feat(SvgButton): Allow custom color (#6268)

src/widgets/buttons/SvgButton.cpp

@@ -23,6 +23,12 @@ void SvgButton::setSource(Src source)
     this->invalidateContent();
 }
 
+void SvgButton::setColor(std::optional<QColor> color)
+{
+    this->color_ = color;
+    this->invalidateContent();
+}
+
 void SvgButton::setPadding(QSize padding)
 {
     if (this->padding_ == padding)
@@ -65,7 +71,22 @@ void SvgButton::paintContent(QPainter &painter)
     QSize actualPadding = this->scale() * this->padding_;
     QPoint topLeft{actualPadding.width(), actualPadding.height()};
     QSize contentSize = this->size() - 2 * actualPadding;
-    this->svg_->render(&painter, {topLeft, contentSize});
+    auto bounds = QRectF{topLeft, contentSize};
+    this->svg_->render(&painter, bounds);
+
+    if (this->color_.has_value())
+    {
+        painter.save();
+
+        // Set the composition mode so that the upcoming color fill only applies the color
+        // on top of the pre-existing SVG contents
+        //
+        // More info on how the composition modes work can be found here: https://doc.qt.io/qt-6/qpainter.html#CompositionMode-enum
+        painter.setCompositionMode(QPainter::CompositionMode_SourceIn);
+        painter.fillRect(bounds, *this->color_);
+
+        painter.restore();
+    }
 }
 
 QString SvgButton::currentSvgPath() const

src/widgets/buttons/SvgButton.hpp

@@ -2,8 +2,11 @@
 
 #include "widgets/buttons/Button.hpp"
 
+#include <QColor>
 #include <QString>
 
+#include <optional>
+
 class QSvgRenderer;
 
 namespace chatterino {
@@ -41,6 +44,13 @@ public:
     /// Setter for #source()
     void setSource(Src source);
 
+    /// Sets a custom color to render over the SVG.
+    /// This allows you to change the color of a button to a solid color
+    /// of your choice without using multiple SVG resources.
+    ///
+    /// Set to std::nullopt to not override the color.
+    void setColor(std::optional<QColor> color);
+
     /// @brief Returns the padding inside the button.
     ///
     /// `width` is the padding applied horizontally (left and right).
@@ -65,6 +75,7 @@ private:
     Src source_;
     QSvgRenderer *svg_;
     QSize padding_;
+    std::optional<QColor> color_;
 };
 
 }  // namespace chatterino