/* -*- Mode: C++; tab-width: 4; indent-tabs-mode: nil; c-basic-offset: 4 -*- */
/* vim:expandtab:shiftwidth=4:tabstop=4:
 */
/* ***** BEGIN LICENSE BLOCK *****
 * Version: MPL 1.1/GPL 2.0/LGPL 2.1
 *
 * The contents of this file are subject to the Mozilla Public License Version
 * 1.1 (the "License"); you may not use this file except in compliance with
 * the License. You may obtain a copy of the License at
 * http://www.mozilla.org/MPL/
 *
 * Software distributed under the License is distributed on an "AS IS" basis,
 * WITHOUT WARRANTY OF ANY KIND, either express or implied. See the License
 * for the specific language governing rights and limitations under the
 * License.
 *
 * The Original Code is mozilla.org code.
 *
 * The Initial Developer of the Original Code is Christopher Blizzard
 * <blizzard@mozilla.org>.  Portions created by the Initial Developer
 * are Copyright (C) 2001 the Initial Developer. All Rights Reserved.
 *
 * Contributor(s):
 *
 * Alternatively, the contents of this file may be used under the terms of
 * either the GNU General Public License Version 2 or later (the "GPL"), or
 * the GNU Lesser General Public License Version 2.1 or later (the "LGPL"),
 * in which case the provisions of the GPL or the LGPL are applicable instead
 * of those above. If you wish to allow use of your version of this file only
 * under the terms of either the GPL or the LGPL, and not to allow others to
 * use your version of this file under the terms of the MPL, indicate your
 * decision by deleting the provisions above and replace them with the notice
 * and other provisions required by the GPL or the LGPL. If you do not delete
 * the provisions above, a recipient may use your version of this file under
 * the terms of any one of the MPL, the GPL or the LGPL.
 *
 * ***** END LICENSE BLOCK ***** */

#include "nsClipboard.h"
#include "nsSupportsPrimitives.h"
#include "nsString.h"
#include "nsReadableUtils.h"
#include "nsXPIDLString.h"
#include "nsPrimitiveHelpers.h"
#include "nsICharsetConverterManager.h"
#include "nsIServiceManager.h"
#include "nsIImage.h"
#include "nsImageToPixbuf.h"
#include "nsStringStream.h"

#include <gtk/gtkclipboard.h>
#include <gtk/gtkinvisible.h>

// For manipulation of the X event queue
#include <X11/Xlib.h>
#include <gdk/gdkx.h>
#include <gtk/gtkmain.h>
#include <sys/time.h>
#include <sys/types.h>
#include <unistd.h>

#ifdef POLL_WITH_XCONNECTIONNUMBER
#include <poll.h>
#endif

// Callback when someone asks us for the selection
void
invisible_selection_get_cb (GtkWidget          *aWidget,
                            GtkSelectionData   *aSelectionData,
                            guint               aTime,
                            guint               aInfo,
                            nsClipboard        *aClipboard);

gboolean
selection_clear_event_cb   (GtkWidget          *aWidget,
                            GdkEventSelection  *aEvent,
                            nsClipboard        *aClipboard);

static void
ConvertHTMLtoUCS2          (guchar             *data,
                            PRInt32             dataLength,
                            PRUnichar         **unicodeData,
                            PRInt32            &outUnicodeLen);

static void
GetHTMLCharset             (guchar * data, PRInt32 dataLength, nsCString& str);


// Our own versions of gtk_clipboard_wait_for_contents and
// gtk_clipboard_wait_for_text, which don't run the event loop while
// waiting for the data.  This prevents a lot of problems related to
// dispatching events at unexpected times.

static GtkSelectionData *
wait_for_contents          (GtkClipboard *clipboard, GdkAtom target);

static gchar *
wait_for_text              (GtkClipboard *clipboard);

static Bool
checkEventProc(Display *display, XEvent *event, XPointer arg);

struct retrieval_context
{
    PRBool   completed;
    void    *data;

    retrieval_context() : completed(PR_FALSE), data(nsnull) { }
};

static void
wait_for_retrieval(GtkClipboard *clipboard, retrieval_context *transferData);

static void
clipboard_contents_received(GtkClipboard     *clipboard,
                            GtkSelectionData *selection_data,
                            gpointer          data);

static void
clipboard_text_received(GtkClipboard *clipboard,
                        const gchar  *text,
                        gpointer      data);

nsClipboard::nsClipboard()
{
    mWidget = nsnull;
}

nsClipboard::~nsClipboard()
{
    if (mWidget)
        gtk_widget_destroy(mWidget);
}

NS_IMPL_ISUPPORTS1(nsClipboard, nsIClipboard)

nsresult
nsClipboard::Init(void)
{
    mWidget = gtk_invisible_new();
    if (!mWidget)
        return NS_ERROR_FAILURE;

    g_signal_connect(G_OBJECT(mWidget), "selection_get",
                     G_CALLBACK(invisible_selection_get_cb), this);

    g_signal_connect(G_OBJECT(mWidget), "selection_clear_event",
                     G_CALLBACK(selection_clear_event_cb), this);

    // XXX make sure to set up the selection_clear event

    return NS_OK;
}

NS_IMETHODIMP
nsClipboard::SetData(nsITransferable *aTransferable,
                     nsIClipboardOwner *aOwner, PRInt32 aWhichClipboard)
{
    // See if we can short cut
    if ((aWhichClipboard == kGlobalClipboard &&
         aTransferable == mGlobalTransferable.get() &&
         aOwner == mGlobalOwner.get()) ||
        (aWhichClipboard == kSelectionClipboard &&
         aTransferable == mSelectionTransferable.get() &&
         aOwner == mSelectionOwner.get())) {
        return NS_OK;
    }

    nsresult rv;
    if (!mPrivacyHandler) {
        rv = NS_NewClipboardPrivacyHandler(getter_AddRefs(mPrivacyHandler));
        NS_ENSURE_SUCCESS(rv, rv);
    }
    rv = mPrivacyHandler->PrepareDataForClipboard(aTransferable);
    NS_ENSURE_SUCCESS(rv, rv);

    // Clear out the clipboard in order to set the new data
    EmptyClipboard(aWhichClipboard);

    if (aWhichClipboard == kSelectionClipboard) {
        mSelectionOwner = aOwner;
        mSelectionTransferable = aTransferable;
    }
    else {
        mGlobalOwner = aOwner;
        mGlobalTransferable = aTransferable;
    }

    // Which selection are we about to claim, CLIPBOARD or PRIMARY?
    GdkAtom selectionAtom = GetSelectionAtom(aWhichClipboard);

    // Make ourselves the owner.  If we fail to, return.
    if (!gtk_selection_owner_set(mWidget, selectionAtom, GDK_CURRENT_TIME))
        return NS_ERROR_FAILURE;

    // Clear the old selection target list.
    gtk_selection_clear_targets(mWidget, selectionAtom);

    // Get the types of supported flavors
    nsCOMPtr<nsISupportsArray> flavors;

    rv = aTransferable->FlavorsTransferableCanExport(getter_AddRefs(flavors));
    if (!flavors || NS_FAILED(rv))
        return NS_ERROR_FAILURE;

    // Add all the flavors to this widget's supported type.
    PRUint32 count;
    flavors->Count(&count);
    for (PRUint32 i=0; i < count; i++) {
        nsCOMPtr<nsISupports> tastesLike;
        flavors->GetElementAt(i, getter_AddRefs(tastesLike));
        nsCOMPtr<nsISupportsCString> flavor = do_QueryInterface(tastesLike);

        if (flavor) {
            nsXPIDLCString flavorStr;
            flavor->ToString(getter_Copies(flavorStr));

            // special case text/unicode since we can handle all of
            // the string types
            if (!strcmp(flavorStr, kUnicodeMime)) {
                AddTarget(gdk_atom_intern("UTF8_STRING", FALSE),
                          selectionAtom);
                AddTarget(gdk_atom_intern("COMPOUND_TEXT", FALSE),
                          selectionAtom);
                AddTarget(gdk_atom_intern("TEXT", FALSE), selectionAtom);
                AddTarget(GDK_SELECTION_TYPE_STRING, selectionAtom);
                // next loop iteration
                continue;
            }

            // very special case for this one. since our selection mechanism doesn't work for images,
            // we must use GTK's clipboard utility functions
            if (!strcmp(flavorStr, kNativeImageMime) || !strcmp(flavorStr, kPNGImageMime) ||
                !strcmp(flavorStr, kJPEGImageMime) || !strcmp(flavorStr, kGIFImageMime)) {
                nsCOMPtr<nsISupports> item;
                PRUint32 len;
                rv = aTransferable->GetTransferData(flavorStr, getter_AddRefs(item), &len);
                nsCOMPtr<nsISupportsInterfacePointer> ptrPrimitive(do_QueryInterface(item));
                if (!ptrPrimitive)
                    continue;

                nsCOMPtr<nsISupports> primitiveData;
                ptrPrimitive->GetData(getter_AddRefs(primitiveData));
                nsCOMPtr<nsIImage> image(do_QueryInterface(primitiveData));
                if (!image) // Not getting an image for an image mime type!?
                    continue;

                if (NS_FAILED(image->LockImagePixels(PR_FALSE)))
                    continue;
                GdkPixbuf* pixbuf = nsImageToPixbuf::ImageToPixbuf(image);
                if (!pixbuf) {
                    image->UnlockImagePixels(PR_FALSE);
                    continue;
                }

                GtkClipboard *aClipboard = gtk_clipboard_get(GetSelectionAtom(aWhichClipboard));
                gtk_clipboard_set_image(aClipboard, pixbuf);
                g_object_unref(pixbuf);
                image->UnlockImagePixels(PR_FALSE);
                continue;
            }

            // Add this to our list of valid targets
            GdkAtom atom = gdk_atom_intern(flavorStr, FALSE);
            AddTarget(atom, selectionAtom);
        }
    }

    return NS_OK;
}

NS_IMETHODIMP
nsClipboard::GetData(nsITransferable *aTransferable, PRInt32 aWhichClipboard)
{
    if (!aTransferable)
        return NS_ERROR_FAILURE;

    GtkClipboard *clipboard;
    clipboard = gtk_clipboard_get(GetSelectionAtom(aWhichClipboard));

    guchar        *data = NULL;
    gint           length = 0;
    PRBool         foundData = PR_FALSE;
    nsCAutoString  foundFlavor;

    // Get a list of flavors this transferable can import
    nsCOMPtr<nsISupportsArray> flavors;
    nsresult rv;
    rv = aTransferable->FlavorsTransferableCanImport(getter_AddRefs(flavors));
    if (!flavors || NS_FAILED(rv))
        return NS_ERROR_FAILURE;

    PRUint32 count;
    flavors->Count(&count);
    for (PRUint32 i=0; i < count; i++) {
        nsCOMPtr<nsISupports> genericFlavor;
        flavors->GetElementAt(i, getter_AddRefs(genericFlavor));

        nsCOMPtr<nsISupportsCString> currentFlavor;
        currentFlavor = do_QueryInterface(genericFlavor);

        if (currentFlavor) {
            nsXPIDLCString flavorStr;
            currentFlavor->ToString(getter_Copies(flavorStr));

            // Special case text/unicode since we can convert any
            // string into text/unicode
            if (!strcmp(flavorStr, kUnicodeMime)) {
                gchar* new_text = wait_for_text(clipboard);
                if (new_text) {
                    // Convert utf-8 into our unicode format.
                    NS_ConvertUTF8toUTF16 ucs2string(new_text);
                    data = (guchar *)ToNewUnicode(ucs2string);
                    length = ucs2string.Length() * 2;
                    g_free(new_text);
                    foundData = PR_TRUE;
                    foundFlavor = kUnicodeMime;
                    break;
                }
                // If the type was text/unicode and we couldn't get
                // text off the clipboard, run the next loop
                // iteration.
                continue;
            }

            // For images, we must wrap the data in an nsIInputStream then return instead of break,
            // because that code below won't help us.
            if (!strcmp(flavorStr, kJPEGImageMime) || !strcmp(flavorStr, kPNGImageMime) || !strcmp(flavorStr, kGIFImageMime)) {
                GdkAtom atom;
                if (!strcmp(flavorStr, kJPEGImageMime)) // This is image/jpg, but X only understands image/jpeg
                    atom = gdk_atom_intern("image/jpeg", FALSE);
                else
                    atom = gdk_atom_intern(flavorStr, FALSE);

                GtkSelectionData *selectionData = wait_for_contents(clipboard, atom);
                if (!selectionData)
                    continue;

                nsCOMPtr<nsIInputStream> byteStream;
                NS_NewByteInputStream(getter_AddRefs(byteStream), (const char*)selectionData->data,
                                      selectionData->length, NS_ASSIGNMENT_COPY);
                aTransferable->SetTransferData(flavorStr, byteStream, sizeof(nsIInputStream*));
                gtk_selection_data_free(selectionData);
                return NS_OK;
            }

            // Get the atom for this type and try to request it off
            // the clipboard.
            GdkAtom atom = gdk_atom_intern(flavorStr, FALSE);
            GtkSelectionData *selectionData;
            selectionData = wait_for_contents(clipboard, atom);
            if (selectionData) {
                length = selectionData->length;
                // Special case text/html since we can convert into UCS2
                if (!strcmp(flavorStr, kHTMLMime)) {
                    PRUnichar* htmlBody= nsnull;
                    PRInt32 htmlBodyLen = 0;
                    // Convert text/html into our unicode format
                    ConvertHTMLtoUCS2((guchar *)selectionData->data, length,
                                      &htmlBody, htmlBodyLen);
                    if (!htmlBodyLen)
                        break;
                    data = (guchar *)htmlBody;
                    length = htmlBodyLen * 2;
                } else {
                    data = (guchar *)nsMemory::Alloc(length);
                    if (!data)
                        break;
                    memcpy(data, selectionData->data, length);
                }
                foundData = PR_TRUE;
                foundFlavor = flavorStr;
                break;
            }
        }
    }

    if (foundData) {
        nsCOMPtr<nsISupports> wrapper;
        nsPrimitiveHelpers::CreatePrimitiveForData(foundFlavor.get(),
                                                   data, length,
                                                   getter_AddRefs(wrapper));
        aTransferable->SetTransferData(foundFlavor.get(),
                                       wrapper, length);
    }

    if (data)
        nsMemory::Free(data);

    return NS_OK;
}

NS_IMETHODIMP
nsClipboard::EmptyClipboard(PRInt32 aWhichClipboard)
{
    if (aWhichClipboard == kSelectionClipboard) {
        if (mSelectionOwner) {
            mSelectionOwner->LosingOwnership(mSelectionTransferable);
            mSelectionOwner = nsnull;
        }
        mSelectionTransferable = nsnull;
    }
    else {
        if (mGlobalOwner) {
            mGlobalOwner->LosingOwnership(mGlobalTransferable);
            mGlobalOwner = nsnull;
        }
        mGlobalTransferable = nsnull;
    }

    return NS_OK;
}

NS_IMETHODIMP
nsClipboard::HasDataMatchingFlavors(const char** aFlavorList, PRUint32 aLength,
                                    PRInt32 aWhichClipboard, PRBool *_retval)
{
    if (!aFlavorList || !_retval)
        return NS_ERROR_NULL_POINTER;

    *_retval = PR_FALSE;

    GtkSelectionData *selection_data =
        GetTargets(GetSelectionAtom(aWhichClipboard));
    if (!selection_data)
        return NS_OK;

    gint n_targets = 0;
    GdkAtom *targets = NULL;

    if (!gtk_selection_data_get_targets(selection_data, 
                                        &targets, &n_targets) ||
        !n_targets)
        return NS_OK;

    // Walk through the provided types and try to match it to a
    // provided type.
    for (PRUint32 i = 0; i < aLength && !*_retval; i++) {
        // We special case text/unicode here.
        if (!strcmp(aFlavorList[i], kUnicodeMime) && 
            gtk_selection_data_targets_include_text(selection_data)) {
            *_retval = PR_TRUE;
            break;
        }

        for (PRInt32 j = 0; j < n_targets; j++) {
            gchar *atom_name = gdk_atom_name(targets[j]);
            if (!strcmp(atom_name, aFlavorList[i]))
                *_retval = PR_TRUE;

            // X clipboard wants image/jpeg, not image/jpg
            if (!strcmp(aFlavorList[i], kJPEGImageMime) && !strcmp(atom_name, "image/jpeg"))
                *_retval = PR_TRUE;

            g_free(atom_name);

            if (*_retval)
                break;
        }
    }
    gtk_selection_data_free(selection_data);
    g_free(targets);

    return NS_OK;
}

NS_IMETHODIMP
nsClipboard::SupportsSelectionClipboard(PRBool *_retval)
{
    *_retval = PR_TRUE; // yeah, unix supports the selection clipboard
    return NS_OK;
}

/* static */
GdkAtom
nsClipboard::GetSelectionAtom(PRInt32 aWhichClipboard)
{
    if (aWhichClipboard == kGlobalClipboard)
        return GDK_SELECTION_CLIPBOARD;

    return GDK_SELECTION_PRIMARY;
}

/* static */
GtkSelectionData *
nsClipboard::GetTargets(GdkAtom aWhichClipboard)
{
    GtkClipboard *clipboard = gtk_clipboard_get(aWhichClipboard);
    return wait_for_contents(clipboard, gdk_atom_intern("TARGETS", FALSE));
}

nsITransferable *
nsClipboard::GetTransferable(PRInt32 aWhichClipboard)
{
    nsITransferable *retval;

    if (aWhichClipboard == kSelectionClipboard)
        retval = mSelectionTransferable.get();
    else
        retval = mGlobalTransferable.get();
        
    return retval;
}

void
nsClipboard::AddTarget(GdkAtom aName, GdkAtom aClipboard)
{
    gtk_selection_add_target(mWidget, aClipboard, aName, 0);
}

void
nsClipboard::SelectionGetEvent (GtkWidget        *aWidget,
                                GtkSelectionData *aSelectionData,
                                guint             aTime)
{
    // Someone has asked us to hand them something.  The first thing
    // that we want to do is see if that something includes text.  If
    // it does, try to give it text/unicode after converting it to
    // utf-8.

    PRInt32 whichClipboard;

    // which clipboard?
    if (aSelectionData->selection == GDK_SELECTION_PRIMARY)
        whichClipboard = kSelectionClipboard;
    else if (aSelectionData->selection == GDK_SELECTION_CLIPBOARD)
        whichClipboard = kGlobalClipboard;
    else
        return; // THAT AIN'T NO CLIPBOARD I EVER HEARD OF

    nsCOMPtr<nsITransferable> trans = GetTransferable(whichClipboard);
    
    nsresult rv;
    nsCOMPtr<nsISupports> item;
    PRUint32 len;

    // Check to see if the selection data includes any of the string
    // types that we support.
    if (aSelectionData->target == gdk_atom_intern ("STRING", FALSE) ||
        aSelectionData->target == gdk_atom_intern ("TEXT", FALSE) ||
        aSelectionData->target == gdk_atom_intern ("COMPOUND_TEXT", FALSE) ||
        aSelectionData->target == gdk_atom_intern ("UTF8_STRING", FALSE)) {
        // Try to convert our internal type into a text string.  Get
        // the transferable for this clipboard and try to get the
        // text/unicode type for it.
        rv = trans->GetTransferData("text/unicode", getter_AddRefs(item),
                                    &len);
        if (!item || NS_FAILED(rv))
            return;
        
        nsCOMPtr<nsISupportsString> wideString;
        wideString = do_QueryInterface(item);
        if (!wideString)
            return;

        nsAutoString ucs2string;
        wideString->GetData(ucs2string);
        char *utf8string = ToNewUTF8String(ucs2string);
        if (!utf8string)
            return;
        
        gtk_selection_data_set_text (aSelectionData, utf8string,
                                     strlen(utf8string));

        nsMemory::Free(utf8string);
        return;
    }

    // Try to match up the selection data target to something our
    // transferable provides.
    gchar *target_name = gdk_atom_name(aSelectionData->target);
    if (!target_name)
        return;

    rv = trans->GetTransferData(target_name, getter_AddRefs(item), &len);
    // nothing found?
    if (!item || NS_FAILED(rv)) {
        g_free(target_name);
        return;
    }

    void *primitive_data = nsnull;
    nsPrimitiveHelpers::CreateDataFromPrimitive(target_name, item,
                                                &primitive_data, len);

    if (primitive_data) {
        // Check to see if the selection data is text/html
        if (aSelectionData->target == gdk_atom_intern (kHTMLMime, FALSE)) {
            /*
             * "text/html" can be encoded UCS2. It is recommended that
             * documents transmitted as UCS2 always begin with a ZERO-WIDTH
             * NON-BREAKING SPACE character (hexadecimal FEFF, also called
             * Byte Order Mark (BOM)). Adding BOM can help other app to
             * detect mozilla use UCS2 encoding when copy-paste.
             */
            guchar *buffer = (guchar *)
                    nsMemory::Alloc((len * sizeof(guchar)) + sizeof(PRUnichar));
            if (!buffer)
                return;
            PRUnichar prefix = 0xFEFF;
            memcpy(buffer, &prefix, sizeof(prefix));
            memcpy(buffer + sizeof(prefix), primitive_data, len);
            nsMemory::Free((guchar *)primitive_data);
            primitive_data = (guchar *)buffer;
            len += sizeof(prefix);
        }
  
        gtk_selection_data_set(aSelectionData, aSelectionData->target,
                               8, /* 8 bits in a unit */
                               (const guchar *)primitive_data, len);
        nsMemory::Free(primitive_data);
    }

    g_free(target_name);
                           
}

void
nsClipboard::SelectionClearEvent (GtkWidget         *aWidget,
                                  GdkEventSelection *aEvent)
{
    PRInt32 whichClipboard;

    // which clipboard?
    if (aEvent->selection == GDK_SELECTION_PRIMARY)
        whichClipboard = kSelectionClipboard;
    else if (aEvent->selection == GDK_SELECTION_CLIPBOARD)
        whichClipboard = kGlobalClipboard;
    else
        return; // THAT AIN'T NO CLIPBOARD I EVER HEARD OF

    EmptyClipboard(whichClipboard);
}

void
invisible_selection_get_cb (GtkWidget          *aWidget,
                            GtkSelectionData   *aSelectionData,
                            guint               aTime,
                            guint               aInfo,
                            nsClipboard        *aClipboard)
{
    aClipboard->SelectionGetEvent(aWidget, aSelectionData, aTime);
}

gboolean
selection_clear_event_cb   (GtkWidget          *aWidget,
                            GdkEventSelection  *aEvent,
                            nsClipboard        *aClipboard)
{
    aClipboard->SelectionClearEvent(aWidget, aEvent);
    return TRUE;
}

/*
 * when copy-paste, mozilla wants data encoded using UCS2,
 * other app such as StarOffice use "text/html"(RFC2854).
 * This function convert data(got from GTK clipboard)
 * to data mozilla wanted.
 *
 * data from GTK clipboard can be 3 forms:
 *  1. From current mozilla
 *     "text/html", charset = utf-16
 *  2. From old version mozilla or mozilla-based app
 *     content("body" only), charset = utf-16
 *  3. From other app who use "text/html" when copy-paste
 *     "text/html", has "charset" info
 *
 * data      : got from GTK clipboard
 * dataLength: got from GTK clipboard
 * body      : pass to Mozilla
 * bodyLength: pass to Mozilla
 */
void ConvertHTMLtoUCS2(guchar * data, PRInt32 dataLength,
                       PRUnichar** unicodeData, PRInt32& outUnicodeLen)
{
    nsCAutoString charset;
    GetHTMLCharset(data, dataLength, charset);// get charset of HTML
    if (charset.EqualsLiteral("UTF-16")) {//current mozilla
        outUnicodeLen = (dataLength / 2) - 1;
        *unicodeData = reinterpret_cast<PRUnichar*>
                                       (nsMemory::Alloc((outUnicodeLen + sizeof('\0')) *
                       sizeof(PRUnichar)));
        if (*unicodeData) {
            memcpy(*unicodeData, data + sizeof(PRUnichar),
                   outUnicodeLen * sizeof(PRUnichar));
            (*unicodeData)[outUnicodeLen] = '\0';
        }
    } else if (charset.EqualsLiteral("UNKNOWN")) {
        outUnicodeLen = 0;
        return;
    } else {
        // app which use "text/html" to copy&paste
        nsCOMPtr<nsIUnicodeDecoder> decoder;
        nsresult rv;
        // get the decoder
        nsCOMPtr<nsICharsetConverterManager> ccm =
            do_GetService(NS_CHARSETCONVERTERMANAGER_CONTRACTID, &rv);
        if (NS_FAILED(rv)) {
#ifdef DEBUG_CLIPBOARD
            g_print("        can't get CHARSET CONVERTER MANAGER service\n");
#endif
            outUnicodeLen = 0;
            return;
        }
        rv = ccm->GetUnicodeDecoder(charset.get(), getter_AddRefs(decoder));
        if (NS_FAILED(rv)) {
#ifdef DEBUG_CLIPBOARD
            g_print("        get unicode decoder error\n");
#endif
            outUnicodeLen = 0;
            return;
        }
        // converting
        decoder->GetMaxLength((const char *)data, dataLength, &outUnicodeLen);
        // |outUnicodeLen| is number of chars
        if (outUnicodeLen) {
            *unicodeData = reinterpret_cast<PRUnichar*>
                                           (nsMemory::Alloc((outUnicodeLen + sizeof('\0')) *
                           sizeof(PRUnichar)));
            if (*unicodeData) {
                PRInt32 numberTmp = dataLength;
                decoder->Convert((const char *)data, &numberTmp,
                                 *unicodeData, &outUnicodeLen);
#ifdef DEBUG_CLIPBOARD
                if (numberTmp != dataLength)
                    printf("didn't consume all the bytes\n");
#endif
                // null terminate. Convert() doesn't do it for us
                (*unicodeData)[outUnicodeLen] = '\0';
            }
        } // if valid length
    }
}

/*
 * get "charset" information from clipboard data
 * return value can be:
 *  1. "UTF-16":      mozilla or "text/html" with "charset=utf-16"
 *  2. "UNKNOWN":     mozilla can't detect what encode it use
 *  3. other:         "text/html" with other charset than utf-16
 */
void GetHTMLCharset(guchar * data, PRInt32 dataLength, nsCString& str)
{
    // if detect "FFFE" or "FEFF", assume UTF-16
    PRUnichar* beginChar =  (PRUnichar*)data;
    if ((beginChar[0] == 0xFFFE) || (beginChar[0] == 0xFEFF)) {
        str.AssignLiteral("UTF-16");
        return;
    }
    // no "FFFE" and "FEFF", assume ASCII first to find "charset" info
    const nsDependentCString htmlStr((const char *)data, dataLength);
    nsACString::const_iterator start, end;
    htmlStr.BeginReading(start);
    htmlStr.EndReading(end);
    nsACString::const_iterator valueStart(start), valueEnd(start);

    if (CaseInsensitiveFindInReadable(
        NS_LITERAL_CSTRING("CONTENT=\"text/html;"),
        start, end)) {
        start = end;
        htmlStr.EndReading(end);

        if (CaseInsensitiveFindInReadable(
            NS_LITERAL_CSTRING("charset="),
            start, end)) {
            valueStart = end;
            start = end;
            htmlStr.EndReading(end);
          
            if (FindCharInReadable('"', start, end))
                valueEnd = start;
        }
    }
    // find "charset" in HTML
    if (valueStart != valueEnd) {
        str = Substring(valueStart, valueEnd);
        ToUpperCase(str);
#ifdef DEBUG_CLIPBOARD
        printf("Charset of HTML = %s\n", charsetUpperStr.get());
#endif
        return;
    }
    str.AssignLiteral("UNKNOWN");
}

static void
DispatchSelectionNotifyEvent(GtkWidget *widget, XEvent *xevent)
{
    GdkEvent event;
    event.selection.type = GDK_SELECTION_NOTIFY;
    event.selection.window = widget->window;
    event.selection.selection = gdk_x11_xatom_to_atom(xevent->xselection.selection);
    event.selection.target = gdk_x11_xatom_to_atom(xevent->xselection.target);
    event.selection.property = gdk_x11_xatom_to_atom(xevent->xselection.property);
    event.selection.time = xevent->xselection.time;

    gtk_widget_event(widget, &event);
}

static void
DispatchPropertyNotifyEvent(GtkWidget *widget, XEvent *xevent)
{
    if (((GdkWindowObject *) widget->window)->event_mask & GDK_PROPERTY_CHANGE_MASK) {
        GdkEvent event;
        event.property.type = GDK_PROPERTY_NOTIFY;
        event.property.window = widget->window;
        event.property.atom = gdk_x11_xatom_to_atom(xevent->xproperty.atom);
        event.property.time = xevent->xproperty.time;
        event.property.state = xevent->xproperty.state;

        gtk_widget_event(widget, &event);
    }
}

struct checkEventContext
{
    GtkWidget *cbWidget;
    Atom       selAtom;
};

static Bool
checkEventProc(Display *display, XEvent *event, XPointer arg)
{
    checkEventContext *context = (checkEventContext *) arg;

    if (event->xany.type == SelectionNotify ||
        (event->xany.type == PropertyNotify &&
         event->xproperty.atom == context->selAtom)) {

        GdkWindow *cbWindow = gdk_window_lookup(event->xany.window);
        if (cbWindow) {
            GtkWidget *cbWidget = NULL;
            gdk_window_get_user_data(cbWindow, (gpointer *)&cbWidget);
            if (cbWidget && GTK_IS_WIDGET(cbWidget)) {
                context->cbWidget = cbWidget;
                return True;
            }
        }
    }

    return False;
}

// Idle timeout for receiving selection and property notify events (microsec)
static const int kClipboardTimeout = 500000;

static void
wait_for_retrieval(GtkClipboard *clipboard, retrieval_context *r_context)
{
    if (r_context->completed)  // the request completed synchronously
        return;

    Display *xDisplay = GDK_DISPLAY();
    checkEventContext context;
    context.cbWidget = NULL;
    context.selAtom = gdk_x11_atom_to_xatom(gdk_atom_intern("GDK_SELECTION",
                                                            FALSE));

    // Send X events which are relevant to the ongoing selection retrieval
    // to the clipboard widget.  Wait until either the operation completes, or
    // we hit our timeout.  All other X events remain queued.

    int select_result;

#ifdef POLL_WITH_XCONNECTIONNUMBER
    struct pollfd fds[1];
    fds[0].fd = XConnectionNumber(xDisplay);
    fds[0].events = POLLIN;
#else
    int cnumber = ConnectionNumber(xDisplay);
    fd_set select_set;
    FD_ZERO(&select_set);
    FD_SET(cnumber, &select_set);
    ++cnumber;
    struct timeval tv;
#endif

    do {
        XEvent xevent;

        while (XCheckIfEvent(xDisplay, &xevent, checkEventProc,
                             (XPointer) &context)) {

            if (xevent.xany.type == SelectionNotify)
                DispatchSelectionNotifyEvent(context.cbWidget, &xevent);
            else
                DispatchPropertyNotifyEvent(context.cbWidget, &xevent);

            if (r_context->completed)
                return;
        }

#ifdef POLL_WITH_XCONNECTIONNUMBER
        select_result = poll(fds, 1, kClipboardTimeout / 1000);
#else
        tv.tv_sec = 0;
        tv.tv_usec = kClipboardTimeout;
        select_result = select(cnumber, &select_set, NULL, NULL, &tv);
#endif
    } while (select_result == 1);

#ifdef DEBUG_CLIPBOARD
    printf("exceeded clipboard timeout\n");
#endif
}

static void
clipboard_contents_received(GtkClipboard     *clipboard,
                            GtkSelectionData *selection_data,
                            gpointer          data)
{
    retrieval_context *context = static_cast<retrieval_context *>(data);
    context->completed = PR_TRUE;

    if (selection_data->length >= 0)
        context->data = gtk_selection_data_copy(selection_data);
}


static GtkSelectionData *
wait_for_contents(GtkClipboard *clipboard, GdkAtom target)
{
    retrieval_context context;
    gtk_clipboard_request_contents(clipboard, target,
                                   clipboard_contents_received,
                                   &context);

    wait_for_retrieval(clipboard, &context);
    return static_cast<GtkSelectionData *>(context.data);
}

static void
clipboard_text_received(GtkClipboard *clipboard,
                        const gchar  *text,
                        gpointer      data)
{
    retrieval_context *context = static_cast<retrieval_context *>(data);
    context->completed = PR_TRUE;
    context->data = g_strdup(text);
}

static gchar *
wait_for_text(GtkClipboard *clipboard)
{
    retrieval_context context;
    gtk_clipboard_request_text(clipboard, clipboard_text_received, &context);

    wait_for_retrieval(clipboard, &context);
    return static_cast<gchar *>(context.data);
}
