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static void wheel_path (cairo_t* cr, int w, int h) {
float cx = w * .5;
float cy = h * .5;
float da = M_PI * .32;
float sx = 0.15;
float dx = w * .40;
float rad = h * .5;
cairo_matrix_t mtrx;
cairo_get_matrix (cr, &mtrx);
cairo_translate (cr, cx - dx, cy);
cairo_scale (cr, sx, 1);
cairo_arc (cr, 0, 0, rad, -M_PI - da, -M_PI + da);
cairo_set_matrix (cr, &mtrx);
cairo_get_matrix (cr, &mtrx);
cairo_translate (cr, cx + dx, cy);
cairo_scale (cr, sx, 1);
cairo_arc (cr, 0, 0, rad, -da, da);
cairo_set_matrix (cr, &mtrx);
cairo_close_path (cr);
}
static void draw_wheel (cairo_t* cr, int w, int h) {
cairo_pattern_t* pat = cairo_pattern_create_linear (0.0, 0.0, 0.0, h);
cairo_pattern_add_color_stop_rgba (pat, 0.00, .3, .3, .3, 0.5);
cairo_pattern_add_color_stop_rgba (pat, 0.47, .6, .6, .6, 0.5);
cairo_pattern_add_color_stop_rgba (pat, 0.66, .2, .2, .2, 0.5);
cairo_pattern_add_color_stop_rgba (pat, 1.00, .0, .0, .0, 0.5);
// shadow
cairo_save (cr);
cairo_translate (cr, 1, 1);
wheel_path (cr, w, h);
for (int i = 8; i > 0; --i) {
const float alpha = 0.1 - 0.1 * i / 9.f;
cairo_set_line_width (cr, i);
cairo_set_source_rgba (cr, .0, .0, .0, alpha);
cairo_stroke_preserve (cr);
}
cairo_new_path (cr);
cairo_restore (cr);
// light
cairo_save (cr);
cairo_translate (cr, -2, -1);
wheel_path (cr, w, h);
for (int i = 6; i > 0; --i) {
const float alpha = 0.1 - 0.1 * i / 7.f;
cairo_set_line_width (cr, i);
cairo_set_source_rgba (cr, .4, .4, .4, alpha);
cairo_stroke_preserve (cr);
}
cairo_new_path (cr);
cairo_restore (cr);
// actual cylinder
wheel_path (cr, w, h);
cairo_set_source_rgba (cr, .25, .25, .25, 1);
cairo_fill_preserve (cr);
cairo_set_source (cr, pat);
cairo_fill_preserve (cr);
cairo_set_source_rgba (cr, 0, 0, 0, 1);
cairo_set_line_width (cr, 1.25);
cairo_stroke_preserve (cr);
cairo_clip (cr);
cairo_pattern_destroy (pat);
// shine
float off = .0330;
pat = cairo_pattern_create_linear (0.0, 0.0, 5.0, h);
cairo_pattern_add_color_stop_rgba (pat, 0.00, .0, .0, .0, 0.0);
cairo_pattern_add_color_stop_rgba (pat, 0.32 - off, .75, .75, .75, 0.0);
cairo_pattern_add_color_stop_rgba (pat, 0.39 - off, .75, .75, .75, 0.1);
cairo_pattern_add_color_stop_rgba (pat, 0.45 - off, .3, .3, .3, 0.0);
cairo_pattern_add_color_stop_rgba (pat, 1.00, .0, .0, .0, 0.0);
cairo_rectangle (cr, 0, 0, w, h);
cairo_set_source (cr, pat);
cairo_fill (cr);
cairo_pattern_destroy (pat);
}
static void draw_bpm_value (cairo_t* cr, PangoLayout* pl, const char* txt, int h, float f) {
int tw, th;
cairo_save (cr);
cairo_set_source_rgba (cr, 1.0, 0.6, 0.2, 1.0);
pango_layout_set_text (pl, txt, -1);
pango_layout_get_pixel_size (pl, &tw, &th);
cairo_scale (cr, 1.0, 1.05 - 0.55 * sqrt (2. * fabs (0.5 - f)));
cairo_translate (cr, -tw / 2.0, -1 - th / 2.0);
cairo_translate (cr, 0 , h * 2.05 * (.5 - f));
pango_cairo_layout_path (cr, pl);
cairo_fill (cr);
cairo_restore (cr);
}
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