
             }
+
+            return false;
         },
 
         .paste_from_clipboard => try self.startClipboardRequest(

src/config/Config.zig

@@ -929,6 +929,15 @@ class: ?[:0]const u8 = null,
 ///     Since they are not associated with a specific terminal surface,
 ///     they're never encoded.
 ///
+///   * `performable:` - Only consume the input if the action is able to be
+///     performed. For example, the `copy_to_clipboard` action will only
+///     consume the input if there is a selection to copy. If there is no
+///     selection, Ghostty behaves as if the keybind was not set. This has
+///     no effect with `global:` or `all:`-prefixed keybinds. For key
+///     sequences, this will reset the sequence if the action is not
+///     performable (acting identically to not having a keybind set at
+///     all).
+///
 /// Keybind triggers are not unique per prefix combination. For example,
 /// `ctrl+a` and `global:ctrl+a` are not two separate keybinds. The keybind
 /// set later will overwrite the keybind set earlier. In this case, the
@@ -2221,45 +2230,53 @@ pub fn default(alloc_gpa: Allocator) Allocator.Error!Config {
     );
 
     // Expand Selection
-    try result.keybind.set.put(
+    try result.keybind.set.putFlags(
         alloc,
         .{ .key = .{ .translated = .left }, .mods = .{ .shift = true } },
         .{ .adjust_selection = .left },
+        .{ .performable = true },
     );
-    try result.keybind.set.put(
+    try result.keybind.set.putFlags(
         alloc,
         .{ .key = .{ .translated = .right }, .mods = .{ .shift = true } },
         .{ .adjust_selection = .right },
+        .{ .performable = true },
     );
-    try result.keybind.set.put(
+    try result.keybind.set.putFlags(
         alloc,
         .{ .key = .{ .translated = .up }, .mods = .{ .shift = true } },
         .{ .adjust_selection = .up },
+        .{ .performable = true },
     );
-    try result.keybind.set.put(
+    try result.keybind.set.putFlags(
         alloc,
         .{ .key = .{ .translated = .down }, .mods = .{ .shift = true } },
         .{ .adjust_selection = .down },
+        .{ .performable = true },
     );
-    try result.keybind.set.put(
+    try result.keybind.set.putFlags(
         alloc,
         .{ .key = .{ .translated = .page_up }, .mods = .{ .shift = true } },
         .{ .adjust_selection = .page_up },
+        .{ .performable = true },
     );
-    try result.keybind.set.put(
+    try result.keybind.set.putFlags(
         alloc,
         .{ .key = .{ .translated = .page_down }, .mods = .{ .shift = true } },
         .{ .adjust_selection = .page_down },
+        .{ .performable = true },
     );
-    try result.keybind.set.put(
+    try result.keybind.set.putFlags(
         alloc,
         .{ .key = .{ .translated = .home }, .mods = .{ .shift = true } },
         .{ .adjust_selection = .home },
+        .{ .performable = true },
     );
-    try result.keybind.set.put(
+    try result.keybind.set.putFlags(
         alloc,
         .{ .key = .{ .translated = .end }, .mods = .{ .shift = true } },
         .{ .adjust_selection = .end },
+        .{ .performable = true },
     );
 
     // Tabs common to all platforms
@@ -2509,10 +2526,11 @@ pub fn default(alloc_gpa: Allocator) Allocator.Error!Config {
             .{ .key = .{ .translated = .q }, .mods = .{ .super = true } },
             .{ .quit = {} },
         );
-        try result.keybind.set.put(
+        try result.keybind.set.putFlags(
             alloc,
             .{ .key = .{ .translated = .k }, .mods = .{ .super = true } },
             .{ .clear_screen = {} },
+            .{ .performable = true },
         );
         try result.keybind.set.put(
             alloc,

src/input/Binding.zig

@@ -36,6 +36,11 @@ pub const Flags = packed struct {
     /// and not just while Ghostty is focused. This may not work on all platforms.
     /// See the keybind config documentation for more information.
     global: bool = false,
+
+    /// True if this binding should only be triggered if the action can be
+    /// performed. If the action can't be performed then the binding acts as
+    /// if it doesn't exist.
+    performable: bool = false,
 };
 
 /// Full binding parser. The binding parser is implemented as an iterator
@@ -90,6 +95,9 @@ pub const Parser = struct {
             } else if (std.mem.eql(u8, prefix, "unconsumed")) {
                 if (!flags.consumed) return Error.InvalidFormat;
                 flags.consumed = false;
+            } else if (std.mem.eql(u8, prefix, "performable")) {
+                if (flags.performable) return Error.InvalidFormat;
+                flags.performable = true;
             } else {
                 // If we don't recognize the prefix then we're done.
                 // There are trigger-specific prefixes like "physical:" so
@@ -1688,6 +1696,16 @@ test "parse: triggers" {
         .flags = .{ .consumed = false },
     }, try parseSingle("unconsumed:physical:a+shift=ignore"));
 
+    // performable keys
+    try testing.expectEqual(Binding{
+        .trigger = .{
+            .mods = .{ .shift = true },
+            .key = .{ .translated = .a },
+        },
+        .action = .{ .ignore = {} },
+        .flags = .{ .performable = true },
+    }, try parseSingle("performable:shift+a=ignore"));
+
     // invalid key
     try testing.expectError(Error.InvalidFormat, parseSingle("foo=ignore"));