[PATCH 2/3] xcompmgr: prevent flicker on root background pixmap change

[Forest Bond]

Changes to the root background pixmap would previously cause the new
image to flicker into visibility briefy before windows were redrawn
over it.  This patch fixes this by dropping a XClearWindow call and
providing a new function ("damage_screen") to force a redraw of the
entire screen.

Signed-off-by: Forest Bond <forest at alittletooquiet.net>
---
 xcompmgr.c |   28 ++++++++++++++++++++++++----
 1 files changed, 24 insertions(+), 4 deletions(-)

diff --git a/xcompmgr.c b/xcompmgr.c
index 3a01cce..47f5667 100644
--- a/xcompmgr.c
+++ b/xcompmgr.c
@@ -128,6 +128,7 @@ static int		composite_event, composite_error;
 static int		render_event, render_error;
 static Bool		synchronize;
 static int		composite_opcode;
+static Bool		screen_damaged = False;
 
 /* find these once and be done with it */
 static Atom		opacityAtom;
@@ -947,7 +948,7 @@ paint_all (Display *dpy, XserverRegion region)
 	    continue;
 #endif
 	/* never painted, ignore it */
-	if (!w->damaged)
+	if ((!screen_damaged) && (!w->damaged))
 	    continue;
 	/* if invisible, ignore it */
 	if (w->a.x + w->a.width < 1 || w->a.y + w->a.height < 1
@@ -1120,6 +1121,7 @@ paint_all (Display *dpy, XserverRegion region)
 	XRenderComposite (dpy, PictOpSrc, rootBuffer, None, rootPicture,
 			  0, 0, 0, 0, 0, 0, root_width, root_height);
     }
+    screen_damaged = False;
 }
 
 static void
@@ -1738,6 +1740,22 @@ damage_win (Display *dpy, XDamageNotifyEvent *de)
 	repair_win (dpy, w);
 }
 
+static void
+damage_screen (Display *dpy)
+{
+	XserverRegion region;
+	XRectangle r;
+
+	r.x = 0;
+	r.y = 0;
+	r.width = root_width;
+	r.height = root_height;
+
+	region = XFixesCreateRegion (dpy, &r, 1);
+	add_damage (dpy, region);
+	screen_damaged = True;
+}
+
 static int
 error (Display *dpy, XErrorEvent *ev)
 {
@@ -2193,9 +2211,10 @@ main (int argc, char **argv)
 		    {
 			if (rootTile)
 			{
-			    XClearArea (dpy, root, 0, 0, 0, 0, True);
 			    XRenderFreePicture (dpy, rootTile);
 			    rootTile = None;
+
+			    damage_screen(dpy);
 			    break;
 			}
 		    }
@@ -2232,12 +2251,13 @@ main (int argc, char **argv)
 	} while (QLength (dpy));
 	if (allDamage && !autoRedirect)
 	{
-	    static int	paint;
 	    paint_all (dpy, allDamage);
-	    paint++;
 	    XSync (dpy, False);
 	    allDamage = None;
 	    clipChanged = False;
 	}
     }
+
+    XClearArea (dpy, root, 0, 0, 0, 0, True);
+    XSync (dpy, False);
 }
-- 
1.7.0.4
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