First-up chord send for keyboard machine

plover/gui_qt/config_keyboard_widget.ui

@@ -6,14 +6,25 @@
    <rect>
     <x>0</x>
     <y>0</y>
-    <width>117</width>
-    <height>38</height>
+    <width>159</width>
+    <height>66</height>
    </rect>
   </property>
   <property name="windowTitle">
    <string notr="true"/>
   </property>
-  <layout class="QGridLayout" name="gridLayout">
+  <layout class="QGridLayout">
+   <item row="1" column="0">
+    <widget class="QCheckBox" name="first_up_chord_send">
+     <property name="toolTip">
+      <string>When the first key in a chord is released, the chord is sent.
+If the key is pressed and released again, another chord is sent.</string>
+     </property>
+     <property name="text">
+      <string>First-up chord send</string>
+     </property>
+    </widget>
+   </item>
    <item row="0" column="0">
     <widget class="QCheckBox" name="arpeggiate">
      <property name="sizePolicy">
@@ -47,8 +58,25 @@
     </hint>
    </hints>
   </connection>
+  <connection>
+   <sender>first_up_chord_send</sender>
+   <signal>clicked(bool)</signal>
+   <receiver>KeyboardWidget</receiver>
+   <slot>on_first_up_chord_send_changed(bool)</slot>
+   <hints>
+    <hint type="sourcelabel">
+     <x>79</x>
+     <y>46</y>
+    </hint>
+    <hint type="destinationlabel">
+     <x>79</x>
+     <y>32</y>
+    </hint>
+   </hints>
+  </connection>
  </connections>
  <slots>
   <slot>on_arpeggiate_changed(bool)</slot>
+  <slot>on_first_up_chord_send_changed(bool)</slot>
  </slots>
 </ui>

plover/gui_qt/machine_options.py

@@ -214,7 +214,12 @@ def __init__(self):
     def setValue(self, value):
         self._value = copy(value)
         self.arpeggiate.setChecked(value['arpeggiate'])
+        self.first_up_chord_send.setChecked(value['first_up_chord_send'])
 
     def on_arpeggiate_changed(self, value):
         self._value['arpeggiate'] = value
         self.valueChanged.emit(self._value)
+
+    def on_first_up_chord_send_changed(self, value):
+        self._value['first_up_chord_send'] = value
+        self.valueChanged.emit(self._value)

plover/machine/keyboard.py

@@ -38,11 +38,20 @@ def __init__(self, params):
         """Monitor the keyboard's events."""
         super().__init__()
         self._arpeggiate = params['arpeggiate']
+        self._first_up_chord_send = params['first_up_chord_send']
+        if self._arpeggiate and self._first_up_chord_send:
+            self._error()
+            raise RuntimeError("Arpeggiate and first-up chord send cannot both be enabled!")
         self._is_suppressed = False
         # Currently held keys.
         self._down_keys = set()
-        # All keys part of the stroke.
-        self._stroke_keys = set()
+        if self._first_up_chord_send:
+            # If this is True, the first key in a stroke has already been released
+            # and subsequent key-up events should not send more strokes
+            self._chord_already_sent = False
+        else:
+            # Collect the keys in the stroke, in case first_up_chord_send is False
+            self._stroke_keys = set()
         self._keyboard_capture = None
         self._last_stroke_key_down_count = 0
         self._stroke_key_down_count = 0
@@ -109,31 +118,46 @@ def _key_down(self, key):
         assert key is not None
         self._stroke_key_down_count += 1
         self._down_keys.add(key)
-        self._stroke_keys.add(key)
+        if self._first_up_chord_send:
+            self._chord_already_sent = False
+        else:
+            self._stroke_keys.add(key)
 
     def _key_up(self, key):
         """Called when a key is released."""
         assert key is not None
+
         self._down_keys.discard(key)
-        # A stroke is complete if all pressed keys have been released,
-        # and — when arpeggiate mode is enabled — the arpeggiate key
-        # is part of it.
-        if (
-            self._down_keys or
-            not self._stroke_keys or
-            (self._arpeggiate and self._arpeggiate_key not in self._stroke_keys)
-        ):
-            return
+
+        if self._first_up_chord_send:
+            if self._chord_already_sent:
+                return
+        else:
+            # A stroke is complete if all pressed keys have been released,
+            # and — when arpeggiate mode is enabled — the arpeggiate key
+            # is part of it.
+            if (
+                self._down_keys or
+                not self._stroke_keys or
+                (self._arpeggiate and self._arpeggiate_key not in self._stroke_keys)
+            ):
+                return
+
         self._last_stroke_key_down_count = self._stroke_key_down_count
-        steno_keys = {self._bindings.get(k) for k in self._stroke_keys}
+        if self._first_up_chord_send:
+            steno_keys = {self._bindings.get(k) for k in self._down_keys | {key}}
+            self._chord_already_sent = True
+        else:
+            steno_keys = {self._bindings.get(k) for k in self._stroke_keys}
+            self._stroke_keys.clear()
         steno_keys -= {None}
         if steno_keys:
             self._notify(steno_keys)
-        self._stroke_keys.clear()
         self._stroke_key_down_count = 0
 
     @classmethod
     def get_option_info(cls):
         return {
             'arpeggiate': (False, boolean),
+            'first_up_chord_send': (False, boolean),
         }