Here is an example that produces the problem.
It seems to happen when calling al_get_text_width and loading many fonts.
1#include <stdio.h>
2#include <allegro5/allegro.h>
3#include <allegro5/allegro5.h>
4#include <allegro5/allegro_primitives.h>
5#include <allegro5/allegro_font.h>
6#include <allegro5/allegro_ttf.h>
7#include "stdlib.h"
8#include <vector>
9struct Example
10{
11 double fps;
12 ALLEGRO_CONFIG *config;
13} ex;
14//Globals are bad but it is an example
15std::vector<ALLEGRO_FONT*> m_fonts;
16
17static const char *get_string(const char *key)
18{
19 const char *v = al_get_config_value(ex.config, "", key);
20 return (v) ? v : key;
21}
22
23static void render(void)
24{
25 al_clear_to_color(al_map_rgb(0,0,0));
26
27 int fontSz = al_get_display_height(al_get_current_display()) * 0.03f;
28 if(fontSz >= m_fonts.size())
29 {
30 fontSz = m_fonts.size() - 1;
31 }
32
33 al_draw_text((m_fonts[fontSz]),al_map_rgb(255,255,255),0,0,0,"ABCDEFGHIJKLMNOPQRSTUVWXYZ");
34
35 al_get_text_width(m_fonts[6],"ALLEGRO");
36}
37
38int main(int argc, const char *argv[])
39{
40 const char *font_file = "data/DejaVuSans.ttf";
41 ALLEGRO_DISPLAY *display;
42 ALLEGRO_TIMER *timer;
43 ALLEGRO_EVENT_QUEUE *queue;
44 int redraw = 0;
45 double t = 0;
46
47 if(!al_init())
48 {
49 return 1;
50 }
51
52
53 if(!al_init_primitives_addon())
54 {
55 return 1;
56 }
57
58 al_init_font_addon();
59
60 if(!al_init_ttf_addon())
61 {
62 return 1;
63 }
64
65
66 al_set_new_display_flags(ALLEGRO_RESIZABLE);
67 display = al_create_display(640, 480);
68 if (!display) {
69 return 1;
70 }
71 al_install_keyboard();
72
73 //load the fonts
74 for(int i = 8; i < 32; ++i)
75 {
76 m_fonts.push_back(al_load_font(font_file,i,0));
77 }
78
79 timer = al_create_timer(1.0 / 60);
80
81 queue = al_create_event_queue();
82 al_register_event_source(queue, al_get_keyboard_event_source());
83 al_register_event_source(queue, al_get_display_event_source(display));
84 al_register_event_source(queue, al_get_timer_event_source(timer));
85
86 al_start_timer(timer);
87 while (true) {
88 ALLEGRO_EVENT event;
89 al_wait_for_event(queue, &event);
90 if (event.type == ALLEGRO_EVENT_DISPLAY_CLOSE)
91 break;
92 if (event.type == ALLEGRO_EVENT_KEY_DOWN &&
93 event.keyboard.keycode == ALLEGRO_KEY_ESCAPE) {
94 break;
95 }
96 if (event.type == ALLEGRO_EVENT_TIMER)
97 redraw++;
98
99 if(event.type == ALLEGRO_EVENT_DISPLAY_RESIZE)
100 {
101 al_acknowledge_resize(display);
102
103 }
104
105 while (redraw > 0 && al_is_event_queue_empty(queue)) {
106 double dt;
107 redraw--;
108
109 dt = al_get_time();
110 render();
111 dt = al_get_time() - dt;
112
113 t = 0.99 * t + 0.01 * dt;
114
115 ex.fps = 1.0 / t;
116 al_flip_display();
117 }
118 }
119 //free mem
120
121 return 0;
122}
123
124/* vim: set sts=4 sw=4 et: */
Just keep resizing the window until you see the image I've attached:
{"name":"605475","src":"\/\/djungxnpq2nug.cloudfront.net\/image\/cache\/6\/0\/6057c40463519de97417fc003c88ed78.png","w":742,"h":308,"tn":"\/\/djungxnpq2nug.cloudfront.net\/image\/cache\/6\/0\/6057c40463519de97417fc003c88ed78"}
It's quite tricky to reproduce. If I draw the alphabet with all the loaded fonts the issue does not occur.
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