hexagram/src/thermo.c

#include <math.h>

#include <hexagram/gauge.h>
#include <hexagram/thermo.h>

void hexagram_thermo_init(hexagram_thermo *thermo,
                          double x,
                          double y,
                          double radius,
                          double redline) {
    hexagram_gauge_init(&thermo->gauge, x, y, radius,
        300.0 * (M_PI / 180.0),
        420.0 * (M_PI / 180.0));

    thermo->redline = redline;
}

void hexagram_thermo_draw_face(hexagram_thermo *thermo,
                               cairo_t *cr) {
    int i;

    cairo_select_font_face(cr, "Helvetica",
        CAIRO_FONT_SLANT_NORMAL,
        CAIRO_FONT_WEIGHT_NORMAL);

    cairo_set_font_size(cr, thermo->gauge.radius * 0.2);

    cairo_set_source_rgb(cr, 1, 1, 1);

    cairo_arc(cr,
              thermo->gauge.x,
              thermo->gauge.y,
              thermo->gauge.radius,
              0,
              2.0 * M_PI);

    cairo_stroke(cr);

    /*
     * Draw face numbers
     */
    cairo_move_to(cr,
                  thermo->gauge.x - 0.8 * thermo->gauge.radius,
                  thermo->gauge.y - 0.1 * thermo->gauge.radius);

    cairo_show_text(cr, "120");

    cairo_move_to(cr,
                  thermo->gauge.x - 0.15 * thermo->gauge.radius,
                  thermo->gauge.y - 0.5  * thermo->gauge.radius);

    cairo_show_text(cr, "190");

    cairo_move_to(cr,
                  thermo->gauge.x + 0.5 * thermo->gauge.radius,
                  thermo->gauge.y - 0.1 * thermo->gauge.radius);

    cairo_show_text(cr, "260");

    /*
     * Draw gauge graduations
     */
    for (i=0; i<=16; i++) {
        double min_radius = (i >= 14)?
            (i % 2? 0.8: 0.7):
            (i % 4? 0.8: 0.7);

        if ((i * 8.23529411) + 120 >= thermo->redline) {
            cairo_set_source_rgb(cr, 1, 0, 0);
        }

        hexagram_gauge_draw_mark(&thermo->gauge,
                                 cr,
                                 min_radius,
                                 0.90,
                                 i / 16.0);
    }
}

void hexagram_thermo_draw_needle(hexagram_thermo *thermo,
                                 cairo_t *cr,
                                 double temp) {
    double fahrenheit = temp * (9.0 / 5.0) + 32.0;

    if (fahrenheit < 120) {
        fahrenheit = 120;
    } else if (fahrenheit > 260) {
        fahrenheit = 260;
    }

    hexagram_gauge_draw_needle(&thermo->gauge,
                               cr,
                               0.9,
                               (fahrenheit - 120) / 140.0);
}