Add basic handler for ktx format texture files

This adds basic support for reading compressed textures stored in .ktx
files, the Khronos texture file format.

Change-Id: Iafb86cff9607eedb26a73989f9b005455ddd316f
Reviewed-by: Kai Koehne <kai.koehne@qt.io>

4 files changed, 271 insertions, 2 deletions

diff --git a/src/quick/scenegraph/compressedtexture/qsgktxhandler.cpp b/src/quick/scenegraph/compressedtexture/qsgktxhandler.cpp
new file mode 100644
index 0000000000..e3e4ca6824
--- /dev/null
+++ b/src/quick/scenegraph/compressedtexture/qsgktxhandler.cpp
@@ -0,0 +1,186 @@
+/****************************************************************************
+**
+** Copyright (C) 2017 The Qt Company Ltd.
+** Contact: https://www.qt.io/licensing/
+**
+** This file is part of the QtQuick module of the Qt Toolkit.
+**
+** $QT_BEGIN_LICENSE:LGPL$
+** Commercial License Usage
+** Licensees holding valid commercial Qt licenses may use this file in
+** accordance with the commercial license agreement provided with the
+** Software or, alternatively, in accordance with the terms contained in
+** a written agreement between you and The Qt Company. For licensing terms
+** and conditions see https://www.qt.io/terms-conditions. For further
+** information use the contact form at https://www.qt.io/contact-us.
+**
+** GNU Lesser General Public License Usage
+** Alternatively, this file may be used under the terms of the GNU Lesser
+** General Public License version 3 as published by the Free Software
+** Foundation and appearing in the file LICENSE.LGPL3 included in the
+** packaging of this file. Please review the following information to
+** ensure the GNU Lesser General Public License version 3 requirements
+** will be met: https://www.gnu.org/licenses/lgpl-3.0.html.
+**
+** GNU General Public License Usage
+** Alternatively, this file may be used under the terms of the GNU
+** General Public License version 2.0 or (at your option) the GNU General
+** Public license version 3 or any later version approved by the KDE Free
+** Qt Foundation. The licenses are as published by the Free Software
+** Foundation and appearing in the file LICENSE.GPL2 and LICENSE.GPL3
+** included in the packaging of this file. Please review the following
+** information to ensure the GNU General Public License requirements will
+** be met: https://www.gnu.org/licenses/gpl-2.0.html and
+** https://www.gnu.org/licenses/gpl-3.0.html.
+**
+** $QT_END_LICENSE$
+**
+****************************************************************************/
+
+#include "qsgktxhandler_p.h"
+#include "qsgcompressedtexture_p.h"
+#include <QOpenGLTexture>
+#include <QtEndian>
+
+//#define KTX_DEBUG
+
+QT_BEGIN_NAMESPACE
+
+#define KTX_IDENTIFIER_LENGTH 12
+static const char ktxIdentifier[KTX_IDENTIFIER_LENGTH] = { '\xAB', 'K', 'T', 'X', ' ', '1', '1', '\xBB', '\r', '\n', '\x1A', '\n' };
+static const quint32 platformEndianIdentifier = 0x04030201;
+static const quint32 inversePlatformEndianIdentifier = 0x01020304;
+
+struct KTXHeader {
+    quint8 identifier[KTX_IDENTIFIER_LENGTH]; //Must match ktxIdentifier
+    quint32 endianness; //Either platformEndianIdentifier or inversePlatformEndianIdentifier, other values not allowed.
+    quint32 glType;
+    quint32 glTypeSize;
+    quint32 glFormat;
+    quint32 glInternalFormat;
+    quint32 glBaseInternalFormat;
+    quint32 pixelWidth;
+    quint32 pixelHeight;
+    quint32 pixelDepth;
+    quint32 numberOfArrayElements;
+    quint32 numberOfFaces;
+    quint32 numberOfMipmapLevels;
+    quint32 bytesOfKeyValueData;
+};
+
+static const int headerSize = sizeof(KTXHeader);
+
+// Currently unused, declared for future reference
+struct KTXKeyValuePairItem {
+    quint32   keyAndValueByteSize;
+    /*
+    quint8 keyAndValue[keyAndValueByteSize];
+    quint8 valuePadding[3 - ((keyAndValueByteSize + 3) % 4)];
+    */
+};
+
+struct KTXMipmapLevel {
+    quint32 imageSize;
+    /*
+    for each array_element in numberOfArrayElements*
+        for each face in numberOfFaces
+            for each z_slice in pixelDepth*
+                for each row or row_of_blocks in pixelHeight*
+                    for each pixel or block_of_pixels in pixelWidth
+                        Byte data[format-specific-number-of-bytes]**
+                    end
+                end
+            end
+            Byte cubePadding[0-3]
+        end
+    end
+    quint8 mipPadding[3 - ((imageSize + 3) % 4)]
+    */
+};
+
+bool QSGKtxHandler::canRead(const QByteArray &suffix, const QByteArray &block)
+{
+    Q_UNUSED(suffix)
+
+    return (qstrncmp(block.constData(), ktxIdentifier, KTX_IDENTIFIER_LENGTH) == 0);
+}
+
+QQuickTextureFactory *QSGKtxHandler::read()
+{
+    if (!device())
+        return nullptr;
+
+    QByteArray buf = device()->readAll();
+    if (buf.size() < headerSize || !canRead(QByteArray(), buf)) {
+        qCDebug(QSG_LOG_TEXTUREIO, "Invalid KTX file %s", logName().constData());
+        return nullptr;
+    }
+
+    const KTXHeader *header = reinterpret_cast<const KTXHeader *>(buf.constData());
+    if (!checkHeader(*header)) {
+        qCDebug(QSG_LOG_TEXTUREIO, "Unsupported KTX file format in %s", logName().constData());
+        return nullptr;
+    }
+
+    QSGCompressedTexture::DataPtr texData(QSGCompressedTexture::DataPtr::create());
+
+    texData->size = QSize(decode(header->pixelWidth), decode(header->pixelHeight));
+    texData->format = decode(header->glInternalFormat);
+    texData->hasAlpha = !QSGCompressedTexture::formatIsOpaque(texData->format);
+
+    // For now, ignore any additional mipmap levels
+    int preambleSize = headerSize + decode(header->bytesOfKeyValueData);
+    if (buf.size() >= preambleSize + int(sizeof(KTXMipmapLevel))) {
+        texData->data = buf;
+        texData->dataOffset = preambleSize + sizeof(quint32); // for the imageSize
+        const KTXMipmapLevel *level = reinterpret_cast<const KTXMipmapLevel *>(buf.constData() + preambleSize);
+        texData->dataLength = decode(level->imageSize);
+    }
+
+    if (!texData->isValid()) {
+        qCDebug(QSG_LOG_TEXTUREIO, "Invalid values in header of KTX file %s", logName().constData());
+        return nullptr;
+    }
+
+    texData->logName = logName();
+#ifdef KTX_DEBUG
+    qDebug() << "KTX file handler read" << texData.data();
+#endif
+
+    return new QSGCompressedTextureFactory(texData);
+}
+
+bool QSGKtxHandler::checkHeader(const KTXHeader &header)
+{
+    if (header.endianness != platformEndianIdentifier && header.endianness != inversePlatformEndianIdentifier)
+        return false;
+    inverseEndian = (header.endianness == inversePlatformEndianIdentifier);
+#ifdef KTX_DEBUG
+    QMetaEnum tfme = QMetaEnum::fromType<QOpenGLTexture::TextureFormat>();
+    QMetaEnum ptme = QMetaEnum::fromType<QOpenGLTexture::PixelType>();
+    qDebug("Header of %s:", logName().constData());
+    qDebug("  glType: 0x%x (%s)", decode(header.glType), ptme.valueToKey(decode(header.glType)));
+    qDebug("  glTypeSize: %u", decode(header.glTypeSize));
+    qDebug("  glFormat: 0x%x (%s)", decode(header.glFormat), tfme.valueToKey(decode(header.glFormat)));
+    qDebug("  glInternalFormat: 0x%x (%s)", decode(header.glInternalFormat), tfme.valueToKey(decode(header.glInternalFormat)));
+    qDebug("  glBaseInternalFormat: 0x%x (%s)", decode(header.glBaseInternalFormat), tfme.valueToKey(decode(header.glBaseInternalFormat)));
+    qDebug("  pixelWidth: %u", decode(header.pixelWidth));
+    qDebug("  pixelHeight: %u", decode(header.pixelHeight));
+    qDebug("  pixelDepth: %u", decode(header.pixelDepth));
+    qDebug("  numberOfArrayElements: %u", decode(header.numberOfArrayElements));
+    qDebug("  numberOfFaces: %u", decode(header.numberOfFaces));
+    qDebug("  numberOfMipmapLevels: %u", decode(header.numberOfMipmapLevels));
+    qDebug("  bytesOfKeyValueData: %u", decode(header.bytesOfKeyValueData));
+#endif
+    return ((decode(header.glType) == 0) &&
+            (decode(header.glFormat) == 0) &&
+            (decode(header.pixelDepth) == 0) &&
+            (decode(header.numberOfFaces) == 1));
+}
+
+quint32 QSGKtxHandler::decode(quint32 val)
+{
+    return inverseEndian ? qbswap<quint32>(val) : val;
+}
+
+QT_END_NAMESPACE
diff --git a/src/quick/scenegraph/compressedtexture/qsgktxhandler_p.h b/src/quick/scenegraph/compressedtexture/qsgktxhandler_p.h
new file mode 100644
index 0000000000..22f4db65b2
--- /dev/null
+++ b/src/quick/scenegraph/compressedtexture/qsgktxhandler_p.h
@@ -0,0 +1,78 @@
+/****************************************************************************
+**
+** Copyright (C) 2017 The Qt Company Ltd.
+** Contact: https://www.qt.io/licensing/
+**
+** This file is part of the QtQuick module of the Qt Toolkit.
+**
+** $QT_BEGIN_LICENSE:LGPL$
+** Commercial License Usage
+** Licensees holding valid commercial Qt licenses may use this file in
+** accordance with the commercial license agreement provided with the
+** Software or, alternatively, in accordance with the terms contained in
+** a written agreement between you and The Qt Company. For licensing terms
+** and conditions see https://www.qt.io/terms-conditions. For further
+** information use the contact form at https://www.qt.io/contact-us.
+**
+** GNU Lesser General Public License Usage
+** Alternatively, this file may be used under the terms of the GNU Lesser
+** General Public License version 3 as published by the Free Software
+** Foundation and appearing in the file LICENSE.LGPL3 included in the
+** packaging of this file. Please review the following information to
+** ensure the GNU Lesser General Public License version 3 requirements
+** will be met: https://www.gnu.org/licenses/lgpl-3.0.html.
+**
+** GNU General Public License Usage
+** Alternatively, this file may be used under the terms of the GNU
+** General Public License version 2.0 or (at your option) the GNU General
+** Public license version 3 or any later version approved by the KDE Free
+** Qt Foundation. The licenses are as published by the Free Software
+** Foundation and appearing in the file LICENSE.GPL2 and LICENSE.GPL3
+** included in the packaging of this file. Please review the following
+** information to ensure the GNU General Public License requirements will
+** be met: https://www.gnu.org/licenses/gpl-2.0.html and
+** https://www.gnu.org/licenses/gpl-3.0.html.
+**
+** $QT_END_LICENSE$
+**
+****************************************************************************/
+
+#ifndef QSGKTXHANDLER_H
+#define QSGKTXHANDLER_H
+
+//
+//  W A R N I N G
+//  -------------
+//
+// This file is not part of the Qt API.  It exists purely as an
+// implementation detail.  This header file may change from version to
+// version without notice, or even be removed.
+//
+// We mean it.
+//
+
+#include "qsgtexturefilehandler_p.h"
+
+QT_BEGIN_NAMESPACE
+
+struct KTXHeader;
+
+class QSGKtxHandler : public QSGTextureFileHandler
+{
+public:
+    using QSGTextureFileHandler::QSGTextureFileHandler;
+
+    static bool canRead(const QByteArray &suffix, const QByteArray &block);
+
+    QQuickTextureFactory *read() override;
+
+private:
+    bool checkHeader(const KTXHeader &header);
+    quint32 decode(quint32 val);
+
+    bool inverseEndian = false;
+};
+
+QT_END_NAMESPACE
+
+#endif // QSGKTXHANDLER_H
diff --git a/src/quick/scenegraph/scenegraph.pri b/src/quick/scenegraph/scenegraph.pri
index bdd694f95e..34396dcf43 100644
--- a/src/quick/scenegraph/scenegraph.pri
+++ b/src/quick/scenegraph/scenegraph.pri
@@ -233,10 +233,12 @@ qtConfig(opengl(es1|es2)?) {
         $$PWD/compressedtexture/qsgcompressedatlastexture_p.h \
         $$PWD/compressedtexture/qsgcompressedtexture_p.h \
         $$PWD/compressedtexture/qsgtexturefilehandler_p.h \
-        $$PWD/compressedtexture/qsgpkmhandler_p.h
+        $$PWD/compressedtexture/qsgpkmhandler_p.h \
+        $$PWD/compressedtexture/qsgktxhandler_p.h
 
     SOURCES += \
         $$PWD/compressedtexture/qsgcompressedatlastexture.cpp \
         $$PWD/compressedtexture/qsgcompressedtexture.cpp \
-        $$PWD/compressedtexture/qsgpkmhandler.cpp
+        $$PWD/compressedtexture/qsgpkmhandler.cpp \
+        $$PWD/compressedtexture/qsgktxhandler.cpp
 }
diff --git a/src/quick/scenegraph/util/qsgtexturereader.cpp b/src/quick/scenegraph/util/qsgtexturereader.cpp
index cf4edf29b8..168afb9e56 100644
--- a/src/quick/scenegraph/util/qsgtexturereader.cpp
+++ b/src/quick/scenegraph/util/qsgtexturereader.cpp
@@ -43,6 +43,7 @@
 
 #if QT_CONFIG(opengl)
 #include <private/qsgpkmhandler_p.h>
+#include <private/qsgktxhandler_p.h>
 #endif
 
 #include <QFileInfo>
@@ -80,6 +81,8 @@ bool QSGTextureReader::isTexture()
         // Currently the handlers are hardcoded; later maybe a list of plugins
         if (QSGPkmHandler::canRead(suffix, headerBlock)) {
             m_handler = new QSGPkmHandler(m_device, logName);
+        } else if (QSGKtxHandler::canRead(suffix, headerBlock)) {
+            m_handler = new QSGKtxHandler(m_device, logName);
         }
         // else if OtherHandler::canRead() ...etc.
     }