C++11 外观模式演示

本例摘选自《Design Pattern in Modern C++》一书的外观模式的demo。作者的源码中，Window类和TextBuffer类没有给实现。这里本人使用OpenCV自己实现了写字的Window类和TextBuffer类。
本例的绘图系统的设计思路图如下。

struct TextBuffer {
    std::vector texts;
    double max_width;
    double max_height;
    double total_height;

    void add_string() {
        // update max_width
        // update_max_height
        // update total_height
    }
};

struct Window {
    std::vector buffers;
    
    void add_buffer() {
        
    }

    void show() {
        // 获取所有buffer的最大宽，作为窗口宽
        // 获取所有buffer的高之和，作为窗口高
        // 从上往下显示buffer
        // 第0个: 0, 0
        // 第1个: 1, buffer0.total_height
        // 第2个: 2, buffer0.total_height + buffer1.total_height
    }

private:
    int width;
    int height;
    int get_width() {
        // std::max  buffer0.max_width, buffer1.max_width, buffer2.max_width ... buffern.max_width
        return result;
    }

    int get_height() {
        // std::accumulate buffer0.total_height, buffer1.total_height, buffer2.total_height ... buffern.total_height
        return result;
    }
};

本例的代码结构如下，

test/CMakeLists.txt

cmake_minimum_required(VERSION 2.6)
project(facade)

set(CMAKE_CXX_STANDARD 20)
add_definitions(-g)


find_package(Boost REQUIRED COMPONENTS
    system
    filesystem
    serialization
    program_options
    thread
    )

find_package(OpenCV REQUIRED )
find_package(glog REQUIRED)

include_directories(${Boost_INCLUDE_DIRS} /usr/local/include /usr/local/include/opencv4 /usr/local/iODBC/include /opt/snowflake/snowflakeodbc/include/ ${CMAKE_CURRENT_SOURCE_DIR}/../../ ${CMAKE_CURRENT_SOURCE_DIR}/../include/ ${CMAKE_CURRENT_SOURCE_DIR}/../../../include/)

LINK_DIRECTORIES(/usr/local/lib /usr/local/iODBC/lib /opt/snowflake/snowflakeodbc/lib/universal)

file( GLOB APP_SOURCES ${CMAKE_CURRENT_SOURCE_DIR}/*.cpp ${CMAKE_CURRENT_SOURCE_DIR}/../impl/*.cpp ${CMAKE_CURRENT_SOURCE_DIR}/*.h ${CMAKE_CURRENT_SOURCE_DIR}/*.cpp ${CMAKE_CURRENT_SOURCE_DIR}/../../../include/death_handler/impl/*.cpp) 
foreach( sourcefile ${APP_SOURCES} )
        file(RELATIVE_PATH filename ${CMAKE_CURRENT_SOURCE_DIR} ${sourcefile})
    
        string(FIND "${filename}"  "test.cpp" "TEMP")
    if( NOT "${TEMP}" STREQUAL "-1" )
        string(REPLACE ".cpp" "" file ${filename})
        add_executable(${file}  ${APP_SOURCES})
        target_link_libraries(${file} ${Boost_LIBRARIES} ${OpenCV_LIBS})
        target_link_libraries(${file} glog::glog ssl crypto libgtest.a libgmock.a iodbc iodbcinst libnanodbc.a pthread)
    endif()
endforeach( sourcefile ${APP_SOURCES})

test/facade_test.cpp

#include "death_handler/death_handler.h"
#include 
#include "facade.hpp"

#include 
#include 



int main(int argc, char** argv) {
    FLAGS_log_dir = "./";
    FLAGS_alsologtostderr = true;
    // 日志级别 INFO, WARNING, ERROR, FATAL 的值分别为0、1、2、3
    FLAGS_minloglevel = 0;

    Debug::DeathHandler dh;

    google::InitGoogleLogging("./logs.log");
    testing::InitGoogleTest(&argc, argv);
    int ret = RUN_ALL_TESTS();
    return ret;
}


GTEST_TEST(FacadeTests, Facade) {
    auto window = Console::instance().multi_buffers(3);

    for (std::size_t i=0; i<20; ++i){
        cv::HersheyFonts font = cv::HersheyFonts::FONT_HERSHEY_DUPLEX;
        if(i%2 == 0) {
            font = cv::HersheyFonts::FONT_HERSHEY_TRIPLEX;
        }
        window->buffers[0].add_string(
            std::string("This is line ") + std::to_string(i), font);
    }
    window->show();
    window->wait_to_dispose();
}

test/include/facade.hpp

#ifndef _FREDRIC_FACADE_HPP_
#define _FREDRIC_FACADE_HPP_

#include "window.h"
#include 

class Console {
public:
    static Console& instance() {
        static Console console;
        return console;
    }

    std::shared_ptr single_buffers(int buffer_count) {
        auto w = std::make_shared();
        w->add_buffer(TextBuffer{});
        return w;
    }

    std::shared_ptr multi_buffers(int buffer_count) {
        auto w = std::make_shared();
        for(int i=0; iadd_buffer(TextBuffer{});
        }
        return w;
    }
};

#endif

test/include/window.h

#include "opencv2/opencv.hpp"

#include 
#include 
#include 
#include 

std::string const window_name = "Draw Fonts";
int const EXIT_KEY = 27;
int const line_distance = 5;
int const title_bar_height = 50;

struct Text {
    std::string text;
    cv::HersheyFonts font;
}; 

struct TextBuffer {
    std::vector texts;
    int max_width{0};
    int max_height{0};
    int total_height{0};

    void add_string(std::string const& text, cv::HersheyFonts const& font_style) {
        texts.emplace_back(Text{text, font_style});
        
        int baseline;
        auto size = cv::getTextSize(text, font_style, 1.0f, 1, &baseline);

        if(size.width > max_width) {
            max_width = size.width;
        }
        if(size.height > max_height) {
            max_height = size.height;
        }
        // 加的5是行间距
        total_height = texts.size() * (max_height + line_distance);
    }

    // 用于std::max_element，求最大行宽
    bool operator<(TextBuffer const& other) const {
        return this->max_width < other.max_width;
    }

    // 用于std::accmulate，求所有buffer的高度
    operator int() {
        return this->total_height;
    }
};

struct Window {
    Window() {
        cv::namedWindow(window_name, cv::WINDOW_NORMAL);
        cv::setWindowProperty(window_name, cv::WND_PROP_TOPMOST, 1);
    }

    void add_buffer(TextBuffer const& buffer) {
        buffers.emplace_back(std::move(buffer));   
    }

    void show() {
        width = get_width();
        height = get_height();
        cv::resizeWindow(window_name, width, height + title_bar_height);
        img_ = cv::Mat::zeros(cv::Size(width, height + title_bar_height), CV_8UC1);
        img_.setTo(cv::Scalar(255));
        int current_y_pos = title_bar_height;

        for(auto&& buffer_: buffers) {
            for(auto&& text_: buffer_.texts) {
                cv::putText(img_, text_.text, cv::Point(0, current_y_pos), text_.font, 1.0, cv::Scalar(0),1);
                current_y_pos += buffer_.max_height + line_distance;
            }
        }
        cv::imshow(window_name, img_);
    }

    void wait_to_dispose() {
        while(EXIT_KEY != cv::waitKey(1000)) {
        }
    }

    std::vector buffers;
private:
    int width;
    int height;
    cv::Mat img_;
    

    int get_width() {
        auto buffer = *std::max_element(buffers.begin(), buffers.end());
        return buffer.max_width;
    }

    int get_height() {
        auto result = std::accumulate(buffers.begin(), buffers.end(), 0);
        return result;
    }
};

程序输出如下，