使用SDL2实现多屏拼接滚动显示文字

一、简介

    用mfc自绘的形式纯手工模拟多屏幕文字滚动的示例，cpu占用率很高。在此改用sdl2编写测试。

二、源代码

#include "stdafx.h"

#include <SDL.h>

#include <SDL_ttf.h>

#include <stdbool.h>

#include <time.h>

// 屏幕分辨率

#define SCREEN_WIDTH 640

#define SCREEN_HEIGHT 480

// 屏幕数量

#define NUM_SCREENS 3

// 文字步进速度

#define TEXT_SPEED 5

SDL_Window *windows[NUM_SCREENS];

SDL_Renderer *renderers[NUM_SCREENS];

TTF_Font *font;

SDL_Texture* textTexture[NUM_SCREENS];

SDL_Rect textRect;

// 文字移动距离

int textX = 0;

void init()

{

SDL_Init(SDL_INIT_VIDEO);

TTF_Init();

font = TTF_OpenFont("monaco.ttf", 24);

if (!font)

exit(1);

for (int i = 0; i < NUM_SCREENS; ++i)

{

windows[i] = SDL_CreateWindow("Scrolling Text Screen " + i, i * SCREEN_WIDTH, 0, SCREEN_WIDTH, SCREEN_HEIGHT, SDL_WINDOW_SHOWN);

renderers[i] = SDL_CreateRenderer(windows[i], -1, SDL_RENDERER_ACCELERATED);

}

const char *text = "Scrolling Text";

SDL_Surface *surface = TTF_RenderText_Solid(font, text, SDL_Color{ 255, 255, 255, 255 });

for (int i = 0; i < NUM_SCREENS; ++i)

{

textTexture[i] = SDL_CreateTextureFromSurface(renderers[i], surface);

}

SDL_FreeSurface(surface);

// 获取文字占用像素尺寸

SDL_QueryTexture(textTexture[0], NULL, NULL, &textRect.w, &textRect.h);

}

void renderText(int screenIndex)

{

SDL_SetRenderDrawColor(renderers[screenIndex], 0, 0, 0, 255);

SDL_RenderClear(renderers[screenIndex]);

int renderX = 0;

if (textX / SCREEN_WIDTH == screenIndex)

{

renderX = textX % SCREEN_WIDTH;

}else if ((textX + textRect.w) / SCREEN_WIDTH == screenIndex){

renderX = (textX + textRect.w) % SCREEN_WIDTH - textRect.w;

}else {

SDL_RenderPresent(renderers[screenIndex]);

return;

}

SDL_Rect renderRect = { renderX, (SCREEN_HEIGHT - textRect.h) / 2, textRect.w, textRect.h };

#define SHOW_TIME

#ifdef SHOW_TIME

// 同时更新文本内容为当前时间

time_t currentTime = time(NULL);

struct tm *localTime = localtime(&currentTime);

char timeStr[9];

strftime(timeStr, sizeof(timeStr), "%H:%M:%S", localTime);

// 创建一个新的纹理来显示新的时间

SDL_DestroyTexture(textTexture[screenIndex]);

SDL_Surface *surface = TTF_RenderText_Solid(font, timeStr, SDL_Color{ 255, 255, 255, 255 });

textTexture[screenIndex] = SDL_CreateTextureFromSurface(renderers[screenIndex], surface);

SDL_FreeSurface(surface);

#endif

// 可以执行多个SDL_RenderCopy绘制多个纹理

SDL_RenderCopy(renderers[screenIndex], textTexture[screenIndex], NULL, &renderRect);

SDL_RenderPresent(renderers[screenIndex]);

}

void moveText()

{

#define RIGHT_MOVE

#ifdef RIGHT_MOVE

if (textX >= SCREEN_WIDTH * NUM_SCREENS)

textX = 0;

textX += TEXT_SPEED;

#endif

#ifdef LEFT_MOVE

if (textX <= -textRect.w)

textX = SCREEN_WIDTH * NUM_SCREENS;

textX -= TEXT_SPEED;

#endif

for (int i = 0; i < NUM_SCREENS; ++i)

renderText(i);

}

int main(int argc, char *argv[])

{

init();

bool running = true;

SDL_Event event;

while (running)

{

while (SDL_PollEvent(&event))

{

if (event.type == SDL_QUIT)

running = false;

}

moveText();

SDL_Delay(16); // 60 FPS

}

for (int i = 0; i < NUM_SCREENS; ++i)

{

SDL_DestroyRenderer(renderers[i]);

SDL_DestroyWindow(windows[i]);

SDL_DestroyTexture(textTexture[i]);

}

TTF_CloseFont(font);

return 0;

}