macOS: Change drag copy shortcut from Command to Option (#7325)

macOS: Replace Command + Drag shortcut key with Option + Drag
Add new header `KeyboardShortcuts.h` for platform-specific keyboard mappings

---------

Co-authored-by: Michael Gregorius <michael.gregorius.git@arcor.de>

include/KeyboardShortcuts.h

@@ -0,0 +1,77 @@
+/*
+ * KeyboardShortcuts.h - Cross-platform handling of keyboard modifier keys
+ *
+ * Copyright (c) 2025 Michael Gregorius
+ * Copyright (c) 2025 Tres Finocchiaro <tres.finocchiaro/at/gmail.com>
+ *
+ * This file is part of LMMS - https://lmms.io
+ *
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU General Public
+ * License as published by the Free Software Foundation; either
+ * version 2 of the License, or (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+ * General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public
+ * License along with this program (see COPYING); if not, write to the
+ * Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor,
+ * Boston, MA 02110-1301 USA.
+ *
+ */
+
+#ifndef LMMS_KEYBOARDSHORTCUTS_H
+#define LMMS_KEYBOARDSHORTCUTS_H
+
+#include "lmmsconfig.h"
+
+#include "qnamespace.h"
+
+
+namespace lmms
+{
+
+// Qt on macOS maps:
+//  - ControlModifier --> Command keys
+//  - MetaModifier value --> Control keys
+//  - Qt::AltModifier --> Option keys
+//
+// Our UI hints need to be adjusted to accommodate for this
+constexpr const char* UI_CTRL_KEY =
+#ifdef LMMS_BUILD_APPLE
+"⌘";
+#else
+"Ctrl";
+#endif
+
+constexpr const char* UI_ALT_KEY =
+#ifdef LMMS_BUILD_APPLE
+"Option";
+#else
+"Alt";
+#endif
+
+// UI hint for copying OR linking a UI component
+// this MUST be consistent with KBD_COPY_MODIFIER
+constexpr const char* UI_COPY_KEY =
+#ifdef LMMS_BUILD_APPLE
+UI_ALT_KEY;
+#else
+UI_CTRL_KEY;
+#endif
+
+// Shortcut for copying OR linking a UI component
+// this MUST be consistent with UI_COPY_KEY
+constexpr Qt::KeyboardModifier KBD_COPY_MODIFIER =
+#ifdef LMMS_BUILD_APPLE
+Qt::AltModifier;
+#else
+Qt::ControlModifier;
+#endif
+
+} // namespace lmms
+
+#endif // LMMS_KEYBOARDSHORTCUTS_H

include/lmms_basics.h

@@ -69,15 +69,6 @@ constexpr char LADSPA_PATH_SEPERATOR =
 #define LMMS_STRINGIFY(s) LMMS_STR(s)
 #define LMMS_STR(PN)	#PN
 
-// Abstract away GUI CTRL key (linux/windows) vs ⌘ (apple)
-constexpr const char* UI_CTRL_KEY =
-#ifdef LMMS_BUILD_APPLE
-"⌘";
-#else
-"Ctrl";
-#endif
-
-
 } // namespace lmms
 
 #endif // LMMS_TYPES_H