1 files changed, 75 insertions, 0 deletions
diff --git a/src/ui/widget/canvas/pixelstreamer.h b/src/ui/widget/canvas/pixelstreamer.h
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+++ b/src/ui/widget/canvas/pixelstreamer.h
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+// SPDX-License-Identifier: GPL-2.0-or-later
+/*
+ * A class hierarchy implementing various ways of streaming pixel buffers to the GPU.
+ * Copyright (C) 2022 PBS <pbs3141@gmail.com>
+ * Released under GNU GPL v2+, read the file 'COPYING' for more information.
+ */
+
+#ifndef INKSCAPE_UI_WIDGET_CANVAS_PIXELSTREAMER_H
+#define INKSCAPE_UI_WIDGET_CANVAS_PIXELSTREAMER_H
+
+#include <memory>
+#include <2geom/int-point.h>
+#include <cairomm/refptr.h>
+#include <cairomm/surface.h>
+
+namespace Inkscape {
+namespace UI {
+namespace Widget {
+
+// A class for turning Cairo image surfaces into OpenGL textures.
+class PixelStreamer
+{
+public:
+    virtual ~PixelStreamer() = default;
+
+    // Method for streaming pixels to the GPU.
+    enum class Method
+    {
+        Auto,         // Use the best option available at runtime.
+        Persistent,   // Persistent buffer mapping. (Best, requires OpenGL 4.4.)
+        Asynchronous, // Ordinary buffer mapping. (Almost as good, requires OpenGL 3.0.)
+        Synchronous   // Synchronous texture uploads. (Worst but still tolerable, requires OpenGL 1.1.)
+    };
+
+    // Create a PixelStreamer using a choice of method specified at runtime, falling back if unsupported.
+    static std::unique_ptr<PixelStreamer> create_supported(Method method);
+
+    // Return the method in use.
+    virtual Method get_method() const = 0;
+
+    /**
+     * Request a drawing surface of the given dimensions. If nogl is true, no GL commands will be issued,
+     * but the request may fail. An effort is made to keep such failures to a minimum.
+     *
+     * The surface must be returned to the PixelStreamer by calling finish(), in order to deallocate
+     * GL resourecs.
+     */
+    virtual Cairo::RefPtr<Cairo::ImageSurface> request(Geom::IntPoint const &dimensions, bool nogl = false) = 0;
+
+    /**
+     * Give back a drawing surface produced by request(), uploading the contents to the currently bound texture.
+     * The texture must be at least as big as the surface.
+     *
+     * If junk is true, then the surface will be junked instead, meaning nothing will be done with the contents,
+     * and its GL resources will simply be deallocated.
+     */
+    virtual void finish(Cairo::RefPtr<Cairo::ImageSurface> surface, bool junk = false) = 0;
+};
+
+} // namespace Widget
+} // namespace UI
+} // namespace Inkscape
+
+#endif // INKSCAPE_UI_WIDGET_CANVAS_PIXELSTREAMER_H
+
+/*
+  Local Variables:
+  mode:c++
+  c-file-style:"stroustrup"
+  c-file-offsets:((innamespace . 0)(inline-open . 0)(case-label . +))
+  indent-tabs-mode:nil
+  fill-column:99
+  End:
+*/
+// vim: filetype=cpp:expandtab:shiftwidth=4:tabstop=8:softtabstop=4 :