Terminal: Allow use of Option as Meta key

Add a configuration setting that allows the left Option key to be used as a
Meta key, and add support for the Escape sequences that control the Meta key's
behaviour.

TermWindow now maintains a copy, shared by all its component TermViews, of the
current key map, and updates this copy automatically when notified by the Input
Server a new key map has been loaded.

The Meta key was an extra modifier key present on early UNIX workstations that
provided access to the "extended" portion of the ASCII character set. Although
it has vanished from modern keyboards certain UNIX software still relies on the
key, most notably GNU Emacs and the GNU readline library, the latter of which
is used by bash and a wide variety of other software that reads input from a
terminal. (Python's interactive mode uses readline, for instance.)

With this patch applied and the new setting enabled, the left Option key can be
used to access additional editing and navigation features at the command line.
It also makes usable the port of GNU Emacs currently available from HaikuDepot.

Fixes #15294.

Change-Id: I150b640b7b18384d56ab2fb017bf16ce8bdbdd78
Reviewed-on: https://review.haiku-os.org/c/haiku/+/1727
Reviewed-by: waddlesplash <waddlesplash@gmail.com>

src/apps/terminal/AppearPrefView.cpp

@@ -65,6 +65,10 @@ AppearancePrefView::AppearancePrefView(const char* name,
 		B_TRANSLATE("Allow bold text"),
 			new BMessage(MSG_ALLOW_BOLD_CHANGED));
 
+	fUseOptionAsMetaKey = new BCheckBox(
+		B_TRANSLATE("Use left Option as Meta key"),
+			new BMessage(MSG_USE_OPTION_AS_META_CHANGED));
+
 	fWarnOnExit = new BCheckBox(
 		B_TRANSLATE("Confirm exit if active programs exist"),
 			new BMessage(MSG_WARN_ON_EXIT_CHANGED));
@@ -140,6 +144,7 @@ AppearancePrefView::AppearancePrefView(const char* name,
 			B_CELLS_32x8, 8.0, "", new BMessage(MSG_COLOR_CHANGED)))
 		.Add(fBlinkCursor)
 		.Add(fAllowBold)
+		.Add(fUseOptionAsMetaKey)
 		.Add(fWarnOnExit);
 
 	fTabTitle->SetAlignment(B_ALIGN_RIGHT, B_ALIGN_LEFT);
@@ -172,6 +177,7 @@ AppearancePrefView::Revert()
 
 	fBlinkCursor->SetValue(pref->getBool(PREF_BLINK_CURSOR));
 	fAllowBold->SetValue(pref->getBool(PREF_ALLOW_BOLD));
+	fUseOptionAsMetaKey->SetValue(pref->getBool(PREF_USE_OPTION_AS_META));
 	fWarnOnExit->SetValue(pref->getBool(PREF_WARN_ON_EXIT));
 
 	_SetCurrentColorScheme();
@@ -194,6 +200,7 @@ AppearancePrefView::AttachedToWindow()
 	fWindowTitle->SetTarget(this);
 	fBlinkCursor->SetTarget(this);
 	fAllowBold->SetTarget(this);
+	fUseOptionAsMetaKey->SetTarget(this);
 	fWarnOnExit->SetTarget(this);
 
 	fFontField->Menu()->SetTargetForItems(this);
@@ -338,6 +345,15 @@ AppearancePrefView::MessageReceived(BMessage* msg)
 			}
 			break;
 
+		case MSG_USE_OPTION_AS_META_CHANGED:
+			if (PrefHandler::Default()->getBool(PREF_USE_OPTION_AS_META)
+				!= fUseOptionAsMetaKey->Value()) {
+					PrefHandler::Default()->setBool(PREF_USE_OPTION_AS_META,
+						fUseOptionAsMetaKey->Value());
+					modified = true;
+			}
+			break;
+
 		case MSG_WARN_ON_EXIT_CHANGED:
 			if (PrefHandler::Default()->getBool(PREF_WARN_ON_EXIT)
 				!= fWarnOnExit->Value()) {

src/apps/terminal/AppearPrefView.h

@@ -25,6 +25,7 @@ static const uint32 MSG_TAB_TITLE_SETTING_CHANGED		= 'mtts';
 static const uint32 MSG_WINDOW_TITLE_SETTING_CHANGED	= 'mwts';
 static const uint32 MSG_BLINK_CURSOR_CHANGED			= 'mbcc';
 static const uint32 MSG_ALLOW_BOLD_CHANGED				= 'mabc';
+static const uint32 MSG_USE_OPTION_AS_META_CHANGED		= 'momc';
 static const uint32 MSG_WARN_ON_EXIT_CHANGED			= 'mwec';
 static const uint32 MSG_COLS_CHANGED					= 'mccl';
 static const uint32 MSG_HISTORY_CHANGED					= 'mhst';
@@ -78,6 +79,7 @@ private:
 
 			BCheckBox*			fBlinkCursor;
 			BCheckBox*			fAllowBold;
+			BCheckBox*			fUseOptionAsMetaKey;
 			BCheckBox*			fWarnOnExit;
 			BMenuField*			fFontField;
 

src/apps/terminal/PrefHandler.cpp

@@ -9,6 +9,7 @@
  * Authors:
  *		Kian Duffy, myob@users.sourceforge.net
  *		Daniel Furrer, assimil8or@users.sourceforge.net
+ *		Simon South, simon@simonsouth.net
  *		Siarzhuk Zharski, zharik@gmx.li
  */
 
@@ -89,6 +90,7 @@ static const pref_defaults kTermDefaults[] = {
 	{ PREF_TAB_TITLE,			"%1d: %p%e" },
 	{ PREF_WINDOW_TITLE,		"%T% i: %t" },
 	{ PREF_BLINK_CURSOR,		PREF_TRUE },
+	{ PREF_USE_OPTION_AS_META,	PREF_FALSE },
 	{ PREF_WARN_ON_EXIT,		PREF_TRUE },
 	{ PREF_CURSOR_STYLE,		PREF_BLOCK_CURSOR },
 	{ PREF_EMULATE_BOLD,		PREF_FALSE },

src/apps/terminal/TermApp.cpp

@@ -8,6 +8,7 @@
  * Authors:
  *		Jeremiah Bailey, <jjbailey@gmail.com>
  *		Kian Duffy, <myob@users.sourceforge.net>
+ *		Simon South, simon@simonsouth.net
  *		Siarzhuk Zharski, <zharik@gmx.li>
  */
 
@@ -179,6 +180,10 @@ void
 TermApp::MessageReceived(BMessage* message)
 {
 	switch (message->what) {
+		case B_KEY_MAP_LOADED:
+			fTermWindow->PostMessage(message);
+			break;
+
 		case MSG_ACTIVATE_TERM:
 			fTermWindow->Activate();
 			break;

src/apps/terminal/TermConst.h

@@ -7,6 +7,7 @@
  *
  * Authors:
  *		Kian Duffy, myob@users.sourceforge.net
+ *		Simon South, simon@simonsouth.net
  *		Siarzhuk Zharski, zharik@gmx.li
  */
 #ifndef TERMCONST_H_INCLUDED
@@ -79,6 +80,7 @@ static const uint32 MSG_SET_TERMINAL_TITLE				= 'sett';
 static const uint32 MSG_SET_TERMINAL_COLORS				= 'setc';
 static const uint32 MSG_RESET_TERMINAL_COLORS			= 'rstc';
 static const uint32 MSG_QUIT_TERMNAL					= 'qutt';
+static const uint32 MSG_ENABLE_META_KEY					= 'emtk';
 static const uint32 MSG_REPORT_MOUSE_EVENT				= 'mous';
 static const uint32 MSG_SAVE_WINDOW_POSITION			= 'swps';
 static const uint32 MSG_MOVE_TAB_LEFT					= 'mvtl';
@@ -133,6 +135,8 @@ static const char* const PREF_TEXT_ENCODING = "Text encoding";
 
 static const char* const PREF_BLINK_CURSOR = "Blinking cursor";
 static const char* const PREF_ALLOW_BOLD = "Allow bold text";
+static const char* const PREF_USE_OPTION_AS_META =
+	"Use left Option as Meta key";
 static const char* const PREF_WARN_ON_EXIT = "Warn on exit";
 static const char* const PREF_CURSOR_STYLE = "Cursor style";
 static const char* const PREF_EMULATE_BOLD = "Emulate bold";

src/apps/terminal/TermParse.cpp

@@ -6,6 +6,7 @@
  *
  * Authors:
  *		Kian Duffy, myob@users.sourceforge.net
+ *		Simon South, simon@simonsouth.net
  *		Siarzhuk Zharski, zharik@gmx.li
  */
 
@@ -1395,12 +1396,12 @@ TermParse::_DecPrivateModeSet(int value)
 			fBuffer->ReportAnyMouseEvent(true);
 			break;
 		case 1034:
-			// TODO: Interprete "meta" key, sets eighth bit.
+			// Interpret "meta" key, sets eighth bit.
-			// Not supported yet.
+			fBuffer->EnableInterpretMetaKey(true);
 			break;
 		case 1036:
-			// TODO: Send ESC when Meta modifies a key
+			// Send ESC when Meta modifies a key
-			// Not supported yet.
+			fBuffer->EnableMetaKeySendsEscape(true);
 			break;
 		case 1039:
 			// TODO: Send ESC when Alt modifies a key
@@ -1470,12 +1471,12 @@ TermParse::_DecPrivateModeReset(int value)
 			fBuffer->ReportAnyMouseEvent(false);
 			break;
 		case 1034:
-			// Don't interprete "meta" key.
+			// Don't interpret "meta" key.
-			// Not supported yet.
+			fBuffer->EnableInterpretMetaKey(false);
 			break;
 		case 1036:
-			// TODO: Don't send ESC when Meta modifies a key
+			// Don't send ESC when Meta modifies a key
-			// Not supported yet.
+			fBuffer->EnableMetaKeySendsEscape(false);
 			break;
 		case 1039:
 			// TODO: Don't send ESC when Alt modifies a key

src/apps/terminal/TermView.cpp

@@ -9,6 +9,7 @@
  *		Kian Duffy, myob@users.sourceforge.net
  *		Y.Hayakawa, hida@sawada.riec.tohoku.ac.jp
  *		Jonathan Schleifer, js@webkeks.org
+ *		Simon South, simon@simonsouth.net
  *		Ingo Weinhold, ingo_weinhold@gmx.de
  *		Clemens Zeidler, haiku@Clemens-Zeidler.de
  *		Siarzhuk Zharski, zharik@gmx.li
@@ -307,6 +308,11 @@ TermView::_InitObject(const ShellParameters& shellParameters)
 	fSelection.SetHighlighter(this);
 	fSelection.SetRange(TermPos(0, 0), TermPos(0, 0));
 	fPrevPos = TermPos(-1, - 1);
+	fKeymap = NULL;
+	fKeymapChars = NULL;
+	fUseOptionAsMetaKey = false;
+	fInterpretMetaKey = true;
+	fMetaKeySendsEscape = true;
 	fReportX10MouseEvent = false;
 	fReportNormalMouseEvent = false;
 	fReportButtonMouseEvent = false;
@@ -719,6 +725,33 @@ TermView::SetEncoding(int encoding)
 }
 
 
+void
+TermView::SetKeymap(const key_map* keymap, const char* chars)
+{
+	delete fKeymap;
+	delete[] fKeymapChars;
+
+	fKeymap = keymap;
+	fKeymapChars = chars;
+
+	fKeymapTableForModifiers.Put(B_SHIFT_KEY,
+		&fKeymap->shift_map);
+	fKeymapTableForModifiers.Put(B_CAPS_LOCK,
+		&fKeymap->caps_map);
+	fKeymapTableForModifiers.Put(B_CAPS_LOCK | B_SHIFT_KEY,
+		&fKeymap->caps_shift_map);
+	fKeymapTableForModifiers.Put(B_CONTROL_KEY,
+		&fKeymap->control_map);
+}
+
+
+void
+TermView::SetUseOptionAsMetaKey(bool enable)
+{
+	fUseOptionAsMetaKey = enable && fKeymap != NULL && fKeymapChars != NULL;
+}
+
+
 void
 TermView::SetMouseClipboard(BClipboard *clipboard)
 {
@@ -1801,6 +1834,16 @@ TermView::MessageReceived(BMessage *msg)
 				fCursorHidden = hidden;
 			break;
 		}
+		case MSG_ENABLE_META_KEY:
+		{
+			bool enable;
+			if (msg->FindBool("enableInterpretMetaKey", &enable) == B_OK)
+				fInterpretMetaKey = enable;
+
+			if (msg->FindBool("enableMetaKeySendsEscape", &enable) == B_OK)
+				fMetaKeySendsEscape = enable;
+			break;
+		}
 		case MSG_REPORT_MOUSE_EVENT:
 		{
 			bool report;

src/apps/terminal/TermView.h

@@ -7,6 +7,7 @@
  * Authors:
  *		Stefano Ceccherini, stefano.ceccherini@gmail.com
  *		Kian Duffy, myob@users.sourceforge.net
+ *		Simon South, simon@simonsouth.net
  *		Ingo Weinhold, ingo_weinhold@gmx.de
  *		Siarzhuk Zharski, zharik@gmx.li
  */
@@ -15,6 +16,8 @@
 
 
 #include <Autolock.h>
+#include <HashMap.h>
+#include <InterfaceDefs.h>
 #include <Messenger.h>
 #include <ObjectList.h>
 #include <String.h>
@@ -98,6 +101,10 @@ public:
 			void				SetScrollBar(BScrollBar* scrollBar);
 			BScrollBar*			ScrollBar() const { return fScrollBar; };
 
+			void				SetKeymap(const key_map* keymap,
+									const char* chars);
+			void				SetUseOptionAsMetaKey(bool enable);
+
 			void				SetMouseClipboard(BClipboard *);
 
 			void				MakeDebugSnapshots();
@@ -335,6 +342,15 @@ private:
 
 			HighlightList		fHighlights;
 
+			// keyboard
+			const key_map*		fKeymap;
+			const char*			fKeymapChars;
+			HashMap<HashKey32<int32>, const int(*)[128]>
+								fKeymapTableForModifiers;
+			bool				fUseOptionAsMetaKey;
+			bool				fInterpretMetaKey;
+			bool				fMetaKeySendsEscape;
+
 			// mouse
 			int32				fMouseButtons;
 			int32				fModifiers;

src/apps/terminal/TermViewStates.cpp

@@ -8,6 +8,7 @@
  *		Stefano Ceccherini, stefano.ceccherini@gmail.com
  *		Kian Duffy, myob@users.sourceforge.net
  *		Y.Hayakawa, hida@sawada.riec.tohoku.ac.jp
+ *		Simon South, simon@simonsouth.net
  *		Ingo Weinhold, ingo_weinhold@gmx.de
  *		Clemens Zeidler, haiku@Clemens-Zeidler.de
  *		Siarzhuk Zharski, zharik@gmx.li
@@ -208,6 +209,55 @@ TermView::DefaultState::KeyDown(const char* bytes, int32 numBytes)
 
 	fView->_ActivateCursor(true);
 
+	// Handle the Option key when used as Meta
+	if ((mod & B_LEFT_OPTION_KEY) != 0 && fView->fUseOptionAsMetaKey
+		&& (fView->fInterpretMetaKey || fView->fMetaKeySendsEscape)) {
+		const char* bytes;
+		int8 numBytes;
+
+		// Determine the character produced by the same keypress without the
+		// Option key
+		mod &= B_SHIFT_KEY | B_CAPS_LOCK | B_CONTROL_KEY;
+		if (mod == 0) {
+			bytes = (const char*)&rawChar;
+			numBytes = 1;
+		} else {
+			const int (*keymapTable)[128] =
+				fView->fKeymapTableForModifiers.Get(mod);
+			bytes = &fView->fKeymapChars[(*keymapTable)[key]];
+			numBytes = *(bytes++);
+		}
+
+		if (numBytes <= 0)
+			return;
+
+		fView->_ScrollTo(0, true);
+
+		char outputBuffer[2];
+		const char* toWrite = bytes;
+
+		if (fView->fMetaKeySendsEscape) {
+			fView->fShell->Write("\e", 1);
+		} else if (numBytes == 1) {
+			char byte = *bytes | 0x80;
+
+			// The eighth bit has special meaning in UTF-8, so if that encoding
+			// is in use recode the output (as xterm does)
+			if (fView->fEncoding == M_UTF8) {
+				outputBuffer[0] = 0xc0 | ((byte >> 6) & 0x03);
+				outputBuffer[1] = 0x80 | (byte & 0x3f);
+				numBytes = 2;
+			} else {
+				outputBuffer[0] = byte;
+				numBytes = 1;
+			}
+			toWrite = outputBuffer;
+		}
+
+		fView->fShell->Write(toWrite, numBytes);
+		return;
+	}
+
 	// handle multi-byte chars
 	if (numBytes > 1) {
 		if (fView->fEncoding != M_UTF8) {

src/apps/terminal/TermWindow.cpp

@@ -10,6 +10,7 @@
  *		Kian Duffy, myob@users.sourceforge.net
  *		Daniel Furrer, assimil8or@users.sourceforge.net
  *		John Scipione, jscipione@gmail.com
+ *		Simon South, simon@simonsouth.net
  *		Siarzhuk Zharski, zharik@gmx.li
  */
 
@@ -202,6 +203,9 @@ TermWindow::TermWindow(const BString& title, Arguments* args)
 	fTerminalRoster.SetListener(this);
 	int32 id = fTerminalRoster.ID();
 
+	// fetch the current keymap
+	get_key_map(&fKeymap, &fKeymapChars);
+
 	// apply the title settings
 	fTitle.pattern = title;
 	if (fTitle.pattern.Length() == 0) {
@@ -272,6 +276,9 @@ TermWindow::~TermWindow()
 
 	for (int32 i = 0; Session* session = _SessionAt(i); i++)
 		delete session;
+
+	delete fKeymap;
+	delete[] fKeymapChars;
 }
 
 
@@ -673,6 +680,10 @@ TermWindow::MessageReceived(BMessage *message)
 	bool findresult;
 
 	switch (message->what) {
+		case B_KEY_MAP_LOADED:
+			_UpdateKeymap();
+			break;
+
 		case B_COPY:
 			_ActiveTermView()->Copy(be_clipboard);
 			break;
@@ -895,6 +906,18 @@ TermWindow::MessageReceived(BMessage *message)
 			break;
 		}
 
+		case MSG_USE_OPTION_AS_META_CHANGED:
+		{
+			bool useOptionAsMetaKey
+				= PrefHandler::Default()->getBool(PREF_USE_OPTION_AS_META);
+
+			for (int32 i = 0; i < fTabView->CountTabs(); i++) {
+				TermView* view = _TermViewAt(i);
+				view->SetUseOptionAsMetaKey(useOptionAsMetaKey);
+			}
+			break;
+		}
+
 		case FULLSCREEN:
 			if (!fSavedFrame.IsValid()) { // go fullscreen
 				_ActiveTermView()->DisableResizeView();
@@ -1306,6 +1329,10 @@ TermWindow::_AddTab(Arguments* args, const BString& currentDirectory)
 		if (charset != NULL)
 			view->SetEncoding(charset->GetConversionID());
 
+		view->SetKeymap(fKeymap, fKeymapChars);
+		view->SetUseOptionAsMetaKey(
+			PrefHandler::Default()->getBool(PREF_USE_OPTION_AS_META));
+
 		_SetTermColors(containerView);
 
 		int32 tabIndex = fTabView->CountTabs() - 1;
@@ -1994,3 +2021,18 @@ TermWindow::_MoveWindowInScreen(BWindow* window)
 	BSize screenSize(BScreen(window).Frame().Size());
 	window->MoveTo(BLayoutUtils::MoveIntoFrame(frame, screenSize).LeftTop());
 }
+
+
+void
+TermWindow::_UpdateKeymap()
+{
+	delete fKeymap;
+	delete[] fKeymapChars;
+
+	get_key_map(&fKeymap, &fKeymapChars);
+
+	for (int32 i = 0; i < fTabView->CountTabs(); i++) {
+		TermView* view = _TermViewAt(i);
+		view->SetKeymap(fKeymap, fKeymapChars);
+	}
+}

src/apps/terminal/TermWindow.h

@@ -32,6 +32,7 @@
 #define TERM_WINDOW_H
 
 
+#include <InterfaceDefs.h>
 #include <MessageRunner.h>
 #include <String.h>
 #include <Window.h>
@@ -188,6 +189,8 @@ private:
 
 			void				_MoveWindowInScreen(BWindow* window);
 
+			void				_UpdateKeymap();
+
 private:
 			TerminalRoster		fTerminalRoster;
 
@@ -228,6 +231,9 @@ private:
 			bool				fMatchWord;
 
 			bool				fFullScreen;
+
+			key_map*			fKeymap;
+			char*				fKeymapChars;
 };
 
 

src/apps/terminal/TerminalBuffer.cpp

@@ -5,6 +5,7 @@
  *
  * Authors:
  *		Ingo Weinhold, ingo_weinhold@gmx.de
+ *		Simon South, simon@simonsouth.net
  *		Siarzhuk Zharski, zharik@gmx.li
  */
 
@@ -90,6 +91,28 @@ TerminalBuffer::Encoding() const
 }
 
 
+void
+TerminalBuffer::EnableInterpretMetaKey(bool enable)
+{
+	if (fListenerValid) {
+		BMessage message(MSG_ENABLE_META_KEY);
+		message.AddBool("enableInterpretMetaKey", enable);
+		fListener.SendMessage(&message);
+	}
+}
+
+
+void
+TerminalBuffer::EnableMetaKeySendsEscape(bool enable)
+{
+	if (fListenerValid) {
+		BMessage message(MSG_ENABLE_META_KEY);
+		message.AddBool("enableMetaKeySendsEscape", enable);
+		fListener.SendMessage(&message);
+	}
+}
+
+
 void
 TerminalBuffer::ReportX10MouseEvent(bool reportX10MouseEvent)
 {

src/apps/terminal/TerminalBuffer.h

@@ -5,6 +5,7 @@
  *
  * Authors:
  *		Ingo Weinhold, ingo_weinhold@gmx.de
+ *		Simon South, simon@simonsouth.net
  *		Siarzhuk Zharski, zharik@gmx.li
  */
 #ifndef TERMINAL_BUFFER_H
@@ -52,6 +53,9 @@ public:
 			void				UseAlternateScreenBuffer(bool clear);
 			void				UseNormalScreenBuffer();
 
+			void				EnableInterpretMetaKey(bool enable);
+			void				EnableMetaKeySendsEscape(bool enable);
+
 			void				ReportX10MouseEvent(bool report);
 			void				ReportNormalMouseEvent(bool report);
 			void				ReportButtonMouseEvent(bool report);