LibGfx/TIFF: Make `TIFFLoadingContext::handle_tag` be a free function

And move it to another file. This code is going to be generated soon, so
let's put it in another file.

Userland/Libraries/LibGfx/CMakeLists.txt

@@ -36,6 +36,7 @@ set(SOURCES
     ImageFormats/BMPWriter.cpp
     ImageFormats/BooleanDecoder.cpp
     ImageFormats/TIFFLoader.cpp
+    ImageFormats/TIFFTagHandler.cpp
     ImageFormats/DDSLoader.cpp
     ImageFormats/GIFLoader.cpp
     ImageFormats/ICOLoader.cpp

Userland/Libraries/LibGfx/ImageFormats/TIFFLoader.cpp

@@ -416,159 +416,7 @@ private:
             }
         }
 
-        TRY(handle_tag(tag, type, count, tiff_value));
-
-        return {};
-    }
-
-    ErrorOr<void> handle_tag(u16 tag, Type type, u32 count, Vector<Value> const& value)
-    {
-        // FIXME: Make that easy to extend
-        switch (tag) {
-        case 256:
-            // ImageWidth
-            if ((type != Type::UnsignedShort && type != Type::UnsignedLong) || count != 1)
-                return Error::from_string_literal("TIFFImageDecoderPlugin: Invalid tag 256");
-
-            value[0].visit(
-                [this]<OneOf<u16, u32> T>(T const& width) {
-                    m_metadata.size.set_width(width);
-                },
-                [&](auto const&) {
-                    VERIFY_NOT_REACHED();
-                });
-            break;
-
-        case 257:
-            // ImageLength
-            if ((type != Type::UnsignedShort && type != Type::UnsignedLong) || count != 1)
-                return Error::from_string_literal("TIFFImageDecoderPlugin: Invalid tag 257");
-
-            value[0].visit(
-                [this]<OneOf<u16, u32> T>(T const& width) {
-                    m_metadata.size.set_height(width);
-                },
-                [&](auto const&) {
-                    VERIFY_NOT_REACHED();
-                });
-            break;
-
-        case 258:
-            // BitsPerSample
-            if (type != Type::UnsignedShort || count != 3)
-                return Error::from_string_literal("TIFFImageDecoderPlugin: Invalid tag 258");
-
-            for (u8 i = 0; i < m_metadata.bits_per_sample.size(); ++i) {
-                value[i].visit(
-                    [this, i](u16 const& bits_per_sample) {
-                        m_metadata.bits_per_sample[i] = bits_per_sample;
-                    },
-                    [&](auto const&) {
-                        VERIFY_NOT_REACHED();
-                    });
-            }
-            break;
-
-        case 259:
-            // Compression
-            if (type != Type::UnsignedShort || count != 1)
-                return Error::from_string_literal("TIFFImageDecoderPlugin: Invalid tag 259");
-
-            TRY(value[0].visit(
-                [this](u16 const& compression) -> ErrorOr<void> {
-                    if (compression > 6 && compression != to_underlying(Compression::PackBits))
-                        return Error::from_string_literal("TIFFImageDecoderPlugin: Invalid compression value");
-
-                    m_metadata.compression = static_cast<Compression>(compression);
-                    return {};
-                },
-                [&](auto const&) -> ErrorOr<void> {
-                    VERIFY_NOT_REACHED();
-                }));
-            break;
-
-        case 273:
-            // StripOffsets
-            if (type != Type::UnsignedShort && type != Type::UnsignedLong)
-                return Error::from_string_literal("TIFFImageDecoderPlugin: Invalid tag 273");
-
-            TRY(m_metadata.strip_offsets.try_ensure_capacity(count));
-            for (u32 i = 0; i < count; ++i) {
-                value[i].visit(
-                    [this]<OneOf<u16, u32> T>(T const& offset) {
-                        m_metadata.strip_offsets.append(offset);
-                    },
-                    [&](auto const&) {
-                        VERIFY_NOT_REACHED();
-                    });
-            }
-            break;
-
-        case 277:
-            // SamplesPerPixel
-            if (type != Type::UnsignedShort || count != 1)
-                return Error::from_string_literal("TIFFImageDecoderPlugin: Invalid tag 277");
-            TRY(value[0].visit(
-                [](u16 const& samples_per_pixels) -> ErrorOr<void> {
-                    if (samples_per_pixels != 3)
-                        return Error::from_string_literal("TIFFImageDecoderPlugin: Invalid tag 277");
-                    return {};
-                },
-                [&](auto const&) -> ErrorOr<void> {
-                    VERIFY_NOT_REACHED();
-                }));
-            break;
-
-        case 278:
-            // RowsPerStrip
-            if ((type != Type::UnsignedShort && type != Type::UnsignedLong) || count != 1)
-                return Error::from_string_literal("TIFFImageDecoderPlugin: Invalid tag 278");
-
-            value[0].visit(
-                [this]<OneOf<u16, u32> T>(T const& rows_per_strip) {
-                    m_metadata.rows_per_strip = rows_per_strip;
-                },
-                [&](auto const&) {
-                    VERIFY_NOT_REACHED();
-                });
-            break;
-
-        case 279:
-            // StripByteCounts
-            if (type != Type::UnsignedShort && type != Type::UnsignedLong)
-                return Error::from_string_literal("TIFFImageDecoderPlugin: Invalid tag 279");
-
-            TRY(m_metadata.strip_bytes_count.try_ensure_capacity(count));
-            for (u32 i = 0; i < count; ++i) {
-                value[i].visit(
-                    [this]<OneOf<u16, u32> T>(T const& offset) {
-                        m_metadata.strip_bytes_count.append(offset);
-                    },
-                    [&](auto const&) {
-                        VERIFY_NOT_REACHED();
-                    });
-            }
-            break;
-        case 317:
-            // Predictor
-            if (type != Type::UnsignedShort || count != 1)
-                return Error::from_string_literal("TIFFImageDecoderPlugin: Invalid tag 317");
-
-            TRY(value[0].visit(
-                [this](u16 const& predictor) -> ErrorOr<void> {
-                    if (predictor != 1 && predictor != 2)
-                        return Error::from_string_literal("TIFFImageDecoderPlugin: Invalid predictor value");
-
-                    m_metadata.predictor = static_cast<Predictor>(predictor);
-                    return {};
-                },
-                [&](auto const&) -> ErrorOr<void> {
-                    VERIFY_NOT_REACHED();
-                }));
-            break;
-        default:
-            dbgln_if(TIFF_DEBUG, "Unknown tag: {}", tag);
-        }
+        TRY(handle_tag(m_metadata, tag, type, count, tiff_value));
 
         return {};
     }

Userland/Libraries/LibGfx/ImageFormats/TIFFMetadata.h

@@ -12,6 +12,8 @@
 
 namespace Gfx {
 
+struct Metadata;
+
 namespace TIFF {
 
 enum class Type {
@@ -54,6 +56,8 @@ enum class Predictor {
     HorizontalDifferencing = 2,
 };
 
+ErrorOr<void> handle_tag(Metadata& metadata, u16 tag, Type type, u32 count, Vector<Value> const& value);
+
 }
 
 struct Metadata {

Userland/Libraries/LibGfx/ImageFormats/TIFFTagHandler.cpp

@@ -0,0 +1,165 @@
+/*
+ * Copyright (c) 2023, Lucas Chollet <lucas.chollet@serenityos.org>
+ *
+ * SPDX-License-Identifier: BSD-2-Clause
+ */
+
+#include <AK/Debug.h>
+#include <AK/String.h>
+#include <LibGfx/ImageFormats/TIFFMetadata.h>
+
+namespace Gfx::TIFF {
+
+ErrorOr<void> handle_tag(Metadata& metadata, u16 tag, Type type, u32 count, Vector<Value> const& value)
+{
+    // FIXME: Make that easy to extend
+    switch (tag) {
+    case 256:
+        // ImageWidth
+        if ((type != Type::UnsignedShort && type != Type::UnsignedLong) || count != 1)
+            return Error::from_string_literal("TIFFImageDecoderPlugin: Invalid tag 256");
+
+        value[0].visit(
+            [&metadata]<OneOf<u16, u32> T>(T const& width) {
+                metadata.size.set_width(width);
+            },
+            [&](auto const&) {
+                VERIFY_NOT_REACHED();
+            });
+        break;
+
+    case 257:
+        // ImageLength
+        if ((type != Type::UnsignedShort && type != Type::UnsignedLong) || count != 1)
+            return Error::from_string_literal("TIFFImageDecoderPlugin: Invalid tag 257");
+
+        value[0].visit(
+            [&metadata]<OneOf<u16, u32> T>(T const& width) {
+                metadata.size.set_height(width);
+            },
+            [&](auto const&) {
+                VERIFY_NOT_REACHED();
+            });
+        break;
+
+    case 258:
+        // BitsPerSample
+        if (type != Type::UnsignedShort || count != 3)
+            return Error::from_string_literal("TIFFImageDecoderPlugin: Invalid tag 258");
+
+        for (u8 i = 0; i < metadata.bits_per_sample.size(); ++i) {
+            value[i].visit(
+                [&metadata, i](u16 const& bits_per_sample) {
+                    metadata.bits_per_sample[i] = bits_per_sample;
+                },
+                [&](auto const&) {
+                    VERIFY_NOT_REACHED();
+                });
+        }
+        break;
+
+    case 259:
+        // Compression
+        if (type != Type::UnsignedShort || count != 1)
+            return Error::from_string_literal("TIFFImageDecoderPlugin: Invalid tag 259");
+
+        TRY(value[0].visit(
+            [&metadata](u16 const& compression) -> ErrorOr<void> {
+                if (compression > 6 && compression != to_underlying(Compression::PackBits))
+                    return Error::from_string_literal("TIFFImageDecoderPlugin: Invalid compression value");
+
+                metadata.compression = static_cast<Compression>(compression);
+                return {};
+            },
+            [&](auto const&) -> ErrorOr<void> {
+                VERIFY_NOT_REACHED();
+            }));
+        break;
+
+    case 273:
+        // StripOffsets
+        if (type != Type::UnsignedShort && type != Type::UnsignedLong)
+            return Error::from_string_literal("TIFFImageDecoderPlugin: Invalid tag 273");
+
+        TRY(metadata.strip_offsets.try_ensure_capacity(count));
+        for (u32 i = 0; i < count; ++i) {
+            value[i].visit(
+                [&metadata]<OneOf<u16, u32> T>(T const& offset) {
+                    metadata.strip_offsets.append(offset);
+                },
+                [&](auto const&) {
+                    VERIFY_NOT_REACHED();
+                });
+        }
+        break;
+
+    case 277:
+        // SamplesPerPixel
+        if (type != Type::UnsignedShort || count != 1)
+            return Error::from_string_literal("TIFFImageDecoderPlugin: Invalid tag 277");
+        TRY(value[0].visit(
+            [](u16 const& samples_per_pixels) -> ErrorOr<void> {
+                if (samples_per_pixels != 3)
+                    return Error::from_string_literal("TIFFImageDecoderPlugin: Invalid tag 277");
+                return {};
+            },
+            [&](auto const&) -> ErrorOr<void> {
+                VERIFY_NOT_REACHED();
+            }));
+        break;
+
+    case 278:
+        // RowsPerStrip
+        if ((type != Type::UnsignedShort && type != Type::UnsignedLong) || count != 1)
+            return Error::from_string_literal("TIFFImageDecoderPlugin: Invalid tag 278");
+
+        value[0].visit(
+            [&metadata]<OneOf<u16, u32> T>(T const& rows_per_strip) {
+                metadata.rows_per_strip = rows_per_strip;
+            },
+            [&](auto const&) {
+                VERIFY_NOT_REACHED();
+            });
+        break;
+
+    case 279:
+        // StripByteCounts
+        if (type != Type::UnsignedShort && type != Type::UnsignedLong)
+            return Error::from_string_literal("TIFFImageDecoderPlugin: Invalid tag 279");
+
+        TRY(metadata.strip_bytes_count.try_ensure_capacity(count));
+        for (u32 i = 0; i < count; ++i) {
+            value[i].visit(
+                [&metadata]<OneOf<u16, u32> T>(T const& offset) {
+                    metadata.strip_bytes_count.append(offset);
+                },
+                [&](auto const&) {
+                    VERIFY_NOT_REACHED();
+                });
+        }
+        break;
+    case 317:
+        // Predictor
+        if (type != Type::UnsignedShort || count != 1)
+            return Error::from_string_literal("TIFFImageDecoderPlugin: Invalid tag 317");
+
+        TRY(value[0].visit(
+            [&metadata](u16 const& predictor) -> ErrorOr<void> {
+                if (predictor != 1 && predictor != 2)
+                    return Error::from_string_literal("TIFFImageDecoderPlugin: Invalid predictor value");
+
+                metadata.predictor = static_cast<Predictor>(predictor);
+                return {};
+            },
+            [&](auto const&) -> ErrorOr<void> {
+                VERIFY_NOT_REACHED();
+            }));
+        break;
+    default:
+        dbgln_if(TIFF_DEBUG, "Unknown tag: {}", tag);
+    }
+
+    return {};
+}
+
+}