1 files changed, 75 insertions, 0 deletions
diff --git a/src/ui/widget/canvas/util.h b/src/ui/widget/canvas/util.h
new file mode 100644
index 0000000..c2c1ad3
--- /dev/null
+++ b/src/ui/widget/canvas/util.h
@@ -0,0 +1,75 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+#ifndef INKSCAPE_UI_WIDGET_CANVAS_UTIL_H
+#define INKSCAPE_UI_WIDGET_CANVAS_UTIL_H
+
+#include <array>
+#include <2geom/int-rect.h>
+#include <2geom/affine.h>
+#include <cairomm/cairomm.h>
+#include "color.h"
+
+namespace Inkscape {
+namespace UI {
+namespace Widget {
+
+// Cairo additions
+
+/**
+ * Turn a Cairo region into a path on a given Cairo context.
+ */
+void region_to_path(Cairo::RefPtr<Cairo::Context> const &cr, Cairo::RefPtr<Cairo::Region> const &reg);
+
+/**
+ * Shrink a region by d/2 in all directions, while also translating it by (d/2 + t, d/2 + t).
+ */
+Cairo::RefPtr<Cairo::Region> shrink_region(Cairo::RefPtr<Cairo::Region> const &reg, int d, int t = 0);
+
+inline auto unioned(Cairo::RefPtr<Cairo::Region> a, Cairo::RefPtr<Cairo::Region> const &b)
+{
+    a->do_union(b);
+    return a;
+}
+
+// Colour operations
+
+inline auto rgb_to_array(uint32_t rgb)
+{
+    return std::array{SP_RGBA32_R_U(rgb) / 255.0f, SP_RGBA32_G_U(rgb) / 255.0f, SP_RGBA32_B_U(rgb) / 255.0f};
+}
+
+inline auto rgba_to_array(uint32_t rgba)
+{
+    return std::array{SP_RGBA32_R_U(rgba) / 255.0f, SP_RGBA32_G_U(rgba) / 255.0f, SP_RGBA32_B_U(rgba) / 255.0f, SP_RGBA32_A_U(rgba) / 255.0f};
+}
+
+inline auto premultiplied(std::array<float, 4> arr)
+{
+    arr[0] *= arr[3];
+    arr[1] *= arr[3];
+    arr[2] *= arr[3];
+    return arr;
+}
+
+std::array<float, 3> checkerboard_darken(std::array<float, 3> const &rgb, float amount = 1.0f);
+
+inline auto checkerboard_darken(uint32_t rgba)
+{
+    return checkerboard_darken(rgb_to_array(rgba), 1.0f - SP_RGBA32_A_U(rgba) / 255.0f);
+}
+
+} // namespace Widget
+} // namespace UI
+} // namespace Inkscape
+
+#endif // INKSCAPE_UI_WIDGET_CANVAS_UTIL_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 :