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Receiving and processing events

Every time you call gm_yield, gama collects all the events which have happened and stores them in a way you can easily access them.

# Mouse events

Events happening to the mouse are stored in a global gm_mouse structure,

        struct _gmMouse {
  gmPos position;
  gmPos movement;

  int32_t pressed;
  int32_t down;
};
struct _gmMouse gm_mouse;

      

As such:

• you can get the mouse last position with gm_mouse.position.x and gm_mouse.position.y.
• You can get the mouse change in position with gm_mouse.movement.
• gm_mouse.down reports if the mouse is currently down, if the user holds the mouse down, this will contiuously be `.
• gm_mouse.pressed reports like gm_mouse.down, except that this is reported only once even if the user holds the mouse down, you can use this to tests for clicks.

See gm_mouse reference

# Little example

        #include <gama.h>

int main() {
    gm_init(500, 500, "test");
    
    do {
        // green if the mouse is pressed else blue
        gmColor color = gm_mouse.down ? GM_GREEN : GM_BLUE;
        double mouse_x = gm_mouse.position.x, // <- a comma
               mouse_y = gm_mouse.position.y; // <- a semicolon
        // draw the circle with radius 0.5 at mouse position
        gm_draw_circle(mouse_x, mouse_y, 0.5, color);
    } while(gm_yield());
}

      

# Keyboard events

Processing keyboard events is a bit more interesting, the fact is that there are plenty of keys on the keyboard, you have a few functions to test if a key is currently being pressed, for convenience I will talk only of that will mostly use.

        int gm_key(char keycode);

      

The keycode is usually the key itself in lowercase, e.g 'a' for key A, ' ' for key space, '.' for key dot. But for special keys you will use upper case letters:

• 'U' for key up
• 'D' for key down
• 'L' for key left
• 'R' for key right
• 'E' for key escape
• 'S' for shift key
• 'C' for control key
• 'A' for alt key
• '\0' for unsupported or invalid keys

# Little example

        int key_a_pressed = gm_key('a');
int key_alt_pressed = gm_key('A');

if(gm_key('U'))
    go_up();
else if(gm_key('D'))
    go_down();