Selection mode: Move each ends of selection separately with slider

When the selection mode is activated, the space bar sliders change how
they affect the selection:

- The left side of the slider moves the left position of the selection.
  To shrink the selection from the left side, the slider must be
  activated by sliding to the left, extending the selection
  temporarilly, then by sliding to the right.

- The right side of the slider affects the right position if the
  selection.

srcs/juloo.keyboard2/KeyEventHandler.java

@@ -254,15 +254,17 @@ public final class KeyEventHandler
     return conn.getExtractedText(_move_cursor_req, 0);
   }
 
-  /** [repeatition] might be negative, in which case the direction is reversed. */
-  void handle_slider(KeyValue.Slider s, int repeatition)
+  /** [r] might be negative, in which case the direction is reversed. */
+  void handle_slider(KeyValue.Slider s, int r)
   {
     switch (s)
     {
-      case Cursor_left: move_cursor(-repeatition); break;
-      case Cursor_right: move_cursor(repeatition); break;
-      case Cursor_up: move_cursor_vertical(-repeatition); break;
-      case Cursor_down: move_cursor_vertical(repeatition); break;
+      case Cursor_left: move_cursor(-r); break;
+      case Cursor_right: move_cursor(r); break;
+      case Cursor_up: move_cursor_vertical(-r); break;
+      case Cursor_down: move_cursor_vertical(r); break;
+      case Selection_cursor_left: move_cursor_sel(r, true); break;
+      case Selection_cursor_right: move_cursor_sel(r, false); break;
     }
   }
 
@@ -276,12 +278,7 @@ public final class KeyEventHandler
     if (conn == null)
       return;
     ExtractedText et = get_cursor_pos(conn);
-    int system_mods =
-      KeyEvent.META_CTRL_ON | KeyEvent.META_ALT_ON | KeyEvent.META_META_ON;
-    // Fallback to sending key events if system modifiers are activated or
-    // ExtractedText is not supported, for example on Termux.
-    if (!_move_cursor_force_fallback && et != null
-        && (_meta_state & system_mods) == 0)
+    if (et != null && can_set_selection(conn))
     {
       int sel_start = et.selectionStart;
       int sel_end = et.selectionEnd;
@@ -300,8 +297,45 @@ public final class KeyEventHandler
           sel_start = sel_end;
       }
       if (conn.setSelection(sel_start, sel_end))
-        return; // [setSelection] succeeded, don't fallback to key events
+        return; // Fallback to sending key events if [setSelection] failed
     }
+    move_cursor_fallback(d);
+  }
+
+  /** Move one of the two side of a selection. If [sel_left] is true, the left
+      position is moved, otherwise the right position is moved. */
+  void move_cursor_sel(int d, boolean sel_left)
+  {
+    InputConnection conn = _recv.getCurrentInputConnection();
+    if (conn == null)
+      return;
+    ExtractedText et = get_cursor_pos(conn);
+    if (et != null && can_set_selection(conn))
+    {
+      int sel_start = et.selectionStart;
+      int sel_end = et.selectionEnd;
+      if (sel_left == (sel_start <= sel_end))
+        sel_start += d;
+      else
+        sel_end += d;
+      if (conn.setSelection(sel_start, sel_end))
+        return; // Fallback to sending key events if [setSelection] failed
+    }
+    move_cursor_fallback(d);
+  }
+
+  /** Returns whether the selection can be set using [conn.setSelection()].
+      This can happen on Termux or when system modifiers are activated for
+      example. */
+  boolean can_set_selection(InputConnection conn)
+  {
+    final int system_mods =
+      KeyEvent.META_CTRL_ON | KeyEvent.META_ALT_ON | KeyEvent.META_META_ON;
+    return !_move_cursor_force_fallback && (_meta_state & system_mods) == 0;
+  }
+
+  void move_cursor_fallback(int d)
+  {
     if (d < 0)
       send_key_down_up_repeat(KeyEvent.KEYCODE_DPAD_LEFT, -d);
     else

srcs/juloo.keyboard2/KeyModifier.java

@@ -397,6 +397,13 @@ public final class KeyModifier
           case ' ': name = "selection_cancel"; break;
         }
         break;
+      case Slider:
+        switch (k.getSlider())
+        {
+          case Cursor_left: name = "selection_cursor_left"; break;
+          case Cursor_right: name = "selection_cursor_right"; break;
+        }
+        break;
       case Keyevent:
         switch (k.getKeyevent())
         {

srcs/juloo.keyboard2/KeyValue.java

@@ -713,6 +713,9 @@ public final class KeyValue implements Comparable<KeyValue>
       case "cursor_right": return sliderKey(Slider.Cursor_right, 1);
       case "cursor_up": return sliderKey(Slider.Cursor_up, 1);
       case "cursor_down": return sliderKey(Slider.Cursor_down, 1);
+      case "selection_cancel": return editingKey("Esc", Editing.SELECTION_CANCEL, FLAG_SMALLER_FONT);
+      case "selection_cursor_left": return sliderKey(Slider.Selection_cursor_left, -1); // Move the left side of the selection
+      case "selection_cursor_right": return sliderKey(Slider.Selection_cursor_right, 1);
       // These keys are not used
       case "replaceText": return editingKey("repl", Editing.REPLACE);
       case "textAssist": return editingKey(0xE038, Editing.ASSIST);
@@ -764,7 +767,6 @@ public final class KeyValue implements Comparable<KeyValue>
 
       /* Internal keys */
       case "selection_mode": return makeInternalModifier(Modifier.SELECTION_MODE);
-      case "selection_cancel": return editingKey("Esc", Editing.SELECTION_CANCEL, FLAG_SMALLER_FONT);
 
       default: return null;
     }
@@ -782,7 +784,9 @@ public final class KeyValue implements Comparable<KeyValue>
     Cursor_left(0xE008),
     Cursor_right(0xE006),
     Cursor_up(0xE005),
-    Cursor_down(0xE007);
+    Cursor_down(0xE007),
+    Selection_cursor_left(0xE008),
+    Selection_cursor_right(0xE006);
 
     final String symbol;