Wayland: Workaround Qt/Wayland bug that prevents popup layout button menu from showing

Sigh. Wayland really is the gift that keeps on giving. For some reason
we cant use QMenu for this so re-implement QMenu like behavior with a
custom widget. Hopefully this doesnt break anything else.

Fixes #2109755 [Layout button doesn't activate options](https://bugs.launchpad.net/calibre/+bug/2109755)

src/calibre/gui2/init.py

@@ -546,7 +546,6 @@ class LayoutMixin:  # {{{
                 ''')
         for button in reversed(self.layout_buttons):
             self.status_bar.insertPermanentWidget(2, button)
-        self.layout_button.setMenu(LayoutMenu(self))
         self.layout_button.setVisible(not gprefs['show_layout_buttons'])
 
     def init_layout_mixin(self):
@@ -592,12 +591,13 @@ class LayoutMixin:  # {{{
         self.search_bar_button.toggled.connect(self.toggle_search_bar)
 
         self.layout_button = b = QToolButton(self)
+        self.layout_button_menu = m = LayoutMenu(self)
         b.setAutoRaise(True), b.setCursor(Qt.CursorShape.PointingHandCursor)
-        b.setPopupMode(QToolButton.ToolButtonPopupMode.InstantPopup)
         b.setToolButtonStyle(Qt.ToolButtonStyle.ToolButtonTextBesideIcon)
         b.setText(_('Layout')), b.setIcon(QIcon.ic('layout.png'))
         b.setToolTip(_(
             'Show and hide various parts of the calibre main window'))
+        b.clicked.connect(m.toggle_visibility)
         self.status_bar.addPermanentWidget(b)
 
         # These must be after the layout button because it can be expanded into

src/calibre/gui2/layout_menu.py

@@ -2,7 +2,22 @@
 # License: GPLv3 Copyright: 2017, Kovid Goyal <kovid at kovidgoyal.net>
 
 
-from qt.core import QFontMetrics, QHBoxLayout, QIcon, QMenu, QPushButton, QSize, QSizePolicy, QStyle, QStyleOption, QStylePainter, Qt, QWidget
+from qt.core import (
+    QEvent,
+    QFontMetrics,
+    QHBoxLayout,
+    QIcon,
+    QKeySequence,
+    QPainter,
+    QPushButton,
+    QSize,
+    QSizePolicy,
+    QStyle,
+    QStyleOption,
+    QStylePainter,
+    Qt,
+    QWidget,
+)
 
 
 class LayoutItem(QWidget):
@@ -72,37 +87,47 @@ class LayoutItem(QWidget):
         painter.end()
 
 
-class LayoutMenu(QMenu):
+class LayoutMenuInner(QWidget):
 
-    def __init__(self, parent=None):
-        QMenu.__init__(self, parent)
+    def __init__(self, parent):
+        super().__init__(parent)
         self.l = l = QHBoxLayout(self)
         l.setSpacing(20)
         self.items = []
-        if parent is None:
-            buttons = [
-                QPushButton(QIcon.ic(i + '.png'), i, self)
-                for i in 'search tags cover_flow grid book'.split()]
-            for b in buttons:
-                b.setVisible(False), b.setCheckable(True), b.setChecked(b.text() in 'tags grid')
-                b.label = b.text().capitalize()
-        else:
-            buttons = parent.layout_buttons
-        for b in buttons:
-            self.items.append(LayoutItem(b, self))
-            l.addWidget(self.items[-1])
-            self.aboutToShow.connect(self.about_to_show)
-        self.current_item = None
+        self.initialized = False
 
-    def about_to_show(self):
+    @property
+    def gui(self):
+        return self.parent().parent()
+
+    def delayed_init(self):
+        if not self.initialized:
+            self.initialized = True
+            gui = self.gui
+            if not hasattr(gui, 'layout_buttons'):
+                buttons = [
+                    QPushButton(QIcon.ic(i + '.png'), i, self)
+                    for i in 'search tags cover_flow grid book'.split()]
+                for b in buttons:
+                    b.setVisible(False), b.setCheckable(True), b.setChecked(b.text() in 'tags grid')
+                    b.label = b.text().capitalize()
+            else:
+                buttons = gui.layout_buttons
+            l = self.layout()
+            for b in buttons:
+                self.items.append(LayoutItem(b, self))
+                l.addWidget(self.items[-1], alignment=Qt.AlignmentFlag.AlignBottom)
+        self.current_item = None
         for x in self.items:
             x.update_tips()
-
-    def sizeHint(self):
-        return QWidget.sizeHint(self)
+        self.resize(self.sizeHint())
 
     def paintEvent(self, ev):
-        return QWidget.paintEvent(self, ev)
+        painter = QPainter(self)
+        col = self.palette().window().color()
+        col.setAlphaF(0.9)
+        painter.fillRect(self.rect(), col)
+        super().paintEvent(ev)
 
     def item_for_ev(self, ev):
         for item in self.items:
@@ -113,8 +138,6 @@ class LayoutMenu(QMenu):
         if ev.button() != Qt.MouseButton.LeftButton:
             ev.ignore()
             return
-        if (ev.pos().isNull() and not ev.screenPos().isNull()) or not self.rect().contains(ev.pos()):
-            self.hide()
         self.current_item = self.item_for_ev(ev)
         if self.current_item is not None:
             ev.accept()
@@ -128,13 +151,81 @@ class LayoutMenu(QMenu):
         item = self.item_for_ev(ev)
         if item is not None and item is self.current_item:
             ev.accept()
-            self.hide()
+            self.parent().hide()
             item.button.click()
 
+    def handle_key_press(self, ev):
+        q = QKeySequence(ev.keyCombination())
+        for item in self.items:
+            sc = item.button.shortcut
+            if callable(sc):
+                sc = item.button.shortcut()
+            else:
+                sc = QKeySequence.fromString(sc)
+            if sc.matches(q) == QKeySequence.SequenceMatch.ExactMatch:
+                self.parent().hide()
+                item.button.click()
+                ev.accept()
+                break
+
+
+class LayoutMenu(QWidget):
+
+    def __init__(self, parent):
+        super().__init__(parent)
+        self.setVisible(False)
+        self.inner = LayoutMenuInner(self)
+        self.setFocusPolicy(Qt.FocusPolicy.StrongFocus)
+
+    def toggle_visibility(self):
+        if self.isVisible():
+            self.hide()
+        else:
+            self.show()
+
+    def show(self):
+        self.inner.delayed_init()
+        parent = self.parent()
+        self.move(0, 0)
+        self.resize(parent.rect().size())
+        r = parent.rect()
+        y = r.height()
+        if hasattr(parent, 'layout_button'):
+            lb = parent.layout_button
+            y = lb.mapTo(parent, lb.rect().topLeft()).y()
+        self.inner.move(r.width() - self.inner.size().width(), y - self.inner.size().height())
+        super().show()
+        self.raise_()
+        self.setFocus(Qt.FocusReason.OtherFocusReason)
+
+    def event(self, ev):
+        if ev.type() == QEvent.Type.ShortcutOverride and self.isVisible():
+            ev.accept()
+        return super().event(ev)
+
+    def keyPressEvent(self, ev):
+        if ev.matches(QKeySequence.StandardKey.Cancel):
+            self.hide()
+        else:
+            self.inner.handle_key_press(ev)
+
+    def mousePressEvent(self, ev):
+        if ev.button() != Qt.MouseButton.LeftButton:
+            ev.ignore()
+            return
+        if self.inner.rect().contains(ev.pos()):
+            ev.ignore()
+        else:
+            self.hide()
+
 
 if __name__ == '__main__':
+    from qt.core import QMainWindow
+
     from calibre.gui2 import Application
     app = Application([])
-    w = LayoutMenu()
+    w = QMainWindow()
+    m = LayoutMenu(w)
     w.show()
-    w.exec()
+    m.show()
+    app.exec()