Add some helpers for exact dpi painting.

CMakeLists.txt

@@ -35,6 +35,9 @@ PRIVATE
 
     qt_conf/win.qrc
 
+    ui/dpr/dpr_icon.cpp
+    ui/dpr/dpr_icon.h
+    ui/dpr/dpr_image.h
     ui/effects/animation_value.cpp
     ui/effects/animation_value.h
     ui/effects/animation_value_f.h

ui/dpr/dpr_icon.cpp

@@ -0,0 +1,32 @@
+// 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/dpr/dpr_icon.h"
+
+namespace dpr {
+
+QImage IconFrame(
+		const style::icon &icon,
+		const QColor &color,
+		double ratio) {
+	const auto scale = style::Scale() * ratio;
+	const auto use = (scale > 200. || style::DevicePixelRatio() > 2)
+		? (300 / style::DevicePixelRatio())
+		: (scale > 100.)
+		? (200 / style::DevicePixelRatio())
+		: (100 / style::DevicePixelRatio());
+	auto image = icon.instance(color, use);
+	image.setDevicePixelRatio(1.);
+	const auto desired = icon.size() * ratio;
+	return (image.size() == desired)
+		? image
+		: image.scaled(
+			desired,
+			Qt::IgnoreAspectRatio,
+			Qt::SmoothTransformation);
+}
+
+} // namespace dpr

ui/dpr/dpr_icon.h

@@ -0,0 +1,20 @@
+// 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
+//
+#pragma once
+
+#include "ui/style/style_core.h"
+
+class QImage;
+
+namespace dpr {
+
+[[nodiscard]] QImage IconFrame(
+	const style::icon &icon,
+	const QColor &color,
+	double ratio);
+
+} // namespace dpr

ui/dpr/dpr_image.h

@@ -0,0 +1,50 @@
+// 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
+//
+#pragma once
+
+#include <rpl/details/callable.h>
+
+#include <QtGui/QImage>
+#include <QtGui/QPainter>
+
+namespace dpr {
+
+// Validate(_cache, devicePixelRatioF(), size, [&](QPainter &p, QSize size) {
+//	... paint using p ...
+// }, (_cacheKey != cacheKey()), Qt::transparent);
+
+template <typename Generator>
+void Validate(
+		QImage &image,
+		double ratio,
+		QSize size,
+		Generator &&generator,
+		bool force,
+		std::optional<QColor> fill = {},
+		bool setResultRatio = true) {
+	size *= ratio;
+	const auto sizeChanged = (image.size() != size);
+	if (sizeChanged || force) {
+		if (sizeChanged) {
+			image = QImage(size, QImage::Format_ARGB32_Premultiplied);
+		}
+		if (fill) {
+			image.fill(*fill);
+		}
+		image.setDevicePixelRatio(1.);
+		auto p = QPainter(&image);
+		using namespace rpl::details;
+		if constexpr (is_callable_plain_v<Generator, QPainter&, QSize>) {
+			generator(p, size);
+		} else {
+			generator(p);
+		}
+	}
+	image.setDevicePixelRatio(setResultRatio ? ratio : 1.);
+}
+
+} // namespace dpr