如何在SDL2中用鼠标突出显示文本例如，像在msword中一样，您可以单击并突出显示文本

问题描述

我正在尝试高效地突出显示SDL2中的文本。假设我显示了一个文本字符串，并且该文本类似于：“ Hello World！”，我想突出显示来自世界的“ orl”。如果我使用单词，则可以单击“ l”并用鼠标向左移动，反之亦然，单击“ o”并从那里向右移动。有什么有效的方法吗？如果是这样，怎么办？我无法获得一种有效的解决方案，该解决方案不会使fps随着文本的增加而呈指数下降。另外（如果可能的话）（如果可能的话），如果我有一个文本框来环绕文本并在文本框不适合时换行，如果我开始单击第一个单词并向下移动鼠标，该如何突出显示文本？突出显示整个行，直到我悬停的字符为止。谢谢

仅供参考：这是我的文本对象（标头和cpp文件）

text.h

#ifndef TEXT_H
#define TEXT_H

#include <SDL2/SDL_ttf.h>
#include <SDL2/SDL.h>

#include "events.h"


#include <iostream>
#include <string>
#include <vector>
using std::vector;
using std::string;
using std::cout;
using std::endl;
using std::exception;



class Text
{
    public:
        Events EVENTS;
        Text(void);


        ///Public variables
        static vector <TTF_Font*> fonts;
        const int lowestFontSize = 1;
        const int highestFontSize = 100;
        int fontIndex;

        int textSize;
        SDL_Rect textRect;
        int x;
        int y;
        int initialX,initialY;
        bool setup;

        static int numOfInstances;



        ///Functions
        void Setup(SDL_Renderer *renderer,string txt,int x,int y,int txtSize,SDL_Color Colour = {0,0},bool isBold = false,string fontType = "arial.ttf",bool isWrapped=false,int theWrapWidth=0);

        string Get_Text();
        void Change_Text(SDL_Renderer *renderer,string newText);
        void Draw_Text(SDL_Renderer *renderer);
        void Change_Position(SDL_Renderer *renderer,int xPos,int yPos);
        void Change_Position_And_Text(SDL_Renderer *renderer,int yPos,string newText);

        int Text_Width(int FirstCharIndex,int numOfCharsPastFirstIndex);
        int Text_Height(int FirstCharIndex,int numOfCharsPastFirstIndex);


        void Free_All();


    private:

        ///SDL stuff
        SDL_Texture *textTexture;
        SDL_Surface *textSurface;



        SDL_Color colour;
        SDL_Point point;

        ///text varibales
        string text;
        int textW;
        int textH;
        bool bold;
        bool wrapped;
        int wrappedWidth;




};


#endif

text.cpp

#include "text.h"


int Text::numOfInstances = 0;

vector <TTF_Font*> Text::fonts;


Text::Text()
{
    setup = false;


    textTexture = NULL;
    textSurface = NULL;


}


void Text::Setup(SDL_Renderer *renderer,SDL_Color Colour,bool isBold,string fontType,bool isWrapped,int theWrapWidth )
{
    if (setup == false){


        numOfInstances += 1;


        wrapped = isWrapped;
        wrappedWidth = theWrapWidth;
        text = txt;
        textSize = txtSize;
        bold = isBold;
        colour = Colour;


        textW = 0;
        textH = 0;
        x = xPos;
        y = yPos;
        initialX = x;
        initialY = y;


        fontIndex = textSize-lowestFontSize -1;


        ///One time setups
        if (numOfInstances == 1){
            try{
                TTF_Init();
                //cout << "Initialised ttf" << endl;
            }
            catch (exception &err){
                cout << "Could not initialise ttf for text \"" << text << "\". Error from SDL is: " << TTF_GetError() << ". Error from C++ is: " << err.what() << endl;
            }

            for (int i=lowestFontSize; i <= highestFontSize; i++){
                TTF_Font *currentFont = TTF_OpenFont(fontType.c_str(),i);
                if (!currentFont){
                    cout << "Error with font in text \"" << txt << "\" Error is: " << SDL_GetError() << endl;
                }

                //TTF_SetFontKerning(currentFont,0);


                fonts.push_back(currentFont);
            }

        }



        if (bold == true){
            TTF_SetFontStyle(fonts[fontIndex],TTF_STYLE_BOLD);
        }


        if (!SDL_SetHint( SDL_HINT_RENDER_SCALE_QUALITY,"2" ) ){  ///2 is highest

            cout << "Text rendering quality not enabled " << text << endl;
        }

        if (text != ""){    ///Only create textures if there is text

            if (wrapped == true){
                textSurface = TTF_RenderText_Blended_Wrapped(fonts[fontIndex],text.c_str(),colour,wrappedWidth);     ///Recreate the textures/surfaces
            }
            else{
                textSurface = TTF_RenderText_Blended(fonts[fontIndex],colour);     ///Recreate the textures/surfaces
            }
            if (!textSurface){
                cout << "Unable to create surface of text " << text << " error is: " << SDL_GetError() << endl;
            }
            textTexture = SDL_CreateTextureFromSurface(renderer,textSurface);
            if (!textTexture){
                cout << "Unable to create texture from surface of text " << text << " error is: " << SDL_GetError() << endl;
            }

            SDL_FreeSurface(textSurface);
            textSurface = NULL;

            SDL_QueryTexture(textTexture,NULL,&textW,&textH);
            textRect = {x,y,textW,textH};
        }






        point = {0,0};

        setup = true;





    }



    else{
        //cout << "Trying to setup a text already setup! " << text << endl;
    }


}





void Text::Change_Position_And_Text(SDL_Renderer *renderer,string newText )
{
    if (setup == true){
        text = newText;
        x = xPos;
        y = yPos;
        textRect.x = x;
        textRect.y = y;



        if (textTexture != NULL){
            SDL_DestroyTexture(textTexture);    ///Free memory not going to be used again.
            textTexture = NULL;
        }

        if (text != ""){

            if (wrapped == true){
             textSurface = TTF_RenderText_Blended_Wrapped(fonts[fontIndex],&textH);   ///neeed this
            textRect = {x,textH};


        }


    }
}



void Text::Change_Position(SDL_Renderer *renderer,int yPos)
{
    if (setup == true){
        x = xPos;
        y = yPos ;
        textRect.x = xPos;
        textRect.y = yPos;
    }
}





void Text::Change_Text(SDL_Renderer *renderer,string newText)
{
    if (setup == true){
        text = newText;

        if (textTexture != NULL){
            SDL_DestroyTexture(textTexture);    ///Free memory not going to be used again.
            textTexture = NULL;
        }


        if (text != ""){

            if (wrapped == true){
                textSurface = TTF_RenderText_Blended_Wrapped(fonts[fontIndex],&textH);      ///neeed this
            textRect = {x,textH};

        }

    }


}



int Text::Text_Width(int FirstCharIndex,int numOfCharsPastFirstIndex)
{
    int w,h;

    string textSelection = text.substr(FirstCharIndex,numOfCharsPastFirstIndex);

    TTF_SizeText(fonts[fontIndex],textSelection.c_str(),&w,&h);

    return w;
}


int Text::Text_Height(int FirstCharIndex,&h);

    return h;
}



string Text::Get_Text()
{
    if (setup == true){
        return text;
    }
    else{
        return "";
        //cout << "Text not setup when trying to obtain text through Get_Text() function" << endl;
    }
}


void Text::Draw_Text(SDL_Renderer *renderer)
{
    if (setup == true){

        if (SDL_PointInRect(&EVENTS.mousePos,&textRect)   &&    EVENTS.currentCursor !=  SDL_SYstem_CURSOR_IBEAM){
            EVENTS.Change_Cursor(SDL_SYstem_CURSOR_IBEAM);
        }

        SDL_Rendercopy(renderer,textTexture,&textRect);
    }
    else{
        //cout << "Text not setup when trying to draw it in Draw_Text() function" << endl;
    }

}




void Text::Free_All()
{
    if (setup == true){


        if (textSurface == NULL){
            //cout << "Text surface already free'd" << endl;
        }
        else{
            SDL_FreeSurface(textSurface);
            textSurface = NULL;
            //cout << "Free'd surface \n";
        }

        if (textTexture == NULL){
            //cout << "Could not free memory for text \"" << text << "\". Error from SDL is: " << TTF_GetError() << endl;
        }
        else{
            SDL_DestroyTexture(textTexture);
            textTexture = NULL;
        }





        if (numOfInstances == 1){

            for (int i=0; i <= (highestFontSize-lowestFontSize); i++){
                TTF_CloseFont(fonts[i]);
                //cout << "Closed " << lowestFontSize+i << endl;
            }

            try{
                TTF_Quit();
                //cout << "Quit ttf" << endl;
            }
            catch (exception &err){
                cout << "Could not quit ttf for text \"" << text << "\". Error from SDL is: " << TTF_GetError() << ". Error from C++ is: " << err.what() << endl;
            }
        }


        ///For TTF_Init();
        numOfInstances -= 1;



        //cout << "Free'd " << text << endl;

    }




    else{
        //cout << "Text not setup yet when trying to free!" << endl;
    }



    setup = false;


}

解决方法

如果有人遇到相同的问题，我会发现一些不错的东西。其有效的零性能损失。就目前而言，我可以获取每个人物的形象，随着我提出更多的方式，我将对其进行更新以突出显示。现在，我有2个属于文本类的整数向量。当我设置文本或更改文本时，我遍历字符串，并使用字符串abcdefg说，第一次迭代时，currentString是a，second，ab，third abc，fourth，abcd等。然后我在每个循环的当前字符串上调用TTF_SizeText。然后，我将从中获得的宽度和高度附加到向量中。您可以使用向量中连续值的宽度变化，而不必像突出显示时那样重做。例如，如果我想要'c'的宽度，我可以做int deltaWidth = widthOfChars[3] - widthOfChars[2]，而不同之处是'c'的宽度。这样，当我遍历字符串时，将创建一个当前字符的矩形，在本例中为“ c”，并在执行此操作时检查鼠标是否悬停在其上。目前，我只是为每个字符绘制一个填充的矩形，并且不会损失任何明显的性能损失！