1 files changed, 103 insertions, 0 deletions
diff --git a/src/trace/trace.h b/src/trace/trace.h
new file mode 100644
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--- /dev/null
+++ b/src/trace/trace.h
@@ -0,0 +1,103 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+/*
+ * Authors:
+ *   Bob Jamison <rjamison@titan.com>
+ *
+ * Copyright (C) 2004-2006 Bob Jamison
+ *
+ * Released under GNU GPL v2+, read the file 'COPYING' for more information.
+ */
+#ifndef INKSCAPE_TRACE_H
+#define INKSCAPE_TRACE_H
+
+#include <vector>
+#include <utility>
+#include <cstring>
+#include <2geom/pathvector.h>
+#include <gdkmm/pixbuf.h>
+#include "async/channel.h"
+#include "object/weakptr.h"
+#include "object/sp-image.h"
+
+namespace Inkscape {
+namespace Async { template <typename... T> class Progress; }
+namespace Trace {
+
+struct TraceResultItem
+{
+    TraceResultItem(std::string style_, Geom::PathVector path_)
+        : style(std::move(style_))
+        , path(std::move(path_)) {}
+
+    std::string style;
+    Geom::PathVector path;
+};
+
+using TraceResult = std::vector<TraceResultItem>;
+
+/**
+ * A generic interface for plugging different autotracers into Inkscape.
+ */
+class TracingEngine
+{
+public:
+    TracingEngine() = default;
+    virtual ~TracingEngine() = default;
+
+    /**
+     * This is the working method of this interface, and all implementing classes. Take a
+     * GdkPixbuf, trace it, and return a style attribute and the path data that is
+     * compatible with the d="" attribute of an SVG <path> element.
+     *
+     * This function will be called off-main-thread, so is required to be thread-safe.
+     * The lack of const however indicates that it is not required to be re-entrant.
+     */
+    virtual TraceResult trace(Glib::RefPtr<Gdk::Pixbuf> const &pixbuf, Async::Progress<double> &progress) = 0;
+
+    /**
+     * Generate a quick preview without any actual tracing. Like trace(), this must be thread-safe.
+     */
+    virtual Glib::RefPtr<Gdk::Pixbuf> preview(Glib::RefPtr<Gdk::Pixbuf> const &pixbuf) = 0;
+
+    /**
+     * Return true if the user should be checked with before tracing because the image is too big.
+     */
+    virtual bool check_image_size(Geom::IntPoint const &size) const { return false; }
+};
+
+namespace detail { struct TraceFutureCreate; }
+
+class TraceFuture
+{
+public:
+    void cancel() { channel.close(); image_watcher.reset(); }
+    explicit operator bool() const { return (bool)channel; }
+
+private:
+    Async::Channel::Dest channel;
+    std::shared_ptr<SPWeakPtr<SPImage>> image_watcher;
+    friend class detail::TraceFutureCreate;
+};
+
+/**
+ * Launch an asynchronous trace operation taking as input \a engine and \a sioxEnabled.
+ * If this returns null, the task failed to launch and no further action will be taken.
+ * Otherwise, a background task is launched which will call \a onprogress some number of times
+ * followed by \a onfinished exactly once. Both callbacks are invoked from the GTK main loop.
+ */
+TraceFuture trace(std::unique_ptr<TracingEngine> engine,
+                  bool sioxEnabled,
+                  std::function<void(double)> onprogress,
+                  std::function<void()> onfinished);
+
+/**
+ * Similar to \a trace(), but computes the preview and passes it to \a onfinished when done.
+ */
+TraceFuture preview(std::unique_ptr<TracingEngine> engine,
+                    bool sioxEnabled,
+                    std::function<void(Glib::RefPtr<Gdk::Pixbuf>)> onfinished);
+
+} // namespace Trace
+} // namespace Inkscape
+
+#endif // INKSCAPE_TRACE_H