Re-added DDS plugin support

Fork of [Qt 5.6 DDS plugin](https://code.qt.io/cgit/qt/qtimageformats.git/tree/src/plugins/imageformats/dds/qddshandler.cpp?h=5.6) under LGPL2.1.

- Merged all files in dds_p.h and dds.cpp
- Added support for Qt 6 image allocation limit
- Added checks for null image and datastream errors
- The plugin is disabled by default

CCBUG: 380956

Closes: #12

src/imageformats/CMakeLists.txt

@@ -31,6 +31,12 @@ endif()
 
 ##################################
 
+if(KIMAGEFORMATS_DDS)
+    kimageformats_add_plugin(kimg_dds SOURCES dds.cpp)
+endif()
+
+##################################
+
 if (BUILD_EPS_PLUGIN)
     if (TARGET Qt6::PrintSupport)
         kimageformats_add_plugin(kimg_eps SOURCES eps.cpp)

src/imageformats/dds.json

@@ -0,0 +1,4 @@
+{
+    "Keys": [ "dds" ],
+    "MimeTypes": [ "image/x-dds" ]
+}

src/imageformats/dds_p.h

@@ -0,0 +1,143 @@
+/*
+    This file is part of the KDE project
+    SPDX-FileCopyrightText: 2015 The Qt Company Ltd
+    SPDX-FileCopyrightText: 2013 Ivan Komissarov
+
+    SPDX-License-Identifier: LGPL-2.1-only OR LGPL-3.0-only
+*/
+
+#ifndef QDDSHANDLER_H
+#define QDDSHANDLER_H
+
+#include <QImageIOPlugin>
+
+struct DDSPixelFormat
+{
+    enum DDSPixelFormatFlags {
+        FlagAlphaPixels     = 0x00000001,
+        FlagAlpha           = 0x00000002,
+        FlagFourCC          = 0x00000004,
+        FlagPaletteIndexed4 = 0x00000008,
+        FlagPaletteIndexed8 = 0x00000020,
+        FlagRGB             = 0x00000040,
+        FlagYUV             = 0x00000200,
+        FlagLuminance       = 0x00020000,
+        FlagNormal          = 0x00080000,
+        FlagRGBA = FlagAlphaPixels | FlagRGB,
+        FlagLA = FlagAlphaPixels | FlagLuminance
+    };
+
+    quint32 size;
+    quint32 flags;
+    quint32 fourCC;
+    quint32 rgbBitCount;
+    quint32 rBitMask;
+    quint32 gBitMask;
+    quint32 bBitMask;
+    quint32 aBitMask;
+};
+
+struct DDSHeader
+{
+    enum DDSFlags {
+        FlagCaps        = 0x000001,
+        FlagHeight      = 0x000002,
+        FlagWidth       = 0x000004,
+        FlagPitch       = 0x000008,
+        FlagPixelFormat = 0x001000,
+        FlagMipmapCount = 0x020000,
+        FlagLinearSize  = 0x080000,
+        FlagDepth       = 0x800000
+    };
+
+    enum DDSCapsFlags {
+        CapsComplex = 0x000008,
+        CapsTexture = 0x001000,
+        CapsMipmap  = 0x400000
+    };
+
+    enum DDSCaps2Flags {
+        Caps2CubeMap          = 0x0200,
+        Caps2CubeMapPositiveX = 0x0400,
+        Caps2CubeMapNegativeX = 0x0800,
+        Caps2CubeMapPositiveY = 0x1000,
+        Caps2CubeMapNegativeY = 0x2000,
+        Caps2CubeMapPositiveZ = 0x4000,
+        Caps2CubeMapNegativeZ = 0x8000,
+        Caps2Volume           = 0x200000
+    };
+
+    enum { ReservedCount = 11 };
+
+    quint32 magic;
+    quint32 size;
+    quint32 flags;
+    quint32 height;
+    quint32 width;
+    quint32 pitchOrLinearSize;
+    quint32 depth;
+    quint32 mipMapCount;
+    quint32 reserved1[ReservedCount];
+    DDSPixelFormat pixelFormat;
+    quint32 caps;
+    quint32 caps2;
+    quint32 caps3;
+    quint32 caps4;
+    quint32 reserved2;
+};
+
+struct DDSHeaderDX10
+{
+    quint32 dxgiFormat;
+    quint32 resourceDimension;
+    quint32 miscFlag;
+    quint32 arraySize;
+    quint32 reserved;
+};
+
+class QDDSHandler : public QImageIOHandler
+{
+public:
+    QDDSHandler();
+
+    bool canRead() const override;
+    bool read(QImage *image) override;
+    bool write(const QImage &image) override;
+
+    QVariant option(QImageIOHandler::ImageOption option) const override;
+    void setOption(ImageOption option, const QVariant &value) override;
+    bool supportsOption(QImageIOHandler::ImageOption option) const override;
+
+    int imageCount() const override;
+    bool jumpToImage(int imageNumber) override;
+
+    static bool canRead(QIODevice *device);
+
+private:
+    bool ensureScanned() const;
+    bool verifyHeader(const DDSHeader &dds) const;
+
+private:
+    enum ScanState {
+        ScanError = -1,
+        ScanNotScanned = 0,
+        ScanSuccess = 1,
+    };
+
+    DDSHeader m_header;
+    int m_format;
+    DDSHeaderDX10 m_header10;
+    int m_currentImage;
+    mutable ScanState m_scanState;
+};
+
+class QDDSPlugin : public QImageIOPlugin
+{
+    Q_OBJECT
+    Q_PLUGIN_METADATA(IID "org.qt-project.Qt.QImageIOHandlerFactoryInterface" FILE "dds.json")
+public:
+    Capabilities capabilities(QIODevice *device, const QByteArray &format) const;
+    QImageIOHandler *create(QIODevice *device, const QByteArray &format = QByteArray()) const;
+};
+
+#endif // QDDSHANDLER_H