Revert "mi: drop obsolete miOverlayComputeCompositeClip()"

This reverts commit bfb69b7316.

Requested by Nvidia - their proprietary driver still needs it.

Signed-off-by: Enrico Weigelt, metux IT consult <info@metux.net>
Part-of: <https://gitlab.freedesktop.org/xorg/xserver/-/merge_requests/1843>

mi/mioverlay.c

@@ -108,6 +108,62 @@ miOverlayCopyUnderlay(ScreenPtr pScreen)
     return MIOVERLAY_GET_SCREEN_PRIVATE(pScreen)->copyUnderlay;
 }
 
+void
+miOverlayComputeCompositeClip(GCPtr pGC, WindowPtr pWin)
+{
+    miOverlayTreePtr pTree = MIOVERLAY_GET_WINDOW_TREE(pWin);
+    RegionPtr pregWin;
+    Bool freeTmpClip, freeCompClip;
+
+    if (!pTree) {
+        miComputeCompositeClip(pGC, &pWin->drawable);
+        return;
+    }
+
+    if (pGC->subWindowMode == IncludeInferiors) {
+        pregWin = RegionCreate(NullBox, 1);
+        freeTmpClip = TRUE;
+        if (pWin->parent || (screenIsSaved != SCREEN_SAVER_ON) ||
+            !HasSaverWindow(pGC->pScreen)) {
+            RegionIntersect(pregWin, &pTree->borderClip, &pWin->winSize);
+        }
+    }
+    else {
+        pregWin = &pTree->clipList;
+        freeTmpClip = FALSE;
+    }
+    freeCompClip = pGC->freeCompClip;
+    if (!pGC->clientClip) {
+        if (freeCompClip)
+            RegionDestroy(pGC->pCompositeClip);
+        pGC->pCompositeClip = pregWin;
+        pGC->freeCompClip = freeTmpClip;
+    }
+    else {
+        RegionTranslate(pGC->clientClip,
+                        pWin->drawable.x + pGC->clipOrg.x,
+                        pWin->drawable.y + pGC->clipOrg.y);
+
+        if (freeCompClip) {
+            RegionIntersect(pGC->pCompositeClip, pregWin, pGC->clientClip);
+            if (freeTmpClip)
+                RegionDestroy(pregWin);
+        }
+        else if (freeTmpClip) {
+            RegionIntersect(pregWin, pregWin, pGC->clientClip);
+            pGC->pCompositeClip = pregWin;
+        }
+        else {
+            pGC->pCompositeClip = RegionCreate(NullBox, 0);
+            RegionIntersect(pGC->pCompositeClip, pregWin, pGC->clientClip);
+        }
+        pGC->freeCompClip = TRUE;
+        RegionTranslate(pGC->clientClip,
+                        -(pWin->drawable.x + pGC->clipOrg.x),
+                        -(pWin->drawable.y + pGC->clipOrg.y));
+    }
+}
+
 static void
 MarkUnderlayWindow(WindowPtr pWin)
 {

mi/mioverlay.h

@@ -9,6 +9,7 @@
 typedef void (*miOverlayTransFunc) (ScreenPtr, int, BoxPtr);
 typedef Bool (*miOverlayInOverlayFunc) (WindowPtr);
 
+extern _X_EXPORT void miOverlayComputeCompositeClip(GCPtr, WindowPtr);
 extern _X_EXPORT Bool miOverlayCopyUnderlay(ScreenPtr);
 extern _X_EXPORT void miOverlaySetRootClip(ScreenPtr, Bool);