modules/droste: implement a droste overlay effectdroste

2 files changed, 234 insertions, 0 deletions

diff --git a/src/modules/droste/Makefile.am b/src/modules/droste/Makefile.am
new file mode 100644
index 0000000..3285815
--- /dev/null
+++ b/src/modules/droste/Makefile.am
@@ -0,0 +1,3 @@
+noinst_LTLIBRARIES = libdroste.la
+libdroste_la_SOURCES = droste.c
+libdroste_la_CPPFLAGS = -I@top_srcdir@/src -I@top_srcdir@/src/libs
diff --git a/src/modules/droste/droste.c b/src/modules/droste/droste.c
new file mode 100644
index 0000000..41a1fcc
--- /dev/null
+++ b/src/modules/droste/droste.c
@@ -0,0 +1,231 @@
+/*
+ *  Copyright (C) 2024 - Vito Caputo - <vcaputo@pengaru.com>
+ *
+ *  This program is free software: you can redistribute it and/or modify it
+ *  under the terms of the GNU General Public License version 2 as published
+ *  by the Free Software Foundation.
+ *
+ *  This program is distributed in the hope that it will be useful,
+ *  but WITHOUT ANY WARRANTY; without even the implied warranty of
+ *  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ *  GNU General Public License for more details.
+ *
+ *  You should have received a copy of the GNU General Public License
+ *  along with this program.  If not, see <http://www.gnu.org/licenses/>.
+ */
+
+#include <stdint.h>
+
+#include "til.h"
+#include "til_fb.h"
+#include "til_module_context.h"
+
+/* This implements a "droste effect", also known as an infinity mirror:
+ * https://en.wikipedia.org/wiki/Droste_effect
+ * https://en.wikipedia.org/wiki/Infinity_mirror
+ */
+
+/* Some potential TODO items:
+ *
+ * - A default base layer so we can clear the experimental flag
+ *
+ * - Fractional, or at least runtime-configurable scaling... though
+ *   exposing a tap for it would be fun
+ *
+ * - Runtime-configurable multisampled scaling
+ *
+ * - The current implementation is very simple but relies on the
+ *   preservation of original contents in til_fb_fragment_snapshot(),
+ *   which causes a full copy.  This is wasteful since we only want
+ *   the unzoomed periphery preserved from the original.  Maybe there
+ *   should be a clip mask for the preservation in
+ *   til_fb_fragment_snapshot(), or just do the peripheral copy ourselves
+ *   and stop asking the snapshot code to do that for us.
+ *
+ */
+
+typedef struct droste_context_t {
+	til_module_context_t	til_module_context;
+
+	til_fb_fragment_t	*snapshot;
+} droste_context_t;
+
+
+static til_module_context_t * droste_create_context(const til_module_t *module, til_stream_t *stream, unsigned seed, unsigned ticks, unsigned n_cpus, til_setup_t *setup)
+{
+	droste_context_t	*ctxt;
+
+	ctxt = til_module_context_new(module, sizeof(droste_context_t), stream, seed, ticks, n_cpus, setup);
+	if (!ctxt)
+		return NULL;
+
+	return &ctxt->til_module_context;
+}
+
+
+static void droste_destroy_context(til_module_context_t *context)
+{
+	droste_context_t	*ctxt = (droste_context_t *)context;
+
+	if (ctxt->snapshot)
+		ctxt->snapshot = til_fb_fragment_reclaim(ctxt->snapshot);
+
+	free(context);
+}
+
+
+/* derived from til_fragmenter_slice_per_cpu_x16(), but tweaked to only fragment the inset area */
+static int droste_fragmenter(til_module_context_t *context, const til_fb_fragment_t *fragment, unsigned number, til_fb_fragment_t *res_fragment)
+{
+	til_fb_fragment_t	inset = *fragment;
+	unsigned		slice, yoff;
+
+	assert(fragment);
+	assert(res_fragment);
+
+	inset.width = fragment->width >> 1;
+	inset.height = fragment->height >> 1;
+	inset.frame_width = inset.width;
+	inset.frame_height = inset.height;
+	inset.x = inset.y = 0;
+	inset.buf += inset.pitch * ((fragment->height - inset.height) >> 1) + ((fragment->width - inset.width) >> 1);
+	inset.stride += fragment->width >> 1;
+
+	slice = MAX(inset.height / context->n_cpus * 16, 1);
+	yoff = slice * number;
+
+	if (yoff >= inset.height)
+		return 0;
+
+	if (fragment->texture) {
+		til_fb_fragment_t	inset_texture;
+
+		inset_texture = *(fragment->texture);
+		inset.texture = &inset_texture;
+
+		/* TODO */
+
+		assert(res_fragment->texture);
+		assert(fragment->frame_width == fragment->texture->frame_width);
+		assert(fragment->frame_height == fragment->texture->frame_height);
+		assert(fragment->width == fragment->texture->width);
+		assert(fragment->height == fragment->texture->height);
+		assert(fragment->x == fragment->texture->x);
+		assert(fragment->y == fragment->texture->y);
+
+		*(res_fragment->texture) = (til_fb_fragment_t){
+				.buf = fragment->texture->buf + yoff * fragment->texture->pitch,
+				.x = fragment->x,
+				.y = fragment->y + yoff,
+				.width = fragment->width,
+				.height = MIN(fragment->height - yoff, slice),
+				.frame_width = fragment->frame_width,
+				.frame_height = fragment->frame_height,
+				.stride = fragment->texture->stride,
+				.pitch = fragment->texture->pitch,
+				.cleared = fragment->texture->cleared,
+		};
+
+	}
+
+	*res_fragment = (til_fb_fragment_t){
+				.texture = inset.texture ? res_fragment->texture : NULL,
+				.buf = inset.buf + yoff * inset.pitch,
+				.x = inset.x,
+				.y = inset.y + yoff,
+				.width = inset.width,
+				.height = MIN(inset.height - yoff, slice),
+				.frame_width = inset.frame_width,
+				.frame_height = inset.frame_height,
+				.stride = inset.stride,
+				.pitch = inset.pitch,
+				.number = number,
+				.cleared = inset.cleared,
+			};
+
+	return 1;
+
+}
+
+
+/* Prepare a frame for concurrent drawing of fragment using multiple fragments */
+static void droste_prepare_frame(til_module_context_t *context, til_stream_t *stream, unsigned ticks, til_fb_fragment_t **fragment_ptr, til_frame_plan_t *res_frame_plan)
+{
+	*res_frame_plan = (til_frame_plan_t){ .fragmenter = droste_fragmenter };
+
+	{
+		droste_context_t	*ctxt = (droste_context_t *)context;
+		til_fb_fragment_t	*fragment = *fragment_ptr;
+		til_fb_fragment_t	*snapshot = ctxt->snapshot;
+
+		if (!snapshot)
+			return;
+
+		if (fragment->frame_width != snapshot->frame_width ||
+		    fragment->frame_height != snapshot->frame_height ||
+		    fragment->height != snapshot->height ||
+		    fragment->width != snapshot->width) {
+
+			/* discard the snapshot which will prevent doing anything this frame,
+			 * since it doesn't match the incoming fragment (like a resize situation)
+			 */
+			ctxt->snapshot = til_fb_fragment_reclaim(ctxt->snapshot);
+
+			return;
+		}
+
+		/* TODO: if we're not used as an overlay, here'd be a good place to generate something or
+		 * just use another module as a base layer...  until we do something sensible here, we should
+		 * keep this as an experimental module so it doesn't get used by automation as a base layer..
+		 * it also needs something to show in montage.
+		 */
+	}
+}
+
+
+static void droste_render_fragment(til_module_context_t *context, til_stream_t *stream, unsigned ticks, unsigned cpu, til_fb_fragment_t **fragment_ptr)
+{
+	droste_context_t	*ctxt = (droste_context_t *)context;
+	til_fb_fragment_t	*fragment = *fragment_ptr;
+	til_fb_fragment_t	*snapshot = ctxt->snapshot;
+
+	if (!snapshot)
+		return;
+
+	for (unsigned y = fragment->y; y < fragment->y + fragment->height; y++) {
+		for (unsigned x = fragment->x; x < fragment->x + fragment->width; x++) {
+			uint32_t	color;
+
+			color = til_fb_fragment_get_pixel_clipped(snapshot, x << 1, y << 1);
+			til_fb_fragment_put_pixel_unchecked(fragment, 0, x, y, color);
+		}
+	}
+}
+
+
+static int droste_finish_frame(til_module_context_t *context, til_stream_t *stream, unsigned int ticks, til_fb_fragment_t **fragment_ptr)
+{
+	droste_context_t	*ctxt = (droste_context_t *)context;
+
+	/* if we have a stowed frame clean it up */
+	if (ctxt->snapshot)
+		ctxt->snapshot = til_fb_fragment_reclaim(ctxt->snapshot);
+
+	/* stow the new frame for the next time around to sample from */
+	ctxt->snapshot = til_fb_fragment_snapshot(fragment_ptr, 1);
+
+	return 0;
+}
+
+
+til_module_t	droste_module = {
+	.create_context = droste_create_context,
+	.destroy_context = droste_destroy_context,
+	.prepare_frame = droste_prepare_frame,
+	.render_fragment = droste_render_fragment,
+	.finish_frame = droste_finish_frame,
+	.name = "droste",
+	.description = "Droste effect (threaded)",
+	.author = "Vito Caputo <vcaputo@pengaru.com>",
+	.flags = TIL_MODULE_OVERLAYABLE | TIL_MODULE_EXPERIMENTAL,
+};