Prioritize the shortcuts from the work areas

* Fix bug #10261 : KDE smartly adds conflicting accelerators.

* Prevent bugs like #9495 in the future.

Issues (non-regression):

* It does not appear possible to prevent Ubuntu's Unity from grabbing the
  accelerators for the menus. For instance Alt+A still opens _Affichage in the
  French localization.

(cherry picked from commit eb8c5905f6)

src/frontends/qt4/GuiApplication.cpp

@@ -2082,24 +2082,48 @@ void GuiApplication::handleKeyFunc(FuncCode action)
 }
 
 
+//Keep this in sync with GuiApplication::processKeySym below
+bool GuiApplication::queryKeySym(KeySymbol const & keysym,
+                                 KeyModifier state) const
+{
+	// Do nothing if we have nothing
+	if (!keysym.isOK() || keysym.isModifier())
+		return false;
+	// Do a one-deep top-level lookup for cancel and meta-fake keys.
+	KeySequence seq;
+	FuncRequest func = seq.addkey(keysym, state);
+	// When not cancel or meta-fake, do the normal lookup.
+	if ((func.action() != LFUN_CANCEL) && (func.action() != LFUN_META_PREFIX)) {
+		seq = d->keyseq;
+		func = seq.addkey(keysym, (state | d->meta_fake_bit));
+	}
+	// Maybe user can only reach the key via holding down shift.
+	// Let's see. But only if shift is the only modifier
+	if (func.action() == LFUN_UNKNOWN_ACTION && state == ShiftModifier)
+		// If addkey looked up a command and did not find further commands then
+		// seq has been reset at this point
+		func = seq.addkey(keysym, NoModifier);
+
+	LYXERR(Debug::KEY, " Key (queried) [action=" << func.action() << "]["
+	       << seq.print(KeySequence::Portable) << ']');
+	return func.action() != LFUN_UNKNOWN_ACTION;
+}
+
+
+//Keep this in sync with GuiApplication::queryKeySym above
 void GuiApplication::processKeySym(KeySymbol const & keysym, KeyModifier state)
 {
 	LYXERR(Debug::KEY, "KeySym is " << keysym.getSymbolName());
 
 	// Do nothing if we have nothing (JMarc)
-	if (!keysym.isOK()) {
+	if (!keysym.isOK() || keysym.isModifier()) {
+		if (!keysym.isOK())
 			LYXERR(Debug::KEY, "Empty kbd action (probably composing)");
 		if (current_view_)
 			current_view_->restartCursor();
 		return;
 	}
 
-	if (keysym.isModifier()) {
-		if (current_view_)
-			current_view_->restartCursor();
-		return;
-	}
-
 	char_type encoded_last_key = keysym.getUCSEncoded();
 
 	// Do a one-deep top-level lookup for
@@ -2140,6 +2164,8 @@ void GuiApplication::processKeySym(KeySymbol const & keysym, KeyModifier state)
 	// Let's see. But only if shift is the only modifier
 	if (func.action() == LFUN_UNKNOWN_ACTION && state == ShiftModifier) {
 		LYXERR(Debug::KEY, "Trying without shift");
+		// If addkey looked up a command and did not find further commands then
+		// seq has been reset at this point
 		func = d->keyseq.addkey(keysym, NoModifier);
 		LYXERR(Debug::KEY, "Action now " << func.action());
 	}

src/frontends/qt4/GuiApplication.h

@@ -165,6 +165,9 @@ public:
 #endif
 	}
 
+	/// return true if the key is part of a shortcut
+	bool queryKeySym(KeySymbol const & key, KeyModifier state) const;
+	///
 	void processKeySym(KeySymbol const & key, KeyModifier state);
 	/// return the status bar state string
 	docstring viewStatusMessage();

src/frontends/qt4/GuiKeySymbol.cpp

@@ -612,7 +612,7 @@ static char encode(string const & encoding, QString const & str)
 #endif
 
 
-void setKeySymbol(KeySymbol * sym, QKeyEvent * ev)
+void setKeySymbol(KeySymbol * sym, QKeyEvent const * ev)
 {
 	sym->setKey(ev->key());
 	if (ev->text().isNull()) {

src/frontends/qt4/GuiKeySymbol.h

@@ -18,7 +18,7 @@ class QKeyEvent;
 namespace lyx {
 
 /// delayed constructor
-void setKeySymbol(KeySymbol * sym, QKeyEvent * ev);
+void setKeySymbol(KeySymbol * sym, QKeyEvent const * ev);
 
 /// return the LyX key state from Qt's
 KeyModifier q_key_state(Qt::KeyboardModifiers state);

src/frontends/qt4/GuiPrefs.cpp

@@ -3194,6 +3194,9 @@ void PrefShortcuts::shortcutOkPressed()
 		shortcutsTW->setCurrentItem(item);
 		shortcutsTW->scrollToItem(item);
 	} else {
+		// FIXME: The error message could be more explicit. This can happen in
+		// particular if the user wants to introduce a LFUN which is Hidden such
+		// as self-insert.
 		Alert::error(_("Failed to create shortcut"),
 			_("Can not insert shortcut to the list"));
 		return;

src/frontends/qt4/GuiWorkArea.cpp

@@ -504,6 +504,14 @@ void GuiWorkArea::redraw(bool update_metrics)
 }
 
 
+// Keep in sync with GuiWorkArea::processKeySym below
+bool GuiWorkArea::queryKeySym(KeySymbol const & key, KeyModifier mod) const
+{
+	return guiApp->queryKeySym(key, mod);
+}
+
+
+// Keep in sync with GuiWorkArea::queryKeySym above
 void GuiWorkArea::processKeySym(KeySymbol const & key, KeyModifier mod)
 {
 	if (d->lyx_view_->isFullScreen() && d->lyx_view_->menuBar()->isVisible()
@@ -723,6 +731,12 @@ bool GuiWorkArea::event(QEvent * e)
 		return true;
 	}
 
+	case QEvent::ShortcutOverride:
+		// keyPressEvent is ShortcutOverride-aware and only accepts the event in
+		// this case
+		keyPressEvent(static_cast<QKeyEvent *>(e));
+		return e->isAccepted();
+
 	case QEvent::KeyPress: {
 		// We catch this event in order to catch the Tab or Shift+Tab key press
 		// which are otherwise reserved to focus switching between controls
@@ -1037,6 +1051,10 @@ void GuiWorkArea::generateSyntheticMouseEvent()
 
 void GuiWorkArea::keyPressEvent(QKeyEvent * ev)
 {
+	// this is also called for ShortcutOverride events. In this case, one must
+	// not act but simply accept the event explicitly.
+	bool const act = (ev->type() != QEvent::ShortcutOverride);
+
 	// Do not process here some keys if dialog_mode_ is set
 	if (d->dialog_mode_
 		&& (ev->modifiers() == Qt::NoModifier
@@ -1054,6 +1072,7 @@ void GuiWorkArea::keyPressEvent(QKeyEvent * ev)
 		switch (ev->key()) {
 		case Qt::Key_Enter:
 		case Qt::Key_Return:
+			if (act)
 				d->completer_->activate();
 			ev->accept();
 			return;
@@ -1064,7 +1083,9 @@ void GuiWorkArea::keyPressEvent(QKeyEvent * ev)
 	// (the auto repeated events come too fast)
 	// it looks like this is only needed on X11
 #if defined(Q_WS_X11) || defined(QPA_XCB)
-	if (qApp->hasPendingEvents() && ev->isAutoRepeat()) {
+	// FIXME: this is a weird way to implement event compression. Also, this is
+	// broken with IBus.
+	if (act && qApp->hasPendingEvents() && ev->isAutoRepeat()) {
 		switch (ev->key()) {
 		case Qt::Key_PageDown:
 		case Qt::Key_PageUp:
@@ -1079,7 +1100,7 @@ void GuiWorkArea::keyPressEvent(QKeyEvent * ev)
 	}
 #endif
 
-	KeyModifier m = q_key_state(ev->modifiers());
+	KeyModifier const m = q_key_state(ev->modifiers());
 
 	std::string str;
 	if (m & ShiftModifier)
@@ -1091,6 +1112,7 @@ void GuiWorkArea::keyPressEvent(QKeyEvent * ev)
 	if (m & MetaModifier)
 		str += "Meta-";
 
+	if (act)
 		LYXERR(Debug::KEY, " count: " << ev->count() << " text: " << ev->text()
 		       << " isAutoRepeat: " << ev->isAutoRepeat() << " key: " << ev->key()
 		       << " keyState: " << str);
@@ -1098,8 +1120,11 @@ void GuiWorkArea::keyPressEvent(QKeyEvent * ev)
 	KeySymbol sym;
 	setKeySymbol(&sym, ev);
 	if (sym.isOK()) {
-		processKeySym(sym, q_key_state(ev->modifiers()));
+		if (act) {
+			processKeySym(sym, m);
 			ev->accept();
+		} else
+			ev->setAccepted(queryKeySym(sym, m));
 	} else {
 		ev->ignore();
 	}

src/frontends/qt4/GuiWorkArea.h

@@ -68,6 +68,8 @@ public:
 	///
 	void redraw(bool update_metrics);
 
+	/// return true if the key is part of a shortcut
+	bool queryKeySym(KeySymbol const & key, KeyModifier mod) const;
 	/// Process Key pressed event.
 	/// This needs to be public because it is accessed externally by GuiView.
 	void processKeySym(KeySymbol const & key, KeyModifier mod);
@@ -141,7 +143,8 @@ private:
 	void mouseMoveEvent(QMouseEvent * ev);
 	/// wheel event
 	void wheelEvent(QWheelEvent * ev);
-	/// key press
+	/// key press event. It also knows how to handle ShortcutOverride events to
+	/// avoid code duplication.
 	void keyPressEvent(QKeyEvent * ev);
 	/// IM events
 	void inputMethodEvent(QInputMethodEvent * ev);