Fix QImageReader::size() to return correct size for .ico files.

According to MSDN, the zero value of ICONDIRENTRY bHeight and bWidth
fields mean a maximum icon size 256 pixels. So QtIcoHandler::option()
should return 256 instead of 0 pixels for such icons. Also there is
fixed wrong seek offset at the second call on this method.

http://blogs.msdn.com/b/oldnewthing/archive/2010/10/18/10077133.aspx

Task-number: QTBUG-48103
Change-Id: I99f0c9720fd58889045b0c73c51498f2065b0b91
Reviewed-by: Friedemann Kleint <Friedemann.Kleint@theqtcompany.com>
Reviewed-by: aavit <eirik.aavitsland@theqtcompany.com>

1 files changed, 8 insertions, 13 deletions

diff --git a/src/plugins/imageformats/ico/qicohandler.cpp b/src/plugins/imageformats/ico/qicohandler.cpp
index 2ddbc4519b..6d2c06c9c8 100644
--- a/src/plugins/imageformats/ico/qicohandler.cpp
+++ b/src/plugins/imageformats/ico/qicohandler.cpp
@@ -100,9 +100,10 @@ public:
 
     static bool write(QIODevice *device, const QVector<QImage> &images);
 
+    bool readIconEntry(int index, ICONDIRENTRY * iconEntry);
+
 private:
     bool readHeader();
-    bool readIconEntry(int index, ICONDIRENTRY * iconEntry);
 
     bool readBMPHeader(quint32 imageOffset, BMP_INFOHDR * header);
     void findColorInfo(QImage & image);
@@ -341,7 +342,7 @@ bool ICOReader::readHeader()
 
 bool ICOReader::readIconEntry(int index, ICONDIRENTRY *iconEntry)
 {
-    if (iod) {
+    if (readHeader()) {
         if (iod->seek(startpos + ICONDIR_SIZE + (index * ICONDIRENTRY_SIZE))) {
             return readIconDirEntry(iod, iconEntry);
         }
@@ -558,10 +559,10 @@ QImage ICOReader::iconAt(int index)
                 if (icoAttrib.ncolors > 256) //color table can't be more than 256
                     return img;
                 icoAttrib.w = iconEntry.bWidth;
-                if (icoAttrib.w == 0)
+                if (icoAttrib.w == 0) // means 256 pixels
                     icoAttrib.w = header.biWidth;
                 icoAttrib.h = iconEntry.bHeight;
-                if (icoAttrib.h == 0)
+                if (icoAttrib.h == 0) // means 256 pixels
                     icoAttrib.h = header.biHeight/2;
 
                 QImage::Format format = QImage::Format_ARGB32;
@@ -779,17 +780,11 @@ QtIcoHandler::~QtIcoHandler()
 QVariant QtIcoHandler::option(ImageOption option) const
 {
     if (option == Size) {
-        QIODevice *device = QImageIOHandler::device();
-        qint64 oldPos = device->pos();
         ICONDIRENTRY iconEntry;
-        if (device->seek(oldPos + ICONDIR_SIZE + (m_currentIconIndex * ICONDIRENTRY_SIZE))) {
-            if (readIconDirEntry(device, &iconEntry)) {
-                device->seek(oldPos);
-                return QSize(iconEntry.bWidth, iconEntry.bHeight);
-            }
+        if (m_pICOReader->readIconEntry(m_currentIconIndex, &iconEntry)) {
+                return QSize(iconEntry.bWidth ? iconEntry.bWidth : 256,
+                            iconEntry.bHeight ? iconEntry.bHeight : 256);
         }
-        if (!device->isSequential())
-            device->seek(oldPos);
     }
     return QVariant();
 }