奇怪的视觉错误与绘图Allegro基元

Question

我使用allegro_primitives.h头文件，并且当我去绘制一个带有al_draw_filled_rectangle的矩形，并且用键移动矩形时，矩形的轮廓朝着矩形正在改变颜色。这里是代码：

#include <allegro5\allegro5.h> 
#include <allegro5\allegro_primitives.h> 
#include <iostream> 
#include "Globals.h" 
using namespace std; 

bool keys[5] = {false, false, false, false, false}; 
enum KEYS {UP, DOWN, LEFT, RIGHT, SPACE}; 
const int WINDOW_WIDTH = 600; 
const int WINDOW_HEIGHT = 600; 
int main() 
{ 
    bool done = false; 
    bool redraw = true; 

    ALLEGRO_DISPLAY *display = NULL; 
    ALLEGRO_TIMER *timer = NULL; 
    ALLEGRO_EVENT_QUEUE *event_queue = NULL; 

    if(!al_init()) 
     return -1; 

    al_set_new_display_option(ALLEGRO_SAMPLE_BUFFERS, 1, ALLEGRO_SUGGEST); 
    al_set_new_display_option(ALLEGRO_SAMPLES, 8, ALLEGRO_SUGGEST); 

    display = al_create_display(WINDOW_WIDTH,WINDOW_HEIGHT); 

    if(!display) 
     return -1; 

    al_init_primitives_addon(); 
    al_install_keyboard(); 

    event_queue = al_create_event_queue(); 
    timer = al_create_timer(1.0/60); 

    if(!timer) 
     return -1; 
    if(!event_queue) 
     return -1; 

    al_register_event_source(event_queue,al_get_keyboard_event_source()); 
    al_register_event_source(event_queue,al_get_timer_event_source(timer)); 
    al_register_event_source(event_queue,al_get_display_event_source(display)); 

    Character player; 
    Character lover; 

    player.x1 = 100; 
    player.x2 = player.x1 + 40; 
    player.y1 = (WINDOW_HEIGHT/2) - 20; 
    player.y2 = player.y1 + 40; 

    lover.x1 = WINDOW_WIDTH - 140; 
    lover.x2 = lover.x1 + 40; 
    lover.y1 = (WINDOW_HEIGHT/2) - 20; 
    lover.y2 = lover.y1 + 40; 

    al_start_timer(timer); 

    while(!done) 
    { 
     ALLEGRO_EVENT ev; 
     al_wait_for_event(event_queue,&ev); 
     if(ev.timer.source == timer) 
     { 
      if(keys[UP]) 
      { 
       player.y1 -= 5; 
       player.y2 -= 5; 
      } 
      if(keys[DOWN]) 
      { 
       player.y1 += 5; 
       player.y2 += 5; 
      } 
      if(keys[LEFT]) 
      { 
       player.x1 -= 5; 
       player.x2 -= 5; 
      } 
      if(keys[RIGHT]) 
      { 
       player.x1 += 5; 
       player.x2 += 5; 
      } 
      if(player.x1 <= 0) 
      { 
       player.x1 = 0; 
       player.x2 = 40; 
      } 
      if(player.x2 >= WINDOW_WIDTH) 
      { 
       player.x1 = WINDOW_WIDTH - 40; 
       player.x2 = WINDOW_WIDTH; 
      } 
      if(player.y1 <= 0) 
      { 
       player.y1 = 0; 
       player.y2 = player.y1 + 40; 
      } 
      if(player.y2 >= WINDOW_HEIGHT) 
      { 
       player.y1 = WINDOW_HEIGHT - 40; 
       player.y2 = WINDOW_HEIGHT; 
      } 
     } 
     if(ev.type == ALLEGRO_EVENT_DISPLAY_CLOSE) 
     { 
      done = true; 
     } 
     if(ev.type == ALLEGRO_EVENT_KEY_DOWN) 
     { 
      switch(ev.keyboard.keycode) 
      { 
      case ALLEGRO_KEY_ESCAPE: 
       done = true; 
       break; 
      case ALLEGRO_KEY_LEFT: 
       keys[LEFT] = true; 
       break; 
      case ALLEGRO_KEY_RIGHT: 
       keys[RIGHT] = true; 
       break; 
      case ALLEGRO_KEY_DOWN: 
       keys[DOWN] = true; 
       break; 
      case ALLEGRO_KEY_UP: 
       keys[UP] = true; 
       break; 
      } 
     } 
     if(ev.type == ALLEGRO_EVENT_KEY_UP) 
     { 
      switch(ev.keyboard.keycode) 
      { 
      case ALLEGRO_KEY_ESCAPE: 
       done = true; 
       break; 
      case ALLEGRO_KEY_LEFT: 
       keys[LEFT] = false; 
       break; 
      case ALLEGRO_KEY_RIGHT: 
       keys[RIGHT] = false; 
       break; 
      case ALLEGRO_KEY_UP: 
       keys[UP] = false; 
       break; 
      case ALLEGRO_KEY_DOWN: 
       keys[DOWN] = false; 
       break; 
      } 
     } 
     if(redraw && al_is_event_queue_empty(event_queue)) 
     { 
      al_draw_filled_rectangle(player.x1,player.y1,player.x2,player.y2,al_map_rgb(0,0,127)); 
      al_draw_filled_rectangle(lover.x1,lover.y1,lover.x2,lover.y2,al_map_rgb(127,0,0)); 
      al_flip_display(); 
      al_clear_to_color(al_map_rgb(255,255,255)); 
     } 
    } 
    al_destroy_timer(timer); 
    al_destroy_display(display); 
    al_destroy_event_queue(event_queue); 
    return 0; 
} 

有人能帮我吗？ “Globals.h”只是一个小的头文件，其中包含一个用于定义它们的x1，x2，y1和y2变量的Character结构。谢谢。

Answer 1

由于您的代码当前是，您的重画不受您的计时器控制。您的重绘变量正在初始化为true，但将其设置为false会更有意义，并让您的计时器在适当时将其设置为true。当您的计时器事件触发时，将重绘设置为true。

ALLEGRO_EVENT ev; 
al_wait_for_event(event_queue,&ev); 
if(ev.timer.source == timer) 
{ 
    redraw = true; 
} 

然后，当您检查重绘时，将其重新设置为false。

if(redraw && al_is_event_queue_empty(event_queue)) 
{ 
    redraw = false; 

    al_draw_filled_rectangle(player.x1,player.y1,player.x2,player.y2,al_map_rgb(0,0,127)); 
    al_draw_filled_rectangle(lover.x1,lover.y1,lover.x2,lover.y2,al_map_rgb(127,0,0)); 
    al_flip_display(); 
    al_clear_to_color(al_map_rgb(255,255,255)); 
}