Added util for calculating of intermediate gradient value.

CMakeLists.txt

@@ -47,6 +47,7 @@ PRIVATE
     ui/effects/cross_line.h
     ui/effects/fade_animation.cpp
     ui/effects/fade_animation.h
+    ui/effects/gradient.cpp
     ui/effects/gradient.h
     ui/effects/numbers_animation.cpp
     ui/effects/numbers_animation.h

ui/effects/gradient.cpp

@@ -0,0 +1,28 @@
+// This file is part of Desktop App Toolkit,
+// a set of libraries for developing nice desktop applications.
+//
+// For license and copyright information please follow this link:
+// https://github.com/desktop-app/legal/blob/master/LEGAL
+//
+#include "ui/effects/gradient.h"
+
+namespace anim {
+
+QColor gradient_color_at(const QGradient &gradient, float64 ratio) {
+	const auto &stops = gradient.stops();
+
+	for (auto i = 1; i < stops.size(); i++) {
+		const auto currentPoint = stops[i].first;
+		const auto previousPoint = stops[i - 1].first;
+
+		if ((ratio <= currentPoint) && (ratio >= previousPoint)) {
+			return anim::color(
+				stops[i - 1].second,
+				stops[i].second,
+				(ratio - previousPoint) / (currentPoint - previousPoint));
+		}
+	}
+	return QColor();
+}
+
+} // namespace anim

ui/effects/gradient.h

@@ -14,6 +14,10 @@
 
 namespace anim {
 
+[[nodiscard]] QColor gradient_color_at(
+	const QGradient &gradient,
+	float64 ratio);
+
 struct gradient_colors {
 	explicit gradient_colors(QColor color) {
 		stops.push_back({ 0., color });