kwin: Insert an input-only window above each decorated client

This input-only window is used to capture events above the
client window and preventing them from reaching the client.

It is currently used to enlarge the borders by an invisible
amount, using the ExtendedBorderRegion provided by the
decoration.

client.cpp

@@ -130,6 +130,7 @@ Client::Client(Workspace* ws)
     , electricMaximizing(false)
     , activitiesDefined(false)
     , needsSessionInteract(false)
+    , input_window(None)
 {
     // TODO: Do all as initialization
 
@@ -348,6 +349,52 @@ void Client::destroyClient()
     deleteClient(this, Allowed);
 }
 
+void Client::updateInputWindow()
+{
+    QRegion region;
+
+    if (!noBorder() && dynamic_cast<KDecorationUnstable*>(decoration)) {
+        // This function is implemented as a slot to avoid breaking binary
+        // compatibility
+        QMetaObject::invokeMethod(decoration, "region", Qt::DirectConnection,
+                Q_RETURN_ARG(QRegion, region),
+                Q_ARG(KDecorationDefines::Region, KDecorationDefines::ExtendedBorderRegion));
+    }
+
+    if (region.isEmpty()) {
+        if (input_window) {
+            XDestroyWindow(display(), input_window);
+            input_window = None;
+        }
+        return;
+    }
+
+    QRect bounds = region.boundingRect();
+    input_offset = bounds.topLeft();
+
+    // Move the bounding rect to screen coordinates
+    bounds.translate(geometry().topLeft());
+
+    // Move the region to input window coordinates
+    region.translate(-input_offset);
+
+    if (!input_window) {
+        XSetWindowAttributes attr;
+        attr.event_mask = EnterWindowMask | LeaveWindowMask |
+                          ButtonPressMask | ButtonReleaseMask | PointerMotionMask;
+        attr.override_redirect = True;
+
+        input_window = XCreateWindow(display(), rootWindow(), bounds.x(), bounds.y(),
+                                     bounds.width(), bounds.height(), 0, 0,
+                                     InputOnly, 0, CWEventMask | CWOverrideRedirect, &attr);
+    } else {
+        XMoveResizeWindow(display(), input_window, bounds.x(), bounds.y(),
+                          bounds.width(), bounds.height());
+    }
+
+    XShapeCombineRegion(display(), input_window, ShapeInput, 0, 0, region.handle(), ShapeSet);
+}
+
 void Client::updateDecoration(bool check_workspace_pos, bool force)
 {
     if (!force &&
@@ -382,6 +429,7 @@ void Client::updateDecoration(bool check_workspace_pos, bool force)
         destroyDecoration();
     if (check_workspace_pos)
         checkWorkspacePosition(oldgeom);
+    updateInputWindow();
     blockGeometryUpdates(false);
     if (!noBorder())
         decoration->widget()->show();
@@ -415,6 +463,10 @@ void Client::destroyDecoration()
             emit geometryShapeChanged(this, oldgeom);
         }
     }
+    if (inputId()) {
+        XDestroyWindow(display(), input_window);
+        input_window = None;
+    }
 }
 
 bool Client::checkBorderSizes(bool also_resize)
@@ -737,6 +789,7 @@ void Client::resizeDecoration(const QSize& s)
     } else { // oldSize != newSize
         resizeDecorationPixmaps();
     }
+    updateInputWindow();
 }
 
 bool Client::noBorder() const
@@ -1185,8 +1238,11 @@ void Client::internalShow(allowed_t)
     mapping_state = Mapped;
     if (old == Unmapped || old == Withdrawn)
         map(Allowed);
-    if (old == Kept)
+    if (old == Kept) {
+        if (inputId())
+            XMapWindow(display(), inputId());
         updateHiddenPreview();
+    }
     workspace()->checkUnredirect();
 }
 
@@ -1214,6 +1270,8 @@ void Client::internalKeep(allowed_t)
     mapping_state = Kept;
     if (old == Unmapped || old == Withdrawn)
         map(Allowed);
+    if (inputId())
+        XUnmapWindow(display(), inputId());
     updateHiddenPreview();
     addWorkspaceRepaint(visibleRect());
     workspace()->clientHidden(this);
@@ -1238,6 +1296,8 @@ void Client::map(allowed_t)
     if (!isShade()) {
         XMapWindow(display(), wrapper);
         XMapWindow(display(), client);
+        if (inputId())
+            XMapWindow(display(), inputId());
         exportMappingState(NormalState);
     } else
         exportMappingState(IconicState);
@@ -1258,6 +1318,8 @@ void Client::unmap(allowed_t)
     XUnmapWindow(display(), frameId());
     XUnmapWindow(display(), wrapper);
     XUnmapWindow(display(), client);
+    if (inputId())
+        XUnmapWindow(display(), inputId());
     XSelectInput(display(), wrapper, ClientWinMask | SubstructureNotifyMask);
     if (decoration != NULL)
         decoration->widget()->hide(); // Not really necessary, but let it know the state
@@ -2182,6 +2244,8 @@ void Client::updateCursor()
     if (decoration != NULL)
         decoration->widget()->setCursor(cursor);
     XDefineCursor(display(), frameId(), cursor.handle());
+    if (inputId())
+        XDefineCursor(display(), inputId(), cursor.handle());
     if (moveResizeMode)   // XDefineCursor doesn't change cursor if there's pointer grab active
         XChangeActivePointerGrab(display(),
                                  ButtonPressMask | ButtonReleaseMask | PointerMotionMask | EnterWindowMask | LeaveWindowMask,

client.h

@@ -90,6 +90,7 @@ public:
     Client(Workspace* ws);
     Window wrapperId() const;
     Window decorationId() const;
+    Window inputId() const { return input_window; }
 
     const Client* transientFor() const;
     Client* transientFor();
@@ -137,6 +138,7 @@ public:
     virtual QPoint clientPos() const; // Inside of geometry()
     virtual QSize clientSize() const;
     virtual QRect visibleRect() const;
+    QPoint inputPos() const { return input_offset; } // Inside of geometry()
 
     bool windowEvent(XEvent* e);
     virtual bool eventFilter(QObject* o, QEvent* e);
@@ -571,6 +573,8 @@ private:
 
     void checkOffscreenPosition (QRect* geom, const QRect& screenArea);
 
+    void updateInputWindow();
+
     Window client;
     Window wrapper;
     KDecoration* decoration;
@@ -726,6 +730,9 @@ private:
     bool activitiesDefined; //whether the x property was actually set
 
     bool needsSessionInteract;
+
+    Window input_window;
+    QPoint input_offset;
 };
 
 /**
@@ -1022,6 +1029,7 @@ inline bool Client::hiddenPreview() const
 }
 
 KWIN_COMPARE_PREDICATE(WrapperIdMatchPredicate, Client, Window, cl->wrapperId() == value);
+KWIN_COMPARE_PREDICATE(InputIdMatchPredicate, Client, Window, cl->inputId() == value);
 
 } // namespace
 

events.cpp

@@ -289,6 +289,9 @@ bool Workspace::workspaceEvent(XEvent * e)
     } else if (Client* c = findClient(FrameIdMatchPredicate(e->xany.window))) {
         if (c->windowEvent(e))
             return true;
+    } else if (Client *c = findClient(InputIdMatchPredicate(e->xany.window))) {
+        if (c->windowEvent(e))
+            return true;
     } else if (Unmanaged* c = findUnmanaged(WindowMatchPredicate(e->xany.window))) {
         if (c->windowEvent(e))
             return true;
@@ -1090,7 +1093,7 @@ bool Client::buttonPressEvent(Window w, int button, int state, int x, int y, int
         return true;
     }
 
-    if (w == wrapperId() || w == frameId() || w == decorationId()) {
+    if (w == wrapperId() || w == frameId() || w == decorationId() || w == inputId()) {
         // FRAME neco s tohohle by se melo zpracovat, nez to dostane dekorace
         updateUserTime();
         workspace()->setWasUserInteraction();
@@ -1173,7 +1176,11 @@ bool Client::buttonPressEvent(Window w, int button, int state, int x, int y, int
         XAllowEvents(display(), ReplayPointer, CurrentTime);  //xTime());
         return true;
     }
-    if (w == decorationId()) {
+    if (w == decorationId() || w == inputId()) {
+        if (w == inputId()) {
+            x = x_root - geometry().x() + padding_left;
+            y = y_root - geometry().y() + padding_top;
+        }
         if (dynamic_cast<KDecorationUnstable*>(decoration))
             // New API processes core events FIRST and only passes unused ones to the decoration
             return processDecorationButtonPress(button, state, x, y, x_root, y_root, true);
@@ -1262,7 +1269,7 @@ bool Client::buttonReleaseEvent(Window w, int /*button*/, int state, int x, int
         XAllowEvents(display(), SyncPointer, CurrentTime);  //xTime());
         return true;
     }
-    if (w != frameId() && w != decorationId() && w != moveResizeGrabWindow())
+    if (w != frameId() && w != decorationId() && w != inputId() && w != moveResizeGrabWindow())
         return true;
     x = this->x(); // translate from grab window to local coords
     y = this->y();
@@ -1348,12 +1355,17 @@ void Client::checkQuickTilingMaximizationZones(int xroot, int yroot)
 // return value matters only when filtering events before decoration gets them
 bool Client::motionNotifyEvent(Window w, int /*state*/, int x, int y, int x_root, int y_root)
 {
-    if (w != frameId() && w != decorationId() && w != moveResizeGrabWindow())
+    if (w != frameId() && w != decorationId() && w != inputId() && w != moveResizeGrabWindow())
         return true; // care only about the whole frame
     if (!buttonDown) {
         QPoint mousePos(x, y);
         if (w == frameId())
             mousePos += QPoint(padding_left, padding_top);
+        if (w == inputId()) {
+            int x = x_root - geometry().x() + padding_left;
+            int y = y_root - geometry().y() + padding_top;
+            mousePos = QPoint(x, y);
+        }
         Position newmode = mousePosition(mousePos);
         if (newmode != mode) {
             mode = newmode;

geometry.cpp

@@ -1917,8 +1917,13 @@ void Client::setGeometry(int x, int y, int w, int h, ForceGeometry_t force, bool
                 XMoveResizeWindow(display(), window(), 0, 0, cs.width(), cs.height());
         }
         updateShape();
-    } else
+    } else {
         XMoveWindow(display(), frameId(), x, y);
+        if (inputId()) {
+            const QPoint pos = QPoint(x, y) + inputPos();
+            XMoveWindow(display(), inputId(), pos.x(), pos.y());
+        }
+    }
     // SELI TODO won't this be too expensive?
     sendSyntheticConfigureNotify();
     updateWindowRules();

layers.cpp

@@ -163,10 +163,16 @@ void Workspace::propagateClients(bool propagate_new_clients)
     }
 #endif
     for (int i = stacking_order.size() - 1; i >= 0; i--) {
-        if (stacking_order.at(i)->hiddenPreview()) {
+        Client *client = stacking_order.at(i);
+        if (client->hiddenPreview()) {
             continue;
         }
-        newWindowStack << (Window*)stacking_order.at(i)->frameId();
+
+        if (client->inputId())
+            // Stack the input window above the frame
+            newWindowStack << (Window*)client->inputId();
+
+        newWindowStack << (Window*)client->frameId();
     }
     // TODO isn't it too inefficient to restack always all clients?
     // TODO don't restack not visible windows?

manage.cpp

@@ -149,6 +149,9 @@ bool Client::manage(Window w, bool isMapped)
     KStartupInfoData asn_data;
     bool asn_valid = workspace()->checkStartupNotification(window(), asn_id, asn_data);
 
+    // Make sure that the input window is created before we update the stacking order
+    updateInputWindow();
+
     workspace()->updateClientLayer(this);
 
     SessionInfo* session = workspace()->takeSessionInfo(this);