QFusionStyle: fix the checkbox rendering in HiDPI situation

1. Make the checkbox's box size hidpi scale-able. Making the size
not only anchored to icon size, but also the menuItem's rect height
in empty or too small icon cases.

2. Make the checkmark's pen width in propotion to the box's size
to keep consistent visual effects among different dpi settings

3. Also make the radio button hidpi scale-able.

Task-number: QTBUG-63576
Change-Id: I4369aaa18ee68908a26a118cf04292ee4c3e9847
Reviewed-by: Richard Moe Gustavsen <richard.gustavsen@qt.io>

src/widgets/styles/qfusionstyle.cpp

@@ -786,7 +786,7 @@ void QFusionStyle::drawPrimitive(PrimitiveElement elem,
             painter->drawRect(rect);
 
             QColor checkMarkColor = option->palette.text().color().darker(120);
-            const int checkMarkPadding = QStyleHelper::dpiScaled(3);
+            const int checkMarkPadding = 1 + rect.width() * 0.2; // at least one pixel padding
 
             if (checkbox->state & State_NoChange) {
                 gradient = QLinearGradient(rect.topLeft(), rect.bottomLeft());
@@ -800,18 +800,20 @@ void QFusionStyle::drawPrimitive(PrimitiveElement elem,
                 painter->drawRect(rect.adjusted(checkMarkPadding, checkMarkPadding, -checkMarkPadding, -checkMarkPadding));
 
             } else if (checkbox->state & (State_On)) {
-                QPen checkPen = QPen(checkMarkColor, QStyleHelper::dpiScaled(1.8));
+                qreal penWidth = QStyleHelper::dpiScaled(1.8);
+                penWidth = qMax(penWidth , 0.18 * rect.height());
+                penWidth = qMin(penWidth , 0.30 * rect.height());
+                QPen checkPen = QPen(checkMarkColor, penWidth);
                 checkMarkColor.setAlpha(210);
-                painter->translate(-1, 0.5);
+                painter->translate(-0.8, 0.5);
                 painter->setPen(checkPen);
                 painter->setBrush(Qt::NoBrush);
-                painter->translate(0.2, 0.0);
 
                 // Draw checkmark
                 QPainterPath path;
-                path.moveTo(2 + checkMarkPadding, rect.height() / 2.0);
+                path.moveTo(1.33 * checkMarkPadding, rect.height() / 2.0);
                 path.lineTo(rect.width() / 2.0, rect.height() - checkMarkPadding);
-                path.lineTo(rect.width() - checkMarkPadding - 0.5, checkMarkPadding);
+                path.lineTo(rect.width() - checkMarkPadding * 0.92, checkMarkPadding);
                 painter->drawPath(path.translated(rect.topLeft()));
             }
         }
@@ -1580,8 +1582,9 @@ void QFusionStyle::drawControl(ControlElement element, const QStyleOption *optio
             bool enabled = menuItem->state & State_Enabled;
 
             bool ignoreCheckMark = false;
-            int checkcol = qMax(menuItem->maxIconWidth, 20);
-
+            const int checkColHOffset = windowsItemHMargin + windowsItemFrame - 1;
+            int checkcol = qMax(menuItem->rect.height() * 0.7,
+                                      qMax(menuItem->maxIconWidth * 1.0, dpiScaled(17))); // icon checkbox's highlihgt column width
             if (
 #if QT_CONFIG(combobox)
                 qobject_cast<const QComboBox*>(widget) ||
@@ -1591,7 +1594,9 @@ void QFusionStyle::drawControl(ControlElement element, const QStyleOption *optio
 
             if (!ignoreCheckMark) {
                 // Check
-                QRect checkRect(option->rect.left() + 7, option->rect.center().y() - 6, 14, 14);
+                const int boxMargin = dpiScaled(4);
+                const int boxWidth = checkcol - 2 * boxMargin;
+                QRect checkRect(option->rect.left() + boxMargin + checkColHOffset, option->rect.center().y() - boxWidth/2 + 1, boxWidth, boxWidth);
                 checkRect = visualRect(menuItem->direction, menuItem->rect, checkRect);
                 if (checkable) {
                     if (menuItem->checkType & QStyleOptionMenuItem::Exclusive) {
@@ -1603,7 +1608,8 @@ void QFusionStyle::drawControl(ControlElement element, const QStyleOption *optio
                             QPalette::ColorRole textRole = !enabled ? QPalette::Text:
                                                                       selected ? QPalette::HighlightedText : QPalette::ButtonText;
                             painter->setBrush(option->palette.brush( option->palette.currentColorGroup(), textRole));
-                            painter->drawEllipse(checkRect.adjusted(4, 4, -4, -4));
+                            const int adjustment = checkRect.height() * 0.3;
+                            painter->drawEllipse(checkRect.adjusted(adjustment, adjustment, -adjustment, -adjustment));
                         }
                     } else {
                         // Check box
@@ -1632,7 +1638,7 @@ void QFusionStyle::drawControl(ControlElement element, const QStyleOption *optio
 
             QPainter *p = painter;
             QRect vCheckRect = visualRect(opt->direction, menuitem->rect,
-                                          QRect(menuitem->rect.x() + 4, menuitem->rect.y(),
+                                          QRect(menuitem->rect.x() + checkColHOffset, menuitem->rect.y(),
                                                 checkcol, menuitem->rect.height()));
             if (!menuItem->icon.isNull()) {
                 QIcon::Mode mode = dis ? QIcon::Disabled : QIcon::Normal;
@@ -1683,7 +1689,7 @@ void QFusionStyle::drawControl(ControlElement element, const QStyleOption *optio
                 discol = menuitem->palette.text().color();
                 p->setPen(discol);
             }
-            int xm = windowsItemFrame + checkcol + windowsItemHMargin + 2;
+            int xm = checkColHOffset + checkcol + windowsItemHMargin;
             int xpos = menuitem->rect.x() + xm;
 
             QRect textRect(xpos, y + windowsItemVMargin, w - xm - windowsRightBorder - tab + 1, h - 2 * windowsItemVMargin);