Implement core protocol backing store exclusively in terms of Composite.

Composite's automatic redirection is a more general mechanism than the
ad-hoc BS machinery, so it's much prettier to implement the one in terms
of the other.  Composite now wraps ChangeWindowAttributes and activates
automatic redirection for windows with backing store requested.  The old
backing store infrastructure is completely gutted: ABI-visible structures
retain the function pointers, but they never get called, and all the
open-coded conditionals throughout the DIX layer to implement BS are gone.

Note that this is still not a strictly complete implementation of backing
store, since Composite will throw the bits away on unmap and therefore
WhenMapped and Always hints are equivalent.

2 files changed, 36 insertions, 0 deletions

diff --git a/composite/compinit.c b/composite/compinit.c
index 630f1042c..c557eebc4 100644
--- a/composite/compinit.c
+++ b/composite/compinit.c
@@ -63,6 +63,7 @@ compCloseScreen (int index, ScreenPtr pScreen)
     pScreen->CloseScreen = cs->CloseScreen;
     pScreen->BlockHandler = cs->BlockHandler;
     pScreen->InstallColormap = cs->InstallColormap;
+    pScreen->ChangeWindowAttributes = cs->ChangeWindowAttributes;
     pScreen->ReparentWindow = cs->ReparentWindow;
     pScreen->MoveWindow = cs->MoveWindow;
     pScreen->ResizeWindow = cs->ResizeWindow;
@@ -109,6 +110,33 @@ compInstallColormap (ColormapPtr pColormap)
     pScreen->InstallColormap = compInstallColormap;
 }
 
+/* Fake backing store via automatic redirection */
+static Bool
+compChangeWindowAttributes(WindowPtr pWin, unsigned long mask)
+{
+    ScreenPtr pScreen = pWin->drawable.pScreen;
+    CompScreenPtr cs = GetCompScreen (pScreen);
+    Bool ret;
+
+    pScreen->ChangeWindowAttributes = cs->ChangeWindowAttributes;
+    ret = pScreen->ChangeWindowAttributes(pWin, mask);
+
+    if (ret && (mask & CWBackingStore)) {
+	if (pWin->backingStore != NotUseful) {
+	    compRedirectWindow(serverClient, pWin, CompositeRedirectAutomatic);
+	    pWin->backStorage = TRUE;
+	} else {
+	    compUnredirectWindow(serverClient, pWin,
+				 CompositeRedirectAutomatic);
+	    pWin->backStorage = FALSE;
+	}
+    }
+
+    pScreen->ChangeWindowAttributes = compChangeWindowAttributes;
+
+    return ret;
+}
+
 static void
 compScreenUpdate (ScreenPtr pScreen)
 {
@@ -424,6 +452,9 @@ compScreenInit (ScreenPtr pScreen)
     cs->InstallColormap = pScreen->InstallColormap;
     pScreen->InstallColormap = compInstallColormap;
 
+    cs->ChangeWindowAttributes = pScreen->ChangeWindowAttributes;
+    pScreen->ChangeWindowAttributes = compChangeWindowAttributes;
+
     cs->BlockHandler = pScreen->BlockHandler;
     pScreen->BlockHandler = compBlockHandler;
 
diff --git a/composite/compint.h b/composite/compint.h
index 2c4d5c002..38b1777a2 100644
--- a/composite/compint.h
+++ b/composite/compint.h
@@ -143,6 +143,11 @@ typedef struct _CompScreen {
      */
     InstallColormapProcPtr	InstallColormap;
 
+    /*
+     * Fake backing store via automatic redirection
+     */
+    ChangeWindowAttributesProcPtr ChangeWindowAttributes;
+
     ScreenBlockHandlerProcPtr	BlockHandler;
     CloseScreenProcPtr		CloseScreen;
     Bool			damaged;