C++ SDL2-假定返回True的函数的计算结果为False

我正在使用SDL2，遵循LazyFoo的教程。我已经到了加载TTF字体部分，我似乎遵循了他所做的一切，除了添加了两个额外的TTF_字体和SDL_渲染器参数

bool LTexture::loadFromRenderedText(TTF_Font *&gFont, std::string textureText, SDL_Color textColor, SDL_Renderer *&gRenderer)
{
    //Get rid of preexisting texture
    free();

    //Render text surface
    SDL_Surface* textSurface = TTF_RenderText_Solid( gFont, textureText.c_str(), textColor );
    if( textSurface == NULL )
    {
        printf( "Unable to render text surface! SDL_ttf Error: %s\n", TTF_GetError() );
    }
    else
    {
        //Create texture from surface pixels
        mTexture = SDL_CreateTextureFromSurface( gRenderer, textSurface );
        if( mTexture == NULL )
        {
            printf( "Unable to create texture from rendered text! SDL Error: %s\n", SDL_GetError() );
        }
        else
        {
            //Get image dimensions
            mWidth = textSurface->w;
            mHeight = textSurface->h;
        }

        //Get rid of old surface
        SDL_FreeSurface( textSurface );
    }

    return 1;
}

这是函数，在这里调用它：

    gFont = TTF_OpenFont( "Font/comicSans.ttf", 28 );
    if( gFont == NULL )
    {
        printf( "Failed to load COMIC_SANS font! SDL_ttf Error: %s\n", TTF_GetError() );
        success = false;
    }
    else
    {
        //Render text
        SDL_Color textColor = { 0, 0, 0 };
        if( !gTextTexture.loadFromRenderedText(gFont, "Hello I am hot", textColor, gRenderer));
        {
            printf( "Failed to render text texture!\n" );
            success = false;
        }
    }

如果

成功

为false，程序将打印“加载介质失败”

这是我从运行程序中获得的输出，请注意，没有实际的SDL或TTF错误，只有当

loadFromRenderedText

返回false时出现的错误，它没有返回false，因为我已将其设置为返回1：

Failed to render text texture!
Failed to load media!

与我的文件和LazyFoo的文件唯一的实际区别是，我的LTexture类位于一个独立于main的文件中，这就是为什么出于某种原因，我不能使用

gFont

和

grender

（全局变量） 你知道是什么引起的吗

完整代码：

main.cpp：

/*This source code copyrighted by Lazy Foo' Productions (2004-2019)
and may not be redistributed without written permission.*/

//Using SDL and standard IO
#include <SDL.h>
#include <SDL_image.h>
#include <SDL_ttf.h>
#include <stdio.h>
#include <string>
#include "LTexture.h"

bool init();
bool loadMedia();
void close();


//The window we'll be rendering to
SDL_Window* gWindow = NULL;

SDL_Renderer* gRenderer = NULL;

//The surface contained by the window
SDL_Surface* gScreenSurface = NULL;

TTF_Font *gFont = NULL;

LTexture gTextTexture;

//Screen dimension constants
const int SCREEN_WIDTH = 500;
const int SCREEN_HEIGHT = 500;

int main(int argc, char* args[])
{
    //Start up SDL and create window
    if( !init() )
    {
        printf( "Failed to initialize!\n" );
    }
    else
    {
        //Load media
        if( !loadMedia() )
        {
            printf( "Failed to load media!\n" );
        }
        else
        {
            //Main loop flag
            bool quit = false;

            //Event handler
            SDL_Event event;

            //While application is running
            while( !quit )
            {
                //Handle events on queue
                while( SDL_PollEvent( &event ) != 0 )
                {
                    //User requests quit
                    if( event.type == SDL_QUIT )
                    {
                        quit = true;
                    }
                }

                //Clear screen
                SDL_SetRenderDrawColor(gRenderer, 0xFF, 0xFF, 0xFF, 0xFF);
                SDL_RenderClear( gRenderer );

                gTextTexture.render(gRenderer, (SCREEN_WIDTH - gTextTexture.getWidth()) / 2, (SCREEN_HEIGHT - gTextTexture.getHeight()) / 2);
                //Update screen
                SDL_RenderPresent( gRenderer );
            }
        }
    }

    //Free resources and close SDL
    close();

    return 0;
}


bool init()
{
    //Initialization flag
    bool success = true;

    //Initialize SDL
    if( SDL_Init( SDL_INIT_VIDEO ) < 0 )
    {
        printf( "SDL could not initialize! SDL_Error: %s\n", SDL_GetError() );
        success = false;
    }
    else
    {
        //Create window
        gWindow = SDL_CreateWindow( "SDL Tutorial", SDL_WINDOWPOS_UNDEFINED, SDL_WINDOWPOS_UNDEFINED, SCREEN_WIDTH, SCREEN_HEIGHT, SDL_WINDOW_SHOWN);
        if( gWindow == NULL )
        {
            printf( "Window could not be created! SDL Error: %s\n", SDL_GetError() );
            success = false;
        }
        else
        {
            //Create renderer for window
            gRenderer = SDL_CreateRenderer( gWindow, -1, SDL_RENDERER_ACCELERATED | SDL_RENDERER_PRESENTVSYNC);
            if( gRenderer == NULL )
            {
                printf( "Renderer could not be created! SDL Error: %s\n", SDL_GetError() );
                success = false;
            }
            else
            {
                //Initialize renderer color
                SDL_SetRenderDrawColor( gRenderer, 0xFF, 0xFF, 0xFF, 0xFF );

                //Initialize PNG loading
                int imgFlags = IMG_INIT_PNG;
                if( !( IMG_Init( imgFlags ) & imgFlags ) )
                {
                    printf( "SDL_image could not initialize! SDL_image Error: %s\n", IMG_GetError() );
                    success = false;
                }
                //Initialize SDL_ttf
                if( TTF_Init() == -1 )
                {
                    printf( "SDL_ttf could not initialize! SDL_ttf Error: %s\n", TTF_GetError() );
                    success = false;
                }
            }
        }
    }

    return success;
}

bool loadMedia()
{
    //Loading success flag
    bool success = true;

    //Open the font
    gFont = TTF_OpenFont( "Font/comicSans.ttf", 28 );
    if( gFont == NULL )
    {
        printf( "Failed to load COMIC_SANS font! SDL_ttf Error: %s\n", TTF_GetError() );
        success = false;
    }
    else
    {
        //Render text
        SDL_Color textColor = { 0, 0, 0 };
        if( !gTextTexture.loadFromRenderedText(gFont, "Hello I am hot", textColor, gRenderer));
        {
            printf( "Failed to render text texture!\n" );
            success = false;
        }
    }


    return success;
}

void close()
{

    //Free loaded images
    gTextTexture.free();

    //Destroy window
    SDL_DestroyRenderer( gRenderer );
    SDL_DestroyWindow( gWindow );
    TTF_CloseFont(gFont);
    gWindow = NULL;
    gRenderer = NULL;
    gFont = NULL;

    //Quit SDL subsystems
    TTF_Quit();
    IMG_Quit();
    SDL_Quit();
}

---

问题是if语句末尾的分号

if( !gTextTexture.loadFromRenderedText(gFont, "Hello I am hot", textColor, gRenderer));
    {
        printf( "Failed to render text texture!\n" );
        success = false;
    }

该分号将为该if块创建一个空语句，它将导致

{
        printf( "Failed to render text texture!\n" );
        success = false;
}

总是执行。就是这样,

if(.....)
   ;

{
   ....
}

---

问题是if语句末尾的分号

if( !gTextTexture.loadFromRenderedText(gFont, "Hello I am hot", textColor, gRenderer));
    {
        printf( "Failed to render text texture!\n" );
        success = false;
    }

该分号将为该if块创建一个空语句，它将导致

{
        printf( "Failed to render text texture!\n" );
        success = false;
}

总是执行。就是这样,

if(.....)
   ;

{
   ....
}

---

如果返回true，则输出“未能渲染文本纹理”。这就是它所做的，它不会返回错误。哦，天哪，我没看到！非常感谢你！我知道if的声明有问题，该死的，非常感谢！如果返回true，则输出“未能渲染文本纹理”。这就是它所做的，它不会返回错误。哦，天哪，我没看到！非常感谢你！我知道if的声明有问题，该死的，非常感谢！