QWizard: Fix frame when using Vista style/MSVC2012

Work around GetSystemMetrics() returning the wrong value using
MSVC2012 and later. The special handling of Windows 8 and later
is then no longer required.

[ChangeLog][QtWidgets][QWizard]  Fixed frame when using Vista style/MSVC2012.

Task-number: QTBUG-36192

Change-Id: I39c2ab70a266f12cd65fa740b10b86edffa60417
Reviewed-by: Joerg Bornemann <joerg.bornemann@digia.com>
(cherry picked from qtbase/852308114ff901b86cca99268f498fc1d56b622e)

2 files changed, 32 insertions, 8 deletions

diff --git a/src/gui/dialogs/qwizard_win.cpp b/src/gui/dialogs/qwizard_win.cpp
index 9cd62927bb..a87982449e 100644
--- a/src/gui/dialogs/qwizard_win.cpp
+++ b/src/gui/dialogs/qwizard_win.cpp
@@ -409,12 +409,12 @@ bool QVistaHelper::winEvent(MSG* msg, long* result)
         break;
     }
     case WM_NCCALCSIZE:
-        if (QSysInfo::WindowsVersion < QSysInfo::WV_WINDOWS8 && vistaState() == VistaAero) {
+        if (vistaState() == VistaAero) {
             NCCALCSIZE_PARAMS* lpncsp = (NCCALCSIZE_PARAMS*)msg->lParam;
             *result = DefWindowProc(msg->hwnd, msg->message, msg->wParam, msg->lParam);
             lpncsp->rgrc[0].top -= titleBarSize();
         } else {
-            return false; // Negative margins no longer work on Windows 8.
+            return false;
         }
         break;
     default:
@@ -737,6 +737,33 @@ bool QVistaHelper::drawBlackRect(const QRect &rect, HDC hdc)
     return value;
 }
 
+#if !defined(_MSC_VER) || _MSC_VER < 1700
+static inline int getWindowBottomMargin()
+{
+    return GetSystemMetrics(SM_CYSIZEFRAME);
+}
+#else // !_MSC_VER || _MSC_VER < 1700
+// QTBUG-36192, GetSystemMetrics(SM_CYSIZEFRAME) returns bogus values
+// for MSVC2012 which leads to the custom margin having no effect since
+// that only works when removing the entire margin.
+static inline int getWindowBottomMargin()
+{
+    RECT rect = {0, 0, 0, 0};
+    AdjustWindowRectEx(&rect, WS_POPUP | WS_CLIPSIBLINGS | WS_CLIPCHILDREN | WS_THICKFRAME | WS_DLGFRAME, FALSE, 0);
+    return qAbs(rect.bottom);
+}
+#endif // _MSC_VER >= 1700
+
+int QVistaHelper::frameSize()
+{
+    return getWindowBottomMargin();
+}
+
+int QVistaHelper::captionSize()
+{
+    return GetSystemMetrics(SM_CYCAPTION);
+}
+
 bool QVistaHelper::resolveSymbols()
 {
     static bool tried = false;
@@ -795,10 +822,7 @@ int QVistaHelper::topOffset()
     static const int aeroOffset =
         QSysInfo::WindowsVersion == QSysInfo::WV_WINDOWS7 ?
         QStyleHelper::dpiScaled(4) : QStyleHelper::dpiScaled(13);
-    int result = aeroOffset;
-    if (QSysInfo::WindowsVersion < QSysInfo::WV_WINDOWS8)
-        result += titleBarSize();
-    return result;
+    return aeroOffset + titleBarSize();
 }
 
 QT_END_NAMESPACE
diff --git a/src/gui/dialogs/qwizard_win_p.h b/src/gui/dialogs/qwizard_win_p.h
index ceb3bf4f8d..8d8ddb057d 100644
--- a/src/gui/dialogs/qwizard_win_p.h
+++ b/src/gui/dialogs/qwizard_win_p.h
@@ -112,8 +112,8 @@ private:
     bool drawTitleText(QPainter *painter, const QString &text, const QRect &rect, HDC hdc);
     static bool drawBlackRect(const QRect &rect, HDC hdc);
 
-    static int frameSize() { return GetSystemMetrics(SM_CYSIZEFRAME); }
-    static int captionSize() { return GetSystemMetrics(SM_CYCAPTION); }
+    static int frameSize();
+    static int captionSize();
 
     static int backButtonSize() { return int(QStyleHelper::dpiScaled(30)); }
     static int iconSize() { return 16; } // Standard Aero