os: add blit/painter.h

This utility eases the application of the 'blit' function when using the
'Texture' and 'Surface' types.

repos/os/include/blit/painter.h

@@ -0,0 +1,59 @@
+/*
+ * \brief  Functor for blitting textures on a surface
+ * \author Norman Feske
+ * \date   2020-07-02
+ */
+
+/*
+ * Copyright (C) 2020 Genode Labs GmbH
+ *
+ * This file is part of the Genode OS framework, which is distributed
+ * under the terms of the GNU Affero General Public License version 3.
+ */
+
+#ifndef _INCLUDE__BLIT__PAINTER_H_
+#define _INCLUDE__BLIT__PAINTER_H_
+
+#include <blit/blit.h>
+#include <os/texture.h>
+
+
+struct Blit_painter
+{
+	typedef Genode::Surface_base::Point Point;
+	typedef Genode::Surface_base::Rect  Rect;
+
+
+	template <typename PT>
+	static inline void paint(Genode::Surface<PT>       &surface,
+	                         Genode::Texture<PT> const &texture,
+	                         Point                      position)
+	{
+		Rect const clipped = Rect::intersect(Rect(position, texture.size()),
+		                                     surface.clip());
+
+		if (!clipped.valid())
+			return;
+
+		int const src_w = texture.size().w();
+		int const dst_w = surface.size().w();
+
+		/* calculate offset of first texture pixel to copy */
+		unsigned long const tex_start_offset = (clipped.y1() - position.y())*src_w
+		                                     +  clipped.x1() - position.x();
+
+		/* start address of source pixels */
+		PT const * const src = texture.pixel() + tex_start_offset;
+
+		/* start address of destination pixels */
+		PT * const dst = surface.addr() + clipped.y1()*dst_w + clipped.x1();
+
+		blit(src, src_w*sizeof(PT),
+		     dst, dst_w*sizeof(PT),
+		     clipped.w()*sizeof(PT), clipped.h());
+
+		surface.flush_pixels(clipped);
+	}
+};
+
+#endif /* _INCLUDE__BLIT__PAINTER_H_ */