Ensure contrast in critical theme parts.

Telegram/SourceFiles/codegen/style/generator.cpp

@@ -28,6 +28,11 @@ namespace {
 
 constexpr int kErrorBadIconSize     = 861;
 
+const auto kMustBeContrast = std::map<QString, QString>{
+	{ "dialogsMenuIconFg", "dialogsBg" },
+	{ "windowBoldFg", "windowBg" },
+};
+
 // crc32 hash, taken somewhere from the internet
 
 class Crc32Table {
@@ -797,6 +802,15 @@ void palette::finalize() {\n\
 	auto count = indexInPalette;
 	auto checksum = hashCrc32(checksumString.constData(), checksumString.size());
 
+	source_->stream() << "\n\n";
+	for (const auto &[over, under] : kMustBeContrast) {
+		const auto overIndex = paletteIndices_.find(over);
+		const auto underIndex = paletteIndices_.find(under);
+		if (overIndex == paletteIndices_.end() || underIndex == paletteIndices_.end()) {
+			return false;
+		}
+		source_->stream() << "\tinternal::EnsureContrast(*data(" << overIndex->second << "), *data(" << underIndex->second << "));\n";
+	}
 	source_->stream() << "\
 }\n\
 \n\

Telegram/SourceFiles/ui/style/style_core.cpp

@@ -11,6 +11,10 @@ namespace style {
 namespace internal {
 namespace {
 
+constexpr auto kMinContrastAlpha = 64;
+constexpr auto kMinContrastDistance = 64 * 64 * 4;
+constexpr auto kContrastDeltaL = 64;
+
 using ModulesList = QList<internal::ModuleBase*>;
 NeverFreedPointer<ModulesList> styleModules;
 
@@ -142,5 +146,51 @@ QImage createCircleMask(int size, QColor bg, QColor fg) {
 	return result;
 }
 
+[[nodiscard]] bool GoodForContrast(const QColor &c1, const QColor &c2) {
+	auto r1 = 0;
+	auto g1 = 0;
+	auto b1 = 0;
+	auto r2 = 0;
+	auto g2 = 0;
+	auto b2 = 0;
+	c1.getRgb(&r1, &g1, &b1);
+	c2.getRgb(&r2, &g2, &b2);
+	const auto rMean = (r1 + r2) / 2;
+	const auto r = r1 - r2;
+	const auto g = g1 - g2;
+	const auto b = b1 - b2;
+	const auto distance = (((512 + rMean) * r * r) >> 8)
+		+ (4 * g * g)
+		+ (((767 - rMean) * b * b) >> 8);
+	return (distance > kMinContrastDistance);
+}
+
+void EnsureContrast(ColorData &over, const ColorData &under) {
+	auto overH = 0;
+	auto overS = 0;
+	auto overL = 0;
+	auto overA = 0;
+	auto underH = 0;
+	auto underS = 0;
+	auto underL = 0;
+	over.c.getHsl(&overH, &overS, &overL, &overA);
+	under.c.getHsl(&underH, &underS, &underL);
+	const auto good = GoodForContrast(over.c, under.c);
+	if (overA >= kMinContrastAlpha && good) {
+		return;
+	}
+	const auto newA = std::max(overA, kMinContrastAlpha);
+	const auto newL = (overL > underL && overL + kContrastDeltaL <= 255)
+		? (overL + kContrastDeltaL)
+		: (overL < underL && overL - kContrastDeltaL >= 0)
+		? (overL - kContrastDeltaL)
+		: (underL > 128)
+		? (underL - kContrastDeltaL)
+		: (underL + kContrastDeltaL);
+	over.c = QColor::fromHsl(overH, overS, newL, newA).toRgb();
+	over.p = QPen(over.c);
+	over.b = QBrush(over.c);
+}
+
 } // namespace internal
 } // namespace style

Telegram/SourceFiles/ui/style/style_core.h

@@ -54,6 +54,8 @@ void unregisterModule(ModuleBase *module);
 // This method is implemented in palette.cpp (codegen).
 bool setPaletteColor(QLatin1String name, uchar r, uchar g, uchar b, uchar a);
 
+void EnsureContrast(ColorData &over, const ColorData &under);
+
 } // namespace internal
 
 void startManager();