From 01ec11507d7ef3de09bad9d1ef8e6d4a3d6c4428 Mon Sep 17 00:00:00 2001
From: Richard Moe Gustavsen <richard.gustavsen@qt.io>
Date: Thu, 10 Oct 2019 14:33:53 +0200
Subject: QStyleSheetStyle: add new property to QPushButton: icon
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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>
---
 src/gui/text/qcssparser.cpp | 32 ++++++++++++++++++++++++++++++++
 src/gui/text/qcssparser_p.h |  2 ++
 2 files changed, 34 insertions(+)

(limited to 'src/gui')

diff --git a/src/gui/text/qcssparser.cpp b/src/gui/text/qcssparser.cpp
index ce7c7610c1..793ef5774b 100644
--- a/src/gui/text/qcssparser.cpp
+++ b/src/gui/text/qcssparser.cpp
@@ -123,6 +123,7 @@ static const QCssKnownValue properties[NumProperties - 1] = {
     { "font-variant", FontVariant },
     { "font-weight", FontWeight },
     { "height", Height },
+    { "icon", QtIcon },
     { "image", QtImage },
     { "image-position", QtImageAlignment },
     { "left", Left },
@@ -1379,6 +1380,37 @@ bool ValueExtractor::extractImage(QIcon *icon, Qt::Alignment *a, QSize *size)
     return hit;
 }
 
+bool ValueExtractor::extractIcon(QIcon *icon, QSize *size)
+{
+    // Find last declaration that specifies an icon
+    const auto declaration = std::find_if(
+                declarations.rbegin(), declarations.rend(),
+                [](const Declaration &decl) { return decl.d->propertyId == QtIcon; });
+    if (declaration == declarations.rend())
+        return false;
+
+    *icon = declaration->iconValue();
+
+    // If the value contains a URI, try to get the size of the icon
+    if (declaration->d->values.isEmpty())
+        return true;
+
+    const auto &propertyValue = declaration->d->values.constFirst();
+    if (propertyValue.type != Value::Uri)
+        return true;
+
+    // First try to read just the size from the image without loading it
+    const QString url(propertyValue.variant.toString());
+    QImageReader imageReader(url);
+    *size = imageReader.size();
+    if (!size->isNull())
+        return true;
+
+    // Get the size by loading the image instead
+    *size = imageReader.read().size();
+    return true;
+}
+
 ///////////////////////////////////////////////////////////////////////////////
 // Declaration
 QColor Declaration::colorValue(const QPalette &pal) const
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);
 
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