c语言 - 为什么 SDL2 渲染器不在我的窗口中绘制任何内容？ - c - Why doesn't the SDL2 Renderer draw anything to my window? 小贝子编程网

我目前正在C中开发Chip-8解释器。对于渲染，我使用SDL2库。问题是我不能在屏幕上画一个矩形。SDL_RenderClear函数也不起作用。也许是Makefile，但我已经尝试将链接器中的控制台标志更改为windows。有人能帮我吗？

我的代码：

main.c

#include "chip.h"
#define NO_ROM_INSERTED 1
const int PIXEL_SIZE = 20;
const int CHIP_WIDTH = 64;
const int CHIP_HEIGHT = 32;
const int SCREEN_WIDTH = CHIP_WIDTH * PIXEL_SIZE;
const int SCREEN_HEIGHT = CHIP_HEIGHT * PIXEL_SIZE;
int main(int argc, char **argv)
{
SDL_Window *window = NULL;
SDL_Renderer *renderer = NULL;
SDL_Event event;
int quit = 0;
Chip *chip = (Chip*)malloc(sizeof(Chip));
chipInitialize(chip);
chip->gfx[23] = 0x01;
/*Checks if a ROM file is inserted by an argument*/
if(argc < 2)    
{
printf("Error, no Rom inserted");
return NO_ROM_INSERTED;
}
else
{
printf("n%s loaded into memoryn", argv[argc-1]);
}
loadProgramInMemory(chip, "./Roms/TETRIS");

if(!init(window, renderer, SCREEN_WIDTH, SCREEN_HEIGHT))
{
printf( "Failed to initialize!n" );
}
else
{   
while(!quit)
{
while(SDL_PollEvent(&event) != 0)
{
if(event.type == SDL_QUIT)
{
quit = 1;
}
}
// Clear screen
SDL_SetRenderDrawColor(renderer, 0xFF, 0x00, 0xFF, 0xFF);
SDL_RenderClear(renderer);
for(int i = 0; i < CHIP_HEIGHT; i++)
{
for(int j = 0; j < CHIP_WIDTH; j++)
{
if(chip->gfx[i * CHIP_WIDTH + j] > 0x00) //Translates the one dimensional gfx to two dimensional screen
{
SDL_SetRenderDrawColor(renderer, 0xFF, 0x00, 0x00, 0xFF);
SDL_Rect fillRect = {CHIP_WIDTH * i, CHIP_HEIGHT * j, PIXEL_SIZE, PIXEL_SIZE};
SDL_RenderFillRect(renderer, &fillRect);
}
}
}
// Update screen
SDL_RenderPresent(renderer);
}
}
close(window, renderer);
free(chip);
return 0;
}

芯片.h

#include "window.h"
typedef struct chip{
unsigned char memory[4096];
unsigned short opcode;
unsigned short pc;
unsigned short stack[16];
unsigned short sp;
unsigned char gfx[64 * 32];
unsigned char V[16];
unsigned short I;
unsigned char delayTimer;
unsigned char soundTimer;
}Chip;
void chipInitialize(Chip *chip);
void loadFontInMemory(Chip *chip);
void loadProgramInMemory(Chip *chip, char *program);

芯片.c

#include "chip.h"
void chipInitialize(Chip *chip)
{
chip->pc            = 0x200;            // Set program counter to 0x200
chip->opcode        = 0x0000;           // Reset current opcode
chip->I             = 0x0000;           // Reset index register
chip->sp            = 0x0000;           // Reset stack pointer
chip->delayTimer    = 0x00;             // Reset delay timer
chip->soundTimer    = 0x00;             // Reset sound timer
for(int i = 0; i < 64 * 32; i++)        // Reset the graphics
chip->gfx[i] = 0x00;
for(int i = 0; i < 16; i++)             // Reset the stack
chip->stack[i] = 0x0000;
for(int i = 0; i < 4069; i++)           // Reset memory
chip->memory[i] = 0x00;
for(int i = 0; i < 16; i++)             // Reset registers
chip->V[i] = 0x00;
loadFontInMemory(chip);                 // Loads the font-set into memory
}
void loadProgramInMemory(Chip *chip, char *program)
{
int bufferSize = 0xFFF - 0x200;         // Size of the memory which is reserved for the program
unsigned char buffer[bufferSize];
FILE *ptr;
ptr = fopen(program, "rb");
fread(buffer, bufferSize, 1, ptr);
for(int i = 0; i < bufferSize; i++)
chip->memory[i + 512] = buffer[i];  // Reads in the program and stores it in memory at location 0x200 or 512
}
void loadFontInMemory(Chip *chip)
{
// Zero                         // Six                          // C
chip->memory[0x000] = 0xF0;     chip->memory[0x01E] = 0xF0;     chip->memory[0x03C] = 0xF0;
chip->memory[0x001] = 0x90;     chip->memory[0x01F] = 0x80;     chip->memory[0x03D] = 0x80;
chip->memory[0x002] = 0x90;     chip->memory[0x020] = 0xF0;     chip->memory[0x03E] = 0x80;
chip->memory[0x003] = 0x90;     chip->memory[0x021] = 0x90;     chip->memory[0x03F] = 0x80;
chip->memory[0x004] = 0xF0;     chip->memory[0x022] = 0xF0;     chip->memory[0x040] = 0xF0;
// One                          // Seven                        // D
chip->memory[0x005] = 0x20;     chip->memory[0x023] = 0xF0;     chip->memory[0x041] = 0xE0;
chip->memory[0x006] = 0x60;     chip->memory[0x024] = 0x10;     chip->memory[0x042] = 0x90;
chip->memory[0x007] = 0x20;     chip->memory[0x025] = 0x20;     chip->memory[0x043] = 0x90;
chip->memory[0x008] = 0x20;     chip->memory[0x026] = 0x40;     chip->memory[0x044] = 0x90;
chip->memory[0x009] = 0x70;     chip->memory[0x027] = 0x40;     chip->memory[0x045] = 0xE0;
// Two                          // Eight                        // E
chip->memory[0x00A] = 0xF0;     chip->memory[0x028] = 0xF0;     chip->memory[0x046] = 0xF0;
chip->memory[0x00B] = 0x10;     chip->memory[0x029] = 0x90;     chip->memory[0x047] = 0x80;
chip->memory[0x00C] = 0xF0;     chip->memory[0x02A] = 0xF0;     chip->memory[0x048] = 0xF0;
chip->memory[0x00D] = 0x80;     chip->memory[0x02B] = 0x90;     chip->memory[0x049] = 0x80;
chip->memory[0x00E] = 0xF0;     chip->memory[0x02C] = 0xF0;     chip->memory[0x04A] = 0xF0;
// Three                        // Nine                         // F
chip->memory[0x00F] = 0xF0;     chip->memory[0x02D] = 0xF0;     chip->memory[0x04B] = 0xF0;
chip->memory[0x010] = 0x10;     chip->memory[0x02E] = 0x90;     chip->memory[0x04C] = 0x80;
chip->memory[0x011] = 0xF0;     chip->memory[0x02F] = 0xF0;     chip->memory[0x04D] = 0xF0;
chip->memory[0x012] = 0x10;     chip->memory[0x030] = 0x10;     chip->memory[0x04E] = 0x80;
chip->memory[0x013] = 0xF0;     chip->memory[0x031] = 0xF0;     chip->memory[0x04F] = 0x80;
// Four                         // A
chip->memory[0x014] = 0x90;     chip->memory[0x032] = 0xF0;
chip->memory[0x015] = 0x90;     chip->memory[0x033] = 0x90;
chip->memory[0x016] = 0xF0;     chip->memory[0x034] = 0xF0;
chip->memory[0x017] = 0x10;     chip->memory[0x035] = 0x90;
chip->memory[0x018] = 0x10;     chip->memory[0x036] = 0x90;
// Five                         // B
chip->memory[0x019] = 0xF0;     chip->memory[0x037] = 0xE0;
chip->memory[0x01A] = 0x80;     chip->memory[0x038] = 0x90;
chip->memory[0x01B] = 0xF0;     chip->memory[0x039] = 0xE0;
chip->memory[0x01C] = 0x10;     chip->memory[0x03A] = 0x90;
chip->memory[0x01D] = 0xF0;     chip->memory[0x03B] = 0xE0;
}

window.h

#include <SDL2/SDL.h>
#include <stdio.h>
#include <stdlib.h>
int init(SDL_Window *window, SDL_Renderer* renderer, const 
int width, const int height);
void close(SDL_Window *window, SDL_Renderer* renderer);

window.c

#include "window.h"
int init(SDL_Window *window, SDL_Renderer *renderer, const 
int width, const int height)
{
//Initialization flag
int success = 1;
//Initialize SDL
if( SDL_Init(SDL_INIT_VIDEO) < 0)
{
printf( "SDL could not initialize! SDL_Error: %sn", SDL_GetError() );
success = 0;
}
else
{
//Create window
window = SDL_CreateWindow( "Chip-8 Emulator", SDL_WINDOWPOS_UNDEFINED, SDL_WINDOWPOS_UNDEFINED, width, height, SDL_WINDOW_SHOWN );
if( window == NULL )
{
printf( "Window could not be created! SDL_Error: %sn", SDL_GetError());
success = 0;
}
else
{
renderer = SDL_CreateRenderer(window, -1, 0);
if(renderer == NULL)
{
printf( "Renderer could not be created! SDL Error: %sn", SDL_GetError() );
success = 0;
}
else
{
SDL_SetRenderDrawColor(renderer, 0xFF, 0x00, 0xFF, 0xFF);
}
}
}
return success;
}
void close(SDL_Window *window, SDL_Renderer* renderer)
{
//Destroy window
SDL_DestroyWindow( window );
window = NULL;
SDL_DestroyRenderer(renderer);
renderer = NULL;
//Quit SDL subsystems
SDL_Quit();
}

生成文件

OBJS = main.c chip.c window.c
OBJ_NAME = Emulator
all : $(OBJS)
gcc $(OBJS) -IC:codeSDL2i686-w64-mingw32include -LC:codeSDL2i686-w64-mingw32lib -w -Wl,-subsystem,console -lmingw32 -lSDL2main -lSDL2 -o $(OBJ_NAME)

让我从一个建议开始-如果你对答案感兴趣，请不要让你的问题比需要的更难回答。想想它对其他人来说是什么样子-一些大量的代码，问题似乎是什么都不画；为什么这个例子必须有6个文件？为什么它依赖于我们没有的外部文件，因此根本无法验证？当然，只需init和render就可以将其缩小到30行的单个文件-实际上SDL2的任何"你好世界"都可以。当它工作时，而你的代码不工作时，你就开始检查有什么不同。

现在回答你的问题。您不能从主循环中提取任何内容，因为这里的window和renderer是NULL——它被初始化为NULL，从未设置为其他任何内容。您似乎对函数参数的工作方式有误解——在C中，函数参数是按值传递的，对该值的任何修改都会对局部函数副本进行。当您传递一个int时，函数将获得该int的副本，并且不将任何更改推回。如果传递SDL_Window*，则传递该指针的值(在本例中为NULL(；当您执行SDL_CreateWindow时，您将其分配给本地变量，一旦angain无法将其返回给调用者，它将保持为NULL。因此，所有的渲染器调用都将NULL作为渲染器传递，这自然不是一个有效的渲染器。

close中也出现了同样的情况——您试图将传递的副本重置为NULL，但这毫无意义，因为您不能修改外部值，只能使用本地副本。

编程类经常教导存在"按值传递"one_answers"按引用传递"，我认为这是造成这种混乱的原因。我宁愿说C中并没有通过引用，您总是传递值，但指针也是一个值。为了能够修改数据，我们传递指向该数据的指针；要使int发生突变，您可以传递int*，但要使SDL_Window*发生突变，需要获取指向的指针，该指针是指针-SDL_Window**。看看SDL本身是如何做到的：https://wiki.libsdl.org/SDL_CreateWindowAndRenderer。

因此，简而言之，将您的init改为int init(SDL_Window **window, SDL_Renderer** renderer, int width, int height);(此处也不需要const int，因为这些是宽度和高度的副本(，并相应地修改其代码。并在调用之后检查window和renderer的值(调试器、调试printf、if(window==NULL)任何情况都会发生(。init可能类似

int init(SDL_Window **owindow, SDL_Renderer **orenderer,
int width, int height)
{
SDL_Window *window = NULL;
SDL_Renderer *renderer = NULL;
//Initialization flag
int success = 1;
//Initialize SDL
if( SDL_Init(SDL_INIT_VIDEO) < 0)
{
printf( "SDL could not initialize! SDL_Error: %sn", SDL_GetError() );
success = 0;
}
else
{
//Create window
window = SDL_CreateWindow( "Chip-8 Emulator", SDL_WINDOWPOS_UNDEFINED, SDL_WINDOWPOS_UNDEFINED, width, height, SDL_WINDOW_SHOWN );
if( window == NULL )
{
printf( "Window could not be created! SDL_Error: %sn", SDL_GetError());
success = 0;
}
else
{
renderer = SDL_CreateRenderer(window, -1, 0);
if(renderer == NULL)
{
printf( "Renderer could not be created! SDL Error: %sn", SDL_GetError() );
success = 0;
}
else
{
SDL_SetRenderDrawColor(renderer, 0xFF, 0x00, 0xFF, 0xFF);
}
}
}
*owindow = window;
*orenderer = renderer;
return success;
}

当然，对init的调用必须修改为init(&window, &renderer, SCREEN_WIDTH, SCREEN_HEIGHT)。

当我们在做的时候，还有两件事：

头文件应该有include保护，否则如果多次(直接或间接(包含它，会导致问题。
永远不要调用函数close。它将(毫无疑问(在linux/UNIX系统上崩溃。想想另一个广泛使用的操作系统没有保留的名称。

c语言 - 为什么 SDL2 渲染器不在我的窗口中绘制任何内容？

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