1 files changed, 78 insertions, 0 deletions
diff --git a/src/ui/widget/canvas/updaters.h b/src/ui/widget/canvas/updaters.h
new file mode 100644
index 0000000..d36685a
--- /dev/null
+++ b/src/ui/widget/canvas/updaters.h
@@ -0,0 +1,78 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+/*
+ * Controls the order to update invalidated regions.
+ * Copyright (C) 2022 PBS <pbs3141@gmail.com>
+ * Released under GNU GPL v2+, read the file 'COPYING' for more information.
+ */
+
+#ifndef INKSCAPE_UI_WIDGET_CANVAS_UPDATERS_H
+#define INKSCAPE_UI_WIDGET_CANVAS_UPDATERS_H
+
+#include <vector>
+#include <memory>
+#include <2geom/int-rect.h>
+#include <cairomm/refptr.h>
+#include <cairomm/region.h>
+
+namespace Inkscape {
+namespace UI {
+namespace Widget {
+
+// A class for tracking invalidation events and producing redraw regions.
+class Updater
+{
+public:
+    virtual ~Updater() = default;
+
+    // The subregion of the store with up-to-date content.
+    Cairo::RefPtr<Cairo::Region> clean_region;
+
+    enum class Strategy
+    {
+        Responsive, // As soon as a region is invalidated, redraw it.
+        FullRedraw, // When a region is invalidated, delay redraw until after the current redraw is completed.
+        Multiscale, // Updates tiles near the mouse faster. Gives the best of both.
+    };
+
+    // Create an Updater using the given strategy.
+    template <Strategy strategy>
+    static std::unique_ptr<Updater> create();
+
+    // Create an Updater using a choice of strategy specified at runtime.
+    static std::unique_ptr<Updater> create(Strategy strategy);
+
+    // Return the strategy in use.
+    virtual Strategy get_strategy() const = 0;
+
+    virtual void reset() = 0;                                          // Reset the clean region to empty.
+    virtual void intersect (Geom::IntRect const &) = 0;                // Called when the store changes position; clip everything to the new store rectangle.
+    virtual void mark_dirty(Geom::IntRect const &) = 0;                // Called on every invalidate event.
+    virtual void mark_dirty(Cairo::RefPtr<Cairo::Region> const &) = 0; // Called on every invalidate event.
+    virtual void mark_clean(Geom::IntRect const &) = 0;                // Called on every rectangle redrawn.
+
+    // Called at the start of a redraw to determine what region to consider clean (i.e. will not be drawn).
+    virtual Cairo::RefPtr<Cairo::Region> get_next_clean_region() = 0;
+
+    // Called after a redraw has finished. Returns true to indicate that further redraws are required with different clean regions.
+    virtual bool report_finished() = 0;
+
+    // Called at the start of each frame. Some updaters (Multiscale) require this information.
+    virtual void next_frame() = 0;
+};
+
+} // namespace Widget
+} // namespace UI
+} // namespace Inkscape
+
+#endif // INKSCAPE_UI_WIDGET_CANVAS_UPDATERS_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 :