gtk2/perf

README for gtk+/perf
--------------------

This is a framework for testing performance in GTK+.   For GTK+, being
performant does not only mean "paint widgets fast".  It also means
things like the time needed to set up widgets, to map and draw a
window for the first time, and emitting/propagating signals.

The following is accurate as of 2005/07/26.


Using the framework
-------------------

Right now the framework is very simple; it just has utility functions
to time widget creation, drawing, and destruction.  To run such a
test, you use the functions in timers.h.  You can call this:

  timer_time_widget (create_func, report_func, user_data);

You must provide the create_funcn and report_func callbacks.

The create_func:

  This simply creates a toplevel window with some widgets inside it.
  It is important that you do not show any of the widgets; the
  framework will call gtk_widget_show_all() on the toplevel window
  automatically at the right time.

The report_func:

  This function will get called when timer_time_widget() reaches an
  interesting point in the lifecycle of your widget.  See timers.h and
  the TimerReport enumeration; this is what gets passed as the
  "report" argument to your report_func.  Right now, your function
  will be called three times for each call to timer_time_widget():

     1. With report = TIMER_REPORT_WIDGET_CREATION.  A timer gets
        started right before timer_time_widget() calls create_func,
        and it gets stopped when your create_func returns.  This
        measures the time it takes to set up a toplevel window (but
        not show it).

     2. With report = TIMER_REPORT_WIDGET_SHOW.  A timer gets started
        right before timer_time_widget() calls gtk_widget_show_all()
        on your toplevel window, and it gets stopped when the window
        has been fully shown and painted to the screen.

     3. With report = TIMER_REPORT_WIDGET_DESTRUCTION.  A timer gets
        started right before timer_time_widget() calls
        gtk_widget_destroy() on your toplevel window, and it gets
        stopped when gtk_widget_destroy() returns.

As a very basic example of using timer_time_widget(), you can use
something like this:

----------------------------------------------------------------------
#include <stdio.h>
#include <gtk/gtk.h>
#include "timers.h"

#define ITERS 20

static GtkWidget *
create_cb (gpointer data)
{
  GtkWidget *window;

  window = gtk_window_new (GTK_WINDOW_TOPLEVEL);
  /* ... fill the window with widgets, and don't show them ... */

  return window;
}

static void
report_cb (TimerReport report, gdouble elapsed, gpointer data)
{
  const char *type;

  switch (report) {
  case TIMER_REPORT_WIDGET_CREATION:
    type = "widget creation";
    break;

  case TIMER_REPORT_WIDGET_SHOW:
    type = "widget show";
    break;

  case TIMER_REPORT_WIDGET_DESTRUCTION:
    type = "widget destruction";
    break;
  }

  fprintf (stderr, "%s: %g sec\n", type, elapsed);
}

int
main (int argc, char **argv)
{
  int i;

  gtk_init (&argc, &argv);

  for (i = 0; i < ITERS; i++)
    timer_time_widget (create_cb, report_cb, NULL);
  
  return 0;
} 
----------------------------------------------------------------------


Getting meaningful results
--------------------------

Getting times for widget creation/drawing/destruction is interesting,
but how do you actually find the places that need optimizing?

Why, you run the tests under a profiler, of course.

FIXME: document how to do this.


Feedback
--------

Please mail your feedback to Federico Mena-Quintero <federico@novell.com>.
This performance framework is a work in progress.