transfer_function_editor.cxx

#include "transfer_function_editor.h"
 
#include <algorithm>
#include <numeric>
 
#include <cgv/gui/key_event.h>
#include <cgv/gui/mouse_event.h>
#include <cgv/gui/theme_info.h>
#include <cgv/math/ftransform.h>
#include <cgv/utils/algorithm.h>
#include <cgv/utils/advanced_scan.h>
#include <cgv/utils/file.h>
#include <cgv_gl/gl/gl.h>
#include <cgv_g2d/msdf_font.h>
#include <cgv_g2d/msdf_gl_font_renderer.h>
 
namespace cgv {
namespace overlay {
 
const vec2 transfer_function_editor::color_point_size = { 12.0f, 18.0f };
const vec2 transfer_function_editor::opacity_point_size = { 12.0f };
 
transfer_function_editor::transfer_function_editor() {
    set_name("Color Scale Editor");
    blocks_events(true);
 
    layout.total_height = supports_opacity ? 200 : 60;
    
    set_size(ivec2(600u, layout.total_height));
    
    color_draggables.set_constraint(layout.color_draggables_rect);
    color_draggables.callback = std::bind(&transfer_function_editor::handle_drag, this, std::placeholders::_1, DraggableType::kColor);
 
    opacity_draggables.set_constraint(layout.opacity_editor_rect);
    opacity_draggables.callback = std::bind(&transfer_function_editor::handle_drag, this, std::placeholders::_1, DraggableType::kOpacity);
 
    color_handle_renderer = cgv::g2d::generic_2d_renderer(cgv::g2d::shaders::arrow);
    opacity_handle_renderer = cgv::g2d::generic_2d_renderer(cgv::g2d::shaders::rectangle);
    line_renderer = cgv::g2d::generic_2d_renderer(cgv::g2d::shaders::line);
    polygon_renderer = cgv::g2d::generic_2d_renderer(cgv::g2d::shaders::polygon);
}
 
void transfer_function_editor::clear(cgv::render::context& ctx) {
    cgv::g2d::ref_msdf_font_regular(ctx, -1);
    cgv::g2d::ref_msdf_gl_font_renderer_2d(ctx, -1);
 
    canvas_overlay::clear(ctx);
 
    color_handle_renderer.destruct(ctx);
    opacity_handle_renderer.destruct(ctx);
    line_renderer.destruct(ctx);
    polygon_renderer.destruct(ctx);
 
    background_tex.destruct(ctx);
    preview_tex.destruct(ctx);
    histogram_tex.destruct(ctx);
}
 
bool transfer_function_editor::handle_mouse_event(cgv::gui::mouse_event& e, cgv::ivec2 local_mouse_pos) {
    bool capture_event = false;
    
    //bool request_clear_selection = false;
 
    if(e.get_action() == cgv::gui::MA_PRESS) {
        if(e.get_button() & cgv::gui::MB_LEFT_BUTTON) {
            //request_clear_selection = is_hit_local(local_mouse_pos);
 
            if(!get_hit_point(local_mouse_pos)) {
                add_point(local_mouse_pos);
                //request_clear_selection = false;
            }
            capture_event = true;
        } else if(e.get_button() & cgv::gui::MB_RIGHT_BUTTON) {
            cgv::g2d::draggable* hit_point = get_hit_point(local_mouse_pos);
            if(hit_point)
                erase_point(hit_point);
        }
    }
 
    if(color_draggables.handle(e, get_viewport_size(), get_rectangle()))
        return true;
    if(opacity_draggables.handle(e, get_viewport_size(), get_rectangle()))
        return true;
    /*
    if(request_clear_selection) {
        selected_color_draggable = nullptr;
        selected_opacity_draggable = nullptr;
        handle_selection_change();
    }*/
    if (capture_event)
        return true;
    return false;
}
 
void transfer_function_editor::handle_member_change(cgv::data::informed_ptr ptr) {
    if(ptr.points_to(layout.total_height)) {
        ivec2 size = get_rectangle().size;
        size.y() = layout.total_height;
        set_size(size);
    }
 
    if(ptr.points_to(opacity_scale_exponent)) {
        opacity_scale_exponent = cgv::math::clamp(opacity_scale_exponent, 1.0f, 5.0f);
 
        update_point_positions();
        sort_points();
        create_geometry();
    }
 
    /*
    if(ptr.points_to(discretization_resolution)) {
        if(cmc.cm)
            cmc.cm->set_resolution(resolution);
        update_color_map(false);
    }
    */
 
    if(ptr.points_to_one_of(color_interpolation, opacity_interpolation)) {
        if(transfer_function) {
            transfer_function->set_color_interpolation(color_interpolation);
            if(supports_opacity)
                transfer_function->set_opacity_interpolation(opacity_interpolation);
 
            create_preview_texture();
            post_damage();
 
            if(on_change_callback)
                on_change_callback();
        }
    }
 
    if(ptr.points_to_data_of(color_draggables.ref_draggables())) {
        update_transfer_function_from_data();
        create_preview_texture();
        create_geometry();
        post_damage();
    }
 
    for(auto& draggable : opacity_draggables) {
        if(ptr.points_to(draggable.uv.y())) {
            draggable.set_uv_and_update_position(draggable.uv);
            update_transfer_function_from_data();
            create_geometry();
            post_damage();
            break;
        }
    }
    
    if(ptr.points_to(supports_opacity)) {
        // Todo: Fixme: This will overwrite the user-defined total height.
        layout.total_height = supports_opacity ? 200 : 60;
        on_set(&layout.total_height);
 
        if(!supports_opacity) {
            if(transfer_function) {
                //transfer_function->clear_opacity_points();
                //opacity_draggables.clear();
 
                update_point_positions();
                //update_color_map(false);
            }
        }
 
        post_recreate_layout();
        post_recreate_gui();
    }
}
 
bool transfer_function_editor::init(cgv::render::context& ctx) {
    cgv::g2d::ref_msdf_font_regular(ctx, 1);
    cgv::g2d::ref_msdf_gl_font_renderer_2d(ctx, 1);
    
    register_shader("rectangle", cgv::g2d::shaders::rectangle);
    register_shader("circle", cgv::g2d::shaders::circle);
    register_shader("histogram", "heightfield1d.glpr");
    //Todo: Rename shader program?
    register_shader("background", "color_map_editor_bg.glpr");
 
    bool success = canvas_overlay::init(ctx);
 
    success &= color_handle_renderer.init(ctx);
    success &= opacity_handle_renderer.init(ctx);
    success &= line_renderer.init(ctx);
    success &= polygon_renderer.init(ctx);
    success &= create_background_texture();
 
    //update_color_map(false);
 
    return success;
}
 
void transfer_function_editor::init_frame(cgv::render::context& ctx) {
    if(ensure_layout(ctx)) {
        ivec2 container_size = get_rectangle().size;
 
        update_layout(container_size);
        force_update_data_from_transfer_function();
 
        auto& bg_prog = content_canvas.enable_shader(ctx, "background");
        float width_factor = static_cast<float>(layout.opacity_editor_rect.w()) / static_cast<float>(layout.opacity_editor_rect.h());
        bg_style.texcoord_scaling = vec2(5.0f * width_factor, 5.0f);
        bg_style.apply(ctx, bg_prog);
        content_canvas.disable_current_shader(ctx);
 
        //update_point_positions();
        //update_geometry();
        
        color_draggables.set_constraint(layout.color_draggables_rect);
        opacity_draggables.set_constraint(layout.opacity_editor_rect);
    }
}
 
void transfer_function_editor::draw_content(cgv::render::context& ctx) {
    begin_content(ctx);
    
    // draw inner border
    ivec2 container_size = get_rectangle().size;
    content_canvas.enable_shader(ctx, "rectangle");
    content_canvas.set_style(ctx, border_style);
    content_canvas.draw_shape(ctx, ivec2(padding() - 1) + ivec2(0, 10), container_size - 2 * padding() + 2 - ivec2(0, 10));
    
    if(transfer_function && preview_tex.is_created()) {
        // draw color scale texture
        content_canvas.set_style(ctx, color_map_style);
        preview_tex.enable(ctx, 0);
        content_canvas.draw_shape(ctx, layout.color_editor_rect);
        preview_tex.disable(ctx);
 
        if(supports_opacity) {
            // draw opacity editor checkerboard background
            auto& bg_prog = content_canvas.enable_shader(ctx, "background");
            bg_style.apply(ctx, bg_prog);
            bg_prog.set_uniform(ctx, "scale_exponent", opacity_scale_exponent);
            background_tex.enable(ctx, 0);
            content_canvas.draw_shape(ctx, layout.opacity_editor_rect);
            background_tex.disable(ctx);
            content_canvas.disable_current_shader(ctx);
 
            // draw histogram
            if(histogram_type != HistogramType::kNone && histogram_tex.is_created()) {
                auto& hist_prog = content_canvas.enable_shader(ctx, "histogram");
                hist_prog.set_uniform(ctx, "max_value", hist_norm_ignore_zero ? hist_max_non_zero : hist_max);
                hist_prog.set_uniform(ctx, "norm_gamma", hist_norm_gamma);
                hist_prog.set_uniform(ctx, "sampling_type", cgv::math::clamp(static_cast<unsigned>(histogram_type) - 1, 0u, 2u));
                hist_style.apply(ctx, hist_prog);
 
                histogram_tex.enable(ctx, 1);
                content_canvas.draw_shape(ctx, layout.opacity_editor_rect);
                histogram_tex.disable(ctx);
                content_canvas.disable_current_shader(ctx);
            }
 
            preview_tex.enable(ctx, 0);
            // draw transfer function area polygon
            polygon_renderer.render(ctx, content_canvas, cgv::render::PT_TRIANGLE_STRIP, triangle_geometry, polygon_style);
 
            // draw transfer function lines
            line_renderer.render(ctx, content_canvas, cgv::render::PT_LINE_STRIP, line_geometry, line_style);
            preview_tex.disable(ctx);
 
            // draw separator line
            content_canvas.enable_shader(ctx, "rectangle");
            content_canvas.set_style(ctx, border_style);
            content_canvas.draw_shape(ctx,
                ivec2(layout.color_editor_rect.x(), layout.color_editor_rect.y1()),
                ivec2(container_size.x() - 2 * padding(), 1)
            );
            content_canvas.disable_current_shader(ctx);
        }
 
        // draw control points
        // color handles
        color_handle_renderer.render(ctx, content_canvas, cgv::render::PT_LINES, color_draggables_geometry, color_handle_style);
 
        // opacity handles
        if(supports_opacity) {
            auto& opacity_handle_prog = opacity_handle_renderer.enable_prog(ctx);
            opacity_handle_prog.set_attribute(ctx, "size", opacity_point_size); // size is constant for all points
            opacity_handle_renderer.render(ctx, content_canvas, cgv::render::PT_POINTS, opacity_draggables_geometry, opacity_handle_style);
        }
    } else {
        content_canvas.disable_current_shader(ctx);
    }
 
    auto& font = cgv::g2d::ref_msdf_font_regular(ctx);
    auto& font_renderer = cgv::g2d::ref_msdf_gl_font_renderer_2d(ctx);
    cgv::g2d::msdf_gl_font_renderer::text_render_info text_render_info;
 
    if(!value_label.empty()) {
        cgv::g2d::irect rectangle = value_label_rectangle;
        rectangle.translate(0, 5);
        rectangle.size += ivec2(10, 6);
 
        content_canvas.enable_shader(ctx, "rectangle");
        content_canvas.set_style(ctx, label_box_style);
        content_canvas.draw_shape(ctx, rectangle);
        content_canvas.disable_current_shader(ctx);
 
        text_render_info.alignment = cgv::render::TextAlignment::TA_BOTTOM;
        font_renderer.render(ctx, content_canvas, font, value_label, value_label_rectangle.position, text_render_info, value_label_style);
    }
 
    end_content(ctx);
}
 
void transfer_function_editor::handle_theme_change(const cgv::gui::theme_info& theme) {
    themed_canvas_overlay::handle_theme_change(theme);
    create_geometry();
    post_recreate_gui();
}
 
void transfer_function_editor::create_gui_impl() {
    if(begin_tree_node("Settings", layout, false)) {
        align("\a");
        std::string height_options = "min=";
        height_options += supports_opacity ? "80" : "40";
        height_options += ";max=500;step=10;ticks=true";
        add_member_control(this, "Height", layout.total_height, "value_slider", height_options);
        //add_member_control(this, "Opacity Scale Exponent", opacity_scale_exponent, "value_slider", "min=1.0;max=5.0;step=0.001;ticks=true");
        //add_member_control(this, "Resolution", discretization_resolution, "dropdown", "enums='2=2,4=4,8=8,16=16,32=32,64=64,128=128,256=256,512=512,1024=1024,2048=2048';w=106", " ");
        align("\b");
        end_tree_node(layout);
    }
 
    add_decorator("Color", "heading", "level=4;font_style=regular;w=94", " ");
    add_decorator("Opacity", "heading", "level=4;font_style=regular;w=94", "%y-=6\n");
    const std::string interpolation_enums = "enums='Step,Linear,Smooth'";
    add_member_control(this, "Interpolation", color_interpolation, "dropdown", interpolation_enums + ";w=94", " ");
    add_member_control(this, "", opacity_interpolation, "dropdown", interpolation_enums + ";w=94");
 
    add_member_control(this, "Domain", input_domain[0], "value", "step=0.001;w=94", " ");
    add_member_control(this, "", input_domain[1], "value", "step=0.001;w=94");
    cgv::signal::connect_copy(add_button("Rescale")->click, cgv::signal::rebind(this, &transfer_function_editor::rescale_domain));
 
    // Todo: Add input and button to set point position through GUI.
 
    if(begin_tree_node("Color Points", color_draggables, false)) {
        align("\a");
        auto& points = color_draggables;
        for(unsigned i = 0; i < points.size(); ++i) {
            std::string label_prefix = "";
            std::string options = "w=48";
            if(&points[i] == selected_color_draggable) {
                label_prefix = "> ";
                options += ";label_color=" + cgv::media::to_hex(highlight_color);
            }
 
            add_view(label_prefix + std::to_string(i), points[i].uv.x(), "", options, " ");
            add_member_control(this, "", points[i].data, "", "w=140");
        }
        align("\b");
        end_tree_node(color_draggables);
    }
 
    if(supports_opacity) {
        if(begin_tree_node("Opacity Points", opacity_draggables, false)) {
            align("\a");
            auto& points = opacity_draggables;
            for(unsigned i = 0; i < points.size(); ++i) {
                std::string label_prefix = "";
                std::string options = "w=48";
                if(&points[i] == selected_opacity_draggable) {
                    label_prefix = "> ";
                    options += ";label_color=" + cgv::media::to_hex(highlight_color);
                }
 
                add_view(label_prefix + std::to_string(i), points[i].uv.x(), "", options, " ");
                add_member_control(this, "", points[i].uv.y(), "value", "w=140");
            }
            align("\b");
            end_tree_node(opacity_draggables);
        }
    }
 
    add_member_control(this, "New position", input_position, "value", "step=0.001");
    cgv::signal::connect_copy(add_button("Set selected position")->click, cgv::signal::rebind(this, &transfer_function_editor::set_selected_point_domain_value));
 
    if(begin_tree_node("Histogram", histogram, false)) {
        align("\a");
        add_member_control(this, "Type", histogram_type, "dropdown", "enums='None,Nearest,Linear,Smooth'");
        add_member_control(this, "Ignore Zero for Normalization", hist_norm_ignore_zero, "check");
        add_member_control(this, "Gamma", hist_norm_gamma, "value_slider", "min=0.001;max=2;step=0.001;ticks=true");
        add_member_control(this, "Fill Color", hist_style.fill_color);
        add_member_control(this, "Border Color", hist_style.border_color);
        add_member_control(this, "Border Width", hist_style.border_width, "value_slider", "min=0;max=10;step=0.5;ticks=true");
        align("\b");
        end_tree_node(histogram);
    }
}
 
void transfer_function_editor::set_opacity_support(bool flag) {
    supports_opacity = flag;
    //set_transfer_function(transfer_function);
    on_set(&supports_opacity);
}
 
void transfer_function_editor::set_transfer_function(std::shared_ptr<cgv::media::transfer_function> transfer_function) {
    if(this->transfer_function != transfer_function) {
        this->transfer_function = transfer_function;
        build_time.reset();
    }
 
    this->transfer_function = transfer_function;
    update_data_from_transfer_function();
    post_damage();
}
 
void transfer_function_editor::set_histogram_data(const std::vector<unsigned> data) {
    histogram = data;
 
    std::vector<float> float_data(histogram.size(), 0.0f);
    hist_max = 1;
    hist_max_non_zero = 1;
    for(size_t i = 0; i < histogram.size(); ++i) {
        unsigned count = histogram[i];
        hist_max = std::max(hist_max, count);
        if(i > 0)
            hist_max_non_zero = std::max(hist_max_non_zero, count);
        float_data[i] = static_cast<float>(count);
    }
 
    if(get_context()) {
        cgv::data::data_view data_view = cgv::data::data_view(new cgv::data::data_format(unsigned(histogram.size()), cgv::type::info::TI_FLT32, cgv::data::CF_R), float_data.data());
        histogram_tex.create(*get_context(), data_view, 0);
        post_damage();
    }
}
 
void transfer_function_editor::set_selected_color(rgb color) {
    if(selected_color_draggable) {
        selected_color_draggable->data = color;
        on_set(&selected_color_draggable->data);
        post_damage();
    }
}
 
void transfer_function_editor::init_styles() {
    auto& theme = cgv::gui::theme_info::instance();
    // Todo: Check if alpha is set to 1.
    handle_color = theme.text();
    highlight_color = theme.highlight();
 
    // configure style for the border rectangles
    border_style.fill_color = theme.border();
    border_style.border_width = 0.0f;
    border_style.feather_width = 0.0f;
    
    // configure style for the color scale rectangle
    color_map_style = border_style;
    color_map_style.use_texture = true;
 
    // configure style for background
    bg_style.use_texture = true;
    bg_style.feather_width = 0.0f;
 
    // configure style for histogram
    hist_style.use_blending = true;
    hist_style.feather_width = 1.0f;
    hist_style.feather_origin = 0.0f;
    hist_style.fill_color = rgba(rgb(0.5f), 0.666f);
    hist_style.border_color = rgba(rgb(0.0f), 0.666f);
    hist_style.border_width = 1.0f;
 
    // configure style for color handles
    color_handle_style.use_blending = true;
    color_handle_style.use_fill_color = false;
    color_handle_style.position_is_center = true;
    color_handle_style.border_color = theme.border();
    color_handle_style.border_width = 1.5f;
    color_handle_style.border_radius = 2.0f;
    color_handle_style.stem_width = color_point_size.x();
    color_handle_style.head_width = color_point_size.x();
 
    label_box_style.position_is_center = true;
    label_box_style.use_blending = true;
    label_box_style.fill_color = handle_color;
    label_box_style.border_color = theme.border();
    label_box_style.border_width = 1.5f;
    label_box_style.border_radius = 4.0f;
 
    // configure style for opacity handles
    opacity_handle_style.use_blending = true;
    opacity_handle_style.use_fill_color = false;
    opacity_handle_style.position_is_center = true;
    opacity_handle_style.border_color = theme.border();
    opacity_handle_style.border_width = 1.5f;
 
    // configure style for the lines and polygon
    line_style.use_blending = true;
    line_style.use_fill_color = false;
    line_style.use_texture = true;
    line_style.use_texture_alpha = false;
    line_style.width = 3.0f;
 
    polygon_style = static_cast<cgv::g2d::shape2d_style>(line_style);
    polygon_style.use_texture_alpha = true;
 
    // label style
    cursor_label_style.fill_color = rgb(0.0f);
    cursor_label_style.font_size = 16.0f;
 
    value_label_style.fill_color = theme.group();
    value_label_style.font_size = 12.0f;
}
 
void transfer_function_editor::update_layout(const ivec2& parent_size) {
    int content_height = layout.total_height - 10 - 2 * padding();
    if(supports_opacity) {
        layout.color_editor_height = static_cast<int>(floor(0.15f * static_cast<float>(content_height)));
        layout.color_editor_height = cgv::math::clamp(layout.color_editor_height, 4, 80);
        layout.opacity_editor_height = content_height - layout.color_editor_height - 1;
    } else {
        layout.color_editor_height = content_height;
        layout.opacity_editor_height = 0;
    }
 
    int y_off = padding();
 
    layout.color_draggables_rect = {
        ivec2(padding(), 16),
        ivec2(parent_size.x() - 2 * padding(), 0)
    };
 
    // move 10px up to clear some space for the color handles rect
    y_off += 10;
 
    layout.color_editor_rect.position = ivec2(padding(), y_off);
    layout.color_editor_rect.size = ivec2(parent_size.x() - 2 * padding(), layout.color_editor_height);
 
    y_off += layout.color_editor_height + 1; // plus 1px border
 
    layout.opacity_editor_rect.position = ivec2(padding(), y_off);
    layout.opacity_editor_rect.size = ivec2(parent_size.x() - 2 * padding(), layout.opacity_editor_height);
}
 
void transfer_function_editor::clear_data() {
    selected_color_draggable = nullptr;
    selected_opacity_draggable = nullptr;
    color_draggables.clear();
    opacity_draggables.clear();
    color_draggables_geometry.clear();
    opacity_draggables_geometry.clear();
    line_geometry.clear();
    triangle_geometry.clear();
}
 
void transfer_function_editor::force_update_data_from_transfer_function() {
    if(!transfer_function)
        return;
 
    clear_data();
 
    const vec2 domain = transfer_function->get_domain();
    input_domain = domain;
    update_member(&input_domain[0]);
    update_member(&input_domain[1]);
 
    for(const auto& point : transfer_function->get_color_points()) {
        color_point draggable = make_color_point();
        draggable.data = point.second;
        const vec2 uv = { cgv::math::normalize(point.first, domain[0], domain[1]), 0.0f };
        draggable.set_uv_and_update_position(uv);
        color_draggables.add(draggable);
    }
 
    if(supports_opacity) {
        for(const auto& point : transfer_function->get_opacity_points()) {
            opacity_point draggable = make_opacity_point();
            const vec2 uv = { cgv::math::normalize(point.first, domain[0], domain[1]), point.second };
            draggable.set_uv_and_update_position(uv);
            opacity_draggables.add(draggable);
        }
    }
 
    create_geometry();
    create_preview_texture();
 
    post_recreate_gui();
    post_damage();
}
 
void transfer_function_editor::update_data_from_transfer_function() {
    if(!transfer_function)
        return;
 
    // Todo: Only update if the tf changed or if forced.
    if(!build_time.is_valid() || transfer_function->get_modified_time() > build_time.get_modified_time()) {
        std::cout << "set editor data from tf" << std::endl;
        //std::cout << transfer_function->get_modified_time().time_since_epoch().count() << " > " << build_time.get_modified_time().time_since_epoch().count() << std::endl;
 
        // Todo: Need force_update?
        force_update_data_from_transfer_function();
 
        build_time.modified();
    }
}
 
void transfer_function_editor::update_transfer_function_from_data() {
    if(!transfer_function)
        return;
 
    std::vector<std::pair<float, rgb>> colors;
    std::vector<std::pair<float, float>> opacities;
 
    const vec2 domain = transfer_function->get_domain();
 
    auto map_to_domain = [domain](float u) {
        return cgv::math::map(u, 0.0f, 1.0f, domain[0], domain[1]);
    };
 
    std::transform(color_draggables.begin(), color_draggables.end(), std::back_inserter(colors), [&map_to_domain](const color_point& point) {
        return std::make_pair(map_to_domain(point.uv.x()), point.data);
    });
    std::transform(opacity_draggables.begin(), opacity_draggables.end(), std::back_inserter(opacities), [&map_to_domain](const opacity_point& point) {
        return std::make_pair(map_to_domain(point.uv.x()), point.uv.y());
    });
 
    transfer_function->set_color_points(colors);
    transfer_function->set_opacity_points(opacities);
 
    // Set the build time to the transfer function's modified time since the geometry is already synchronized.
    // This avoids a rebuild at the next draw.
    //build_time = transfer_function->get_modified_time();
    //build_time.modified();
 
    if(on_change_callback)
        on_change_callback();
}
 
void transfer_function_editor::rescale_domain() {
    if(transfer_function) {
        transfer_function->rescale(input_domain);
        update_data_from_transfer_function();
 
        if(on_change_callback)
            on_change_callback();
    }
}
 
cgv::g2d::draggable* transfer_function_editor::get_hit_point(const vec2& pos) {
    const auto& contains = [&pos](const auto& draggable) {
        return draggable.contains(pos);
    };
 
    auto color_it = std::find_if(color_draggables.begin(), color_draggables.end(), contains);
    if(color_it != color_draggables.end())
        return &*color_it;
 
    auto opacity_it = std::find_if(opacity_draggables.begin(), opacity_draggables.end(), contains);
    if(opacity_it != opacity_draggables.end())
        return &*opacity_it;
 
    return nullptr;
}
 
template<typename T>
bool is_boundary_point(const T* point, cgv::g2d::draggable_collection<T>& draggables) {
    if(draggables.empty())
        return false;
    return point == &draggables.ref_draggables().front() || point == &draggables.ref_draggables().back();
}
 
void transfer_function_editor::add_point(const vec2& pos) {
    if(!transfer_function)
        return;
 
    ivec2 test_pos = static_cast<ivec2>(pos);
 
    selected_color_draggable = nullptr;
    selected_opacity_draggable = nullptr;
 
    if(layout.color_editor_rect.contains(test_pos)) {
        color_point draggable = make_color_point();
        draggable.set_position_and_update_uv({ pos.x(), 0.0f });
        draggable.data = transfer_function->get_mapped_color(draggable.uv.x());
        size_t index = color_draggables.add(draggable);
        // Todo: Allow drag after add.
        //color_draggables.set_dragged(index);
        selected_color_draggable = &color_draggables[index];
    } else if(supports_opacity && layout.opacity_editor_rect.contains(test_pos)) {
        opacity_point draggable = make_opacity_point();
        draggable.set_position_and_update_uv(pos);
        size_t index = opacity_draggables.add(draggable);
        selected_opacity_draggable = &opacity_draggables[index];
    }
 
    sort_points();
    update_transfer_function_from_data();
    handle_selection_change();
    create_geometry();
    post_damage();
}
 
void transfer_function_editor::erase_point(const cgv::g2d::draggable* point) {
    const auto& try_erase_point_from = [point](auto& draggables) {
        if(draggables.size() > 1) {
            if(point == &draggables.ref_draggables().front() || point == &draggables.ref_draggables().back())
                return false;
 
            auto it = std::remove_if(draggables.begin(), draggables.end(), [point](const cgv::g2d::draggable& draggable) {
                return &draggable == point;
            });
            if(it != draggables.end()) {
                draggables.ref_draggables().erase(it);
                return true;
            }
        }
        return false;
    };
 
    if(try_erase_point_from(color_draggables) || try_erase_point_from(opacity_draggables)) {
        selected_color_draggable = nullptr;
        selected_opacity_draggable = nullptr;
        update_transfer_function_from_data();
        handle_selection_change();
        create_preview_texture();
        create_geometry();
        post_damage();
    }
}
 
void transfer_function_editor::set_selected_point_domain_value() {
    if(!transfer_function)
        return;
 
    const vec2 domain = transfer_function->get_domain();
    const float x = cgv::math::clamp(input_position, domain[0], domain[1]);
    const float u = cgv::math::normalize(x, domain[0], domain[1]);
 
    if(selected_color_draggable && !is_boundary_point(selected_color_draggable, color_draggables))
        selected_color_draggable->set_uv_and_update_position({ u, 0.0f });
    else if(selected_opacity_draggable && !is_boundary_point(selected_opacity_draggable, opacity_draggables))
        selected_opacity_draggable->set_uv_and_update_position({ u, selected_opacity_draggable->uv.y() });
 
    sort_points();
    update_transfer_function_from_data();
    create_preview_texture();
    create_geometry();
    post_damage();
}
 
void transfer_function_editor::set_value_label(vec2 position, const std::string& text) {
    value_label = text;
    value_label_rectangle.position = position;
 
    if(get_context()) {
        auto& font = cgv::g2d::ref_msdf_font_regular(*get_context());
        value_label_rectangle.size = font.compute_render_size(value_label, value_label_style.font_size);
    }
 
    cgv::g2d::rect constraint = get_content_rectangle();
    constraint.scale(-0.5f * (value_label_rectangle.size + 4.0f));
    value_label_rectangle.position = cgv::math::clamp(value_label_rectangle.position, constraint.a(), constraint.b());
}
 
void transfer_function_editor::handle_drag(cgv::g2d::DragAction action, DraggableType type) {
    bool modified = false;
 
    switch(action) {
    case cgv::g2d::DragAction::kDragStart:
        if(type == DraggableType::kColor) {
            color_point* dragged = color_draggables.get_dragged();
            if(dragged)
                color_draggable_start_position = dragged->position;
        } else if(type == DraggableType::kOpacity) {
            opacity_point* dragged = opacity_draggables.get_dragged();
            if(dragged)
                opacity_draggable_start_position = dragged->position;
        }
    case cgv::g2d::DragAction::kDrag:
        if(type == DraggableType::kColor) {
            color_point* dragged = color_draggables.get_dragged();
            
            if(is_boundary_point(dragged, color_draggables))
                dragged->position = color_draggable_start_position;
 
            if(dragged) {
                dragged->set_position_and_update_uv(dragged->position);
                set_value_label(
                    dragged->position + cgv::vec2(0.0f, 25.0f),
                    value_to_string(dragged->uv.x())
                );
                selected_color_draggable = dragged;
                selected_opacity_draggable = nullptr;
                modified = true;
            }
        } else if(type == DraggableType::kOpacity) {
            opacity_point* dragged = opacity_draggables.get_dragged();
 
            if(is_boundary_point(dragged, opacity_draggables))
                dragged->position.x() = opacity_draggable_start_position.x();
 
            if(dragged) {
                dragged->set_position_and_update_uv(dragged->position);
 
                set_value_label(
                    dragged->position + cgv::vec2(0.0f, 10.0f),
                    value_to_string(dragged->uv.x()) + ", " + cgv::utils::to_string(dragged->uv.y(), -1, 3u)
                );
                selected_opacity_draggable = dragged;
                selected_color_draggable = nullptr;
                modified = true;
            }
        }
        if(modified)
            handle_selection_change();
        break;
    case cgv::g2d::DragAction::kDragEnd:
        handle_selection_change();
        value_label.clear();
        modified = true;
        break;
    default:
        break;
    }
 
    //press_inside = has_constraint && !use_individual_constraints ? constraint_area.contains(mouse_position) : true;
 
    if(modified) {
        sort_points();
        update_transfer_function_from_data();
        create_preview_texture();
        create_geometry();
        post_damage();
    }
}
 
void transfer_function_editor::handle_selection_change() {
    if(selected_color_draggable) {
        if(on_color_point_select_callback)
            on_color_point_select_callback(selected_color_draggable->data);
    } else {
        if(on_color_point_deselect_callback)
            on_color_point_deselect_callback();
    }
    post_recreate_gui();
}
 
std::string transfer_function_editor::value_to_string(float value) {
    if(!transfer_function)
        return "";
 
    const vec2 domain = transfer_function->get_domain();
    float display_value = cgv::math::lerp(domain.x(), domain.y(), value);
 
    float total = domain.y() - domain.x();
    if(total < 100.0f) {
        // show as float
        return cgv::utils::to_string(display_value, -1, 3u);
    } else {
        // show as int
        int display_value_int = static_cast<int>(round(display_value));
        return std::to_string(display_value_int);
    }
}
 
template<typename T>
void sort_draggables(cgv::g2d::draggable_collection<T>& draggables, T*& selected) {
    if(draggables.empty())
        return;
 
    int dragged_idx = -1;
    int selected_idx = -1;
 
    for(size_t i = 0; i < draggables.size(); ++i) {
        if(&draggables[i] == draggables.get_dragged())
            dragged_idx = static_cast<int>(i);
        if(&draggables[i] == selected)
            selected_idx = static_cast<int>(i);
    }
 
    std::vector<T> draggables_copy = draggables.ref_draggables();
    std::vector<size_t> permutation = cgv::utils::stable_sort_indices(draggables_copy.begin(), draggables_copy.end());
 
    for(size_t i = 0; i < permutation.size(); ++i) {
        int permuted_index = static_cast<int>(permutation[i]);
        draggables[i] = draggables_copy[permuted_index];
        if(permuted_index == dragged_idx)
            draggables.set_dragged(i);
        if(permuted_index == selected_idx)
            selected = &draggables[i];
    }
}
 
void transfer_function_editor::sort_points() {
    sort_draggables(color_draggables, selected_color_draggable);
    if(supports_opacity)
        sort_draggables(opacity_draggables, selected_opacity_draggable);
}
 
void transfer_function_editor::update_point_positions() {
    for(auto& draggable : color_draggables)
        draggable.set_position_and_update_uv(draggable.position);
    
    for(auto& draggable : opacity_draggables)
        draggable.set_position_and_update_uv(draggable.position);
}
 
bool transfer_function_editor::create_preview_texture() {
    const size_t size = static_cast<size_t>(256);// discretization_resolution);
    std::vector<rgba> cs_data = transfer_function->quantize(size);
 
    std::vector<cgv::rgba8> texture_data;
    texture_data.reserve(size);
    std::transform(cs_data.begin(), cs_data.end(), std::back_inserter(texture_data), [](const cgv::rgba& color) {
        return cgv::rgba8(color);
    });
 
    cgv::data::data_format data_format(size, 1, cgv::type::info::TI_UINT8, cgv::data::CF_RGBA);
    cgv::data::data_view data_view(&data_format, texture_data.data());
 
    const cgv::render::TextureFilter filter = cgv::render::TF_LINEAR;
 
    if(get_context()) {
        preview_tex.set_min_filter(filter);
        preview_tex.set_mag_filter(filter);
        return preview_tex.create(*get_context(), data_view, 0);
    }
    return false;
}
 
bool transfer_function_editor::create_background_texture() {
    const rgb dark(0.75f);
    const rgb light(0.9f);
    std::vector<rgb> data = { dark, light, light, dark };
    cgv::data::data_format format(2, 2, cgv::type::info::TI_FLT32, cgv::data::CF_RGB);
    cgv::data::data_view data_view = cgv::data::data_view(&format, data.data());
    if(get_context())
        return background_tex.create(*get_context(), data_view, 0);
    return false;
}
 
void transfer_function_editor::create_geometry() {
    color_draggables_geometry.clear();
    opacity_draggables_geometry.clear();
    line_geometry.clear();
    triangle_geometry.clear();
 
    vec2 pos_offset = vec2(0.0f, 0.5f * color_point_size.y());
 
    for(const auto& draggable : color_draggables) {
        vec2 pos = draggable.center();
        rgba col = selected_color_draggable == &draggable ? highlight_color : handle_color;
        color_draggables_geometry.add(pos - pos_offset, col);
        color_draggables_geometry.add(pos + pos_offset, col);
    }
 
    if(!opacity_draggables.empty()) {
        const auto& first = *opacity_draggables.begin();
 
        vec2 tex_coord(0.0f, 0.5f);
 
        line_geometry.add(vec2(static_cast<float>(layout.opacity_editor_rect.x()), first.center().y()), tex_coord);
        
        triangle_geometry.add(vec2(static_cast<float>(layout.opacity_editor_rect.x()), first.center().y()), tex_coord);
        triangle_geometry.add(layout.opacity_editor_rect.position, tex_coord);
 
        for(const auto& draggable : opacity_draggables) {
            vec2 pos = draggable.center();
            rgba col = selected_opacity_draggable == &draggable ? highlight_color : handle_color;
            opacity_draggables_geometry.add(pos, col);
 
            tex_coord.x() = draggable.uv.x();
 
            line_geometry.add(pos, tex_coord);
 
            triangle_geometry.add(pos, tex_coord);
            triangle_geometry.add(vec2(pos.x(), static_cast<float>(layout.opacity_editor_rect.y())), tex_coord);
        }
 
        const auto& last = *(--opacity_draggables.end());
        vec2 max_pos = layout.opacity_editor_rect.position + vec2(1.0f, 0.0f) * layout.opacity_editor_rect.size;
 
        tex_coord.x() = 1.0f;
 
        line_geometry.add(vec2(max_pos.x(), last.center().y()), tex_coord);
 
        triangle_geometry.add(vec2(max_pos.x(), last.center().y()), tex_coord);
        triangle_geometry.add(max_pos, tex_coord);
    }
}
 
} // namespace overlay
} // namespace cgv