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livetrax/libs/gtkmm2ext/motionfeedback.cc

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/*
Copyright (C) 2010-2011 Paul Davis
This program is free software; you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
the Free Software Foundation; either version 2 of the License, or
(at your option) any later version.
This program is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
GNU General Public License for more details.
You should have received a copy of the GNU General Public License
along with this program; if not, write to the Free Software
Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
$Id: motionfeedback.cc,v 1.5 2004/03/01 03:44:19 pauld Exp $
*/
#include <iostream>
#include <cmath>
#include <cstdlib>
#include <algorithm>
#include <unistd.h>
#include <stdio.h> /* for snprintf, grrr */
#include <gdk/gdkkeysyms.h>
#include <gtkmm.h>
#include "pbd/controllable.h"
#include "gtkmm2ext/motionfeedback.h"
#include "gtkmm2ext/keyboard.h"
#include "gtkmm2ext/prolooks-helpers.h"
#include "gtkmm2ext/gui_thread.h"
using namespace Gtk;
using namespace Gtkmm2ext;
using namespace sigc;
MotionFeedback::MotionFeedback (Glib::RefPtr<Gdk::Pixbuf> pix,
Type t,
boost::shared_ptr<PBD::Controllable> c,
double default_val,
double step_increment,
double page_increment,
const char *widget_name,
bool with_numeric_display,
int subw,
int subh)
: _controllable (c)
, value (0)
, default_value (default_val)
, step_inc (step_increment)
, page_inc (page_increment)
, type (t)
, value_packer (0)
, pixbuf (pix)
, subwidth (subw)
, subheight (subh)
{
char value_name[1024];
print_func = default_printer;
print_arg = 0;
HBox* hpacker = manage (new HBox);
hpacker->pack_start (pixwin, true, true);
hpacker->show ();
pack_start (*hpacker, false, false);
pixwin.show ();
if (with_numeric_display) {
value_packer = new EventBox;
value_packer->set_name ("MotionControllerValue");
value_packer->show ();
value_packer->set_border_width (6);
value = new Label;
value->set_justify (Gtk::JUSTIFY_RIGHT);
value->show ();
value_packer->add (*value);
hpacker = manage (new HBox);
hpacker->pack_start (*value_packer, true, false);
hpacker->show ();
pack_start (*hpacker, false, false);
if (widget_name) {
snprintf (value_name, sizeof(value_name), "%sValue", widget_name);
value->set_name (value_name);
}
if (_controllable) {
char buf[32];
print_func (buf, _controllable, print_arg);
value->set_text (buf);
}
}
pixwin.set_events (Gdk::BUTTON_PRESS_MASK|
Gdk::BUTTON_RELEASE_MASK|
Gdk::POINTER_MOTION_MASK|
Gdk::ENTER_NOTIFY_MASK|
Gdk::LEAVE_NOTIFY_MASK|
Gdk::SCROLL_MASK|
Gdk::KEY_PRESS_MASK|
Gdk::KEY_RELEASE_MASK);
pixwin.set_flags (CAN_FOCUS);
/* Proxy all important events on the pixwin to ourselves */
pixwin.signal_button_press_event().connect(mem_fun (*this,&MotionFeedback::pixwin_button_press_event));
pixwin.signal_button_release_event().connect(mem_fun (*this,&MotionFeedback::pixwin_button_release_event));
pixwin.signal_motion_notify_event().connect(mem_fun (*this,&MotionFeedback::pixwin_motion_notify_event));
pixwin.signal_enter_notify_event().connect(mem_fun (*this,&MotionFeedback::pixwin_enter_notify_event));
pixwin.signal_leave_notify_event().connect(mem_fun (*this,&MotionFeedback::pixwin_leave_notify_event));
pixwin.signal_key_press_event().connect(mem_fun (*this,&MotionFeedback::pixwin_key_press_event));
pixwin.signal_scroll_event().connect(mem_fun (*this,&MotionFeedback::pixwin_scroll_event));
pixwin.signal_expose_event().connect(mem_fun (*this,&MotionFeedback::pixwin_expose_event), true);
pixwin.signal_size_request().connect(mem_fun (*this,&MotionFeedback::pixwin_size_request));
}
MotionFeedback::~MotionFeedback()
{
delete value;
delete value_packer;
}
bool
MotionFeedback::pixwin_button_press_event (GdkEventButton *ev)
{
if (binding_proxy.button_press_handler (ev)) {
return true;
}
switch (ev->button) {
case 1:
grab_is_fine = false;
break;
case 2:
grab_is_fine = true;
break;
case 3:
return false;
}
gtk_grab_add(GTK_WIDGET(pixwin.gobj()));
grabbed_y = ev->y_root;
grabbed_x = ev->x_root;
return false;
}
bool
MotionFeedback::pixwin_button_release_event (GdkEventButton *ev)
{
if (!_controllable) {
return false;
}
switch (ev->button) {
case 1:
if (pixwin.has_grab()) {
if (!grab_is_fine) {
gtk_grab_remove
(GTK_WIDGET(pixwin.gobj()));
}
}
if (Keyboard::modifier_state_equals (ev->state, Keyboard::TertiaryModifier)) {
/* shift click back to the default */
_controllable->set_value (default_value);
return true;
}
break;
case 3:
if (pixwin.has_grab()) {
if (grab_is_fine) {
gtk_grab_remove
(GTK_WIDGET(pixwin.gobj()));
}
}
break;
}
return VBox::on_button_release_event (ev);
}
bool
MotionFeedback::pixwin_motion_notify_event (GdkEventMotion *ev)
{
if (!_controllable) {
return false;
}
gfloat multiplier;
gfloat x_delta;
gfloat y_delta;
if (!pixwin.has_grab()) {
return VBox::on_motion_notify_event (ev);
}
multiplier = ((ev->state & Keyboard::TertiaryModifier) ? 100 : 1) *
((ev->state & Keyboard::PrimaryModifier) ? 10 : 1) *
((ev->state & Keyboard::SecondaryModifier) ? 0.1 : 1);
if (ev->state & Gdk::BUTTON1_MASK) {
/* vertical control */
y_delta = grabbed_y - ev->y_root;
grabbed_y = ev->y_root;
x_delta = ev->x_root - grabbed_x;
if (y_delta == 0) return TRUE;
y_delta *= 1 + (x_delta/100);
y_delta *= multiplier;
y_delta /= 10;
_controllable->set_value (adjust ((grab_is_fine ? step_inc : page_inc) * y_delta));
} else if (ev->state & Gdk::BUTTON2_MASK) {
/* rotary control */
double x = ev->x - subwidth/2;
double y = - ev->y + subwidth/2;
double angle = std::atan2 (y, x) / M_PI;
if (angle < -0.5) {
angle += 2.0;
}
angle = -(2.0/3.0) * (angle - 1.25);
angle *= multiplier;
_controllable->set_value (to_control_value (angle));
}
return true;
}
bool
MotionFeedback::pixwin_enter_notify_event (GdkEventCrossing *ev)
{
pixwin.grab_focus();
return false;
}
bool
MotionFeedback::pixwin_leave_notify_event (GdkEventCrossing *ev)
{
pixwin.unset_flags (HAS_FOCUS);
return false;
}
bool
MotionFeedback::pixwin_key_press_event (GdkEventKey *ev)
{
if (!_controllable) {
return false;
}
bool retval = false;
double multiplier;
multiplier = ((ev->state & Keyboard::TertiaryModifier) ? 100.0 : 1.0) *
((ev->state & Keyboard::SecondaryModifier) ? 10.0 : 1.0) *
((ev->state & Keyboard::PrimaryModifier) ? 2.0 : 1.0);
switch (ev->keyval) {
case GDK_Page_Up:
retval = true;
_controllable->set_value (adjust (multiplier * page_inc));
break;
case GDK_Page_Down:
retval = true;
_controllable->set_value (adjust (multiplier * page_inc));
break;
case GDK_Up:
retval = true;
_controllable->set_value (adjust (multiplier * step_inc));
break;
case GDK_Down:
retval = true;
_controllable->set_value (adjust (multiplier * step_inc));
break;
case GDK_Home:
retval = true;
_controllable->set_value (_controllable->lower());
break;
case GDK_End:
retval = true;
_controllable->set_value (_controllable->upper());
break;
}
return retval;
}
bool
MotionFeedback::pixwin_expose_event (GdkEventExpose* ev)
{
if (!_controllable) {
return true;
}
GdkWindow *window = pixwin.get_window()->gobj();
double display_val = to_display_value (_controllable->get_value());
int32_t phase = lrint (display_val * 64.0);
// skip middle phase except for true middle value
if (type == Rotary && phase == 32) {
double pt = (display_val * 2.0) - 1.0;
if (pt < 0)
phase = 31;
if (pt > 0)
phase = 33;
}
// endless knob: skip 90deg highlights unless the value is really a multiple of 90deg
if (type == Endless && !(phase % 16)) {
if (phase == 64) {
phase = 0;
}
double nom = phase / 64.0;
double diff = display_val - nom;
if (diff > 0.0001)
phase = (phase + 1) % 64;
if (diff < -0.0001)
phase = (phase + 63) % 64;
}
phase = std::min (phase, (int32_t) 63);
GtkWidget* widget = GTK_WIDGET(pixwin.gobj());
gdk_draw_pixbuf (GDK_DRAWABLE(window), widget->style->fg_gc[0],
pixbuf->gobj(),
phase * subwidth, type * subheight,
/* center image in allocated area */
(get_width() - subwidth)/2,
0,
subwidth, subheight, GDK_RGB_DITHER_NORMAL, 0, 0);
return true;
}
bool
MotionFeedback::pixwin_scroll_event (GdkEventScroll* ev)
{
double scale;
if (!_controllable) {
return false;
}
if ((ev->state & (Keyboard::PrimaryModifier|Keyboard::TertiaryModifier)) == (Keyboard::PrimaryModifier|Keyboard::TertiaryModifier)) {
scale = 0.01;
} else if (ev->state & Keyboard::PrimaryModifier) {
scale = 0.1;
} else {
scale = 1.0;
}
switch (ev->direction) {
case GDK_SCROLL_UP:
case GDK_SCROLL_RIGHT:
_controllable->set_value (adjust (scale * step_inc));
break;
case GDK_SCROLL_DOWN:
case GDK_SCROLL_LEFT:
_controllable->set_value (adjust (-scale * step_inc));
break;
}
return true;
}
void
MotionFeedback::pixwin_size_request (GtkRequisition* req)
{
req->width = subwidth;
req->height = subheight;
}
void
MotionFeedback::controllable_value_changed ()
{
if (value) {
char buf[32];
print_func (buf, _controllable, print_arg);
value->set_text (buf);
}
pixwin.queue_draw ();
}
void
MotionFeedback::set_controllable (boost::shared_ptr<PBD::Controllable> c)
{
_controllable = c;
binding_proxy.set_controllable (c);
controller_connection.disconnect ();
if (c) {
c->Changed.connect (controller_connection, MISSING_INVALIDATOR, boost::bind (&MotionFeedback::controllable_value_changed, this), gui_context());
char buf[32];
print_func (buf, _controllable, print_arg);
value->set_text (buf);
}
pixwin.queue_draw ();
}
boost::shared_ptr<PBD::Controllable>
MotionFeedback::controllable () const
{
return _controllable;
}
void
MotionFeedback::default_printer (char buf[32], const boost::shared_ptr<PBD::Controllable>& c, void *)
{
if (c) {
sprintf (buf, "%.2f", c->get_value());
} else {
buf[0] = '\0';
}
}
Glib::RefPtr<Gdk::Pixbuf>
MotionFeedback::render_pixbuf (int size)
{
Glib::RefPtr<Gdk::Pixbuf> pixbuf;
char path[32];
int fd;
snprintf (path, sizeof (path), "/tmp/mfimg%dXXXXXX", size);
if ((fd = mkstemp (path)) < 0) {
return pixbuf;
}
GdkColor col2 = {0,0,0,0};
GdkColor col3 = {0,0,0,0};
Gdk::Color base ("#b9feff");
GdkColor dark;
GdkColor bright;
ProlooksHSV* hsv;
hsv = prolooks_hsv_new_for_gdk_color (base.gobj());
bright = (prolooks_hsv_to_gdk_color (hsv, &col2), col2);
prolooks_hsv_set_saturation (hsv, 0.66);
prolooks_hsv_set_value (hsv, 0.67);
dark = (prolooks_hsv_to_gdk_color (hsv, &col3), col3);
cairo_surface_t *surface = cairo_image_surface_create (CAIRO_FORMAT_ARGB32, size * 64, size);
cairo_t* cr = cairo_create (surface);
for (int i = 0; i < 64; ++i) {
cairo_save (cr);
core_draw (cr, i, size, 20, size*i, 0, &bright, &dark);
cairo_restore (cr);
}
if (cairo_surface_write_to_png (surface, path) != CAIRO_STATUS_SUCCESS) {
std::cerr << "could not save image set to " << path << std::endl;
return pixbuf;
}
close (fd);
cairo_destroy (cr);
cairo_surface_destroy (surface);
try {
pixbuf = Gdk::Pixbuf::create_from_file (path);
} catch (const Gdk::PixbufError &e) {
std::cerr << "Caught PixbufError: " << e.what() << std::endl;
unlink (path);
throw;
} catch (...) {
unlink (path);
g_message("Caught ... ");
throw;
}
unlink (path);
return pixbuf;
}
void
MotionFeedback::core_draw (cairo_t* cr, int phase, double size, double progress_width, double xorigin, double yorigin,
const GdkColor* bright, const GdkColor* dark)
{
double xc;
double yc;
double start_angle;
double end_angle;
double value_angle;
double value;
double value_x;
double value_y;
double start_angle_x;
double start_angle_y;
double end_angle_x;
double end_angle_y;
double progress_radius;
double progress_radius_inner;
double progress_radius_outer;
double knob_disc_radius;
cairo_pattern_t* pattern;
double progress_rim_width;
cairo_pattern_t* progress_shine;
double degrees;
cairo_pattern_t* knob_ripples;
double pxs;
double pys;
g_return_if_fail (cr != NULL);
progress_radius = 40.0;
progress_radius_inner = progress_radius - (progress_width / 2.0);
progress_radius_outer = progress_radius + (progress_width / 2.0);
knob_disc_radius = progress_radius_inner - 5.0;
const double pad = 2.0; /* line width for boundary of progress ring */
const double actual_width = ((2.0 * pad) + (2.0 * progress_radius_outer));
const double scale_factor = size / actual_width;
/* knob center is at middle of the area bounded by (xorigin,yorigin) and (xorigin+size, yorigin+size)
but the coordinates will be scaled by the scale factor when cairo uses them so first
adjust them by the reciprocal of the scale factor.
*/
xc = (xorigin + (size / 2.0)) * (1.0/scale_factor);
yc = (yorigin + (size / 2.0)) * (1.0/scale_factor);
pxs = xorigin * (1.0/scale_factor);
pys = yorigin * (1.0/scale_factor);
start_angle = 0.0;
end_angle = 0.0;
value_angle = 0.0;
value = (phase * 1.0) / (65 - 1);
start_angle = ((180 - 65) * G_PI) / 180;
end_angle = ((360 + 65) * G_PI) / 180;
value_angle = start_angle + (value * (end_angle - start_angle));
value_x = cos (value_angle);
value_y = sin (value_angle);
start_angle_x = cos (start_angle);
start_angle_y = sin (start_angle);
end_angle_x = cos (end_angle);
end_angle_y = sin (end_angle);
cairo_scale (cr, scale_factor, scale_factor);
pattern = prolooks_create_gradient_str (pxs + 32.0, pys + 16.0, pxs + 75.0, pys + 16.0, "#d4c8b9", "#ae977b", 1.0, 1.0);
cairo_set_source (cr, pattern);
cairo_pattern_destroy (pattern);
cairo_set_line_width (cr, 2.0);
cairo_arc (cr, xc, yc, 31.5, 0.0, 2 * G_PI);
cairo_stroke (cr);
pattern = prolooks_create_gradient_str (pxs + 20.0, pys + 20.0, pxs + 89.0, pys + 87.0, "#2f2f4c", "#090a0d", 1.0, 1.0);
cairo_set_source (cr, pattern);
cairo_pattern_destroy (pattern);
cairo_set_line_width (cr, progress_width);
cairo_arc (cr, xc, yc, progress_radius, start_angle, end_angle);
cairo_stroke (cr);
pattern = prolooks_create_gradient (pxs + 20.0, pys + 20.0, pxs + 89.0, pys + 87.0, bright, dark, 1.0, 1.0);
cairo_set_source (cr, pattern);
cairo_pattern_destroy (pattern);
cairo_set_line_width (cr, progress_width);
cairo_arc (cr, xc, yc, progress_radius, start_angle, value_angle);
cairo_stroke (cr);
cairo_set_line_cap (cr, CAIRO_LINE_CAP_ROUND);
progress_rim_width = 2.0;
cairo_set_line_width (cr, progress_rim_width);
pattern = prolooks_create_gradient_str (pxs + 18.0, pys + 79.0, pxs + 35.0, pys + 79.0, "#dfd5c9", "#dfd5c9", 1.0, 0.0);
cairo_set_source (cr, pattern);
cairo_pattern_destroy (pattern);
cairo_move_to (cr, xc + (progress_radius_outer * start_angle_x), yc + (progress_radius_outer * start_angle_y));
cairo_line_to (cr, xc + (progress_radius_inner * start_angle_x), yc + (progress_radius_inner * start_angle_y));
cairo_stroke (cr);
prolooks_set_source_color_string (cr, "#000000", 1.0);
cairo_move_to (cr, xc + (progress_radius_outer * end_angle_x), yc + (progress_radius_outer * end_angle_y));
cairo_line_to (cr, xc + (progress_radius_inner * end_angle_x), yc + (progress_radius_inner * end_angle_y));
cairo_stroke (cr);
// pattern = prolooks_create_gradient_str (95.0, 6.0, 5.0, 44.0, "#dfd5c9", "#b0a090", 1.0, 1.0);
pattern = prolooks_create_gradient_str (pxs + 95.0, pys + 6.0, pxs + 5.0, pys + 44.0, "#000000", "#000000", 1.0, 1.0);
cairo_set_source (cr, pattern);
cairo_pattern_destroy (pattern);
cairo_arc (cr, xc, yc, progress_radius_outer, start_angle, end_angle);
cairo_stroke (cr);
cairo_set_line_cap (cr, CAIRO_LINE_CAP_BUTT);
pattern = prolooks_create_gradient (pxs + 20.0, pys + 20.0, pxs + 89.0, pys + 87.0, bright, dark, 0.25, 0.25);
cairo_set_source (cr, pattern);
cairo_pattern_destroy (pattern);
cairo_set_line_width (cr, progress_width);
cairo_arc (cr, xc, yc, progress_radius, start_angle, value_angle + (G_PI / 180.0));
cairo_stroke (cr);
progress_shine = prolooks_create_gradient_str (pxs + 89.0, pys + 73.0, pxs + 34.0, pys + 16.0, "#ffffff", "#ffffff", 0.3, 0.04);
cairo_pattern_add_color_stop_rgba (progress_shine, 0.5, 1.0, 1.0, 1.0, 0.0);
if (size > 50) {
cairo_pattern_add_color_stop_rgba (progress_shine, 0.75, 1.0, 1.0, 1.0, 0.3);
} else {
cairo_pattern_add_color_stop_rgba (progress_shine, 0.75, 1.0, 1.0, 1.0, 0.2);
}
cairo_set_source (cr, progress_shine);
cairo_set_line_width (cr, progress_width);
cairo_arc (cr, xc, yc, progress_radius, start_angle, end_angle);
cairo_stroke (cr);
cairo_pattern_destroy (progress_shine);
cairo_set_line_width (cr, 1.0);
cairo_set_source_rgb (cr, 0.0, 0.0, 0.0);
cairo_arc (cr, xc, yc, progress_radius_inner, 0.0, 2 * G_PI);
pattern = prolooks_create_gradient_str (pxs + 35.0, pys + 31.0, pxs + 75.0, pys + 72.0, "#68625c", "#44494b", 1.0, 1.0);
cairo_set_source (cr, pattern);
cairo_pattern_destroy (pattern);
cairo_fill (cr);
cairo_set_source_rgb (cr, 0.0, 0.0, 0.0);
cairo_arc (cr, xc, yc, progress_radius_inner, 0.0, 2 * G_PI);
cairo_stroke (cr);
pattern = prolooks_create_gradient_str (pxs + 42.0, pys + 34.0, pxs + 68.0, pys + 70.0, "#e7ecef", "#9cafb8", 1.0, 1.0);
cairo_set_source (cr, pattern);
cairo_pattern_destroy (pattern);
cairo_arc (cr, xc, yc, knob_disc_radius, 0.0, 2 * G_PI);
cairo_fill (cr);
cairo_set_line_width (cr, 2.0);
degrees = G_PI / 180.0;
pattern = prolooks_create_gradient_str (pxs + 38.0, pys + 34.0, pxs + 70.0, pys + 68.0, "#ffffff", "#caddf2", 0.2, 0.2);
cairo_set_source (cr, pattern);
cairo_pattern_destroy (pattern);
cairo_move_to (cr, xc, yc);
cairo_arc (cr, xc, yc, knob_disc_radius - 1, (-154) * degrees, (-120) * degrees);
cairo_move_to (cr, xc, yc);
cairo_arc (cr, xc, yc, knob_disc_radius - 1, (G_PI / 2.0) - (60 * degrees), (G_PI / 2.0) - (29 * degrees));
cairo_fill (cr);
pattern = prolooks_create_gradient_str (pxs + 50.0, pys + 40.0, pxs + 62.0, pys + 60.0, "#a1adb6", "#47535c", 0.07, 0.15);
cairo_set_source (cr, pattern);
cairo_pattern_destroy (pattern);
cairo_move_to (cr, xc, yc);
cairo_arc (cr, xc, yc, knob_disc_radius - 1, (-67) * degrees, (-27) * degrees);
cairo_move_to (cr, xc, yc);
cairo_arc (cr, xc, yc, knob_disc_radius - 1, G_PI - (67 * degrees), G_PI - (27 * degrees));
cairo_fill (cr);
knob_ripples = cairo_pattern_create_radial (xc, yc, 0.0, xc, yc, 4.0);
prolooks_add_color_stop_str (knob_ripples, 0.0, "#e7ecef", 0.05);
prolooks_add_color_stop_str (knob_ripples, 0.5, "#58717d", 0.05);
prolooks_add_color_stop_str (knob_ripples, 0.75, "#d1d9de", 0.05);
prolooks_add_color_stop_str (knob_ripples, 1.0, "#5d7682", 0.05);
cairo_pattern_set_extend (knob_ripples, CAIRO_EXTEND_REPEAT);
cairo_set_line_width (cr, 0.0);
cairo_set_source (cr, knob_ripples);
cairo_arc (cr, xc, yc, knob_disc_radius, 0.0, 2 * G_PI);
cairo_fill (cr);
cairo_save (cr);
cairo_translate (cr, xc + (knob_disc_radius * value_x), yc + (knob_disc_radius * value_y));
cairo_rotate (cr, value_angle - G_PI);
pattern = prolooks_create_gradient_str (pxs + 16.0, pys + -2.0, pxs + 9.0, pys + 13.0, "#e7ecef", "#9cafb8", 0.8, 0.8);
cairo_set_source (cr, pattern);
cairo_pattern_destroy (pattern);
cairo_move_to (cr, 0.0, 4.0);
cairo_line_to (cr, 17.0, 4.0);
cairo_curve_to (cr, 19.0, 4.0, 21.0, 2.0, 21.0, 0.0);
cairo_curve_to (cr, 21.0, -2.0, 19.0, -4.0, 17.0, -4.0);
cairo_line_to (cr, 0.0, -4.0);
cairo_close_path (cr);
cairo_fill (cr);
pattern = prolooks_create_gradient_str (pxs + 9.0, pys + -2.0, pxs + 9.0, pys + 2.0, "#68625c", "#44494b", 1.0, 1.0);
cairo_set_source (cr, pattern);
cairo_pattern_destroy (pattern);
cairo_move_to (cr, 0.0, 2.0);
cairo_line_to (cr, 16.0, 2.0);
cairo_curve_to (cr, 17.0, 2.0, 18.0, 1.0, 18.0, 0.0);
cairo_curve_to (cr, 18.0, -1.0, 17.0, -2.0, 16.0, -2.0);
cairo_line_to (cr, 0.0, -2.0);
cairo_close_path (cr);
cairo_fill (cr);
cairo_restore (cr);
cairo_set_line_width (cr, 2.0);
pattern = prolooks_create_gradient_str (pxs + 38.0, pys + 32.0, pxs + 70.0, pys + 67.0, "#3d3d3d", "#000000", 1.0, 1.0);
cairo_set_source (cr, pattern);
cairo_pattern_destroy (pattern);
cairo_arc (cr, xc, yc, knob_disc_radius, 0.0, 2 * G_PI);
cairo_stroke (cr);
cairo_pattern_destroy (knob_ripples);
}