From 67b0b6465335de810f184bde31b35854ad9f22d5 Mon Sep 17 00:00:00 2001 From: Federico Mena Quintero Date: Wed, 14 Jun 2006 21:41:23 +0000 Subject: [PATCH] Update the README with some background information - Federico --- perf/README | 64 ++++++++++++++++++++++++++++++++++++++++++++++++++++- 1 file changed, 63 insertions(+), 1 deletion(-) diff --git a/perf/README b/perf/README index 7f2670d54..f61d7f101 100644 --- a/perf/README +++ b/perf/README @@ -6,7 +6,67 @@ 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 2005/07/28. +The following is accurate as of 2006/Jun/14. + + +Background +---------- + +A widget's lifetime looks more or less like this: + + 1. Instantiation + 2. Size request + 3. Size allocate + 5. Realize + 4. Map + 5. Expose + 6. Destroy + +Some of these stages are particularly interesting: + +- Instantiation means creating the widget. This may be as simple as a + few malloc()s and setting some fields. It could also be a + complicated operation if the widget needs to contact an external + server to create itself, or if it needs to read data files. + +- Size requisition is when GTK+ asks the widget, "how big do you want + to be on the screen"? This can be an expensive operation. The + widget has to measure its text, measure its icons (and thus load its + icons), and generally run through its internal layout code. + +- Realization is when the widget creates its GDK resources, like its + GdkWindow and graphics contexts it may need. This could be + expensive if the widget needs to load data files for cursors or + backgrounds. + +- Expose is when the widget gets repainted. This will happen many + times throughout the lifetime of the widget: every time you drag a + window on top of it, every time its data changes and it needs to + redraw, every time it gets resized. + +GtkWidgetProfiler is a mechanism to let you get individual timings for +each of the stages in the lifetime of a widget. It also lets you run +some stages many times in a sequence, so that you can run a real +profiler and get an adequate number of samples. For example, +GtkWidgetProfiler lets you say "repaint this widget 1000 times". + +Why is this not as simple as doing + + start_timer (); + for (i = 0; i < 1000; i++) { + gtk_widget_queue_draw (widget); + while (gtk_events_pending ()) + gtk_main_iteration (); + } + stop_timer (); + +Huh? + +Because X is an asynchronous window system. So, when you send the +"paint" commands, your program will regain control but it will take +some time for the X server to actually process those commands. +GtkWidgetProfiler has special code to wait for the X server and give +you accurate timings. Using the framework @@ -132,6 +192,8 @@ main (int argc, char **argv) gtk_widget_profiler_set_num_iterations (profiler, 100); gtk_widget_profiler_profile_boot (profiler); + + gtk_widget_profiler_profile_expose (profiler); return 0; } -- 2.43.2