/usr/share/doc/libgtk2.0-doc/faq/x862.html

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>How do I use color allocation?</TITLE
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>7.2. How do I use color allocation?</A
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>One of the nice things about GDK is that it's based on
top of Xlib; this is also a problem, especially in the area of
color management. If you want  to use color in your program
(drawing a rectangle or such, your code  should look something
like this:</P
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  GdkColor *color;
  int width, height;
  GtkWidget *widget;
  GdkGC *gc;

  ...
  
  /* first, create a GC to draw on */
  gc = gdk_gc_new(widget-&#62;window);

  /* find proper dimensions for rectangle */
  gdk_window_get_size(widget-&#62;window, &amp;width, &amp;height);

  /* the color we want to use */
  color = (GdkColor *)malloc(sizeof(GdkColor));
  
  /* red, green, and blue are passed values, indicating the RGB triple
   * of the color we want to draw. Note that the values of the RGB components
   * within the GdkColor are taken from 0 to 65535, not 0 to 255.
   */
  color-&#62;red = red * (65535/255);
  color-&#62;green = green * (65535/255);
  color-&#62;blue = blue * (65535/255);
  
  /* the pixel value indicates the index in the colormap of the color.
   * it is simply a combination of the RGB values we set earlier
   */
  color-&#62;pixel = (gulong)(red*65536 + green*256 + blue);

  /* However, the pixel valule is only truly valid on 24-bit (TrueColor)
   * displays. Therefore, this call is required so that GDK and X can
   * give us the closest color available in the colormap
   */
  gdk_color_alloc(gtk_widget_get_colormap(widget), color);

  /* set the foreground to our color */
  gdk_gc_set_foreground(gc, color);
  
  /* draw the rectangle */
  gdk_draw_rectangle(widget-&#62;window, gc, 1, 0, 0, width, height);

  ...
}</PRE
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libgtk2.0-doc 2.24.30-1ubuntu1 / usr / share / doc / libgtk2.0-doc / faq / x862.html
