path: root/src/lib/render_text.cc

/*
    Copyright (C) 2014-2021 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 "cross.h"
#include "dcpomatic_assert.h"
#include "font.h"
#include "font_config.h"
#include "image.h"
#include "render_text.h"
#include "util.h"
#include <dcp/warnings.h>
#include <cairomm/cairomm.h>
LIBDCP_DISABLE_WARNINGS
#include <pangomm.h>
#include <pangommconfig.h>
LIBDCP_ENABLE_WARNINGS
#include <pango/pangocairo.h>
#include <fmt/format.h>
#include <boost/algorithm/string.hpp>
#include <iostream>


using std::cerr;
using std::cout;
using std::make_pair;
using std::make_shared;
using std::max;
using std::min;
using std::pair;
using std::shared_ptr;
using std::string;
using std::vector;
using boost::optional;
using namespace dcpomatic;


#if CAIROMM_MAJOR_VERSION == 1 && CAIROMM_MINOR_VERSION <= 14
#define DCPOMATIC_OLD_CAIROMM_API
#endif

#if PANGOMM_MAJOR_VERSION == 2 && PANGOMM_MINOR_VERSION <= 46
#define DCPOMATIC_OLD_PANGOMM_API
#endif


/** Create a Pango layout using a dummy context which we can use to calculate the size
 *  of the text we will render.  Then we can transfer the layout over to the real context
 *  for the actual render.
 */
static Glib::RefPtr<Pango::Layout>
create_layout(string font_name, string markup)
{
	auto c_font_map = pango_cairo_font_map_new();
	DCPOMATIC_ASSERT(c_font_map);
	auto font_map = Glib::wrap(c_font_map);
	auto c_context = pango_font_map_create_context(c_font_map);

	cairo_font_options_t *options = cairo_font_options_create();
	/* CAIRO_ANTIALIAS_BEST is totally broken here: see e.g.
	 * https://gitlab.freedesktop.org/cairo/cairo/-/issues/152
	 */
	cairo_font_options_set_antialias(options, CAIRO_ANTIALIAS_GOOD);
	cairo_font_options_set_hint_style(options, CAIRO_HINT_STYLE_FULL);
	pango_cairo_context_set_font_options(c_context, options);
	cairo_font_options_destroy(options);

	DCPOMATIC_ASSERT(c_context);
	auto context = Glib::wrap(c_context);
	auto layout = Pango::Layout::create(context);

#ifdef DCPOMATIC_OLD_PANGOMM_API
	layout->set_alignment(Pango::ALIGN_LEFT);
#else
	layout->set_alignment(Pango::Alignment::LEFT);
#endif
	Pango::FontDescription font(font_name);
	layout->set_font_description(font);
	layout->set_markup(markup);

	return layout;
}


string
marked_up(vector<StringText> subtitles, int target_height, float fade_factor, string font_name)
{
	auto constexpr pixels_to_1024ths_point = 72 * 1024 / 96;

	auto make_span = [target_height, fade_factor](StringText const& subtitle, string text, string extra_attribute) {
		string span;
		span += "<span ";
		if (subtitle.italic()) {
			span += "style=\"italic\" ";
		}
		if (subtitle.bold()) {
			span += "weight=\"bold\" ";
		}
		if (subtitle.underline()) {
			span += "underline=\"single\" ";
		}
		span += "size=\"" + fmt::to_string(lrintf(subtitle.size_in_pixels(target_height) * pixels_to_1024ths_point)) + "\" ";
		/* Between 1-65535 inclusive, apparently... */
		span += "alpha=\"" + fmt::to_string(int(floor(fade_factor * 65534)) + 1) + "\" ";
		span += "color=\"#" + subtitle.colour().to_rgb_string() + "\"";
		if (!extra_attribute.empty()) {
			span += " " + extra_attribute;
		}
		span += ">";

		boost::algorithm::replace_all(text, "&", "&amp;");
		boost::algorithm::replace_all(text, "<", "&lt;");
		boost::algorithm::replace_all(text, ">", "&gt;");
		boost::algorithm::replace_all(text, "\n", "");

		span += text;
		span += "</span>";
		return span;
	};

	string out;
	for (auto const& i: subtitles) {
		if (std::abs(i.space_before()) > dcp::SPACE_BEFORE_EPSILON) {
			/* We need to insert some horizontal space into the layout.  The only way I can find to do this
			 * is to write a " " with some special letter_spacing.  As far as I can see, such a space will
			 * be written with letter_spacing either side.  This means that to get a horizontal space x we
			 * need to write a " " with letter spacing (x - s) / 2, where s is the width of the " ".
			 */
			auto layout = create_layout(font_name, make_span(i, " ", {}));
			int space_width;
			int dummy;
			layout->get_pixel_size(space_width, dummy);
			auto spacing = ((i.space_before() * i.size_in_pixels(target_height) - space_width) / 2) * pixels_to_1024ths_point;
			out += make_span(i, " ", "letter_spacing=\"" + fmt::to_string(std::round(spacing)) + "\"");
		}

		if (i.string_text()) {
			out += make_span(i, *i.string_text(), {});
		} else {
			out += make_span(i, i.ruby_text()->base, {});
		}
	}

	return out;
}


static void
set_source_rgba(Cairo::RefPtr<Cairo::Context> context, dcp::Colour colour, float fade_factor)
{
	context->set_source_rgba(float(colour.r) / 255, float(colour.g) / 255, float(colour.b) / 255, fade_factor);
}


static shared_ptr<Image>
create_image(dcp::Size size)
{
	/* FFmpeg BGRA means first byte blue, second byte green, third byte red, fourth byte alpha.
	 * This must be COMPACT as we're using it with Cairo::ImageSurface::create
	 */
	auto image = make_shared<Image>(AV_PIX_FMT_BGRA, size, Image::Alignment::COMPACT);
	image->make_black();
	return image;
}


static Cairo::RefPtr<Cairo::ImageSurface>
create_surface(shared_ptr<Image> image)
{
	/* XXX: I don't think it's guaranteed that format_stride_for_width will return a stride without any padding,
	 * so it's lucky that this works.
	 */
	DCPOMATIC_ASSERT(image->alignment() == Image::Alignment::COMPACT);
	DCPOMATIC_ASSERT(image->pixel_format() == AV_PIX_FMT_BGRA);
	return Cairo::ImageSurface::create(
		image->data()[0],
#ifdef DCPOMATIC_OLD_CAIROMM_API
		Cairo::FORMAT_ARGB32,
#else
		Cairo::ImageSurface::Format::ARGB32,
#endif
		image->size().width,
		image->size().height,
		/* Cairo ARGB32 means first byte blue, second byte green, third byte red, fourth byte alpha */
		Cairo::ImageSurface::format_stride_for_width(
#ifdef DCPOMATIC_OLD_CAIROMM_API
			Cairo::FORMAT_ARGB32,
#else
			Cairo::ImageSurface::Format::ARGB32,
#endif
			image->size().width
			)
		);
}


static float
calculate_fade_factor(StringText const& first, DCPTime time, int frame_rate)
{
	float fade_factor = 1;

	/* Round the fade start/end to the nearest frame start.  Otherwise if a subtitle starts just after
	   the start of a frame it will be faded out.
	*/
	auto const fade_in_start = DCPTime::from_seconds(first.in().as_seconds()).round(frame_rate);
	auto const fade_in_end = fade_in_start + DCPTime::from_seconds(first.fade_up_time().as_seconds());

	if (fade_in_start <= time && time <= fade_in_end && fade_in_start != fade_in_end) {
		fade_factor *= DCPTime(time - fade_in_start).seconds() / DCPTime(fade_in_end - fade_in_start).seconds();
	}

	if (time < fade_in_start) {
		fade_factor = 0;
	}

	/* first.out() may be zero if we don't know when this subtitle will finish.  We can only think about
	 * fading out if we _do_ know when it will finish.
	 */
	if (first.out() != dcp::Time()) {
		auto const fade_out_end = DCPTime::from_seconds(first.out().as_seconds()).round(frame_rate);
		auto const fade_out_start = fade_out_end - DCPTime::from_seconds(first.fade_down_time().as_seconds());

		if (fade_out_start <= time && time <= fade_out_end && fade_out_start != fade_out_end) {
			fade_factor *= 1 - DCPTime(time - fade_out_start).seconds() / DCPTime(fade_out_end - fade_out_start).seconds();
		}
		if (time > fade_out_end) {
			fade_factor = 0;
		}
	}

	return fade_factor;
}


static int
x_position(dcp::HAlign align, float position, int target_width, int layout_width)
{
	int x = 0;
	switch (align) {
	case dcp::HAlign::LEFT:
		/* h_position is distance between left of frame and left of subtitle */
		x = position * target_width;
		break;
	case dcp::HAlign::CENTER:
		/* h_position is distance between centre of frame and centre of subtitle */
		x = (0.5 + position) * target_width - layout_width / 2;
		break;
	case dcp::HAlign::RIGHT:
		/* h_position is distance between right of frame and right of subtitle */
		x = (1.0 - position) * target_width - layout_width;
		break;
	}

	return x;
}


/** @param align_standard Standard with which to interpret this subtitle's position.
 *  @param align alignment.
 *  @param position position (between 0 and 1)
 *  @param target_height Height of the target screen (in pixels).
 *  @param baseline_to_bottom Distance from text baseline to the bottom of the bounding box (in pixels).
 *  @param layout_height Height of the subtitle bounding box (in pixels).
 *  @return y position of the top of the subtitle bounding box (in pixels) from the top of the screen.
 */
static int
y_position(dcp::SubtitleStandard standard, dcp::VAlign align, float position, int target_height, int baseline_to_bottom, int layout_height)
{
	int y = 0;
	switch (standard) {
	case dcp::SubtitleStandard::INTEROP:
	case dcp::SubtitleStandard::SMPTE_2014:
		switch (align) {
		case dcp::VAlign::TOP:
			/* position is distance from top of frame to subtitle baseline */
			y = position * target_height - (layout_height - baseline_to_bottom);
			break;
		case dcp::VAlign::CENTER:
			/* position is distance from centre of frame to subtitle baseline */
			y = (0.5 + position) * target_height - (layout_height - baseline_to_bottom);
			break;
		case dcp::VAlign::BOTTOM:
			/* position is distance from bottom of frame to subtitle baseline */
			y = (1.0 - position) * target_height - (layout_height - baseline_to_bottom);
			break;
		}
		break;
	case dcp::SubtitleStandard::SMPTE_2007:
	case dcp::SubtitleStandard::SMPTE_2010:
		switch (align) {
		case dcp::VAlign::TOP:
			/* v_position is distance from top of frame to top of subtitle */
			y = position * target_height;
			break;
		case dcp::VAlign::CENTER:
			/* v_position is distance from centre of frame to centre of subtitle */
			y = (0.5 + position) * target_height - layout_height / 2;
			break;
		case dcp::VAlign::BOTTOM:
			/* v_position is distance from bottom of frame to bottom of subtitle */
			y = (1.0 - position) * target_height - layout_height;
			break;
		}
	}

	return y;
}


struct Layout
{
	Position<int> position;
	int baseline_position;
	dcp::Size size;
	Glib::RefPtr<Pango::Layout> pango;

	int baseline_to_bottom(int border_width)
	{
		return position.y + size.height - baseline_position - border_width;
	}
};


/** @param subtitles A list of subtitles that are all on the same line,
 *  at the same time and with the same fade in/out.
 */
static Layout
setup_layout(vector<StringText> subtitles, dcp::Size target, DCPTime time, int frame_rate)
{
	DCPOMATIC_ASSERT(!subtitles.empty());
	auto const& first = subtitles.front();

	auto const font_name = FontConfig::instance()->make_font_available(first.font);
	auto const fade_factor = calculate_fade_factor(first, time, frame_rate);
	auto const markup = marked_up(subtitles, target.height, fade_factor, font_name);
	auto layout = create_layout(font_name, markup);
	auto ink = layout->get_ink_extents();

	Layout description;
	description.position = { ink.get_x() / Pango::SCALE, ink.get_y() / Pango::SCALE };
	description.baseline_position = layout->get_baseline() / Pango::SCALE;
	description.size = { ink.get_width() / Pango::SCALE, ink.get_height() / Pango::SCALE };
	description.pango = layout;

	return description;
}


static
float
dcp_pixels_to_pixels(dcp::Size target, int pixels)
{
	return pixels * target.width / 2048.0;
}


static
float
border_width_for_subtitle(StringText const& subtitle, dcp::Size target)
{
	return subtitle.effect() == dcp::Effect::BORDER ? dcp_pixels_to_pixels(target, subtitle.outline_width) : 0;
}


/** @param subtitles A list of subtitles that are all on the same line,
 *  at the same time and with the same fade in/out.
 */
static PositionImage
render_line(vector<StringText> subtitles, dcp::Size target, DCPTime time, int frame_rate)
{
	/* XXX: this method can only handle italic / bold changes mid-line,
	   nothing else yet.
	*/

	DCPOMATIC_ASSERT(!subtitles.empty());
	auto const& first = subtitles.front();
	auto const fade_factor = calculate_fade_factor(first, time, frame_rate);

	auto layout = setup_layout(subtitles, target, time, frame_rate);

	/* Calculate x and y scale factors.  These are only used to stretch
	   the font away from its normal aspect ratio.
	*/
	float x_scale = 1;
	float y_scale = 1;
	if (fabs(first.aspect_adjust() - 1.0) > dcp::ASPECT_ADJUST_EPSILON) {
		if (first.aspect_adjust() < 1) {
			x_scale = max(0.25f, first.aspect_adjust());
			y_scale = 1;
		} else {
			x_scale = 1;
			y_scale = 1 / min(4.0f, first.aspect_adjust());
		}
	}

	auto const border_width = border_width_for_subtitle(first, target);
	auto const shadow_offset = dcp_pixels_to_pixels(target, 4);
	layout.size.width += 2 * ceil(border_width) + ceil(shadow_offset);
	layout.size.height += 2 * ceil(border_width) + ceil(shadow_offset);

	layout.size.width *= x_scale;
	layout.size.height *= y_scale;

	/* Shuffle the subtitle over by the border width (if we have any) so it's not cut off */
	int const x_offset = -layout.position.x + ceil(border_width);
	int const y_offset = -layout.position.y + ceil(border_width);

	auto image = create_image(layout.size);
	auto surface = create_surface(image);
	auto context = Cairo::Context::create(surface);

	layout.pango->update_from_cairo_context(context);

	context->set_line_width(1);
	context->scale(x_scale, y_scale);

	if (first.effect() == dcp::Effect::SHADOW) {
		/* Drop-shadow effect */
		set_source_rgba(context, first.effect_colour(), fade_factor);
		context->move_to(x_offset + shadow_offset, y_offset + shadow_offset);
		layout.pango->add_to_cairo_context(context);
		context->fill();
	}

	if (first.effect() == dcp::Effect::BORDER) {
		/* Border effect */
		set_source_rgba(context, first.effect_colour(), fade_factor);
		context->set_line_width(border_width);
#ifdef DCPOMATIC_OLD_CAIROMM_API
		context->set_line_join(Cairo::LINE_JOIN_ROUND);
#else
		context->set_line_join(Cairo::Context::LineJoin::ROUND);
#endif
		context->move_to(x_offset, y_offset);
		layout.pango->add_to_cairo_context(context);
		context->stroke();
	}

	/* The actual subtitle */
	context->move_to(x_offset, y_offset);
	layout.pango->show_in_cairo_context(context);

	int const x = x_position(first.h_align(), first.h_position(), target.width, layout.size.width);
	int const y = y_position(first.valign_standard, first.v_align(), first.v_position(), target.height, layout.baseline_to_bottom(border_width), layout.size.height);
	return PositionImage(image, Position<int>(max(0, x), max(0, y)));
}


/** @param time Time of the frame that these subtitles are going on.
 *  @param target Size of the container that this subtitle will end up in.
 *  @param frame_rate DCP frame rate.
 */
vector<PositionImage>
render_text(vector<StringText> subtitles, dcp::Size target, DCPTime time, int frame_rate)
{
	vector<StringText> pending;
	vector<PositionImage> images;

	for (auto const& i: subtitles) {
		if (!pending.empty()) {
			auto const last = pending.back();
			auto const different_v = i.v_align() != last.v_align() || !text_positions_close(i.v_position(), last.v_position());
			auto const different_h = i.h_align() != last.h_align() || !text_positions_close(i.h_position(), pending.back().h_position());
			if (different_v || different_h) {
				/* We need a new line if any new positioning (horizontal or vertical) changes for this section */
				images.push_back(render_line(pending, target, time, frame_rate));
				pending.clear();
			}
		}
		pending.push_back(i);
	}

	if (!pending.empty()) {
		images.push_back(render_line(pending, target, time, frame_rate));
	}

	return images;
}


vector<dcpomatic::Rect<int>>
bounding_box(vector<StringText> subtitles, dcp::Size target, optional<dcp::SubtitleStandard> override_standard)
{
	vector<StringText> pending;
	vector<dcpomatic::Rect<int>> rects;

	auto use_pending = [&pending, &rects, target, override_standard]() {
		auto const& subtitle = pending.front();
		auto standard = override_standard.get_value_or(subtitle.valign_standard);
		/* We can provide dummy values for time and frame rate here as they are only used to calculate fades */
		auto layout = setup_layout(pending, target, DCPTime(), 24);
		int const x = x_position(subtitle.h_align(), subtitle.h_position(), target.width, layout.size.width);
		auto const border_width = border_width_for_subtitle(subtitle, target);
		int const y = y_position(standard, subtitle.v_align(), subtitle.v_position(), target.height, layout.baseline_to_bottom(border_width), layout.size.height);
		rects.push_back({Position<int>(x, y), layout.size.width, layout.size.height});
	};

	for (auto const& i: subtitles) {
		if (!pending.empty() && (i.v_align() != pending.back().v_align() || !text_positions_close(i.v_position(), pending.back().v_position()))) {
			use_pending();
			pending.clear();
		}
		pending.push_back(i);
	}

	if (!pending.empty()) {
		use_pending();
	}

	return rects;
}


float
FontMetrics::height(StringText const& subtitle)
{
	return get(subtitle)->second.second;
}


float
FontMetrics::baseline_to_bottom(StringText const& subtitle)
{
	return get(subtitle)->second.first;
}


FontMetrics::Cache::iterator
FontMetrics::get(StringText const& subtitle)
{
	auto id = Identifier(subtitle);

	auto iter = _cache.find(id);
	if (iter != _cache.end()) {
		return iter;
	}

	auto const font_name = FontConfig::instance()->make_font_available(subtitle.font);
	auto copy = subtitle;
	copy.set_text("Qypjg");
	auto layout = create_layout(font_name, marked_up({copy}, _target_height, 1, font_name));
	auto ink = layout->get_ink_extents();
	auto const scale = float(_target_height * Pango::SCALE);
	return _cache.insert({id, { ink.get_y() / scale, ink.get_height() / scale}}).first;
}


FontMetrics::Identifier::Identifier(StringText const& subtitle)
	: font(subtitle.font)
	, size(subtitle.size())
	, aspect_adjust(subtitle.aspect_adjust())
{

}


bool
FontMetrics::Identifier::operator<(FontMetrics::Identifier const& other) const
{
	if (font != other.font) {
		return font < other.font;
	}

	if (size != other.size) {
		return size < other.size;
	}

	return aspect_adjust < other.aspect_adjust;
}