[x11] Hold a passive grab on buttons only when needed

Due to a bug in the XI2 protocol, clients have to reset scroll valuators
on XI_Enter because the scroll valuators might have changed while the
pointer was elsewhere. The XI_Enter event is usually sent when an input
device enters the window, but it can also be generated by a passive grab.

If an XI_Enter event has been generated by a passive grab, the client
should not reset scroll valuators. Unfortunately, there is no any
reliable way for the client to determine if an XI_Enter event has been
sent in response to a deactivated passive grab. A correct fix for the
scroll issues in GTK apps would involve changes in the XI2 protocol.

As a work around, we can hold a passive grab only if the current mouse
wheel action is either "Activate and scroll" or "Activate, raise, and
scroll."

BUG: 394772
FIXED-IN: 5.19.3

events.cpp

@@ -823,21 +823,22 @@ void X11Client::leaveNotifyEvent(xcb_leave_notify_event_t *e)
 #define XCapL KKeyServer::modXLock()
 #define XNumL KKeyServer::modXNumLock()
 #define XScrL KKeyServer::modXScrollLock()
-void X11Client::grabButton(int modifier)
+void X11Client::grabButton(Qt::KeyboardModifier modifier, uint8_t button)
 {
-    unsigned int mods[ 8 ] = {
+    uint16_t x11Modifier;
-        0, XCapL, XNumL, XNumL | XCapL,
+
-        XScrL, XScrL | XCapL,
+    switch (modifier) {
-        XScrL | XNumL, XScrL | XNumL | XCapL
+    case Qt::MetaModifier:
-    };
+        x11Modifier = KKeyServer::modXMeta();
-    for (int i = 0;
+        break;
-            i < 8;
+    case Qt::AltModifier:
-            ++i)
+        x11Modifier = KKeyServer::modXAlt();
-        m_wrapper.grabButton(XCB_GRAB_MODE_SYNC, XCB_GRAB_MODE_ASYNC, modifier | mods[ i ]);
+        break;
-}
+    default:
+        x11Modifier = 0;
+        break;
+    }
 
-void X11Client::ungrabButton(int modifier)
-{
     unsigned int mods[ 8 ] = {
         0, XCapL, XNumL, XNumL | XCapL,
         XScrL, XScrL | XCapL,
@@ -846,47 +847,69 @@ void X11Client::ungrabButton(int modifier)
     for (int i = 0;
             i < 8;
             ++i)
-        m_wrapper.ungrabButton(modifier | mods[ i ]);
+        m_wrapper.grabButton(XCB_GRAB_MODE_SYNC, XCB_GRAB_MODE_ASYNC, x11Modifier | mods[ i ], button);
 }
 #undef XCapL
 #undef XNumL
 #undef XScrL
 
-/**
+bool X11Client::isMostRecentlyRaised() const
- * Releases the passive grab for some modifier combinations when a
+{
- * window becomes active. This helps broken X programs that
+    // The last toplevel in the unconstrained stacking order is the most recently raised one.
- * missinterpret LeaveNotify events in grab mode to work properly
+    return workspace()->topClientOnDesktop(VirtualDesktopManager::self()->current(), -1, true, false) == this;
- * (Motif, AWT, Tk, ...)
+}
- */
+
 void X11Client::updateMouseGrab()
 {
-    if (workspace()->globalShortcutsDisabled()) {
+    xcb_ungrab_button(connection(), XCB_BUTTON_INDEX_ANY, m_wrapper, XCB_MOD_MASK_ANY);
-        m_wrapper.ungrabButton();
+
-        // keep grab for the simple click without modifiers if needed (see below)
+    if (TabBox::TabBox::self()->forcedGlobalMouseGrab()) { // see TabBox::establishTabBoxGrab()
-        bool not_obscured = workspace()->topClientOnDesktop(VirtualDesktopManager::self()->current(), -1, true, false) == this;
+        m_wrapper.grabButton(XCB_GRAB_MODE_SYNC, XCB_GRAB_MODE_ASYNC);
-        if (!(!options->isClickRaise() || not_obscured))
-            grabButton(XCB_NONE);
         return;
     }
-    if (isActive() && !TabBox::TabBox::self()->forcedGlobalMouseGrab()) { // see TabBox::establishTabBoxGrab()
+
-        // first grab all modifier combinations
+    // When a passive grab is activated or deactivated, the X server will generate crossing
-        m_wrapper.grabButton(XCB_GRAB_MODE_SYNC, XCB_GRAB_MODE_ASYNC);
+    // events as if the pointer were suddenly to warp from its current position to some position
-        // remove the grab for no modifiers only if the window
+    // in the grab window. Some /broken/ X11 clients do get confused by such EnterNotify and
-        // is unobscured or if the user doesn't want click raise
+    // LeaveNotify events so we release the passive grab for the active window.
-        // (it is unobscured if it the topmost in the unconstrained stacking order, i.e. it is
+    //
-        // the most recently raised window)
+    // The passive grab below is established so the window can be raised or activated when it
-        bool not_obscured = workspace()->topClientOnDesktop(VirtualDesktopManager::self()->current(), -1, true, false) == this;
+    // is clicked.
-        if (!options->isClickRaise() || not_obscured)
+    if ((options->focusPolicyIsReasonable() && !isActive()) ||
-            ungrabButton(XCB_NONE);
+            (options->isClickRaise() && !isMostRecentlyRaised())) {
-        else
+        if (options->commandWindow1() != Options::MouseNothing) {
-            grabButton(XCB_NONE);
+            grabButton(Qt::NoModifier, XCB_BUTTON_INDEX_1);
-        ungrabButton(XCB_MOD_MASK_SHIFT);
+        }
-        ungrabButton(XCB_MOD_MASK_CONTROL);
+        if (options->commandWindow2() != Options::MouseNothing) {
-        ungrabButton(XCB_MOD_MASK_CONTROL | XCB_MOD_MASK_SHIFT);
+            grabButton(Qt::NoModifier, XCB_BUTTON_INDEX_2);
-    } else {
+        }
-        m_wrapper.ungrabButton();
+        if (options->commandWindow3() != Options::MouseNothing) {
-        // simply grab all modifier combinations
+            grabButton(Qt::NoModifier, XCB_BUTTON_INDEX_3);
-        m_wrapper.grabButton(XCB_GRAB_MODE_SYNC, XCB_GRAB_MODE_ASYNC);
+        }
+        if (options->commandWindowWheel() != Options::MouseNothing) {
+            grabButton(Qt::NoModifier, XCB_BUTTON_INDEX_4);
+            grabButton(Qt::NoModifier, XCB_BUTTON_INDEX_5);
+        }
+    }
+
+    // We want to grab <command modifier> + buttons no matter what state the window is in. The
+    // client will receive funky EnterNotify and LeaveNotify events, but there is nothing that
+    // we can do about it, unfortunately.
+
+    if (!workspace()->globalShortcutsDisabled()) {
+        if (options->commandAll1() != Options::MouseNothing) {
+            grabButton(options->commandAllModifier(), XCB_BUTTON_INDEX_1);
+        }
+        if (options->commandAll2() != Options::MouseNothing) {
+            grabButton(options->commandAllModifier(), XCB_BUTTON_INDEX_2);
+        }
+        if (options->commandAll3() != Options::MouseNothing) {
+            grabButton(options->commandAllModifier(), XCB_BUTTON_INDEX_3);
+        }
+        if (options->commandAllWheel() != Options::MouseWheelNothing) {
+            grabButton(options->commandAllModifier(), XCB_BUTTON_INDEX_4);
+            grabButton(options->commandAllModifier(), XCB_BUTTON_INDEX_5);
+        }
     }
 }
 

options.h

@@ -447,6 +447,9 @@ public:
     MouseCommand commandAll3() const {
         return CmdAll3;
     }
+    MouseWheelCommand commandAllWheel() const {
+        return CmdAllWheel;
+    }
     uint keyCmdAllModKey() const {
         return CmdAllModKey;
     }

x11client.cpp

@@ -162,6 +162,7 @@ X11Client::X11Client()
     m_frameGeometry = QRect(0, 0, 100, 100);   // So that decorations don't start with size being (0,0)
 
     connect(clientMachine(), &ClientMachine::localhostChanged, this, &X11Client::updateCaption);
+    connect(options, &Options::configChanged, this, &X11Client::updateMouseGrab);
     connect(options, &Options::condensedTitleChanged, this, &X11Client::updateCaption);
 
     connect(this, &X11Client::moveResizeCursorChanged, this, [this] (CursorShape cursor) {

x11client.h

@@ -397,6 +397,7 @@ Q_SIGNALS:
 private:
     void exportMappingState(int s);   // ICCCM 4.1.3.1, 4.1.4, NETWM 2.5.1
     bool isManaged() const; ///< Returns false if this client is not yet managed
+    bool isMostRecentlyRaised() const;
     void updateAllowedActions(bool force = false);
     QRect fullscreenMonitorsArea(NETFullscreenMonitors topology) const;
     void changeMaximize(bool horizontal, bool vertical, bool adjust) override;
@@ -417,8 +418,7 @@ private:
     void sendSyncRequest();
     void leaveMoveResize() override;
     void positionGeometryTip() override;
-    void grabButton(int mod);
+    void grabButton(Qt::KeyboardModifier modifier, uint8_t button);
-    void ungrabButton(int mod);
     void resizeDecoration();
     void createDecoration(const QRect &oldgeom) override;