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

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.

1 files changed, 15 insertions, 3 deletions

diff --git a/Userland/Services/SpiceAgent/SpiceAgent.cpp b/Userland/Services/SpiceAgent/SpiceAgent.cpp
index 9119ab84b5..fcd52767e2 100644
--- a/Userland/Services/SpiceAgent/SpiceAgent.cpp
+++ b/Userland/Services/SpiceAgent/SpiceAgent.cpp
@@ -142,11 +142,23 @@ void SpiceAgent::on_message_received()
         } else {
             ErrorOr<Gfx::ImageFrameDescriptor> frame_or_error = Gfx::ImageFrameDescriptor {};
             if (type == ClipboardType::PNG) {
-                frame_or_error = Gfx::PNGImageDecoderPlugin(data_buffer.data(), data_buffer.size()).frame(0);
+                if (Gfx::PNGImageDecoderPlugin::sniff({ data_buffer.data(), data_buffer.size() }).release_value_but_fixme_should_propagate_errors()) {
+                    auto png_decoder = Gfx::PNGImageDecoderPlugin::create({ data_buffer.data(), data_buffer.size() }).release_value_but_fixme_should_propagate_errors();
+                    if (png_decoder->initialize())
+                        frame_or_error = png_decoder->frame(0);
+                }
             } else if (type == ClipboardType::BMP) {
-                frame_or_error = Gfx::BMPImageDecoderPlugin(data_buffer.data(), data_buffer.size()).frame(0);
+                if (Gfx::BMPImageDecoderPlugin::sniff({ data_buffer.data(), data_buffer.size() }).release_value_but_fixme_should_propagate_errors()) {
+                    auto bmp_decoder = Gfx::BMPImageDecoderPlugin::create({ data_buffer.data(), data_buffer.size() }).release_value_but_fixme_should_propagate_errors();
+                    if (bmp_decoder->initialize())
+                        frame_or_error = bmp_decoder->frame(0);
+                }
             } else if (type == ClipboardType::JPG) {
-                frame_or_error = Gfx::JPGImageDecoderPlugin(data_buffer.data(), data_buffer.size()).frame(0);
+                if (Gfx::JPGImageDecoderPlugin::sniff({ data_buffer.data(), data_buffer.size() }).release_value_but_fixme_should_propagate_errors()) {
+                    auto jpg_decoder = Gfx::JPGImageDecoderPlugin::create({ data_buffer.data(), data_buffer.size() }).release_value_but_fixme_should_propagate_errors();
+                    if (jpg_decoder->initialize())
+                        frame_or_error = jpg_decoder->frame(0);
+                }
             } else {
                 dbgln("Unknown clipboard type: {}", (u32)type);
                 return;