Introduce a QVariant themeHint() to QPlatformTheme.

Start on removing platform-specific code from QtWidgets.

Change-Id: Ic2163a0ce6f2db2151cdf7ca93766b2d861eeb55
Reviewed-by: Samuel Rødal <samuel.rodal@nokia.com>

src/gui/kernel/qplatformtheme_qpa.cpp

@@ -41,8 +41,36 @@
 
 #include "qplatformtheme_qpa.h"
 
+#include <QtCore/QVariant>
+
 QT_BEGIN_NAMESPACE
 
+/*!
+    \class QPlatformTheme
+    \since 5.0
+    \internal
+    \preliminary
+    \ingroup qpa
+    \brief The QPlatformTheme class allows customizing the UI based on themes.
+
+*/
+
+/*!
+    \enum QPlatformTheme::ThemeHint
+
+    This enum describes the available theme hints.
+
+    \value TextCursorWidth  (int) Determines the width of the text cursor.
+
+    \value DropShadow       (bool) Determines whether the drop shadow effect for
+                            tooltips or whatsthis is enabled.
+
+    \value MaximumScrollBarDragDistance (int) Determines the value returned by
+                            QStyle::pixelMetric(PM_MaximumDragDistance)
+
+    \sa themeHint(), QStyle::pixelMetric()
+*/
+
 QPlatformMenu *QPlatformTheme::createPlatformMenu(QMenu *menu) const
 {
     Q_UNUSED(menu);
@@ -67,4 +95,17 @@ QPlatformDialogHelper *QPlatformTheme::createPlatformDialogHelper(QDialog *dialo
     return 0;
 }
 
+QVariant QPlatformTheme::themeHint(ThemeHint hint) const
+{
+    switch (hint) {
+    case TextCursorWidth:
+        return QVariant(1);
+    case DropShadow:
+        return QVariant(false);
+    case MaximumScrollBarDragDistance:
+        return QVariant(-1);
+    }
+    return QVariant();
+}
+
 QT_END_NAMESPACE

src/gui/kernel/qplatformtheme_qpa.h

@@ -56,15 +56,24 @@ class QPlatformMenu;
 class QPlatformMenuBar;
 class QPlatformDialogHelper;
 class QDialog;
+class QVariant;
 
 class Q_GUI_EXPORT QPlatformTheme
 {
 public:
+    enum ThemeHint {
+        TextCursorWidth,
+        DropShadow,
+        MaximumScrollBarDragDistance
+    };
+
     virtual QPlatformMenu *createPlatformMenu(QMenu *menu = 0) const;
     virtual QPlatformMenuBar *createPlatformMenuBar(QMenuBar *menuBar = 0) const;
 
     virtual bool usePlatformNativeDialog(const QDialog *dialog = 0) const;
     virtual QPlatformDialogHelper *createPlatformDialogHelper(QDialog *dialog = 0) const;
+
+    virtual QVariant themeHint(ThemeHint hint) const;
 };
 
 QT_END_NAMESPACE

src/plugins/platforms/windows/qwindowstheme.cpp

@@ -41,13 +41,46 @@
 
 #include "qwindowstheme.h"
 #include "qwindowsdialoghelpers.h"
+#include "qwindowscontext.h"
+#include "qt_windows.h"
+
+#include <QtCore/QVariant>
 
 QT_BEGIN_NAMESPACE
 
+static inline bool booleanSystemParametersInfo(UINT what, bool defaultValue)
+{
+    BOOL result;
+    if (SystemParametersInfo(what, 0, &result, 0))
+        return result ? true : false;
+    return defaultValue;
+}
+
+static inline bool dWordSystemParametersInfo(UINT what, DWORD defaultValue)
+{
+    DWORD result;
+    if (SystemParametersInfo(what, 0, &result, 0))
+        return result;
+    return defaultValue;
+}
+
 QWindowsTheme::QWindowsTheme()
 {
 }
 
+QVariant QWindowsTheme::themeHint(ThemeHint hint) const
+{
+    switch (hint) {
+    case TextCursorWidth:
+        return QVariant(int(dWordSystemParametersInfo(SPI_GETCARETWIDTH, 1u)));
+    case DropShadow:
+        return QVariant(booleanSystemParametersInfo(SPI_GETDROPSHADOW, false));
+    case MaximumScrollBarDragDistance:
+        return QVariant(qRound(qreal(QWindowsContext::instance()->defaultDPI()) * 1.375));
+    }
+    return QVariant();
+}
+
 bool QWindowsTheme::usePlatformNativeDialog(const QDialog *dialog) const
 {
     return QWindowsDialogs::useHelper(dialog);

src/plugins/platforms/windows/qwindowstheme.h

@@ -53,6 +53,7 @@ public:
 
     virtual bool usePlatformNativeDialog(const QDialog *dialog = 0) const;
     virtual QPlatformDialogHelper *createPlatformDialogHelper(QDialog *dialog = 0) const;
+    virtual QVariant themeHint(ThemeHint) const;
 };
 
 QT_END_NAMESPACE

src/widgets/kernel/qwhatsthis.cpp

@@ -43,6 +43,7 @@
 #ifndef QT_NO_WHATSTHIS
 #include "qpointer.h"
 #include "qapplication.h"
+#include <private/qguiapplication_p.h>
 #include "qdesktopwidget.h"
 #include "qevent.h"
 #include "qpixmap.h"
@@ -59,12 +60,6 @@
 #ifndef QT_NO_ACCESSIBILITY
 #include "qaccessible.h"
 #endif
-#if defined(Q_WS_WIN)
-#include "qt_windows.h"
-#ifndef SPI_GETDROPSHADOW
-#define SPI_GETDROPSHADOW                   0x1024
-#endif
-#endif
 
 QT_BEGIN_NAMESPACE
 
@@ -221,15 +216,9 @@ QWhatsThat::QWhatsThat(const QString& txt, QWidget* parent, QWidget *showTextFor
                                         + Qt::TextWordWrap + Qt::TextExpandTabs,
                                         text);
     }
-#if defined(Q_WS_WIN)
-    if ((QSysInfo::WindowsVersion >= QSysInfo::WV_XP
-        && QSysInfo::WindowsVersion < QSysInfo::WV_NT_based))
-    {
-        BOOL shadow;
-        SystemParametersInfo(SPI_GETDROPSHADOW, 0, &shadow, 0);
-        shadowWidth = shadow ? 0 : 6;
-    }
-#endif
+    shadowWidth =
+        QGuiApplicationPrivate::platformTheme()->themeHint(QPlatformTheme::DropShadow).toBool() ?
+        0 : 6;
     resize(r.width() + 2*hMargin + shadowWidth, r.height() + 2*vMargin + shadowWidth);
 }
 

src/widgets/styles/qcommonstyle.cpp

@@ -44,6 +44,7 @@
 
 #include <qfile.h>
 #include <qapplication.h>
+#include <private/qguiapplication_p.h>
 #include <qbitmap.h>
 #include <qcache.h>
 #include <qdockwidget.h>
@@ -72,6 +73,7 @@
 #include <qfileinfo.h>
 #include <qdir.h>
 #include <qsettings.h>
+#include <qvariant.h>
 #include <qpixmapcache.h>
 #include <private/qguiplatformplugin_p.h>
 
@@ -4313,7 +4315,7 @@ int QCommonStyle::pixelMetric(PixelMetric m, const QStyleOption *opt, const QWid
         break;
 #endif
     case PM_MaximumDragDistance:
-        ret = -1;
+        ret = QGuiApplicationPrivate::platformTheme()->themeHint(QPlatformTheme::MaximumScrollBarDragDistance).toInt();
         break;
 
 #ifndef QT_NO_SLIDER
@@ -4550,7 +4552,7 @@ int QCommonStyle::pixelMetric(PixelMetric m, const QStyleOption *opt, const QWid
         }
         break;
     case PM_TextCursorWidth:
-        ret = 1;
+        ret = QGuiApplicationPrivate::platformTheme()->themeHint(QPlatformTheme::TextCursorWidth).toInt();
         break;
     case PM_TabBar_ScrollButtonOverlap:
         ret = 1;

src/widgets/styles/qwindowsstyle.cpp

@@ -392,16 +392,9 @@ int QWindowsStyle::pixelMetric(PixelMetric pm, const QStyleOption *opt, const QW
         break;
 #endif
     case PM_MaximumDragDistance:
-#if defined(Q_OS_WIN)
-        {
-            HDC hdcScreen = GetDC(0);
-            int dpi = GetDeviceCaps(hdcScreen, LOGPIXELSX);
-            ReleaseDC(0, hdcScreen);
-            ret = (int)(dpi * 1.375);
-        }
-#else
-        ret = 60;
-#endif
+        ret = QCommonStyle::pixelMetric(PM_MaximumDragDistance);
+        if (ret == -1)
+            ret = 60;
         break;
 
 #ifndef QT_NO_SLIDER
@@ -530,13 +523,6 @@ int QWindowsStyle::pixelMetric(PixelMetric pm, const QStyleOption *opt, const QW
         ret = GetSystemMetrics(SM_CYFRAME);
 #endif
         break;
-    case PM_TextCursorWidth: {
-        DWORD caretWidth = 1;
-#if defined(SPI_GETCARETWIDTH)
-        SystemParametersInfo(SPI_GETCARETWIDTH, 0, &caretWidth, 0);
-#endif
-        ret = (int)caretWidth;
-        break; }
 #endif
     case PM_ToolBarItemMargin:
         ret = 1;