init

Telegram/SourceFiles/ui/effects/scroll_content_shadow.cpp

@@ -0,0 +1,48 @@
+/*
+This file is part of Telegram Desktop,
+the official desktop application for the Telegram messaging service.
+
+For license and copyright information please follow this link:
+https://github.com/telegramdesktop/tdesktop/blob/master/LEGAL
+*/
+#include "ui/effects/scroll_content_shadow.h"
+
+#include "ui/rp_widget.h"
+#include "ui/widgets/scroll_area.h"
+#include "ui/wrap/fade_wrap.h"
+#include "ui/ui_utility.h"
+
+namespace Ui {
+
+void SetupShadowsToScrollContent(
+		not_null<Ui::RpWidget*> parent,
+		not_null<Ui::ScrollArea*> scroll,
+		rpl::producer<int> &&innerHeightValue) {
+	using namespace rpl::mappers;
+
+	const auto topShadow = Ui::CreateChild<Ui::FadeShadow>(parent.get());
+	const auto bottomShadow = Ui::CreateChild<Ui::FadeShadow>(parent.get());
+	scroll->geometryValue(
+	) | rpl::on_next_done([=](const QRect &geometry) {
+		topShadow->resizeToWidth(geometry.width());
+		topShadow->move(
+			geometry.x(),
+			geometry.y());
+		bottomShadow->resizeToWidth(geometry.width());
+		bottomShadow->move(
+			geometry.x(),
+			geometry.y() + geometry.height() - st::lineWidth);
+	}, [t = base::make_weak(topShadow), b = base::make_weak(bottomShadow)] {
+		Ui::DestroyChild(t.get());
+		Ui::DestroyChild(b.get());
+	}, topShadow->lifetime());
+
+	topShadow->toggleOn(scroll->scrollTopValue() | rpl::map(_1 > 0));
+	bottomShadow->toggleOn(rpl::combine(
+		scroll->scrollTopValue(),
+		scroll->heightValue(),
+		std::move(innerHeightValue),
+		_1 + _2 < _3));
+}
+
+} // namespace Ui