main, refresh_rate.h: add support for passing decimal refresh rates t…

…o gamescope thru the command line (-r, -o)

src/main.cpp

@@ -541,6 +541,29 @@ static bool IsInDebugSession()
 	return nTracePid != 0;
 }
 #endif
+namespace gamescope {
+	static int32_t ConvertHztomHz( char* refreshHz ) {
+		std::vector svParts = Split(refreshHz, ".,");
+
+		size_t ulWholeNumLen = svParts[0].size();
+		if (svParts.size() > 1)
+			refreshHz[ulWholeNumLen] = '\0'; //replace the decimal separator with null terminator, so that atol can be used
+		uint64_t ulWholeNum = (uint64_t) atol(refreshHz);
+
+		std::array<uint64_t, 2> decimalParts = [svParts]() -> std::array<uint64_t, 2> {
+			if (svParts.size()>1)
+				return {(uint64_t)atol(svParts[1].data()), (uint64_t)svParts[1].size()};
+			return {0ul, 1ul};
+		}();
+		const uint64_t ulDec = decimalParts[0], ulDecLen = decimalParts[1];
+
+		uint64_t ulDecDenom = (uint64_t)lrintf(powf(10.0f, (int32_t)ulDecLen));
+		uint64_t ulMultiplied = ulWholeNum * 1'000lu * ulDecDenom + ulDec * 1'000lu; //don't divide the decimal part by its denominator(/number of decimal places) first, instead multiply the wholeNum by the number of decimal places, and then divide the result of adding the multiplied wholeNum & decimal parts.
+
+		//This, along with doing all intermediate calculations w/ 64-bit unsigned ints, ensures there's no precision loss.
+		return (int32_t)(ulMultiplied/ulDecDenom);
+	}
+}
 
 bool steamMode = false;
 bool g_bLaunchMangoapp = false;
@@ -684,7 +707,7 @@ int main(int argc, char **argv)
 				g_nNestedHeight = atoi( optarg );
 				break;
 			case 'r':
-				g_nNestedRefresh = gamescope::ConvertHztomHz( atoi( optarg ) );
+				g_nNestedRefresh = gamescope::ConvertHztomHz( optarg );
 				break;
 			case 'W':
 				g_nPreferredOutputWidth = atoi( optarg );
@@ -693,7 +716,7 @@ int main(int argc, char **argv)
 				g_nPreferredOutputHeight = atoi( optarg );
 				break;
 			case 'o':
-				g_nNestedUnfocusedRefresh = gamescope::ConvertHztomHz( atoi( optarg ) );
+				g_nNestedUnfocusedRefresh = gamescope::ConvertHztomHz( optarg );
 				break;
 			case 'm':
 				g_flMaxWindowScale = atof( optarg );

src/refresh_rate.h

@@ -4,6 +4,9 @@
 
 namespace gamescope
 {
+    int32_t ConvertHztomHz( const char* refreshHz ); //function definition in main.cpp
+    //function definition not included here, because having the function definition here gave me linker errors - sharkautarch
+
     constexpr int32_t ConvertHztomHz( int32_t nRefreshHz )
     {
         return nRefreshHz * 1'000;