Merge lp:~vanvugt/compiz/fix-1095001 into lp:compiz/0.9.9

[Daniel van Vugt]

Avoid calling code that results in calls to regexec as much as possible.
Regular expression matching is too expensive to do very often and compiz
was spending 31% of its CPU time in regexec().
(LP: #1095001)

Before: 31%
After: 0.01%

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PASSED: Continuous integration, rev:3534
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review: Approve (continuous-integration)

[Sam Spilsbury (smspillaz)]

review: Approve

[Sam Spilsbury (smspillaz)]

2 if (unredirectFS &&
23 !blacklisted &&
24 - unredirectable.evaluate (w) &&
25 !(mask & PAINT_SCREEN_TRANSFORMED_MASK) &&
26 !(mask & PAINT_SCREEN_WITH_TRANSFORMED_WINDOWS_MASK) &&
27 - fs.isCoveredBy (w->region (), flags))
28 + fs.isCoveredBy (w->region (), flags) &&
29 + (!cw->redirected () || unredirectable.evaluate (w)))

It might be worth trying to fix that wall of conditionals to be more readable in future too.

=== modified file 'plugins/opengl/src/paint.cpp'
--- plugins/opengl/src/paint.cpp	2012-12-13 10:12:23 +0000
+++ plugins/opengl/src/paint.cpp	2013-01-01 10:11:23 +0000
@@ -354,22 +354,31 @@
 	    if (w->alpha ())
 		flags |= FullscreenRegion::Alpha;
 	    
+	    CompositeWindow *cw = CompositeWindow::get (w);
+
 	    /*
 	     * Windows with alpha channels can partially occlude windows
 	     * beneath them and so neither should be unredirected in that case.
+	     *
+	     * Performance note:  unredirectable.evaluate is SLOW because it
+	     * involves regex matching. Too slow to do on every window for
+	     * every frame. So we only call it if a window is redirected AND
+	     * potentially needs unredirecting. This means changes to
+	     * unredirect_match while a window is unredirected already may not
+	     * take effect until it is un-fullscreened again. But that's better
+	     * than the high price of regex matching on every frame.
 	     */
 	    if (unredirectFS &&
 		!blacklisted &&
-		unredirectable.evaluate (w) &&
 		!(mask & PAINT_SCREEN_TRANSFORMED_MASK) &&
 		!(mask & PAINT_SCREEN_WITH_TRANSFORMED_WINDOWS_MASK) &&
-		fs.isCoveredBy (w->region (), flags))
+		fs.isCoveredBy (w->region (), flags) &&
+		(!cw->redirected () || unredirectable.evaluate (w)))
 	    {
 		unredirected.insert (w);
 	    }
 	    else
 	    {
-		CompositeWindow *cw = CompositeWindow::get (w);
 		if (!cw->redirected ())
 		{
 		    if (fs.allowRedirection (w->region ()))
 
=== modified file 'plugins/opengl/src/privates.h'
--- plugins/opengl/src/privates.h	2012-12-13 10:12:23 +0000
+++ plugins/opengl/src/privates.h	2013-01-01 10:11:23 +0000
@@ -222,6 +222,9 @@
 	CompSize rootPixmapSize;
 
 	const char *glVendor, *glRenderer, *glVersion;
+
+	mutable CompString prevRegex;
+	mutable bool       prevBlacklisted;
 };
 
 class PrivateGLWindow :
 
=== modified file 'plugins/opengl/src/screen.cpp'
--- plugins/opengl/src/screen.cpp	2012-12-12 07:33:12 +0000
+++ plugins/opengl/src/screen.cpp	2013-01-01 10:11:23 +0000
@@ -1248,7 +1248,9 @@
     rootPixmapSize (),
     glVendor (NULL),
     glRenderer (NULL),
-    glVersion (NULL)
+    glVersion (NULL),
+    prevRegex (),
+    prevBlacklisted (false)
 {
     ScreenInterface::setHandler (screen);
 }
@@ -2155,7 +2157,16 @@
 bool
 PrivateGLScreen::driverIsBlacklisted (const char *regex) const
 {
-    return blacklisted (regex, glVendor, glRenderer, glVersion);
+    /*
+     * regex matching is VERY expensive, so only do it when the result might
+     * be different to last time. The gl* variables never change value...
+     */
+    if (prevRegex != regex)
+    {
+	prevBlacklisted = blacklisted (regex, glVendor, glRenderer, glVersion);
+	prevRegex = regex;
+    }
+    return prevBlacklisted;
 }
 
 GLTexture::BindPixmapHandle