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LibGfx: Re-structure the whole initialization pattern for image decoders

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When trying to figure out the correct implementation, we now have a very
strong distinction on plugins that are well suited for sniffing, and
plugins that need a MIME type to be chosen.

Instead of having multiple calls to non-static virtual sniff methods for
each Image decoding plugin, we have 2 static methods for each
implementation:
1. The sniff method, which in contrast to the old method, gets a
    ReadonlyBytes parameter and ensures we can figure out the result
    with zero heap allocations for most implementations.
2. The create method, which just creates a new instance so we don't
    expose the constructor to everyone anymore.

In addition to that, we have a new virtual method called initialize,
which has a per-implementation initialization pattern to actually ensure
each implementation can construct a decoder object, and then have a
correct context being applied to it for the actual decoding.
This commit is contained in:
Liav A 2023-01-20 10:13:14 +02:00 • committed by Linus Groh
parent 6e6999ce57
commit 57e19a7e56
33 changed files with 493 additions and 206 deletions
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30
Userland/Libraries/LibGfx/PortableImageMapLoader.h
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@ -49,6 +49,9 @@ struct PortableImageMapLoadingContext {
template<typename TContext>
class PortableImageDecoderPlugin final : public ImageDecoderPlugin {
public:
static ErrorOr<bool> sniff(ReadonlyBytes);
static ErrorOr<NonnullOwnPtr<ImageDecoderPlugin>> create(ReadonlyBytes);
PortableImageDecoderPlugin(u8 const*, size_t);
virtual ~PortableImageDecoderPlugin() override = default;
@ -57,8 +60,7 @@ public:
virtual void set_volatile() override;
[[nodiscard]] virtual bool set_nonvolatile(bool& was_purged) override;
virtual bool sniff() override;
virtual bool initialize() override;
virtual bool is_animated() override;
virtual size_t loop_count() override;
virtual size_t frame_count() override;
@ -108,7 +110,7 @@ bool PortableImageDecoderPlugin<TContext>::set_nonvolatile(bool& was_purged)
}
template<typename TContext>
bool PortableImageDecoderPlugin<TContext>::sniff()
bool PortableImageDecoderPlugin<TContext>::initialize()
{
using Context = TContext;
if (m_context->data_size < 2)
@ -123,6 +125,28 @@ bool PortableImageDecoderPlugin<TContext>::sniff()
return false;
}
template<typename TContext>
ErrorOr<NonnullOwnPtr<ImageDecoderPlugin>> PortableImageDecoderPlugin<TContext>::create(ReadonlyBytes data)
{
return adopt_nonnull_own_or_enomem(new (nothrow) PortableImageDecoderPlugin<TContext>(data.data(), data.size()));
}
template<typename TContext>
ErrorOr<bool> PortableImageDecoderPlugin<TContext>::sniff(ReadonlyBytes data)
{
using Context = TContext;
if (data.size() < 2)
return false;
if (data.data()[0] == 'P' && data.data()[1] == Context::FormatDetails::ascii_magic_number)
return true;
if (data.data()[0] == 'P' && data.data()[1] == Context::FormatDetails::binary_magic_number)
return true;
return false;
}
template<typename TContext>
bool PortableImageDecoderPlugin<TContext>::is_animated()
{