Fix DCP content font ID allocation to cope with DCPs that have multiple fonts

with the same name in the same reel (#2600).

Previously we had this id_for_font_in_reel() which would give an ID
of N_font-ID.  This means we got duplicate font IDs.

Here we replace that method with FontAllocator, which gives an ID of
N_font-ID for the first font and M_font-ID, where M is a number higher than
the highest reel index.  The idea is to support the required new IDs
without breaking exisiting projects.

There is some documentation of how it works  in doc/design/fonts

1 files changed, 119 insertions, 0 deletions

diff --git a/src/lib/font_id_allocator.cc b/src/lib/font_id_allocator.cc
new file mode 100644
index 000000000..ef25dc642
--- /dev/null
+++ b/src/lib/font_id_allocator.cc
@@ -0,0 +1,119 @@
+/*
+    Copyright (C) 2023 Carl Hetherington <cth@carlh.net>
+
+    This file is part of DCP-o-matic.
+
+    DCP-o-matic is free software; you can redistribute it and/or modify
+    it under the terms of the GNU General Public License as published by
+    the Free Software Foundation; either version 2 of the License, or
+    (at your option) any later version.
+
+    DCP-o-matic 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 DCP-o-matic.  If not, see <http://www.gnu.org/licenses/>.
+
+*/
+
+
+#include "compose.hpp"
+#include "constants.h"
+#include "dcpomatic_assert.h"
+#include "font_id_allocator.h"
+#include <dcp/reel.h>
+#include <dcp/reel_closed_caption_asset.h>
+#include <dcp/reel_subtitle_asset.h>
+#include <dcp/subtitle_asset.h>
+#include <set>
+#include <string>
+#include <vector>
+
+
+using std::shared_ptr;
+using std::set;
+using std::string;
+using std::vector;
+
+
+void
+FontIDAllocator::add_fonts_from_reels(vector<shared_ptr<dcp::Reel>> const& reels)
+{
+	int reel_index = 0;
+	for (auto reel: reels) {
+		if (auto sub = reel->main_subtitle()) {
+			add_fonts_from_asset(reel_index, sub->asset());
+		}
+
+		for (auto ccap: reel->closed_captions()) {
+			add_fonts_from_asset(reel_index, ccap->asset());
+		}
+
+		++reel_index;
+	}
+}
+
+
+void
+FontIDAllocator::add_fonts_from_asset(int reel_index, shared_ptr<const dcp::SubtitleAsset> asset)
+{
+	for (auto const& font: asset->font_data()) {
+		_map[Font(reel_index, asset->id(), font.first)] = 0;
+	}
+
+	if (asset->font_data().empty()) {
+		_map[Font(reel_index, asset->id(), "")] = 0;
+	}
+}
+
+
+void
+FontIDAllocator::add_font(int reel_index, string asset_id, string font_id)
+{
+	_map[Font(reel_index, asset_id, font_id)] = 0;
+}
+
+
+void
+FontIDAllocator::allocate()
+{
+	/* Last reel index that we have; i.e. the last prefix number that would be used by "old"
+	 * font IDs (i.e. ones before this FontIDAllocator was added and used)
+	 */
+	auto const last_reel = std::max_element(
+		_map.begin(),
+		_map.end(),
+		[] (std::pair<Font, int> const& a, std::pair<Font, int> const& b) {
+			return a.first.reel_index < b.first.reel_index;
+		})->first.reel_index;
+
+	/* Number of times each ID has been used */
+	std::map<string, int> used_count;
+
+	for (auto& font: _map) {
+		auto const proposed = String::compose("%1_%2", font.first.reel_index, font.first.font_id);
+		if (used_count.find(proposed) != used_count.end()) {
+			/* This ID was already used; we need to disambiguate it.  Do so by using
+			 * an ID above last_reel
+			 */
+			font.second = last_reel + used_count[proposed];
+			++used_count[proposed];
+		} else {
+			/* This ID was not yet used */
+			used_count[proposed] = 1;
+			font.second = font.first.reel_index;
+		}
+	}
+}
+
+
+string
+FontIDAllocator::font_id(int reel_index, string asset_id, string font_id) const
+{
+	auto iter = _map.find(Font(reel_index, asset_id, font_id));
+	DCPOMATIC_ASSERT(iter != _map.end());
+	return String::compose("%1_%2", iter->second, font_id);
+}
+