Fix the size calculation of QHeaderView when stylesheet is used

When calculating the header section size based on its contents when a
stylesheet is used, the size hints from the stylesheet are used. In case
if the stylesheet specifies only one of the sizes, the other is set to
-1. Because of this the actual content size is ignored.

The solution is to calculate the size based on the application style, in
case if it's not specified in the stylesheet.

Fixes: QTBUG-75615
Change-Id: I3453fa623d75b6b32832edf753de6e3e4e7f5a22
Reviewed-by: Frederik Gladhorn <frederik.gladhorn@qt.io>

1 files changed, 8 insertions, 0 deletions

diff --git a/src/widgets/styles/qstylesheetstyle.cpp b/src/widgets/styles/qstylesheetstyle.cpp
index 88c6c288e8..3f57992311 100644
--- a/src/widgets/styles/qstylesheetstyle.cpp
+++ b/src/widgets/styles/qstylesheetstyle.cpp
@@ -5035,6 +5035,14 @@ QSize QStyleSheetStyle::sizeFromContents(ContentsType ct, const QStyleOption *op
                 QRenderRule subRule = renderRule(w, opt, PseudoElement_HeaderViewSection);
                 if (subRule.hasGeometry() || subRule.hasBox() || !subRule.hasNativeBorder() || subRule.hasFont) {
                     sz = subRule.adjustSize(csz);
+                    if (!sz.isValid()) {
+                        // Try to set the missing values based on the base style.
+                        const auto baseSize = baseStyle()->sizeFromContents(ct, opt, sz, w);
+                        if (sz.width() < 0)
+                            sz.setWidth(baseSize.width());
+                        if (sz.height() < 0)
+                            sz.setHeight(baseSize.height());
+                    }
                     if (!subRule.hasGeometry()) {
                         QSize nativeContentsSize;
                         bool nullIcon = hdr->icon.isNull();