Re: [gtk-list] instant draw

[John C Atkeson <jcatkeson juno com>]

>>
Since I use multi threads( using gdk_thread_lock....), I wonder whether
there is some way to instantly drawing.
Which means, after calling gdk_draw_line() (and other drawing
functions), the screen immediately shows what you have drawed.
<<
  I do it two ways...
  
  One is to draw onto the pixmap and repeatedly copy the pixmap to the
widget window with gdk_draw_pixmap(widget->window, somecolor, pixmap,
0,0, 0,0, widgetwidth, widgetheight);  
  (Better look up gdk_draw_pixmap yourself than trust my memory, it's
used in the "scribble.c" demo at the official tutorial site.)
  
  The other way is to make gdk_draw_line draw directly on the
widget->window space:  gdk_draw_line(drawing_area->window, mycolor,
x1,y1,x2,y2);
  That shows up instantly.  The downside is, when you cover the window
the picture gets wiped and doesn't refresh, so when I do this I call
gdk_draw_line twice for every line, once for direct-window draw and again
for the refreshing pixmap.  
  
  void MyDrawLine(int x1,int y1,int x2,int y2,GdkGC *mycolor)
  {
    gdk_draw_line(drawing_area->window, mycolor, x1,y1,x2,y2);
    gdk_draw_line(pixmap, mycolor, x1,y1,x2,y2);
  };
  
  Which of these two ways is more efficient depends on what you are
doing...
  
  Good luck, 
  John  
  

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