I'm having a little problem, which, I think, is related to threads. First I'll explain the situation.
I have split my game into two threads: The logic thread (running at 25 FPS) and the display thread (running at any FPS, 60 with my current settings). It'll only be a simple Mario-styled platformer, so two threads should be enough. Since I love internationalization I included a language feature, which I wanted to be powerful, yet easy to use and player-friendly. Language files called "lang[name].lng" are saved in the language folder. The game then reads strings from the currently selected language file. Anyways, I also wanted to have a proper language selection screen that recognizes all valid language files in the folder, so that the player doesn't have to mess around with the config file. The screen looks somewhat like this:
{"name":"langscreen1.png","src":"\/\/djungxnpq2nug.cloudfront.net\/image\/cache\/7\/7\/7797045a3e2a3cb983ada6cdf4da0cb6.png","w":320,"h":240,"tn":"\/\/djungxnpq2nug.cloudfront.net\/image\/cache\/7\/7\/7797045a3e2a3cb983ada6cdf4da0cb6"}
To make the selection as fast as possible (while still keeping it player-friendly and easy to program) only the graphics (flag, name) of the currently selected language file are loaded. The pathes are read from the language files themselfs. This means: Whenever you press left or right, the graphics currently in RAM are cleared and the new graphics are loaded. This happens in the logic thread. Since I obviously also need the graphics for the display thread I'm using mutexes. Now for the problem: In some rare cases when I press left or right and the new graphics are supposed to load some of the graphics stay black or keep their magic pink. So instead of
{"name":"langscreen3.png","src":"\/\/djungxnpq2nug.cloudfront.net\/image\/cache\/e\/9\/e9f3e76ea90d7f77a1f06d2877ac8e5f.png","w":320,"h":240,"tn":"\/\/djungxnpq2nug.cloudfront.net\/image\/cache\/e\/9\/e9f3e76ea90d7f77a1f06d2877ac8e5f"}
I get
{"name":"langscreen2.png","src":"\/\/djungxnpq2nug.cloudfront.net\/image\/cache\/9\/4\/94cc8a060c5d791d06eb2716e683dac0.png","w":320,"h":240,"tn":"\/\/djungxnpq2nug.cloudfront.net\/image\/cache\/9\/4\/94cc8a060c5d791d06eb2716e683dac0"}
Since this error stays until I press left/right again I suppose it can only be happening while loading the graphics. I'm also pretty sure it's a threading related problem, since I can't think of any other reason for this. Here are some code extracts with the concerning functions.
Loading new graphics:
#SelectExpand
1/* Load language graphics */
2void LoadLangGFX
(ALLEGRO_BITMAP *&LangFlagGFX,
ALLEGRO_BITMAP *&LangNameGFX,
ALLEGRO_BITMAP *&LangArrowGFX,
char *Language
)
3{
4 /* Destroy old graphics */
5 if (LangFlagGFX
!= NULL
)
6 {
7 al_destroy_bitmap(LangFlagGFX
);
8 LangFlagGFX
= NULL
;
9 }
10 if (LangNameGFX
!= NULL
)
11 {
12 al_destroy_bitmap(LangNameGFX
);
13 LangNameGFX
= NULL
;
14 }
15
16 /* Load arrow graphic */
17 if (LangArrowGFX
== NULL
)
18 {
19 LangArrowGFX
= al_load_bitmap("graphics\\RPG_Hacker-Lang_Arrow_Left.png");
20 if (LangArrowGFX
== NULL
)
21 Shutdown
(10,
"graphics\\RPG_Hacker-Lang_Arrow_Left.png");
22 }
23
24 char *FilePath
= NULL
; // Path to graphic to be loaded
25
26 /* Load flag graphic */
27 FilePath
= GetLangString
(Language,
"icon");
28 if (FilePath
!= NULL
)
29 {
30 LangFlagGFX
= al_load_bitmap(FilePath
);
31 delete FilePath
;
32 }
33 else
34 LangFlagGFX
= NULL
;
35
36 if (LangFlagGFX
== NULL
)
37 {
38 LangFlagGFX
= al_load_bitmap("graphics\\RPG_Hacker-Flag_XX.png");
39 if (LangFlagGFX
== NULL
)
40 Shutdown
(10,
"graphics\\RPG_Hacker-Flag_XX.png");
41 }
42
43 /* Load name graphic */
44 FilePath
= GetLangString
(Language,
"namegfx");
45 if (FilePath
!= NULL
)
46 {
47 LangNameGFX
= al_load_bitmap(FilePath
);
48 delete FilePath
;
49 }
50 else
51 LangNameGFX
= NULL
;
52
53 if (LangNameGFX
== NULL
)
54 {
55 LangNameGFX
= al_load_bitmap("graphics\\RPG_Hacker-Name_XX.png");
56 if (LangNameGFX
== NULL
)
57 Shutdown
(10,
"graphics\\RPG_Hacker-Name_XX.png");
58 }
59
60 /* Convert transparency masks */
61 if (LangArrowGFX
!= NULL
)
62 al_convert_mask_to_alpha(LangArrowGFX,
al_map_rgb(255,
0,
255));
63 if (LangFlagGFX
!= NULL
)
64 al_convert_mask_to_alpha(LangFlagGFX,
al_map_rgb(255,
0,
255));
65 if (LangNameGFX
!= NULL
)
66 al_convert_mask_to_alpha(LangNameGFX,
al_map_rgb(255,
0,
255));
67}
Removing old graphics:
Jump to next language file when pressing right (it's the same for left except for the first line).
#SelectExpand
1[...
]
2else if (CursorKey
(RightKey
))
3 {
4 /* Find next language */
5 LangNext
(Language
);
6
7 al_lock_mutex(LangMutex
);
8 DestroyLangGFX
(LangFlagGFX, LangNameGFX, LangArrowGFX
);
9 LoadLangGFX
(LangFlagGFX, LangNameGFX, LangArrowGFX, Language
);
10 al_unlock_mutex(LangMutex
);
11 al_rest(0);
12
13 LangArrowTimer
= 0; // For blinking arrows
14 al_play_sample(SoundEffect
[0],
1.
0,
0.
0,
1.
0, ALLEGRO_PLAYMODE_ONCE, NULL
);
15
16 }
17[...
]
Display thread (only the part, where the concerning graphics are displayed):
#SelectExpand
1[...
]
2 al_lock_mutex(LangMutex
);
3 al_lock_mutex(DisplayMutex
); // This mutex protects the ALLEGRO_DISPLAY and probably isn't necessary
4
5 al_set_target_bitmap(Backbuffer
);
6
7 if (LangFlagGFX
!= NULL
)
8 al_draw_bitmap(
9 LangFlagGFX,
(BackbufferWidth
() / 2) - (al_get_bitmap_width(LangFlagGFX
) / 2),
10 (GameHeight
/ 2) - (al_get_bitmap_height(LangFlagGFX
) / 2) - 5,
0);
11
12 if (LangNameGFX
!= NULL
)
13 al_draw_bitmap(
14 LangNameGFX,
(BackbufferWidth
() / 2) - (al_get_bitmap_width(LangNameGFX
) / 2),
15 (GameHeight
/ 2) - (al_get_bitmap_height(LangArrowGFX
) / 2) +
16 (al_get_bitmap_height(LangFlagGFX
) / 2) + 5,
0);
17
18 if (LangArrowTimer
>= FPS
/ 2 && LangArrowTimer
<= FPS
&& LangArrowGFX
!= NULL
)
19 {
20 al_draw_bitmap(
21 LangArrowGFX,
(BackbufferWidth
() / 2) - (al_get_bitmap_width(LangArrowGFX
) / 2) - 20,
22 (GameHeight
/ 2) - (al_get_bitmap_height(LangArrowGFX
) / 2) - 5,
0);
23 al_draw_bitmap(
24 LangArrowGFX,
(BackbufferWidth
() / 2) - (al_get_bitmap_width(LangArrowGFX
) / 2) + 20,
25 (GameHeight
/ 2) - (al_get_bitmap_height(LangArrowGFX
) / 2) - 5, ALLEGRO_FLIP_HORIZONTAL
);
26 }
27
28 al_unlock_mutex(DisplayMutex
);
29 al_unlock_mutex(LangMutex
);
30 al_rest(0);
31[...
]
Any ideas?
]]>
are you drawing in both threads?
.
Take your own advice and make it simpler. You can still make graphics recognizable at run-time by waiting to load the flags until the last second, but then loading them all. Whenever the user gets to the flag screen (or just before, if you can predict it), load up all detected flag files.