Introduce Qt::ExpandedClientAreaHint

The hint requests that the window's client area is expanded to fill
parts of the window that might be (partially) covered by, or
conflicting with, other (system) UI elements, such as the window's
title bar, resize controls, or a status bar.

The safe area margins of the window will reflect any areas that
may have conflicting UI elements.

If the client area is expanded into the area previously covered
by the frame margins, the frame margins are reduced accordingly,
as the frame margins represent the non-client-area parts of the
window.

This new flag replaces, and overlaps in value, with the existing
Qt::MaximizeUsingFullscreenGeometryHint, as the latter was added
to cover this exact use-case for mobile platforms. Now that we
have the use-case on desktop platforms as well we want to use a
more generic flag, so the old flag has been deprecated.

Semantically, on iOS and Android, without the flags set, the
window can be seen as being maximized to take up the entire
screen, but with a frameMargin() that reflects the system
status bar and resize controls. That's not technically how
we implement things right now, but this is an implementation
detail that will be changed in a follow-up.

On macOS the flag maps to NSWindowStyleMaskFullSizeContentView,
and on Windows we have an implementation cooking that uses the
DwmExtendFrameIntoClientArea function.

Task-number: QTBUG-127634
Change-Id: I9b6863b1550ccc056c16bce235d87b26a7d239b9
Reviewed-by: Assam Boudjelthia <[email protected]>
Reviewed-by: Wladimir Leuschner <[email protected]>

1 files changed, 7 insertions, 0 deletions

diff --git a/tests/manual/windowflags/controls.cpp b/tests/manual/windowflags/controls.cpp
index 9262eb8bc60..dd96eea5069 100644
--- a/tests/manual/windowflags/controls.cpp
+++ b/tests/manual/windowflags/controls.cpp
@@ -32,6 +32,7 @@ HintControl::HintControl(QWidget *parent)
     , customizeWindowGroup(new QGroupBox(tr("Customize window title bar controls")))
     , transparentForInputCheckBox(new QCheckBox(tr("Transparent for input")))
     , noDropShadowCheckBox(new QCheckBox(tr("No drop shadow")))
+    , expandedClientAreaCheckBox(new QCheckBox(tr("Expanded client area")))
 {
     connect(msWindowsFixedSizeDialogCheckBox, SIGNAL(clicked()), this, SLOT(slotCheckBoxChanged()));
     connect(x11BypassWindowManagerCheckBox, SIGNAL(clicked()), this, SLOT(slotCheckBoxChanged()));
@@ -49,6 +50,8 @@ HintControl::HintControl(QWidget *parent)
     connect(customizeWindowGroup, SIGNAL(clicked()), this, SLOT(slotCheckBoxChanged()));
     connect(transparentForInputCheckBox, SIGNAL(clicked()), this, SLOT(slotCheckBoxChanged()));
     connect(noDropShadowCheckBox, SIGNAL(clicked()), this, SLOT(slotCheckBoxChanged()));
+    connect(expandedClientAreaCheckBox, SIGNAL(clicked()), this, SLOT(slotCheckBoxChanged()));
+
     auto *layout = new QHBoxLayout(this);
     layout->setSpacing(0);
     layout->setContentsMargins(ControlLayoutMargin, ControlLayoutMargin,
@@ -66,6 +69,7 @@ HintControl::HintControl(QWidget *parent)
     basicHintsLayout->addWidget(transparentForInputCheckBox);
     basicHintsLayout->addWidget(msWindowsFixedSizeDialogCheckBox);
     basicHintsLayout->addWidget(x11BypassWindowManagerCheckBox);
+    basicHintsLayout->addWidget(expandedClientAreaCheckBox);
     layout->addLayout(basicHintsLayout);
 
     customizeWindowGroup->setCheckable(true);
@@ -122,6 +126,8 @@ Qt::WindowFlags HintControl::hints() const
         flags |= Qt::WindowTransparentForInput;
     if (noDropShadowCheckBox->isChecked())
         flags |= Qt::NoDropShadowWindowHint;
+    if (expandedClientAreaCheckBox->isChecked())
+        flags |= Qt::ExpandedClientAreaHint;
     return flags;
 }
 
@@ -143,6 +149,7 @@ void HintControl::setHints(Qt::WindowFlags flags)
     customizeWindowGroup->setChecked(flags & Qt::CustomizeWindowHint);
     transparentForInputCheckBox->setChecked(flags & Qt::WindowTransparentForInput);
     noDropShadowCheckBox->setChecked(flags & Qt::NoDropShadowWindowHint);
+    expandedClientAreaCheckBox->setChecked(flags & Qt::ExpandedClientAreaHint);
 }
 
 void HintControl::slotCheckBoxChanged()