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Example of registermousehandler

/* mouse example */
#include "graphics.h"
// The click_handler will be called whenever the left mouse button is
// clicked. It checks copies the x,y coordinates of the click to
// see if the click was on a red pixel. If so, then the boolean
// variable red_clicked is set to true. Note that in general
// all handlers should be quick. If they need to do more than a little
// work, they should set a variable that will trigger the work going,
// and then return.
bool red_clicked = false;
void click_handler(int x, int y)
    if (getpixel(x,y) == RED)
  red_clicked = true;
// Call this function to draw an isosoles triangle with the given base
// height. The triangle will be drawn just above the botton of the
void triangle(int base, int height)
    int maxx = getmaxx( );
    int maxy = getmaxy( );
    line(maxx/2 - base/2, maxy - 10, maxx/2 + base/2, maxy - 10);
    line(maxx/2 - base/2, maxy - 10, maxx/2, maxy - 10 - height);
    line(maxx/2 + base/2, maxy - 10, maxx/2, maxy - 10 - height);
void main(void)
    int maxx, maxy;  // Maximum x and y pixel coordinates
    int divisor;     // Divisor for the length of a triangle side
    // Put the machine into graphics mode and get the maximum
    initwindow(450, 300);
    maxx = getmaxx( );
    maxy = getmaxy( );
    // Register the function that handles a left mouse click
    registermousehandler(WM_LBUTTONDOWN, click_handler);
    // Draw a white circle with red inside and a radius of 50 pixels:
    setfillstyle(SOLID_FILL, RED);
    fillellipse(maxx/2, maxy/2, 50, 50);
    // Print a message and wait for a red pixel to be double clicked:
    settextstyle(DEFAULT_FONT, HORIZ_DIR, 2);
    outtextxy(20, 20, "Left click in RED to end.");
    red_clicked = false;
    divisor = 2;
    while (!red_clicked)
  triangle(maxx/divisor, maxy/divisor);
    cout << "The mouse was clicked at: ";
    cout << "x=" << mousex( );
    cout << " y=" << mousey( ) << endl;
    // Switch back to text mode:
    closegraph( );

See also

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c/graphics.h/registermousehandler.txt · Last modified: 2024/02/16 01:05 (external edit)

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