Flickering Explanation

AMCerasoli

Aloha.

I has being messing around with allegro and stuff, and found an strange behavior when I use al_flip_display without al_clear_to_color. I'ts some kind of flickering only when it's full screen.

Does have something to do with monitor Hz or vsync?

This is an executable example (Windows)

Well I just was curious about this... What it causes that behavior?.

torhu

Could you post the source?

AMCerasoli

Yep.

That is inside a class...

#SelectExpand
   1
   2#ifndef MENU_H
   3#define MENU_H
   4
   5#include <iostream>
   6#include <vector>
   7#include <fstream>
   8#include "fade.h"
   9
  10#define ALLEGRO_STATICLINK
  11#include "allegro5/allegro.h"
  12#include "allegro5/allegro_font.h"
  13#include "allegro5/allegro_ttf.h"
  14#include "allegro5/allegro_image.h"
  15#include <allegro5/allegro_audio.h>
  16#include <allegro5/allegro_acodec.h>
  17
  18
  19
  20class MENU
  21{
  22
  23 private:
  24
  25  ALLEGRO_BITMAP *fondo;
  26  ALLEGRO_BITMAP *fondo2;
  27  ALLEGRO_EVENT event;
  28
  29  //FADE fade;
  30
  31  int R, G, B, A;
  32  int mouse_x, mouse_y;
  33  bool cerrar_menu;
  34
  35  ALLEGRO_FONT *font;
  36
  37 public:
  38
  39  MENU() {
  40
  41     fondo = al_load_bitmap("menu_img/1.png");
  42     //fondo2 = al_load_bitmap("menu_img/packed.png");
  43     font = al_load_font("consola.ttf",14,0);
  44     R=0; G=0; B=0; A=0;
  45     cerrar_menu=false;
  46
  47  }
  48
  49  ~MENU() {
  50
  51     al_destroy_bitmap(fondo);
  52     //al_destroy_bitmap(fondo2);
  53
  54  }
  55
  56  unsigned short mostr_menu(ALLEGRO_EVENT_QUEUE* event_queue){
  57
  58     while(!cerrar_menu){
  59
  60           al_wait_for_event(event_queue, &event);
  61
  62           switch(event.type){
  63
  64              case ALLEGRO_EVENT_TIMER:
  65              if(al_is_event_queue_empty(event_queue))
  66              dibujar();
  67              break;
  68
  69              case ALLEGRO_EVENT_MOUSE_AXES:
  70              Mouse_Axes();
  71              break;
  72
  73              case ALLEGRO_EVENT_KEY_CHAR:
  74              Key_Down();
  75              break;
  76
  77           };
  78     }
  79
  80  return 2;
  81  }
  82
  83  void dibujar(){
  84
  85     //al_clear_to_color(al_map_rgb(0,0,0));
  86
  87     //al_draw_tinted_bitmap(fondo2, al_map_rgba(255, 255, 255, 255),0, 0, 0);
  88     al_draw_tinted_bitmap(fondo, al_map_rgba(R, G, B, A),mouse_x-330, mouse_y-250, 0);
  89     al_draw_tinted_bitmap(fondo, al_map_rgba(0, 0, 0, 125),400, 280, 0);
  90
  91     //fade.in();
  92
  93     al_draw_textf(font, al_map_rgba(255, 255, 255, 255),780, 500, ALLEGRO_ALIGN_RIGHT,"R: %f", R);
  94     al_draw_textf(font, al_map_rgba(255, 255, 255, 255),780, 515, ALLEGRO_ALIGN_RIGHT,"G: %f", G);
  95     al_draw_textf(font, al_map_rgba(255, 255, 255, 255),780, 530, ALLEGRO_ALIGN_RIGHT,"B: %f", B);
  96     al_draw_textf(font, al_map_rgba(255, 255, 255, 255),780, 545, ALLEGRO_ALIGN_RIGHT,"A: %f", A);
  97     al_draw_text(font,al_map_rgba(255, 255, 255, 255), 0, 0, 0, "Press the keys: R,G,B and A to increse its value, and the left key to decrease it <exept A> ");
  98     al_draw_text(font,al_map_rgba(255, 255, 255, 255), 0, 18, 0, "then move arround the mouse ");
  99     al_draw_text(font,al_map_rgba(255, 255, 255, 255), 0, 36, 0, "Press enter to reset the colors ");
 100
 101     al_flip_display();
 102  }
 103
 104  void Mouse_Axes(){
 105
 106     mouse_x = event.mouse.x;
 107     mouse_y = event.mouse.y;
 108  }
 109
 110  void Key_Down(){
 111
 112     int cantidad=5;
 113
 114
 115
 116     if(event.keyboard.keycode == ALLEGRO_KEY_R&&R<=250)
 117     R+=cantidad;
 118     else if(event.keyboard.keycode == ALLEGRO_KEY_E&&R>=5)
 119     R-=cantidad;
 120
 121     else if(event.keyboard.keycode == ALLEGRO_KEY_G&&G<=250)
 122     G+=cantidad;
 123     else if(event.keyboard.keycode == ALLEGRO_KEY_F&&G>=5)
 124     G-=cantidad;
 125
 126     else if(event.keyboard.keycode == ALLEGRO_KEY_B&&B<=250)
 127     B+=cantidad;
 128     else if(event.keyboard.keycode == ALLEGRO_KEY_V&&B>=5)
 129     B-=cantidad;
 130
 131     else if(event.keyboard.keycode == ALLEGRO_KEY_A&&A<=250)
 132     A+=cantidad;
 133     else if(event.keyboard.keycode == ALLEGRO_KEY_S&&A>=5)
 134     A-=cantidad;
 135
 136     else if(event.keyboard.keycode == ALLEGRO_KEY_ESCAPE)
 137
 138        cerrar_menu=true;
 139
 140     else if(event.keyboard.keycode == ALLEGRO_KEY_ENTER){
 141
 142        R=0; G=0; B=0; A=0;
 143
 144     }
 145
 146
 147  }
 148
 149
 150
 151};
 152
 153#endif // MENU_H

Edit: This is the initialization process... I forgot it...

#SelectExpand
   1#include <iostream>
   2#include <vector>
   3#include <fstream>
   4
   5#include "Menu.h"
   6#include "presentacion.h"
   7
   8#define ALLEGRO_STATICLINK
   9#include "allegro5/allegro.h"
  10#include "allegro5/allegro_font.h"
  11#include "allegro5/allegro_ttf.h"
  12#include "allegro5/allegro_image.h"
  13#include <allegro5/allegro_audio.h>
  14#include <allegro5/allegro_acodec.h>
  15#include <allegro5/allegro_native_dialog.h>
  16
  17
  18
  19int main(int argc, char **argv){
  20
  21   ALLEGRO_DISPLAY *display = NULL;
  22   ALLEGRO_EVENT_QUEUE *event_queue = NULL;
  23   ALLEGRO_TIMER *FPS = NULL; //Frames
  24   unsigned short suiche=1;
  25
  26   ///Variables
  27   bool cerrar_juego=false;
  28
  29   if(!al_init()) {
  30   al_show_native_message_box(display, "Error", "Error", "Failed to initialize allegro!", NULL, ALLEGRO_MESSAGEBOX_ERROR);
  31      return -1;
  32   }
  33
  34   if(!al_init_image_addon()) {
  35   al_show_native_message_box(display, "Error", "Error", "Failed to initialize al_init_image_addon!", NULL, ALLEGRO_MESSAGEBOX_ERROR);
  36      return -1;
  37   }
  38
  39   al_init_font_addon();
  40
  41   if(!al_init_ttf_addon()) {
  42   al_show_native_message_box(display, "Error", "Error", "Failed to initialize al_init_ttf_addon!", NULL, ALLEGRO_MESSAGEBOX_ERROR);
  43      return -1;
  44   }
  45
  46   if(!al_install_audio()) {
  47   al_show_native_message_box(display, "Error", "Error", "Failed to initialize al_install_audio!", NULL, ALLEGRO_MESSAGEBOX_ERROR);
  48      return -1;
  49   }
  50
  51   if(!al_init_acodec_addon()) {
  52   al_show_native_message_box(display, "Error", "Error", "Failed to initialize al_init_acodec_addon!", NULL, ALLEGRO_MESSAGEBOX_ERROR);
  53      return -1;
  54   }
  55
  56   if(!al_reserve_samples(5)) {
  57   al_show_native_message_box(display, "Error", "Error", "Failed to initialize al_reserve_samples!", NULL, ALLEGRO_MESSAGEBOX_ERROR);
  58      return -1;
  59   }
  60
  61
  62   FPS = al_create_timer(1.0 / 30); //Frames
  63
  64   if(!FPS) {
  65   al_show_native_message_box(display, "Error", "Error", "Failed to initialize FPS!", NULL, ALLEGRO_MESSAGEBOX_ERROR);
  66      return -1;
  67   }
  68
  69   if(!al_install_keyboard()) {
  70   al_show_native_message_box(display, "Error", "Error", "Failed to initialize al_install_keyboard!", NULL, ALLEGRO_MESSAGEBOX_ERROR);
  71      return -1;
  72   }
  73
  74   if(!al_install_mouse()) {
  75   al_show_native_message_box(display, "Error", "Error", "Failed to initialize al_install_mouse!", NULL, ALLEGRO_MESSAGEBOX_ERROR);
  76      return -1;
  77   }
  78
  79   //al_set_new_bitmap_flags(ALLEGRO_MIN_LINEAR | ALLEGRO_MAG_LINEAR );
  80   al_set_new_display_flags(ALLEGRO_FULLSCREEN);
  81
  82
  83   display = al_create_display(800, 600);
  84
  85   if(!display) {
  86   al_show_native_message_box(display, "Error", "Error", "Failed to initialize display!", NULL, ALLEGRO_MESSAGEBOX_ERROR);
  87      return -1;
  88   }
  89   //al_set_new_display_option(ALLEGRO_SINGLE_BUFFER, 1, ALLEGRO_REQUIRE );
  90   event_queue = al_create_event_queue();
  91
  92   if(!event_queue) {
  93   al_show_native_message_box(display, "Error", "Error", "Failed to initialize event_queue!", NULL, ALLEGRO_MESSAGEBOX_ERROR);
  94      return -1;
  95   }
  96
  97   al_register_event_source(event_queue, al_get_display_event_source(display));
  98   al_register_event_source(event_queue, al_get_timer_event_source(FPS));
  99   al_register_event_source(event_queue, al_get_mouse_event_source());
 100   al_register_event_source(event_queue, al_get_keyboard_event_source());
 101   al_clear_to_color(al_map_rgb(0,0,0));
 102   al_flip_display();
 103   al_start_timer(FPS);
 104   al_set_window_title(display, "Trivial Relax 2011");
 105
 106   while(!cerrar_juego)
 107   {
 108
 109      switch(suiche){
 110
 111         case 0:{
 112            //PRESENTACION presentacion;
 113            //suiche = presentacion.mostr_presentacion(event_queue);
 114            break;
 115         }
 116         case 1:{
 117            MENU menu;
 118            suiche = menu.mostr_menu(event_queue);
 119            break;
 120         }
 121
 122      };
 123    if(suiche==2)
 124    break;
 125   }
 126
 127
 128   al_destroy_timer(FPS);
 129   al_destroy_display(display);
 130   al_destroy_event_queue(event_queue);
 131   al_uninstall_audio();
 132
 133   return 0;
 134}

Matthew Leverton

Does al_get_display_option(display, ALLEGRO_UPDATE_DISPLAY_REGION) indicate the display supports partial updates?

But that aside, I don't think al_flip_display() isn't guaranteed to clear your backbuffer. So if you are only updating a partial part of the backbuffer, then I would expect "odd" behavior if you don't first clear it.

torhu

I don't know, sorry. Just try making some changes and see what happens.

AMCerasoli

No actually there is no problem... I shouldn't being doing that anyway... I just wanted to know...

Matthew Leverton said:

Does al_get_display_option(display, ALLEGRO_UPDATE_DISPLAY_REGION) indicate the display supports partial updates?

Let me process that...

Quote:

Yes that is what I thought.

kenmasters1976

This code, for example, will flicker like crazy on my machine if I use OpenGL but not if I use Direct3D. So I guess whether the backbuffer is cleared or not depends on the driver.

#SelectExpand
  1#include <allegro5/allegro.h>
  2#include <allegro5/allegro_primitives.h>
  3
  4
  5
  6ALLEGRO_DISPLAY *display;
  7ALLEGRO_EVENT_QUEUE *events;
  8
  9
 10
 11int main() {
 12    al_init();
 13    al_install_keyboard();
 14    al_set_new_display_flags(ALLEGRO_WINDOWED | ALLEGRO_OPENGL);
 15    display = al_create_display(640, 480);
 16    al_init_primitives_addon();
 17  
 18    events = al_create_event_queue();
 19    al_register_event_source(events, al_get_keyboard_event_source());
 20  
 21    al_clear_to_color(al_map_rgb(0, 128, 128));
 22    while (al_is_event_queue_empty(events)) {
 23        al_draw_line(0, 0, 640, 480, al_map_rgb(255, 255, 255), 2);
 24        al_flip_display();
 25        al_rest(0.015);
 26    }
 27}

AMCerasoli

Yes on my computer also flicks a lot with OpenGL.

I think when I don't do this: al_set_new_display_flags(ALLEGRO_OPENGL); Automatically is using Direct3D but when I do this: al_set_new_display_flags(ALLEGRO_DIRECT3D); Tells me that 'ALLEGRO_DIRECT3D' was not declared in this scope. Why's that?

Edit: If I use 'ALLEGRO_OPENGL_3_0' instead of 'ALLEGRO_OPENGL' doesn't flicks anymore on windowed mode, but if I go fullscreen do it again.

Edgar Reynaldo

AMCerasoli said:

Tells me that 'ALLEGRO_DIRECT3D' was not declared in this scope. Why's that?

~~ALLEGRO_DIRECT3D is not defined on non-Windows platforms. If you're compiling this on Windows there is something wrong...~~ It doesn't work for me either. There's something wrong with the includes somehow.

You have to include <allegro5/allegro_direct3d.h> for it to work. The manual neglects to mention that little fact.

AMCerasoli

Finally you could download the last driver for your PC? I think mines is very similar to yours. Mines is a Toshiba Satellite A215, but I couldn't find the Drivers. You downloaded it from Toshiba or from AMD?

kenmasters1976

Edgar Reynaldo said:

You have to include <allegro5/allegro_direct3d.h> for it to work. The manual neglects to mention that little fact.

At some point in 4.9.x you had to include allegro5/allegro_opengl.h so that you could use ALLEGRO_OPENGL. I never tried to use ALLEGRO_DIRECT3D since it's the default.

AMCerasoli said:

My PC is an old IBM with integrated Intel graphics card. I have the latest drivers (dated 2005). You should be able to find the latest drivers for your machine at Toshiba.

Anyway, you should always clear the backbuffer. Even for a simple program like the one I posted you could do:

al_clear_to_color(al_map_rgb(0, 128, 128));
al_flip_display();
al_clear_to_color(al_map_rgb(0, 128, 128));

or simply force ALLEGRO_SINGLE_BUFFER.

Thread #607175. Printed from Allegro.cc