canvas.cpp

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/*
    Copyright (C) 2007 - 2025
    by Mark de Wever <koraq@xs4all.nl>
    Part of the Battle for Wesnoth Project https://www.wesnoth.org/
 
    This program 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.
    This program is distributed in the hope that it will be useful,
    but WITHOUT ANY WARRANTY.
 
    See the COPYING file for more details.
*/
 
/**
 * @file
 * Implementation of canvas.hpp.
 */
 
#define GETTEXT_DOMAIN "wesnoth-lib"
 
#include "gui/core/canvas.hpp"
#include "gui/core/canvas_private.hpp"
 
#include "draw.hpp"
#include "draw_manager.hpp"
#include "font/text.hpp"
#include "font/attributes.hpp"
#include "font/font_options.hpp"
#include "formatter.hpp"
#include "gettext.hpp"
#include "gui/auxiliary/typed_formula.hpp"
#include "gui/core/log.hpp"
#include "gui/widgets/helper.hpp"
#include "font/font_config.hpp"
#include "font/standard_colors.hpp"
#include "picture.hpp"
#include "sdl/point.hpp"
#include "sdl/rect.hpp"
#include "sdl/surface.hpp"
#include "sdl/texture.hpp"
#include "sdl/utils.hpp" // blur_surface
#include "utils/general.hpp"
#include "video.hpp" // read_pixels_low_res, only used for blurring
#include "wml_exception.hpp"
 
namespace gui2
{
 
/***** ***** ***** ***** ***** LINE ***** ***** ***** ***** *****/
 
line_shape::line_shape(const config& cfg)
    : shape(cfg)
    , x1_(cfg["x1"])
    , y1_(cfg["y1"])
    , x2_(cfg["x2"])
    , y2_(cfg["y2"])
    , color_(cfg["color"])
    , thickness_(cfg["thickness"].to_unsigned())
{
    const std::string& debug = (cfg["debug"]);
    if(!debug.empty()) {
        DBG_GUI_P << "Line: found debug message '" << debug << "'.";
    }
}
 
void line_shape::draw(wfl::map_formula_callable& variables)
{
    /**
     * @todo formulas are now recalculated every draw cycle which is a bit silly
     * unless there has been a resize. So to optimize we should use an extra
     * flag or do the calculation in a separate routine.
     */
 
    const unsigned x1 = x1_(variables);
    const unsigned y1 = y1_(variables);
    const unsigned x2 = x2_(variables);
    const unsigned y2 = y2_(variables);
 
    DBG_GUI_D << "Line: draw from " << x1 << ',' << y1 << " to " << x2 << ',' << y2 << ".";
 
    // @todo FIXME respect the thickness.
 
    draw::line(x1, y1, x2, y2, color_(variables));
}
 
/***** ***** ***** ***** ***** Rectangle ***** ***** ***** ***** *****/
 
rectangle_shape::rectangle_shape(const config& cfg)
    : rect_bounded_shape(cfg)
    , border_thickness_(cfg["border_thickness"].to_int())
    , border_color_(cfg["border_color"], color_t::null_color())
    , fill_color_(cfg["fill_color"], color_t::null_color())
{
    // Check if a raw color string evaluates to a null color.
    if(!border_color_.has_formula() && border_color_().null()) {
        border_thickness_ = 0;
    }
 
    const std::string& debug = (cfg["debug"]);
    if(!debug.empty()) {
        DBG_GUI_P << "Rectangle: found debug message '" << debug << "'.";
    }
}
 
rectangle_shape::rectangle_shape(
    const rect& bounds,
    const color_t& border_color,
    const unsigned thickness,
    const color_t& fill_color)
    : rect_bounded_shape(bounds)
    , border_thickness_(thickness)
    , border_color_(border_color)
    , fill_color_(fill_color)
{
}
 
void rectangle_shape::draw(wfl::map_formula_callable& variables)
{
    const rect area {
        x_(variables),
        y_(variables),
        w_(variables),
        h_(variables)
    };
 
    const color_t fill_color = fill_color_(variables);
 
    // Fill the background, if applicable
    if(!fill_color.null()) {
        DBG_GUI_D << "fill " << fill_color;
        draw::set_color(fill_color);
        draw::fill(area.padded_by(-border_thickness_));
    }
 
    const color_t border_color = border_color_(variables);
 
    // Draw the border
    draw::set_color(border_color);
    DBG_GUI_D << "border thickness " << border_thickness_ << ", colour " << border_color;
    for(int i = 0; i < border_thickness_; ++i) {
        draw::rect(area.padded_by(-i));
    }
}
 
/***** ***** ***** ***** ***** Rounded Rectangle ***** ***** ***** ***** *****/
 
round_rectangle_shape::round_rectangle_shape(const config& cfg)
    : rect_bounded_shape(cfg)
    , r_(cfg["corner_radius"])
    , border_thickness_(cfg["border_thickness"].to_int())
    , border_color_(cfg["border_color"], color_t::null_color())
    , fill_color_(cfg["fill_color"], color_t::null_color())
{
    // Check if a raw color string evaluates to a null color.
    if(!border_color_.has_formula() && border_color_().null()) {
        border_thickness_ = 0;
    }
 
    const std::string& debug = (cfg["debug"]);
    if(!debug.empty()) {
        DBG_GUI_P << "Rounded Rectangle: found debug message '" << debug << "'.";
    }
}
 
void round_rectangle_shape::draw(wfl::map_formula_callable& variables)
{
    const int x = x_(variables);
    const int y = y_(variables);
    const int w = w_(variables);
    const int h = h_(variables);
    const int r = r_(variables);
 
    DBG_GUI_D << "Rounded Rectangle: draw from " << x << ',' << y << " width " << w << " height " << h << ".";
 
    const color_t fill_color = fill_color_(variables);
 
    // Fill the background, if applicable
    if(!fill_color.null() && w && h) {
        draw::set_color(fill_color);
 
        draw::fill(rect{x + r,                 y + border_thickness_, w - r                 * 2, r - border_thickness_ + 1});
        draw::fill(rect{x + border_thickness_, y + r + 1,             w - border_thickness_ * 2, h - r * 2});
        draw::fill(rect{x + r,                 y - r + h + 1,         w - r                 * 2, r - border_thickness_});
 
        draw::disc(x + r,     y + r,     r, 0xc0);
        draw::disc(x + w - r, y + r,     r, 0x03);
        draw::disc(x + r,     y + h - r, r, 0x30);
        draw::disc(x + w - r, y + h - r, r, 0x0c);
    }
 
    const color_t border_color = border_color_(variables);
 
    // Draw the border
    draw::set_color(border_color);
 
    for(int i = 0; i < border_thickness_; ++i) {
        draw::line(x + r, y + i,     x + w - r, y + i);
        draw::line(x + r, y + h - i, x + w - r, y + h - i);
 
        draw::line(x + i,     y + r, x + i,     y + h - r);
        draw::line(x + w - i, y + r, x + w - i, y + h - r);
 
        draw::circle(x + r,     y + r,     r - i, 0xc0);
        draw::circle(x + w - r, y + r,     r - i, 0x03);
        draw::circle(x + r,     y + h - r, r - i, 0x30);
        draw::circle(x + w - r, y + h - r, r - i, 0x0c);
    }
}
 
/***** ***** ***** ***** ***** CIRCLE ***** ***** ***** ***** *****/
 
circle_shape::circle_shape(const config& cfg)
    : shape(cfg)
    , x_(cfg["x"])
    , y_(cfg["y"])
    , radius_(cfg["radius"])
    , border_color_(cfg["border_color"])
    , fill_color_(cfg["fill_color"])
    , border_thickness_(cfg["border_thickness"].to_int(1))
{
    const std::string& debug = (cfg["debug"]);
    if(!debug.empty()) {
        DBG_GUI_P << "Circle: found debug message '" << debug << "'.";
    }
}
 
void circle_shape::draw(wfl::map_formula_callable& variables)
{
    /**
     * @todo formulas are now recalculated every draw cycle which is a bit
     * silly unless there has been a resize. So to optimize we should use an
     * extra flag or do the calculation in a separate routine.
     */
    const int x = x_(variables);
    const int y = y_(variables);
    const unsigned radius = radius_(variables);
    const color_t fill_color = fill_color_(variables);
    if (!fill_color.null()) {
        draw::cairo_disc(x, y, radius, fill_color);
    }
 
    const color_t border_color = border_color_(variables);
    draw::cairo_circle(x, y, radius, border_color, border_thickness_);
 
    DBG_GUI_D << "Circle: drawn at " << x << ',' << y << " radius " << radius << ".";
}
 
/***** ***** ***** ***** ***** IMAGE ***** ***** ***** ***** *****/
 
image_shape::image_shape(const config& cfg, wfl::action_function_symbol_table& functions)
    : shape(cfg)
    , x_(cfg["x"])
    , y_(cfg["y"])
    , w_(cfg["w"])
    , h_(cfg["h"])
    , image_name_(cfg["name"], "")  // avoid ambiguous ctor error
    , resize_mode_(get_resize_mode(cfg["resize_mode"]))
    , mirror_(cfg.get_old_attribute("mirror", "vertical_mirror", "image"))
    , actions_formula_(cfg["actions"], &functions)
    , failure_logged_(false)
{
    const std::string& debug = (cfg["debug"]);
    if(!debug.empty()) {
        DBG_GUI_P << "Image: found debug message '" << debug << "'.";
    }
}
 
image_shape::image_shape(
    const point& origin,
    const std::string& img_path)
    : shape()
    , x_(origin.x)
    , y_(origin.y)
    , w_("(image_width)")
    , h_("(image_height)")
    , image_name_(img_path, img_path) // avoid ambiguous ctor error
    , resize_mode_(get_resize_mode("scale_sharp"))
    , mirror_(false)
    , actions_formula_("")
{
}
 
void image_shape::dimension_validation(unsigned value, const std::string& name, const std::string& key)
{
    const int as_int = static_cast<int>(value);
 
    VALIDATE_WITH_DEV_MESSAGE(as_int >= 0, _("Image doesn’t fit on canvas."),
        formatter() << "Image '" << name << "', " << key << " = " << as_int << "."
    );
}
 
void image_shape::draw(wfl::map_formula_callable& variables)
{
    DBG_GUI_D << "Image: draw.";
 
    // The name will be passed to the texture loading code on each draw, any caching is left to the
    // image loading code itself. A name can point to a different image file due to i18n support,
    // even when the image_name_ isn't a formula.
    const std::string& name = image_name_(variables);
 
    if(name.empty()) {
        if(!failure_logged_) {
            DBG_GUI_D << "Image: name is empty or contains invalid formula, will not be drawn.";
            failure_logged_ = true;
        }
        return;
    }
 
    // Texture filtering mode must be set on texture creation,
    // so check whether we need smooth scaling or not here.
    image::scale_quality scale_quality = image::scale_quality::nearest;
    if (resize_mode_ == resize_mode::stretch
        || resize_mode_ == resize_mode::scale)
    {
        scale_quality = image::scale_quality::linear;
    }
    texture tex = image::get_texture(image::locator(name), scale_quality);
 
    if(!tex) {
        if(!failure_logged_) {
            ERR_GUI_D << "Image: '" << name << "' not found and won't be drawn.";
            failure_logged_ = true;
        }
        return;
    }
 
    wfl::map_formula_callable local_variables(variables);
    local_variables.add("image_original_width", wfl::variant(tex.w()));
    local_variables.add("image_original_height", wfl::variant(tex.h()));
 
    int w = w_(local_variables);
    dimension_validation(w, name, "w");
 
    int h = h_(local_variables);
    dimension_validation(h, name, "h");
 
    local_variables.add("image_width", wfl::variant(w ? w : tex.w()));
    local_variables.add("image_height", wfl::variant(h ? h : tex.h()));
 
    const int x = x_(local_variables);
    const int y = y_(local_variables);
 
    // used in gui/dialogs/story_viewer.cpp
    local_variables.add("clip_x", wfl::variant(x));
    local_variables.add("clip_y", wfl::variant(y));
 
    if (variables.has_key("fake_draw") && variables.query_value("fake_draw").as_bool()) {
        variables.add("image_original_width", wfl::variant(tex.w()));
        variables.add("image_original_height", wfl::variant(tex.h()));
        variables.add("image_width", wfl::variant(w ? w : tex.w()));
        variables.add("image_height", wfl::variant(h ? h : tex.h()));
        return;
    }
 
    // Execute the provided actions for this context.
    wfl::execute_actions(actions_formula_.evaluate(local_variables), wfl::variant(variables.fake_ptr()));
 
    // If w or h is 0, assume it means the whole image.
    if (!w) { w = tex.w(); }
    if (!h) { h = tex.h(); }
 
    const rect dst_rect { x, y, w, h };
 
    // What to do with the image depends on whether we need to tile it or not.
    switch(resize_mode_) {
    case resize_mode::tile:
        draw::tiled(tex, dst_rect, false, mirror_(variables));
        break;
    case resize_mode::tile_center:
        draw::tiled(tex, dst_rect, true, mirror_(variables));
        break;
    case resize_mode::tile_highres:
        draw::tiled_highres(tex, dst_rect, false, mirror_(variables));
        break;
    case resize_mode::stretch:
        // Stretching is identical to scaling in terms of handling.
        // Is this intended? That's what previous code was doing.
    case resize_mode::scale:
        // Filtering mode is set on texture creation above.
        // Handling is otherwise identical to sharp scaling.
    case resize_mode::scale_sharp:
        if(mirror_(variables)) {
            draw::flipped(tex, dst_rect);
        } else {
            draw::blit(tex, dst_rect);
        }
        break;
    default:
        ERR_GUI_D << "Image: unrecognized resize mode.";
        break;
    }
}
 
image_shape::resize_mode image_shape::get_resize_mode(const std::string& resize_mode)
{
    if(resize_mode == "tile") {
        return resize_mode::tile;
    } else if(resize_mode == "tile_center") {
        return resize_mode::tile_center;
    } else if(resize_mode == "tile_highres") {
        return resize_mode::tile_highres;
    } else if(resize_mode == "stretch") {
        return resize_mode::stretch;
    } else if(resize_mode == "scale_sharp") {
        return resize_mode::scale_sharp;
    } else if(resize_mode == "scale") {
        return resize_mode::scale;
    } else {
        if(!resize_mode.empty()) {
            ERR_GUI_E << "Invalid resize mode '" << resize_mode << "' falling back to 'scale'.";
        }
 
        // Linear scaling just looks horrible as a default, especially on HDPI screens, and even
        // for some non-pixel art (the logo, for example). Nearest-neighbor isn't perfect for those
        // usecases, but it's definitely better, in my opinion.
        //
        // -- vultraz, 2022-08-20
        return resize_mode::scale_sharp;
    }
}
 
/***** ***** ***** ***** ***** TEXT ***** ***** ***** ***** *****/
 
namespace
{
/** Populates the attribute list from the given config child range. */
auto parse_attributes(const config::const_child_itors& range)
{
    // TODO: most of the time this will be empty, unless you're using rich_label.
    // It's a lot of memory allocations to always have a valid object here...
    // Do we need store it as an optional?
    font::attribute_list text_attributes;
 
    for(const config& attr : range) {
        const std::string name = attr["name"];
 
        if(name.empty()) {
            continue;
        }
 
        const unsigned start = attr["start"].to_int(PANGO_ATTR_INDEX_FROM_TEXT_BEGINNING);
        const unsigned end = attr["end"].to_int(PANGO_ATTR_INDEX_TO_TEXT_END);
 
        // Attributes with start == end set won't do anything, so skip
        if (start == end) {
            WRN_GUI_D << "attribute " << name << " has equal start and end indices, will not be added.";
            continue;
        }
 
        if (name == "color" || name == "fgcolor" || name == "foreground") {
            add_attribute_fg_color(text_attributes, start, end, attr["value"].empty() ? font::NORMAL_COLOR : font::string_to_color(attr["value"]));
        } else if (name == "bgcolor" || name == "background") {
            add_attribute_bg_color(text_attributes, start, end, attr["value"].empty() ? font::GOOD_COLOR : font::string_to_color(attr["value"]));
        } else if (name == "font_size" || name == "size") {
            add_attribute_size(text_attributes, start, end, attr["value"].to_int(font::SIZE_NORMAL));
        } else if (name == "font_family" || name == "face") {
            add_attribute_font_family(text_attributes, start, end, font::decode_family_class(attr["value"]));
        } else if (name == "weight") {
            add_attribute_weight(text_attributes, start, end, decode_text_weight(attr["value"]));
        } else if (name == "style") {
            add_attribute_style(text_attributes, start, end, decode_text_style(attr["value"]));
        } else if (name == "bold" || name == "b") {
            add_attribute_weight(text_attributes, start, end, PANGO_WEIGHT_BOLD);
        } else if (name == "italic" || name == "i") {
            add_attribute_style(text_attributes, start, end, PANGO_STYLE_ITALIC);
        } else if (name == "underline" || name == "u") {
            add_attribute_underline(text_attributes, start, end, PANGO_UNDERLINE_SINGLE);
        } else if (name == "line_height") {
            add_attribute_line_height(text_attributes, start, end, attr["value"].to_double());
        } else if (name == "image") { // An inline image that behave as a custom text glyph
            add_attribute_image_shape(text_attributes, start, end, attr["value"]);
        } else {
            // Unsupported formatting or normal text
            add_attribute_weight(text_attributes, start, end, PANGO_WEIGHT_NORMAL);
            add_attribute_style(text_attributes, start, end, PANGO_STYLE_NORMAL);
        }
    }
 
    return text_attributes;
}
 
} // anon namespace
 
text_shape::text_shape(const config& cfg, wfl::action_function_symbol_table& functions)
    : rect_bounded_shape(cfg)
    , font_family_(font::decode_family_class(cfg["font_family"]))
    , font_size_(cfg["font_size"], font::SIZE_NORMAL)
    , font_style_(decode_font_style(cfg["font_style"]))
    , text_alignment_(cfg["text_alignment"])
    , color_(cfg["color"], font::NORMAL_COLOR)
    , text_(cfg["text"])
    , parse_text_as_formula_(cfg["parse_text_as_formula"].to_bool(true))
    , text_markup_(cfg["text_markup"], false)
    , link_aware_(cfg["text_link_aware"], false)
    , link_color_(cfg["text_link_color"], font::YELLOW_COLOR)
    , maximum_width_(cfg["maximum_width"], -1)
    , characters_per_line_(cfg["text_characters_per_line"].to_unsigned())
    , maximum_height_(cfg["maximum_height"], -1)
    , highlight_start_(cfg["highlight_start"])
    , highlight_end_(cfg["highlight_end"])
    , highlight_color_(cfg["highlight_color"], color_t::from_hex_string("215380"))
    , line_spacing_(cfg["line_spacing"].to_double(font::get_line_spacing_factor()))
    , outline_(cfg["outline"], false)
    , actions_formula_(cfg["actions"], &functions)
    , text_attributes_(parse_attributes(cfg.child_range("attribute")))
{
    const std::string& debug = (cfg["debug"]);
    if(!debug.empty()) {
        DBG_GUI_P << "Text: found debug message '" << debug << "'.";
    }
}
 
text_shape::text_shape(
    const point& origin,
    font::family_class family,
    const unsigned size,
    font::pango_text::FONT_STYLE style,
    const std::string& align,
    const unsigned width)
    : rect_bounded_shape(origin, "(text_width)", "(text_height)")
    , font_family_(family)
    , font_size_(size)
    , font_style_(style)
    , text_alignment_(align)
    , color_(font::NORMAL_COLOR)
    , parse_text_as_formula_(false)
    , text_markup_(false)
    , link_aware_(false)
    , link_color_(font::YELLOW_COLOR)
    , maximum_width_(width)
    , characters_per_line_(0)
    , maximum_height_(-1)
    , highlight_start_("")
    , highlight_end_("")
    , highlight_color_(color_t::from_hex_string("215380"))
    , line_spacing_(0)
    , outline_(false)
    , actions_formula_("")
    , text_attributes_()
{
}
 
t_string text_shape::get_text() const {
    return text_.t_str();
}
 
void text_shape::set_text(const t_string& text) {
    text_ = text;
}
 
std::pair<std::size_t, std::size_t> text_shape::add_text(const t_string& text)
{
    t_string old_text = get_text();
    std::size_t start = old_text.size();
    set_text(old_text + text);
    std::size_t end = start + text.size();
    return { start, end };
}
 
void text_shape::set_wrap_width(const unsigned wrap_width) {
    maximum_width_.set_value(wrap_width);
}
 
void text_shape::add_attribute(
    const std::string& name,
    const std::string& extra_data,
    std::size_t start,
    std::size_t end)
{
    if(name.empty()) {
        return;
    }
 
    // Attributes with start == end set won't do anything, so skip
    if (start == end) {
        WRN_GUI_D << "attribute " << name << " has equal start and end indices, will not be added.";
        return;
    }
 
    if (name == "color" || name == "fgcolor" || name == "foreground") {
        add_attribute_fg_color(text_attributes_, start, end, extra_data.empty() ? font::NORMAL_COLOR : font::string_to_color(extra_data));
    } else if (name == "bgcolor" || name == "background") {
        add_attribute_bg_color(text_attributes_, start, end, extra_data.empty() ? font::GOOD_COLOR : font::string_to_color(extra_data));
    } else if (name == "font_size" || name == "size") {
        add_attribute_size(text_attributes_, start, end, std::stoi(extra_data));
    } else if (name == "font_family" || name == "face") {
        add_attribute_font_family(text_attributes_, start, end, font::decode_family_class(extra_data));
    } else if (name == "weight") {
        add_attribute_weight(text_attributes_, start, end, decode_text_weight(extra_data));
    } else if (name == "style") {
        add_attribute_style(text_attributes_, start, end, decode_text_style(extra_data));
    } else if (name == "bold" || name == "b") {
        add_attribute_weight(text_attributes_, start, end, PANGO_WEIGHT_BOLD);
    } else if (name == "italic" || name == "i") {
        add_attribute_style(text_attributes_, start, end, PANGO_STYLE_ITALIC);
    } else if (name == "underline" || name == "u") {
        add_attribute_underline(text_attributes_, start, end, PANGO_UNDERLINE_SINGLE);
    } else if (name == "line_height") {
        add_attribute_line_height(text_attributes_, start, end, std::stod(extra_data));
    } else if (name == "image") { // An inline image that behave as a custom text glyph
        add_attribute_image_shape(text_attributes_, start, end, extra_data);
    } else {
        // Unsupported formatting or normal text
        add_attribute_weight(text_attributes_, start, end, PANGO_WEIGHT_NORMAL);
        add_attribute_style(text_attributes_, start, end, PANGO_STYLE_NORMAL);
    }
}
 
void text_shape::add_attributes_from(text_shape& tshape2, const unsigned attr_start)
{
    text_attributes_.splice_into(tshape2.text_attributes_, attr_start);
}
 
void text_shape::draw(wfl::map_formula_callable& variables)
{
    assert(variables.has_key("text"));
 
    // We first need to determine the size of the text which need the rendered
    // text. So resolve and render the text first and then start to resolve
    // the other formulas.
    const auto text = parse_text_as_formula_
        ? typed_formula<t_string>{text_}(variables)
        : text_.t_str();
 
    if(text.empty()) {
        DBG_GUI_D << "Text: no text to render, leave.";
        return;
    }
 
    //
    // Highlight
    //
    const int highlight_start = highlight_start_(variables);
    const int highlight_end = highlight_end_(variables);
 
    if(highlight_start != highlight_end) {
        add_attribute_bg_color(text_attributes_, highlight_start, highlight_end, highlight_color_(variables));
    }
 
    font::pango_text& text_renderer = font::get_text_renderer();
    text_renderer.clear_attributes();
 
    text_renderer
        .set_link_aware(link_aware_(variables))
        .set_link_color(link_color_(variables))
        .set_text(text, text_markup_(variables));
 
    text_renderer
        .set_family_class(font_family_)
        .set_font_size(font_size_(variables))
        .set_font_style(font_style_)
        .set_alignment(text_alignment_(variables))
        .set_foreground_color(color_(variables))
        .set_maximum_width(maximum_width_(variables))
        .set_maximum_height(maximum_height_(variables), true)
        .set_ellipse_mode(variables.has_key("text_wrap_mode")
                ? static_cast<PangoEllipsizeMode>(variables.query_value("text_wrap_mode").as_int())
                : PANGO_ELLIPSIZE_END)
        .set_characters_per_line(characters_per_line_)
        .set_add_outline(outline_(variables))
        .set_line_spacing(line_spacing_);
 
    // Do this last so it can merge with attributes from markup
    text_renderer.apply_attributes(text_attributes_);
 
    wfl::map_formula_callable local_variables(variables);
    const auto [tw, th] = text_renderer.get_size();
 
    // Translate text width and height back to draw-space, rounding up.
    local_variables.add("text_width", wfl::variant(tw));
    local_variables.add("text_height", wfl::variant(th));
 
    if (variables.has_key("fake_draw") && variables.query_value("fake_draw").as_bool()) {
        variables.add("text_width", wfl::variant(tw));
        variables.add("text_height", wfl::variant(th));
        return;
    }
 
    const int x = x_(local_variables);
    const int y = y_(local_variables);
    const int w = w_(local_variables);
    const int h = h_(local_variables);
    rect dst_rect{x, y, w, h};
 
    // Execute the provided actions for this context.
    wfl::execute_actions(actions_formula_.evaluate(local_variables), wfl::variant(variables.fake_ptr()));
 
    texture tex = text_renderer.render_and_get_texture();
    if(!tex) {
        DBG_GUI_D << "Text: Rendering '" << text << "' resulted in an empty canvas, leave.";
        return;
    }
 
    dst_rect.w = std::min(dst_rect.w, tex.w());
    dst_rect.h = std::min(dst_rect.h, tex.h());
 
    draw::blit(tex, dst_rect);
}
 
/***** ***** ***** ***** ***** CANVAS ***** ***** ***** ***** *****/
 
canvas::canvas(const config& cfg)
    : shapes_()
    , blur_depth_(0)
    , blur_region_()
    , deferred_(false)
    , w_(0)
    , h_(0)
    , variables_()
    , functions_()
{
    parse_cfg(cfg);
}
 
// It would be better if the blur effect was managed at a higher level.
// But for now this works and should be both general and robust.
bool canvas::update_blur(const rect& screen_region, bool force)
{
    if(!blur_depth_) {
        // No blurring needed.
        return true;
    }
 
    if(screen_region != blur_region_) {
        DBG_GUI_D << "blur region changed from " << blur_region_
            << " to " << screen_region;
        // something has changed. regenerate the texture.
        blur_texture_.reset();
        blur_region_ = screen_region;
    }
 
    if(blur_texture_ && !force) {
        // We already made the blur. It's expensive, so don't do it again.
        return true;
    }
 
    // To blur what is underneath us, it must already be rendered somewhere.
    // This is okay for sub-elements of an opaque window (panels on the main
    // title screen for example) as the window will already have rendered
    // its background to the render buffer before we get here.
    // If however we are blurring elements behind the window, such as if
    // the window itself is translucent (objectives popup), or it is
    // transparent with a translucent element (character dialogue),
    // then we need to render what will be behind it before capturing that
    // and rendering a blur.
    // We could use the previous render frame, but there could well have been
    // another element there last frame such as a popup window which we
    // don't want to be part of the blur.
    // The stable solution is to render in multiple passes,
    // so that is what we shall do.
 
    // For the first pass, this element and its children are not rendered.
    if(!deferred_) {
        DBG_GUI_D << "Deferring blur at " << screen_region;
        deferred_ = true;
        draw_manager::request_extra_render_pass();
        return false;
    }
 
    // For the second pass we read the result of the first pass at
    // this widget's location, and blur it.
    DBG_GUI_D << "Blurring " << screen_region << " depth " << blur_depth_;
    rect read_region = screen_region;
    auto setter = draw::set_render_target({});
    surface s = video::read_pixels_low_res(&read_region);
    if (!s) {
        // Reading pixels can fail for reasons outside our control. The
        // failure may not be transient, so skip the blur for this frame.
        ERR_GUI_D << "Failed to read pixels to blur " << screen_region << ", skipping.";
        deferred_ = false;
        return true;
    }
    blur_surface(s, {0, 0, s->w, s->h}, blur_depth_);
    blur_texture_ = texture(s);
    deferred_ = false;
    return true;
}
 
void canvas::queue_reblur()
{
    blur_texture_.reset();
}
 
void canvas::draw()
{
    // This early-return has to come before the `validate(rect.w <= w_)` check, as during the boost_unit_tests execution
    // the debug_clock widget will have no shapes, 0x0 size, yet be given a larger rect to draw.
    if(shapes_.empty()) {
        DBG_GUI_D << "Canvas: empty (no shapes to draw).";
        return;
    }
 
    if(deferred_) {
        // We will draw next frame.
        return;
    }
 
    // Draw blurred background.
    // TODO: hwaccel - this should be able to be removed at some point with shaders
    if(blur_depth_ && blur_texture_) {
        DBG_GUI_D << "blitting blur size " << blur_texture_.draw_size();
        draw::blit(blur_texture_);
    }
 
    // Draw items
    for(auto& shape : shapes_) {
        assert(shape);
        const lg::scope_logger inner_scope_logging_object__{log_gui_draw, "Canvas: draw shape."};
        shape->draw(variables_);
    }
}
 
void canvas::parse_cfg(const config& cfg)
{
    log_scope2(log_gui_parse, "Canvas: parsing config.");
 
    for(const auto [type, data] : cfg.all_children_view())
    {
        DBG_GUI_P << "Canvas: found shape of the type " << type << ".";
 
        if(type == "line") {
            shapes_.emplace_back(std::make_unique<line_shape>(data));
        } else if(type == "rectangle") {
            shapes_.emplace_back(std::make_unique<rectangle_shape>(data));
        } else if(type == "round_rectangle") {
            shapes_.emplace_back(std::make_unique<round_rectangle_shape>(data));
        } else if(type == "circle") {
            shapes_.emplace_back(std::make_unique<circle_shape>(data));
        } else if(type == "image") {
            shapes_.emplace_back(std::make_unique<image_shape>(data, functions_));
        } else if(type == "text") {
            shapes_.emplace_back(std::make_unique<text_shape>(data, functions_));
        } else if(type == "pre_commit") {
 
            /* note this should get split if more preprocessing is used. */
            for(const auto [func_key, func_cfg] : data.all_children_view())
            {
                if(func_key == "blur") {
                    blur_depth_ = func_cfg["depth"].to_unsigned();
                } else {
                    ERR_GUI_P << "Canvas: found a pre commit function"
                              << " of an invalid type " << type << ".";
                }
            }
 
        } else {
            ERR_GUI_P << "Canvas: found a shape of an invalid type " << type
                      << ".";
        }
    }
}
 
void canvas::update_size_variables()
{
    get_screen_size_variables(variables_);
    variables_.add("width", wfl::variant(w_));
    variables_.add("height", wfl::variant(h_));
}
 
void canvas::set_size(const point& size)
{
    w_ = size.x;
    h_ = size.y;
    update_size_variables();
}
 
void canvas::clear_shapes(const bool force)
{
    if(force) {
        shapes_.clear();
    } else {
        utils::erase_if(shapes_, [](const std::unique_ptr<shape>& s) { return !s->immutable(); });
    }
}
 
/***** ***** ***** ***** ***** SHAPE ***** ***** ***** ***** *****/
 
} // namespace gui2