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+/*  This file is part of the KDE project
+    Copyright (C) 2000 Keunwoo Lee <klee@cs.washington.edu>
+
+    This program is free software; you can redistribute it and/or
+    modify it under the terms of the GNU Library 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 Library General Public License for more details.
+
+    You should have received a copy of the GNU Library General Public License
+    along with this library; see the file COPYING.LIB. If not, write to
+    the Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor,
+    Boston, MA  02110-1301, USA.
+*/
+
+#ifndef KACCELGEN_H
+#define KACCELGEN_H
+
+#include <qmap.h>
+#include <qstring.h>
+#include <qstringlist.h>
+
+#include <kdelibs_export.h>
+
+/**
+ * Provides functions that, given a collection of QStrings, will
+ * automatically and intelligently assign menu accelerators to the
+ * QStrings in the collection.
+ *
+ * NOTE: When this file speaks of "accelerators", we really mean
+ * accelerators as defined by the KDE User Interface Guidelines.  We
+ * do NOT mean "shortcuts", which are what's handled by most other KDE
+ * libraries with "accel" in the name.
+ *
+ * In the Qt library, the mechanism for adding a keyboard accelerator
+ * to a menu item is to insert an '&' before the letter. Since we
+ * usually don't want to disturb the original collection, the idiom in
+ * these functions is to populate a "target" QStringList parameter
+ * with the input collectin's QStrings, plus possibly some added '&'
+ * characters.
+ *
+ * That is the mechanism. Here is the policy, in order of decreasing
+ * importance (it may seem like these are implementation details, but
+ * IMHO the policy is an important part of the interface):
+ *
+ * 1. If the string already contains an '&' character, skip this
+ * string, because we consider such strings to be "user-specified"
+ * accelerators.
+ *
+ * 2. No accelerator may clash with a previously defined accelerator,
+ * including any legal (alphanumeric) user-specified accelerator
+ * anywhere in the collection
+ *
+ * 3. Prefer alphanumerics at the start of the string.
+ *
+ * 4. Otherwise, prefer alphanumerics at the start of a word.
+ *
+ * 5. Otherwise, choose any alphanumeric character not already
+ * taken. If no such character is available, give up & skip this
+ * string.
+ *
+ * A typical use of these functions would be to automatically assign
+ * accelerators to a dynamically populated popup menu.  For example,
+ * the core code was written to automatically set accelerators for the
+ * "Load View Profile" popup menu for Konqueror.  We quickly realized
+ * that it would be useful to make this facility more generally
+ * available, so I abstracted it out into a set of templates.
+ *
+ * TODO:
+ *
+ * + Add sugar functions for more collections.
+ *
+ * + Add more Deref classes so that we can access a wider variety of
+ * collections.
+ * */
+namespace KAccelGen
+{
+
+// HELPERS
+
+/**
+ * Static dereference class, for use as a template parameter.
+ */
+template <class Iter>
+class Deref
+{
+public:
+    static QString deref(Iter i) { return *i; }
+};
+
+/**
+ * Static dereference class that calls the key() method on its
+ * target; for use as a template parameter.
+ */
+template <class Iter>
+class Deref_Key
+{
+public:
+    static QString deref(Iter i) { return i.key(); }
+};
+
+/**
+ * Helper to determine if the given offset in the string could be a
+ * legal alphanumeric accelerator.
+ *
+ * @param str   base string
+ * @param index offset to check
+ */
+inline bool
+isLegalAccelerator(const QString& str, uint index)
+{
+    return index < str.length()
+        && str[index].isLetterOrNumber();
+}
+
+/**
+ * Loads all legal predefined accelerators in the (implicitly
+ * specified) collection into the given QMap.
+ *
+ * @param begin start iterator
+ * @param end   (last+1) iterator
+ * @param keys map to store output
+ */
+template <class Iter, class Deref>
+inline void
+loadPredefined(Iter begin, Iter end, QMap<QChar,bool>& keys)
+{
+    for (Iter i = begin; i != end; ++i) {
+        QString item = Deref::deref(i);
+        int user_ampersand = item.find(QChar('&'));
+        if( user_ampersand >= 0 ) {
+            // Sanity check.  Note that we don't try to find an
+            // accelerator if the user shoots him/herself in the foot
+            // by adding a bad '&'.
+            if( isLegalAccelerator(item, user_ampersand+1) ) {
+                keys.insert(item[user_ampersand+1], true);
+            }
+        }
+    }
+}
+
+
+// ///////////////////////////////////////////////////////////////////
+// MAIN USER FUNCTIONS
+
+
+/**
+ * Main, maximally flexible template function that assigns
+ * accelerators to the elements of a collection of QStrings. Clients
+ * will seldom use this directly, as it's usually easier to use one of
+ * the wrapper functions that simply takes a collection (see below).
+ *
+ * The Deref template parameter is a class containing a static
+ * dereferencing function, modeled after the comparison class C in
+ * Stroustrup 13.4.
+ *
+ * @param begin  (you know)
+ * @param end    (you know)
+ * @param target collection to store generated strings
+ */
+template <class Iter, class Iter_Deref >
+void
+generate(Iter begin, Iter end, QStringList& target)
+{
+    // Will keep track of used accelerator chars
+    QMap<QChar,bool> used_accels;
+
+    // Prepass to detect manually user-coded accelerators
+    loadPredefined<Iter,Iter_Deref>(begin, end, used_accels);
+
+    // Main pass
+    for (Iter i = begin; i != end; ++i) {
+        QString item = Iter_Deref::deref(i);
+
+        // Attempt to find a good accelerator, but only if the user
+        // has not manually hardcoded one.
+        int user_ampersand = item.find(QChar('&'));
+        if( user_ampersand < 0 || item[user_ampersand+1] == '&') {
+            bool found = false;
+            uint found_idx;
+            uint j;
+
+            // Check word-starting letters first.
+            for( j=0; j < item.length(); ++j ) {
+                if( isLegalAccelerator(item, j)
+                    && !used_accels.contains(item[j])
+                    && (0 == j || (j > 0 && item[j-1].isSpace())) ) {
+                    found = true;
+                    found_idx = j;
+                    break;
+                }
+            }
+
+            if( !found ) {
+                // No word-starting letter; search for any letter.
+                for( j=0; j < item.length(); ++j ) {
+                    if( isLegalAccelerator(item, j)
+                        && !used_accels.contains(item[j]) ) {
+                        found = true;
+                        found_idx = j;
+                        break;
+                    }
+                }
+            }
+
+            if( found ) {
+                // Both upper and lower case marked as used
+                used_accels.insert(item[j].upper(),true);
+                used_accels.insert(item[j].lower(),true);
+                item.insert(j,QChar('&'));
+            }
+        }
+
+        target.append( item );
+    }
+}
+
+/**
+ * Another convenience function; looks up the key instead of
+ * dereferencing directly for the given iterator.
+ *
+ * @param begin
+ * @param end
+ * @param target
+ */
+template <class Iter>
+inline void
+generateFromKeys(Iter begin, Iter end, QStringList& target)
+{
+    generate< Iter, Deref_Key<Iter> >(begin, end, target);
+}
+
+
+/**
+ * Convenience function; generates accelerators for all the items in
+ * a QStringList.
+ *
+ * @param source Strings for which to generate accelerators
+ * @param target Output for accelerator-added strings */
+inline void
+generate(const QStringList& source, QStringList& target)
+{
+    generate<QStringList::ConstIterator, Deref<QStringList::ConstIterator> >(source.begin(), source.end(), target);
+}
+
+/**
+ * Convenience function; generates accelerators for all the values in
+ * a QMap<T,QString>.
+ *
+ * @param source Map with input strings as VALUES.
+ * @param target Output for accelerator-added strings */
+template <class Key>
+inline void
+generateFromValues(const QMap<Key,QString>& source, QStringList& target)
+{
+    generate<QMapConstIterator<Key,QString>, Deref_Key<QMapConstIterator<Key,QString> > >(source.begin(), source.end(), target);
+}
+
+/**
+ * Convenience function; generates an accelerator mapping from all the
+ * keys in a QMap<QString,T>
+ *
+ * @param source Map with input strings as KEYS.
+ * @param target Output for accelerator-added strings */
+template <class Data>
+inline void
+generateFromKeys(const QMap<QString,Data>& source, QStringList& target)
+{
+    generateFromKeys(source.begin(), source.end(), target);
+}
+
+
+} // end namespace KAccelGen
+
+#endif
+