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gtk 入门教程,适用于初学者。一般问题都能找到答案

  points[0].x = xc + s*dial->pointer_width/2;
  points[0].y = yc + c*dial->pointer_width/2;
  points[1].x = xc + c*dial->radius;
  points[1].y = yc - s*dial->radius;
  points[2].x = xc - s*dial->pointer_width/2;
  points[2].y = yc - c*dial->pointer_width/2;
  points[3].x = xc - c*dial->radius/10;
  points[3].y = yc + s*dial->radius/10;
  points[4].x = points[0].x;
  points[4].y = points[0].y;

  blankstyle = gtk_style_new ();
  blankstyle->bg_gc[GTK_STATE_NORMAL] =
                widget->style->bg_gc[GTK_STATE_NORMAL];
  blankstyle->dark_gc[GTK_STATE_NORMAL] =
                widget->style->bg_gc[GTK_STATE_NORMAL];
  blankstyle->light_gc[GTK_STATE_NORMAL] =
                widget->style->bg_gc[GTK_STATE_NORMAL];
  blankstyle->black_gc =
                widget->style->bg_gc[GTK_STATE_NORMAL];

  gtk_paint_polygon (blankstyle,
                    widget->window,
                    GTK_STATE_NORMAL,
                    GTK_SHADOW_OUT,
	            NULL,
                    widget,
                    NULL,
                    points, 5,
                    FALSE);

  g_object_unref (blankstyle);


  /* 绘制刻度 */

  if ((upper - lower) == 0)
    return FALSE;

  increment = (100*M_PI) / (dial->radius*dial->radius);

  inc = (upper - lower);

  while (inc < 100) inc *= 10;
  while (inc >= 1000) inc /= 10;
  last = -1;

  for (i = 0; i <= inc; i++)
    {
      theta = ((gfloat)i*M_PI / (18*inc/24.) - M_PI/6.);

      if ((theta - last) < (increment))
	continue;     
      last = theta;

      s = sin (theta);
      c = cos (theta);

      tick_length = (i%(inc/10) == 0) ? dial->pointer_width : dial->pointer_width / 2;

      gdk_draw_line (widget->window,
                     widget->style->fg_gc[widget->state],
                     xc + c*(dial->radius - tick_length),
                     yc - s*(dial->radius - tick_length),
                     xc + c*dial->radius,
                     yc - s*dial->radius);
    }

  /* 绘制指针 */

  s = sin (dial->angle);
  c = cos (dial->angle);
  dial->last_angle = dial->angle;

  points[0].x = xc + s*dial->pointer_width/2;
  points[0].y = yc + c*dial->pointer_width/2;
  points[1].x = xc + c*dial->radius;
  points[1].y = yc - s*dial->radius;
  points[2].x = xc - s*dial->pointer_width/2;
  points[2].y = yc - c*dial->pointer_width/2;
  points[3].x = xc - c*dial->radius/10;
  points[3].y = yc + s*dial->radius/10;
  points[4].x = points[0].x;
  points[4].y = points[0].y;


  gtk_paint_polygon (widget->style,
		    widget->window,
		    GTK_STATE_NORMAL,
		    GTK_SHADOW_OUT,
	            NULL,
                    widget,
                    NULL,
		    points, 5,
		    TRUE);

  return FALSE;
}

static gint
gtk_dial_button_press (GtkWidget      *widget,
		       GdkEventButton *event)
{
  GtkDial *dial;
  gint dx, dy;
  double s, c;
  double d_parallel;
  double d_perpendicular;

  g_return_val_if_fail (widget != NULL, FALSE);
  g_return_val_if_fail (GTK_IS_DIAL (widget), FALSE);
  g_return_val_if_fail (event != NULL, FALSE);

  dial = GTK_DIAL (widget);

  /* 判断按钮是否是在表盘指针里按下 - 我们通过计算鼠标按下
     点到表盘指针中线的水平和垂直距离来判断。 */
  
  dx = event->x - widget->allocation.width / 2;
  dy = widget->allocation.height / 2 - event->y;
  
  s = sin (dial->angle);
  c = cos (dial->angle);
  
  d_parallel = s*dy + c*dx;
  d_perpendicular = fabs (s*dx - c*dy);
  
  if (!dial->button &&
      (d_perpendicular < dial->pointer_width/2) &&
      (d_parallel > - dial->pointer_width))
    {
      gtk_grab_add (widget);

      dial->button = event->button;

      gtk_dial_update_mouse (dial, event->x, event->y);
    }

  return FALSE;
}

static gint
gtk_dial_button_release (GtkWidget      *widget,
			  GdkEventButton *event)
{
  GtkDial *dial;

  g_return_val_if_fail (widget != NULL, FALSE);
  g_return_val_if_fail (GTK_IS_DIAL (widget), FALSE);
  g_return_val_if_fail (event != NULL, FALSE);

  dial = GTK_DIAL (widget);

  if (dial->button == event->button)
    {
      gtk_grab_remove (widget);

      dial->button = 0;

      if (dial->policy == GTK_UPDATE_DELAYED)
	gtk_timeout_remove (dial->timer);
      
      if ((dial->policy != GTK_UPDATE_CONTINUOUS) &&
	  (dial->old_value != dial->adjustment->value))
	g_signal_emit_by_name (GTK_OBJECT (dial->adjustment), "value_changed");
    }

  return FALSE;
}

static gint
gtk_dial_motion_notify (GtkWidget      *widget,
			 GdkEventMotion *event)
{
  GtkDial *dial;
  GdkModifierType mods;
  gint x, y, mask;

  g_return_val_if_fail (widget != NULL, FALSE);
  g_return_val_if_fail (GTK_IS_DIAL (widget), FALSE);
  g_return_val_if_fail (event != NULL, FALSE);

  dial = GTK_DIAL (widget);

  if (dial->button != 0)
    {
      x = event->x;
      y = event->y;

      if (event->is_hint || (event->window != widget->window))
	gdk_window_get_pointer (widget->window, &x, &y, &mods);

      switch (dial->button)
	{
	case 1:
	  mask = GDK_BUTTON1_MASK;
	  break;
	case 2:
	  mask = GDK_BUTTON2_MASK;
	  break;
	case 3:
	  mask = GDK_BUTTON3_MASK;
	  break;
	default:
	  mask = 0;
	  break;
	}

      if (mods & mask)
	gtk_dial_update_mouse (dial, x,y);
    }

  return FALSE;
}

static gint
gtk_dial_timer (GtkDial *dial)
{
  g_return_val_if_fail (dial != NULL, FALSE);
  g_return_val_if_fail (GTK_IS_DIAL (dial), FALSE);

  if (dial->policy == GTK_UPDATE_DELAYED)
    g_signal_emit_by_name (GTK_OBJECT (dial->adjustment), "value_changed");

  return FALSE;
}

static void
gtk_dial_update_mouse (GtkDial *dial, gint x, gint y)
{
  gint xc, yc;
  gfloat old_value;

  g_return_if_fail (dial != NULL);
  g_return_if_fail (GTK_IS_DIAL (dial));

  xc = GTK_WIDGET(dial)->allocation.width / 2;
  yc = GTK_WIDGET(dial)->allocation.height / 2;

  old_value = dial->adjustment->value;
  dial->angle = atan2(yc-y, x-xc);

  if (dial->angle < -M_PI/2.)
    dial->angle += 2*M_PI;

  if (dial->angle < -M_PI/6)
    dial->angle = -M_PI/6;

  if (dial->angle > 7.*M_PI/6.)
    dial->angle = 7.*M_PI/6.;

  dial->adjustment->value = dial->adjustment->lower + (7.*M_PI/6 - dial->angle) *
    (dial->adjustment->upper - dial->adjustment->lower) / (4.*M_PI/3.);

  if (dial->adjustment->value != old_value)
    {
      if (dial->policy == GTK_UPDATE_CONTINUOUS)
	{
	  g_signal_emit_by_name (GTK_OBJECT (dial->adjustment), "value_changed");
	}
      else
	{
	  gtk_widget_queue_draw (GTK_WIDGET (dial));

	  if (dial->policy == GTK_UPDATE_DELAYED)
	    {
	      if (dial->timer)
		gtk_timeout_remove (dial->timer);

	      dial->timer = gtk_timeout_add (SCROLL_DELAY_LENGTH,
					     (GtkFunction) gtk_dial_timer,
					     (gpointer) dial);
	    }
	}
    }
}

static void
gtk_dial_update (GtkDial *dial)
{
  gfloat new_value;
  
  g_return_if_fail (dial != NULL);
  g_return_if_fail (GTK_IS_DIAL (dial));

  new_value = dial->adjustment->value;
  
  if (new_value < dial->adjustment->lower)
    new_value = dial->adjustment->lower;

  if (new_value > dial->adjustment->upper)
    new_value = dial->adjustment->upper;

  if (new_value != dial->adjustment->value)
    {
      dial->adjustment->value = new_value;
      g_signal_emit_by_name (GTK_OBJECT (dial->adjustment), "value_changed");
    }

  dial->angle = 7.*M_PI/6. - (new_value - dial->adjustment->lower) * 4.*M_PI/3. /
    (dial->adjustment->upper - dial->adjustment->lower);

  gtk_widget_queue_draw (GTK_WIDGET (dial));
}

static void
gtk_dial_adjustment_changed (GtkAdjustment *adjustment,
			      gpointer       data)
{
  GtkDial *dial;

  g_return_if_fail (adjustment != NULL);
  g_return_if_fail (data != NULL);

  dial = GTK_DIAL (data);

  if ((dial->old_value != adjustment->value) ||
      (dial->old_lower != adjustment->lower) ||
      (dial->old_upper != adjustment->upper))
    {
      gtk_dial_update (dial);

      dial->old_value = adjustment->value;
      dial->old_lower = adjustment->lower;
      dial->old_upper = adjustment->upper;
    }
}

static void
gtk_dial_adjustment_value_changed (GtkAdjustment *adjustment,
				    gpointer       data)
{
  GtkDial *dial;

  g_return_if_fail (adjustment != NULL);
  g_return_if_fail (data != NULL);

  dial = GTK_DIAL (data);

  if (dial->old_value != adjustment->value)
    {
      gtk_dial_update (dial);

      dial->old_value = adjustment->value;
    }
}</PRE
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><A
NAME="AEN2867">dial_test.c</H2
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><PRE
CLASS="PROGRAMLISTING"
>&#13;#include &#60;stdio.h&#62;
#include &#60;stdlib.h&#62;
#include &#60;gtk/gtk.h&#62;
#include "gtkdial.h"

void value_changed( GtkAdjustment *adjustment,
                    GtkWidget     *label )
{
  char buffer[16];

  sprintf(buffer,"%4.2f",adjustment-&#62;value);
  gtk_label_set_text (GTK_LABEL (label), buffer);
}

int main( int   argc,
          char *argv[])
{
  GtkWidget *window;
  GtkAdjustment *adjustment;
  GtkWidget *dial;
  GtkWidget *frame;
  GtkWidget *vbox;
  GtkWidget *label;
  
  gtk_init (&#38;argc, &#38;argv);

  window = gtk_window_new (GTK_WINDOW_TOPLEVEL);
  
  gtk_window_set_title (GTK_WINDOW (window), "Dial");
  
  g_signal_connect (G_OBJECT (window), "destroy",
		    G_CALLBACK (exit), NULL);
  
  gtk_container_set_border_width (GTK_CONTAINER (window), 10);

  vbox = gtk_vbox_new (FALSE, 5);
  gtk_container_add (GTK_CONTAINER (window), vbox);
  gtk_widget_show (vbox);

  frame = gtk_frame_new (NULL);
  gtk_frame_set_shadow_type (GTK_FRAME (frame), GTK_SHADOW_IN);
  gtk_container_add (GTK_CONTAINER (vbox), frame);
  gtk_widget_show (frame); 
 
  adjustment = GTK_ADJUSTMENT (gtk_adjustment_new (0, 0, 100, 0.01, 0.1, 0));
  
  dial = gtk_dial_new (adjustment);
  gtk_dial_set_update_policy (GTK_DIAL (dial), GTK_UPDATE_DELAYED);
  /*  gtk_widget_set_size_request (dial, 100, 100); */
  
  gtk_container_add (GTK_CONTAINER (frame), dial);
  gtk_widget_show (dial);

  label = gtk_label_new ("0.00");
  gtk_box_pack_end (GTK_BOX (vbox), label, 0, 0, 0);
  gtk_widget_show (label);

  g_signal_connect (G_OBJECT (adjustment), "value_changed",
		    G_CALLBACK (value_changed), label);
  
  gtk_widget_show (window);
  
  gtk_main ();
  
  return 0;
}</PRE
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