Added background analysis in main menu for better readability.

Telegram/SourceFiles/window/window.style

@@ -128,6 +128,7 @@ mainMenu: Menu(defaultMenu) {
 	}
 	itemToggleShift: 11px;
 }
+mainMenuShadow: icon {{ "menu_shadow", windowShadowFg }};
 mainMenuNewGroup: icon {{ "menu_new_group", menuIconFg }};
 mainMenuNewGroupOver: icon {{ "menu_new_group", menuIconFgOver }};
 mainMenuNewChannel: icon {{ "menu_new_channel", menuIconFg }};

Telegram/SourceFiles/window/window_main_menu.cpp

@@ -33,6 +33,30 @@ https://github.com/telegramdesktop/tdesktop/blob/master/LEGAL
 #include "styles/style_settings.h"
 #include "styles/style_boxes.h"
 
+namespace {
+
+constexpr auto kMinDiffIntensity = 0.25;
+
+float64 IntensityOfColor(QColor color) {
+	return (0.299 * color.red()
+			+ 0.587 * color.green()
+			+ 0.114 * color.blue()) / 255.0;
+}
+
+bool IsShadowShown(const QImage &img, const QRect r, float64 intensityText) {
+	for (auto x = r.x(); x < r.x() + r.width(); x++) {
+		for (auto y = r.y(); y < r.y() + r.height(); y++) {
+			const auto intensity = IntensityOfColor(QColor(img.pixel(x, y)));
+			if ((std::abs(intensity - intensityText)) < kMinDiffIntensity) {
+				return true;
+			}
+		}
+	}
+	return false;
+}
+
+}
+
 namespace Window {
 
 class MainMenu::ResetScaleButton : public Ui::AbstractButton {
@@ -122,6 +146,7 @@ MainMenu::MainMenu(
 				Window::Theme::ToggleNightMode();
 				Window::Theme::KeepApplied();
 			}
+			refreshBackground();
 		}
 	});
 
@@ -130,6 +155,7 @@ MainMenu::MainMenu(
 		emit action->triggered();
 	});
 	refreshMenu();
+	refreshBackground();
 
 	_telegram->setRichText(textcmdLink(1, qsl("Telegram Desktop")));
 	_telegram->setLink(1, std::make_shared<UrlClickHandler>(qsl("https://desktop.telegram.org")));
@@ -148,6 +174,7 @@ MainMenu::MainMenu(
 	subscribe(Window::Theme::Background(), [this](const Window::Theme::BackgroundUpdate &update) {
 		if (update.type == Window::Theme::BackgroundUpdate::Type::ApplyingTheme) {
 			refreshMenu();
+			refreshBackground();
 		}
 	});
 	updatePhone();
@@ -220,6 +247,45 @@ void MainMenu::refreshMenu() {
 	updatePhone();
 }
 
+void MainMenu::refreshBackground() {
+	const auto fill = QRect(0, 0, width(), st::mainMenuCoverHeight);
+	const auto intensityText = IntensityOfColor(st::mainMenuCoverFg->c);
+	QImage backgroundImage(
+		st::mainMenuWidth * cIntRetinaFactor(),
+		st::mainMenuCoverHeight * cIntRetinaFactor(),
+		QImage::Format_ARGB32_Premultiplied);
+	QPainter p(&backgroundImage);
+
+	// Solid color.
+	if (const auto color = Window::Theme::Background()->colorForFill()) {
+		const auto intensity = IntensityOfColor(*color);
+		_isShadowShown = 
+			(std::abs(intensity - intensityText) < kMinDiffIntensity);
+		p.fillRect(fill, *color);
+		_background = backgroundImage;
+		return;
+	}
+
+	// Background image.
+	const auto &pixmap = Window::Theme::Background()->pixmap();
+	QRect to, from;
+	Window::Theme::ComputeBackgroundRects(fill, pixmap.size(), to, from);
+
+	p.drawPixmap(to, pixmap, from);
+	_background = backgroundImage;
+
+	// Cut off the part of the background that is under text.
+	const QRect underText(
+		st::mainMenuCoverTextLeft,
+		st::mainMenuCoverNameTop,
+		std::max(
+			st::semiboldFont->width(Auth().user()->nameText.toString()),
+			st::normalFont->width(_phoneText)),
+		st::semiboldFont->height * 2);
+
+	_isShadowShown = IsShadowShown(backgroundImage, underText, intensityText);
+}
+
 void MainMenu::resizeEvent(QResizeEvent *e) {
 	_menu->setForceWidth(width());
 	updateControlsGeometry();
@@ -248,25 +314,30 @@ void MainMenu::updatePhone() {
 void MainMenu::paintEvent(QPaintEvent *e) {
 	Painter p(this);
 	const auto clip = e->rect();
-	const auto fill = QRect(0, 0, width(), st::mainMenuCoverHeight);
-	const auto cover = fill.intersected(clip);
+	const auto cover = QRect(0, 0, width(), st::mainMenuCoverHeight)
+		.intersected(e->rect());
 
-	if (const auto color = Window::Theme::Background()->colorForFill()) {
-		p.fillRect(fill, *color);
-	} else {
+	if (!_background.isNull()) {
 		PainterHighQualityEnabler hq(p);
-
-		const auto &pix = Window::Theme::Background()->pixmap();
-		QRect to, from;
-		Window::Theme::ComputeBackgroundRects(fill, pix.size(), to, from);
-		p.drawPixmap(to, pix, from);
+		p.drawImage(0, 0, _background);
 	}
 
 	if (!cover.isEmpty()) {
 		const auto widthText = _cloudButton
 			? _cloudButton->x() - st::mainMenuCloudSize
 			: width() - 2 * st::mainMenuCoverTextLeft;
-		p.fillRect(cover, QColor(0, 0, 0, 51)); // 20% opacity.
+
+		if (_isShadowShown) {
+			st::mainMenuShadow.paint(
+				p,
+				0,
+				st::mainMenuCoverHeight - st::mainMenuShadow.height(),
+				st::mainMenuWidth,
+				IntensityOfColor(st::mainMenuCoverFg->c) < 0.5
+					? Qt::white
+					: Qt::black);
+		}
+
 		p.setPen(st::mainMenuCoverFg);
 		p.setFont(st::semiboldFont);
 		Auth().user()->nameText.drawLeftElided(

Telegram/SourceFiles/window/window_main_menu.h

@@ -38,6 +38,7 @@ private:
 	void updatePhone();
 	void initResetScaleButton();
 	void refreshMenu();
+	void refreshBackground();
 
 	class ResetScaleButton;
 	not_null<Controller*> _controller;
@@ -51,6 +52,8 @@ private:
 	base::Timer _nightThemeSwitch;
 
 	QString _phoneText;
+	QImage _background;
+	bool _isShadowShown = false;
 
 };