mouse.c

This example shows how to use the mouse input functions to detect if the user clicks on any of several rectangles.

#include <stdio.h>
#include <stdlib.h>
#include <stdarg.h>
#include <math.h>

#include "mgsLib.h"

#define WIDTH   100
#define HEIGHT  80
#define INTER   50

//Left, top, right and bottom coordinates
struct rectangle {
    int l, t, r, b;
};

// Prototype of the function
inline int inRectangle(int x, int y, struct rectangle r);

int main()
{
    // Colors for the rectangles and other variables
    int i, scr, colors[5] = {MGS_CRED, MGS_CMAGENTA, MGS_CGREEN, MGS_CCYAN, MGS_CBLUE};
    int x, y, selected = -1, pressed = 0;
    struct rectangle rect[5];
    
    // Create a screen
    if ((scr = mgsCreateScreen(800, 600, "Mouse input", MGS_CGREY, NULL)) < 0)
        exit(EXIT_FAILURE);
    
    // Align the rectangles horizontally
    for(i = 0; i < 5; i++) {
        rect[i].t = 180;
        rect[i].b = 180 + HEIGHT;
        rect[i].l = INTER + i * (INTER + WIDTH);
        rect[i].r = rect[i].l + WIDTH;
    }
    
    // Set the default font
    mgsSetFont(scr, 80, MGS_CBLACK, MGS_TRANSPARENT);
    
    // And work until S is pressed
    puts("Press S to exit");
    while(!mgsKeyPressed('S')) {
        // Always read the mouse position. It does not cost much time
        x = mgsMouseX(scr);
        y = mgsMouseY(scr);
        // pressed is the state of the left mouse button.
        // If it was pressed the previous frame
        if (pressed) {
            // See if it has ben released
            if (!(mgsMouseButtons(scr) & MGS_MOUSELEFT)) {
                // It is no longer pressed
                pressed = 0;
                // And no rectangle is selected for sure
                selected = -1;
            }
            // Else if we have any rectangle selected
            else if (selected > -1) 
                // If the cursor has left its surface, deselect it
                if (!inRectangle(x, y, rect[selected]))
                    selected = -1;
        }
        // If it was not pressed verifiy if it is pressed now
        else if (mgsMouseButtons(scr) & MGS_MOUSELEFT) {
            // If so, mark it as pressed
                pressed = 1;
                // And if over a rectangle, select it
                for (i = 0; i < 5; i++)
                    if (inRectangle(x, y, rect[i])) {
                        selected = i;
                        break;
                    }
        }
        
        // Clear the old screen
        mgsClearScreen(scr);
        
        // Put the main text in the default font
        mgsPuts(scr, 37, 20, "Click on any rectangle");
        // Draw all the rectangles. If any is selected use a color darker than the default
        for(i = 0; i < 5; i++)
            mgsRectangle(scr, rect[i].l, rect[i].t, rect[i].r, rect[i].b, (i == selected) ? colors[i] & 0x7F7F7F : colors[i]);
        // If any rectangle is selected, display an effect keeping the default font
        if (selected > -1) {
            mgsSetFont(scr, 70, colors[selected], MGS_TRANSPARENT);
            mgsPuts(scr, 130, 370, "You clicked on the");
            mgsPuts(scr, 90, 440, "rectangle of this color");
            mgsRectangle(scr, 10, 520, 790, 540, colors[selected] & 0x7F7F7F);
            mgsRectangle(scr, 10, 350, 790, 370, colors[selected] & 0x7F7F7F);
            mgsSetFont(scr, 80, MGS_CBLACK, MGS_TRANSPARENT);
        }
        
        // Wait until the frame time expires
        mgsWaitFrame();
        
        // And show the new image frame
        mgsUpdateScreen(scr);
    }
    
    exit(EXIT_SUCCESS);
}

// Just verify (x,y) are inside the rectangle.
inline int inRectangle(int x, int y, struct rectangle r)
{
    return((x >= r.l) && (x <= r.r) && (y >= r.t) && (y <= r.b));
}