GUI: Add Ctrl+V handling in EditableWidget

In SDL2 there is SDL_GetClipboardText(), so EditableWidget could support
pasting into it.

No copying yet, as there is no selecting.

gui/widgets/editable.cpp

@@ -20,6 +20,13 @@
  *
  */
 
+#ifdef USE_SDL2
+#define FORBIDDEN_SYMBOL_ALLOW_ALL
+
+#include <SDL2/SDL.h>
+#include <SDL2/SDL_clipboard.h>
+#endif
+
 #include "common/rect.h"
 #include "common/system.h"
 #include "gui/widgets/editable.h"
@@ -185,6 +192,25 @@ bool EditableWidget::handleKeyDown(Common::KeyState state) {
 		forcecaret = true;
 		break;
 
+#ifdef USE_SDL2
+		case Common::KEYCODE_v:
+			if (state.flags & Common::KBD_CTRL) {
+				if (SDL_HasClipboardText() == SDL_TRUE) {
+					char *text = SDL_GetClipboardText();
+					if (text != nullptr) {
+						for (char *ptr = text; *ptr; ++ptr) {
+							if (tryInsertChar(*ptr, _caretPos))
+								++_caretPos;
+						}
+						dirty = true;
+					}
+				}
+			} else {
+				defaultKeyDownHandler(state, dirty, forcecaret, handled);
+			}
+			break;
+#endif
+
 #ifdef MACOSX
 	// Let ctrl-a / ctrl-e move the caret to the start / end of the line.
 	//