Mouse-enabled program immediately exits due to error

Mouse-enabled program immediately exits due to error

David_at_wedu

Member #7,407

June 2006

Chances are, this problem reeks of newbieness -- that maybe I'm just not initializing something right -- but it's a problem nonetheless. A program I copied from the book I'm reading, for the sake of messing around with mouse input, compiles just fine, but every time I execute it, the program immediately crashes and gives me one of those "Do you wish to report this error to MS?" dialogs.

If it helps to produce a solution, I'm working on a notebook computer with Windows XP Profesional. I'm kind of baffled here.

Here's the code:

1#include <allegro.h>
2 
3#define WHITE makecol(255,255,255)
4#define BLACK makecol(0,0,0)
5#define RED makecol(255,0,0)
6#define GREEN makecol(0,255,0)
7#define BLUE makecol(0,0,255)
8#define SMOKE makecol(140,130,120)
9 
10// point structure used to draw lines
11typedef struct POINT
12{
13    int x, y;
14}POINT;
15 
16// points array holds do_line points for drawing a line
17POINT points[2000];
18int curpoint, totalpoints;
19 
20// bitmap images
21BITMAP* buffer;
22BITMAP* crosshair;
23BITMAP* city;
24 
25// misc variables
26int st_x,st_y,en_x,en_y;
27int done = 0;
28int destroyed = 1;
29int n;
30int mx,my,mb;
31int score = -1;
32 
33void updatescore()
34{
35    // update and display the score
36    score = score+1;
37    textprintf_right_ex(buffer, font, SCREEN_W-5, 1, WHITE, -1, "SCORE: %d", score);
38}
39 
40void explosion(BITMAP* bmp, int x, int y, int finalcolor)
41{
42    int color, size;
43 
44    for (n=0;n<20;n++)
45    {
46        // generate a random color
47        color = makecol(rand()%255,rand()%255,rand()%255);
48        // random explosion side
49        size = 20+rand()%20;
50        // draw the filled circle
51        circlefill(bmp, x, y, size, color);
52        // short pause
53        rest(2);
54    }
55    // missile tracker looks for this explosion color
56    circlefill(bmp, x, y, 40, finalcolor);
57}
58 
59void doline(BITMAP* bmp, int x, int y, int d)
60{
61    // line callback function... fills the points array
62    points[totalpoints].x = x;
63    points[totalpoints].y = y;
64    totalpoints++;
65}
66 
67void firenewmissile()
68{
69    // activate the new missile
70    destroyed = 0;
71    totalpoints = 0;
72    curpoint = 0;
73 
74    // random starting location
75    st_x = rand() % (SCREEN_W-1);
76    st_y = 20;
77 
78    // random ending location
79    en_x = rand() % (SCREEN_W-1);
80    en_y = SCREEN_H-50;
81 
82    // construct the line point-by-point
83    do_line(buffer, st_x, st_y, en_x, en_y, 0, &doline);
84}
85 
86void movemissile()
87{
88    // grab a local copy of the current point
89    int x = points[curpoint].x;
90    int y = points[curpoint].y;
91 
92    // hide mouse pointer
93    scare_mouse();
94 
95    // erase missile
96    rectfill(buffer, x-6, y-3, x+6, y+1, BLACK);
97 
98    // see if missile was hit by defense weapon
99    if (getpixel(screen, x, y) == GREEN)
100    {
101        // missile destroyed! score a point
102        destroyed++;
103        updatescore();
104    } else {
105        // no hit, just draw the missile and smoke trail
106        //draw the smoke trail
107        putpixel(buffer, x, y-3, SMOKE);
108        // draw the missle
109        circlefill(buffer, x, y, 2, BLUE);
110    }
111    // show mouse pointer
112    unscare_mouse();
113 
114    // did the missle hit a city?
115    curpoint++;
116    if (curpoint >= totalpoints)
117    {
118        // destroy the missile
119        destroyed++;
120        // animate explosion directly on screen
121        explosion(screen, x, y, BLACK);
122        // show the damage on the backbuffer
123        circlefill(buffer, x, y, 40, BLACK);
124    }
125}
126 
127 
128int main()
129{
130    allegro_init();
131    set_color_depth(16);
132    set_gfx_mode(GFX_AUTODETECT_WINDOWED, 640, 480, 0, 0);
133    install_keyboard();
134    install_mouse();
135    install_timer();
136    srand(time(NULL));
137 
138    //create a secondary screen buffer
139    buffer = create_bitmap(640,480);
140 
141    // display title
142    textout_ex(buffer, font, "Strategic Defense (ESC to quit)", 0, 1, WHITE, -1);
143 
144    //display score
145    updatescore();
146 
147    //draw border around screen
148    rect(buffer, 0, 12, SCREEN_W-2, SCREEN_H-2, RED);
149 
150    // load and draw the city images
151    city = load_bitmap("city.bmp", NULL);
152 
153    for (n=0;n<5;n++)
154    {
155        masked_blit(city, buffer, 0, 0, 50+n*120, SCREEN_H-city->h-2, city->w, city->h);
156    }
157 
158    // load the mouse cursor
159    crosshair = load_bitmap("crosshair.bmp", NULL);
160    set_mouse_sprite(crosshair);
161    set_mouse_sprite_focus(15,15);
162    show_mouse(buffer);
163 
164    while (!key[KEY_ESC])
165    {
166        // grab the current mouse values
167        mx = mouse_x;
168        my = mouse_y;
169        mb = (mouse_b & 1);
170 
171        // fire another missile if needed
172        if (destroyed)
173        {
174            firenewmissile();
175        }
176 
177        // left mouse button, fire the defense weapon
178        if (mb)
179        {
180            explosion(screen, mx, my, GREEN);
181        }
182 
183        // update enemy missile position
184        movemissile();
185 
186        // update_screen
187        blit(buffer, screen, 0, 0, 0, 0, 640, 480);
188 
189        // pause
190        rest(10);
191    }
192 
193    set_mouse_sprite(NULL);
194    destroy_bitmap(city);
195    destroy_bitmap(crosshair);
196    allegro_exit();
197}
198END_OF_MAIN();

If anyone can help, it would be greatly appreciated!

miran

Member #2,407

June 2002

Why do you not do any error checking?

EDIT: Oh yeah, I see now. You're reading that book...

Solution: check for errors and it will soon all be clear. Most probably one or more bitmaps that you try to load can't be loaded.

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Christopher Bludau

Member #5,401

January 2005

What is this famous book, that people talk about here on the boards from time to time?

gnolam

Member #2,030

March 2002

The Necronomicon All In One, by Jonathan Alhazred.

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David_at_wedu

Member #7,407

June 2006

Quote:

What is this famous book, that people talk about here on the boards from time to time?

It's called Game Programming All in One: second edition and the author is Jonathan Harbour. I really don't think the book is all that bad, but I have picked up on some of what people here have been saying in regards to bad coding practices, how he's basically anti-C++ (because he probably doesn't get it), and apparently the guy's a jerk if anyone dares to call him on any of his mistakes.

But, if the book gets me at least rolling on working with Allegro -- I'm about halfway through the book -- then I'll be happy.

BrknPhoenix

Member #7,304

June 2006

I found the book pretty handy to get started, as well as for random things here and there, but now that I'm started I've pretty much already left that book behind As soon as the example programs in it started crashing I knew something was terribly wrong, hehe.

I don't know why he hates C++ though I went ahead and put all my allegro stuff in classes anyway, screw him >_>

David_at_wedu

Member #7,407

June 2006

Quote:

As soon as the example programs in it started crashing I knew something was terribly wrong, hehe.

I haven't really had any of the examples crash, save for a few that used variable names that were defined elsewhere already (MAX comes to mind). Other than that, I've only encountered depreciated text handling functions, which I quickly looked up in the Allegro manual and updated.

Still, I do wish the book were C++-centric, if only because I learn better off seeing examples.