[cairo-commit] [cairo-www] src/threaded_animation_with_cairo.mdwn

[Carl Worth]

 src/threaded_animation_with_cairo.mdwn |   19 +++++++++++++++++--
 1 file changed, 17 insertions(+), 2 deletions(-)

New commits:
commit 169ecb0cba145e52b11caef3cb6aed044ee49405
Author: Carl Worth <cworth at freedesktop.org>
Date:   Sat Feb 9 19:04:55 2008 -0800

    web commit by Albert

diff --git a/src/threaded_animation_with_cairo.mdwn b/src/threaded_animation_with_cairo.mdwn
index 53188b1..ac06f05 100644
--- a/src/threaded_animation_with_cairo.mdwn
+++ b/src/threaded_animation_with_cairo.mdwn
@@ -100,6 +100,8 @@ Before, we implement our timer function, we must consider one important issue.
 
 	gboolean timer_exe(GtkWidget * window){
 		
+		static gboolean first_execution = TRUE;
+
 		//use a safe function to get the value of currently_drawing so
 		//we don't run into the usual multithreading issues
 		int drawing_status = g_atomic_int_get(&currently_drawing);
@@ -107,8 +109,11 @@ Before, we implement our timer function, we must consider one important issue.
 		//if we are not currently drawing anything, launch a thread to 
 		//update our pixmap
 		if(drawing_status == 0){
-			pthread_t thread_info;
+			static pthread_t thread_info;
 			int  iret;
+			if(first_execution != TRUE){
+				pthread_join(thread_info, NULL);
+			}
 			iret = pthread_create( &thread_info, NULL, do_draw, NULL);
 		}
 
@@ -117,6 +122,8 @@ Before, we implement our timer function, we must consider one important issue.
 		gdk_drawable_get_size(pixmap, &width, &height);
 		gtk_widget_queue_draw_area(window, 0, 0, width, height);
 
+		first_execution = FALSE;
+
 		return TRUE;
 
 	}
@@ -124,6 +131,7 @@ Before, we implement our timer function, we must consider one important issue.
  * `g_atomic_int_get(&currently_drawing)` is a thread-safe way to get the value of our global integer `currently_drawing`.  Using this function allows us to avoid the possibility of reading a number at the same moment our other thread is trying to change it.  It is also much easier to implement than mutexes for reading a single integer.
  * `pthread_create( &thread_info, NULL, do_draw, NULL)` is the `unistd.h` way to launch the function `do_draw()` as a separate thread.  (The final `NULL` is actually a `(void *)` to a data structure that we pass to `do_draw()`.)
  * `gtk_widget_queue_draw_area(window, 0, 0, width, height)` sends an artificial expose event with upper left corner 0,0 and width and heigh of `width`, `height`, respectively.  This allows our `expose_event` to do the actual painting.
+ * `pthread_join(thread_info, NULL)` re-joins the drawing thread and ensures that it terminates and it's OS-related memory is freed.  
 
 ##Do the Drawing
 
@@ -323,6 +331,8 @@ For your compiling pleasure, the full source in proper order.
 
 	gboolean timer_exe(GtkWidget * window){
 		
+		static gboolean first_execution = TRUE;
+
 		//use a safe function to get the value of currently_drawing so
 		//we don't run into the usual multithreading issues
 		int drawing_status = g_atomic_int_get(&currently_drawing);
@@ -330,8 +340,11 @@ For your compiling pleasure, the full source in proper order.
 		//if we are not currently drawing anything, launch a thread to 
 		//update our pixmap
 		if(drawing_status == 0){
-			pthread_t thread_info;
+			static pthread_t thread_info;
 			int  iret;
+			if(first_execution != TRUE){
+				pthread_join(thread_info, NULL);
+			}
 			iret = pthread_create( &thread_info, NULL, do_draw, NULL);
 		}
 
@@ -340,6 +353,8 @@ For your compiling pleasure, the full source in proper order.
 		gdk_drawable_get_size(pixmap, &width, &height);
 		gtk_widget_queue_draw_area(window, 0, 0, width, height);
 
+		first_execution = FALSE;
+
 		return TRUE;
 
 	}