xwayland/glamor: Avoid implicit redirection with depth 32 parent windows

glamor ensures that a depth 32 pixmap backing a depth 24 window contains
fully opaque alpha channel values for the window's pixels, so we can
allow this without implicit redirection, saving pixmap storage and
intermediate copies.

hw/xwayland/xwayland-glamor.c

@@ -25,6 +25,8 @@
 
 #include <xwayland-config.h>
 
+#include <compositeext.h>
+
 #define MESA_EGL_NO_X11_HEADERS
 #define EGL_NO_X11
 #include <glamor_egl.h>
@@ -893,6 +895,108 @@ xwl_glamor_allow_commits(struct xwl_window *xwl_window)
         return TRUE;
 }
 
+static void
+xwl_avoid_implicit_redirect(WindowPtr window)
+{
+    ScreenPtr screen = window->drawable.pScreen;
+    WindowOptPtr parent_optional;
+    VisualPtr parent_visual = NULL;
+    VisualPtr window_visual = NULL;
+    DepthPtr depth32 = NULL;
+    int i;
+
+    if (!window->optional)
+        return;
+
+    parent_optional = FindWindowWithOptional(window)->optional;
+    if (window->optional == parent_optional ||
+        window->optional->visual == parent_optional->visual ||
+        CompositeIsImplicitRedirectException(screen, parent_optional->visual,
+                                             window->optional->visual))
+        return;
+
+    for (i = 0; i < screen->numDepths; i++) {
+        if (screen->allowedDepths[i].depth == 32) {
+            depth32 = &screen->allowedDepths[i];
+            break;
+        }
+    }
+
+    if (!depth32)
+        return;
+
+    for (i = 0; i < depth32->numVids; i++) {
+        XID argb_vid = depth32->vids[i];
+
+        if (argb_vid != parent_optional->visual)
+            continue;
+
+        if (!compIsAlternateVisual(screen, argb_vid))
+            break;
+
+        for (i = 0; i < screen->numVisuals; i++) {
+            if (screen->visuals[i].vid == argb_vid) {
+                parent_visual = &screen->visuals[i];
+                break;
+            }
+        }
+    }
+
+    if (!parent_visual)
+        return;
+
+    for (i = 0; i < screen->numVisuals; i++) {
+        if (screen->visuals[i].vid == window->optional->visual) {
+            window_visual = &screen->visuals[i];
+            break;
+        }
+    }
+
+    if ((window_visual->class != TrueColor &&
+         window_visual->class != DirectColor) ||
+        window_visual->redMask != parent_visual->redMask ||
+        window_visual->greenMask != parent_visual->greenMask ||
+        window_visual->blueMask != parent_visual->blueMask ||
+        window_visual->offsetRed != parent_visual->offsetRed ||
+        window_visual->offsetGreen != parent_visual->offsetGreen ||
+        window_visual->offsetBlue != parent_visual->offsetBlue)
+        return;
+
+    CompositeRegisterImplicitRedirectionException(screen, parent_visual->vid, window_visual->vid);
+}
+
+static Bool
+xwl_glamor_create_window(WindowPtr window)
+{
+    ScreenPtr screen = window->drawable.pScreen;
+    struct xwl_screen *xwl_screen = xwl_screen_get(screen);
+    Bool ret;
+
+    if (window->parent)
+        xwl_avoid_implicit_redirect(window);
+
+    screen->CreateWindow = xwl_screen->CreateWindow;
+    ret = (*screen->CreateWindow) (window);
+    xwl_screen->CreateWindow = screen->CreateWindow;
+    screen->CreateWindow = xwl_glamor_create_window;
+
+    return ret;
+}
+
+static void
+xwl_glamor_reparent_window(WindowPtr window, WindowPtr old_parent)
+{
+    ScreenPtr screen = window->drawable.pScreen;
+    struct xwl_screen *xwl_screen = xwl_screen_get(screen);
+
+    xwl_avoid_implicit_redirect(window);
+
+    screen->ReparentWindow = xwl_screen->ReparentWindow;
+    (*screen->ReparentWindow) (window, old_parent);
+    xwl_screen->ReparentWindow = screen->ReparentWindow;
+    screen->ReparentWindow = xwl_glamor_reparent_window;
+}
+
 static Bool
 xwl_glamor_create_screen_resources(ScreenPtr screen)
 {
@@ -907,6 +1011,11 @@ xwl_glamor_create_screen_resources(ScreenPtr screen)
     if (!ret)
         return ret;
 
+    xwl_screen->CreateWindow = screen->CreateWindow;
+    screen->CreateWindow = xwl_glamor_create_window;
+    xwl_screen->ReparentWindow = screen->ReparentWindow;
+    screen->ReparentWindow = xwl_glamor_reparent_window;
+
     if (xwl_screen->rootless) {
         screen->devPrivate =
             fbCreatePixmap(screen, 0, 0, screen->rootDepth, 0);

hw/xwayland/xwayland-screen.h

@@ -70,12 +70,14 @@ struct xwl_screen {
 
     CreateScreenResourcesProcPtr CreateScreenResources;
     CloseScreenProcPtr CloseScreen;
+    CreateWindowProcPtr CreateWindow;
     RealizeWindowProcPtr RealizeWindow;
     UnrealizeWindowProcPtr UnrealizeWindow;
     DestroyWindowProcPtr DestroyWindow;
     XYToWindowProcPtr XYToWindow;
     SetWindowPixmapProcPtr SetWindowPixmap;
     ChangeWindowAttributesProcPtr ChangeWindowAttributes;
+    ReparentWindowProcPtr ReparentWindow;
     ResizeWindowProcPtr ResizeWindow;
     MoveWindowProcPtr MoveWindow;