QStyleSheetStyle: add new property to QPushButton: icon

There is currently no proper way to change the icon of a
pushbutton from css. But there is a need for doing so
(QTBUG-2982), and the typical work-around is to instead use
the css property 'qproperty-icon'. But setting qproperties
from the style is not a good idea in the first place, since
it modifies the state of the widget it draws. Moreover, such
properties are only set once (in QStyle::polish()), and
will not have any effect on pseudo states, like hover.

To close this gap, this patch will add a css property
'icon' that can be set on a QPushButton. This property
will follow normal css cascading, and respect pseudo
states, equal to any other css property.

[ChangeLog][QtWidgets][QStyle] You can now set the
CSS property 'icon' on a QPushButton to override
which icon to draw.

Fixes: QTBUG-79137
Change-Id: Ie7e0b0fa4f19471f51108cd4ca931356219d562e
Reviewed-by: Christian Ehrlicher <ch.ehrlicher@gmx.de>
Reviewed-by: Jan Arve Sæther <jan-arve.saether@qt.io>

1 files changed, 2 insertions, 0 deletions

diff --git a/src/gui/text/qcssparser_p.h b/src/gui/text/qcssparser_p.h
index ab85e76cf3..b8bf259dda 100644
--- a/src/gui/text/qcssparser_p.h
+++ b/src/gui/text/qcssparser_p.h
@@ -198,6 +198,7 @@ enum Property {
     QtLineHeightType,
     FontKerning,
     QtForegroundTextureCacheKey,
+    QtIcon,
     NumProperties
 };
 
@@ -855,6 +856,7 @@ struct Q_GUI_EXPORT ValueExtractor
     bool extractPalette(QBrush *fg, QBrush *sfg, QBrush *sbg, QBrush *abg);
     int  extractStyleFeatures();
     bool extractImage(QIcon *icon, Qt::Alignment *a, QSize *size);
+    bool extractIcon(QIcon *icon, QSize *size);
 
     int lengthValue(const Declaration &decl);