Add QPlatformWindow::windowClosestAcceptableGeometry().

Add a function to determine the closest acceptable geometry
(height-for-width) to QPlatformWindow similar to the existing
QPlatformWindow::windowMinimumSize(), windowMaximumSize()...
Clean up the hack in the Windows platform plugin accordingly.

Change-Id: I96e943cfdbafdd0ff444e0d53ee0bdf8603d33df
Reviewed-by: Paul Olav Tvete <paul.tvete@theqtcompany.com>

3 files changed, 17 insertions, 2 deletions

diff --git a/src/gui/kernel/qplatformwindow.cpp b/src/gui/kernel/qplatformwindow.cpp
index 34a1fabc76..9217aca400 100644
--- a/src/gui/kernel/qplatformwindow.cpp
+++ b/src/gui/kernel/qplatformwindow.cpp
@@ -690,6 +690,20 @@ QRect QPlatformWindow::windowGeometry() const
 }
 
 /*!
+    Returns the closest acceptable geometry for a given geometry before
+    a resize/move event for platforms that support it, for example to
+    implement heightForWidth().
+*/
+QRectF QPlatformWindow::windowClosestAcceptableGeometry(const QRectF &nativeRect) const
+{
+    QWindow *qWindow = window();
+    const QRectF rectF = QHighDpi::fromNativePixels(nativeRect, qWindow);
+    const QRectF correctedGeometryF = qt_window_private(qWindow)->closestAcceptableGeometry(rectF);
+    return !correctedGeometryF.isEmpty() && rectF != correctedGeometryF
+        ? QHighDpi::toNativePixels(correctedGeometryF, qWindow) : nativeRect;
+}
+
+/*!
     \class QPlatformWindow
     \since 4.8
     \internal
diff --git a/src/gui/kernel/qplatformwindow.h b/src/gui/kernel/qplatformwindow.h
index c1f2a4bdf1..692ae862db 100644
--- a/src/gui/kernel/qplatformwindow.h
+++ b/src/gui/kernel/qplatformwindow.h
@@ -138,6 +138,8 @@ public:
     QSize windowBaseSize() const;
     QSize windowSizeIncrement() const;
     QRect windowGeometry() const;
+    QRectF windowClosestAcceptableGeometry(const QRectF &nativeRect) const;
+
 protected:
     static QString formatWindowTitle(const QString &title, const QString &separator);
     QPlatformScreen *screenForGeometry(const QRect &newGeometry) const;
diff --git a/src/plugins/platforms/windows/qwindowswindow.cpp b/src/plugins/platforms/windows/qwindowswindow.cpp
index d6677bb228..0f32ff1f98 100644
--- a/src/plugins/platforms/windows/qwindowswindow.cpp
+++ b/src/plugins/platforms/windows/qwindowswindow.cpp
@@ -1811,8 +1811,7 @@ bool QWindowsWindow::handleGeometryChangingMessage(MSG *message, const QWindow *
     const QRect suggestedFrameGeometry(windowPos->x, windowPos->y,
                                        windowPos->cx, windowPos->cy);
     const QRect suggestedGeometry = suggestedFrameGeometry - margins;
-    const QRectF correctedGeometryF =
-        qt_window_private(const_cast<QWindow *>(qWindow))->closestAcceptableGeometry(suggestedGeometry);
+    const QRectF correctedGeometryF = qWindow->handle()->windowClosestAcceptableGeometry(suggestedGeometry);
     if (!correctedGeometryF.isValid())
         return false;
     const QRect correctedFrameGeometry = correctedGeometryF.toRect() + margins;