Use symmetric functions when rounding. (#176)

Author: QuickStick123

src/Modules/Common.lua

@@ -649,6 +649,60 @@ function floor(val, dec)
 	end
 end
 
+-- Symmetric round with precision: Rounds towards zero to <dec> decimal places.
+function roundSymmetric(val, dec)
+    if dec then
+        local factor = 10 ^ dec
+        if val >= 0 then
+            return m_floor(val * factor + 0.5) / factor
+        else
+            return m_ceil(val * factor - 0.5) / factor
+        end
+    else
+        if val >= 0 then
+            return m_floor(val + 0.5)
+        else
+            return m_ceil(val - 0.5)
+        end
+    end
+end
+
+-- Symmetric floor with precision: Rounds down towards zero to <dec> decimal places.
+function floorSymmetric(val, dec)
+    if dec then
+        local factor = 10 ^ dec
+        if val >= 0 then
+            return m_floor(val * factor) / factor
+        else
+            return m_ceil(val * factor) / factor
+        end
+    else
+        if val >= 0 then
+            return m_floor(val)
+        else
+            return m_ceil(val)
+		end
+    end
+end
+
+-- Symmetric ceil with precision: Rounds up towards zero to <dec> decimal places.
+function ceilSymmetric(val, dec)
+    if dec then
+        local factor = 10 ^ dec
+        if val >= 0 then
+            return m_ceil(val * factor) / factor
+        else
+            return m_floor(val * factor) / factor
+        end
+    else
+        if val >= 0 then
+            return m_ceil(val)
+        else
+            return m_floor(val)
+        end
+    end
+end
+
 ---@param n number
 ---@return number
 function triangular(n)

src/Modules/ItemTools.lua

@@ -43,17 +43,17 @@ end
 -- precision is express a multiplier/divide and displayPrecision is expresed as decimal precision on rounding.
 -- ifRequired determines whether trailing zeros are displayed or not.
 function itemLib.formatValue(value, baseValueScalar, valueScalar, precision, displayPrecision, ifRequired)
-	value = round(value * precision) -- resolve range to internal value
-	if baseValueScalar and baseValueScalar ~= 1 then value = round(value * baseValueScalar) end -- apply corrupted mult
-	if valueScalar and valueScalar ~= 1 then value = m_floor(value * valueScalar) end -- apply modifier magnitude
+	value = roundSymmetric(value * precision) -- resolve range to internal value
+	if baseValueScalar and baseValueScalar ~= 1 then value = roundSymmetric(value * baseValueScalar) end -- apply corrupted mult
+	if valueScalar and valueScalar ~= 1 then value = floorSymmetric(value * valueScalar) end -- apply modifier magnitude
 	value = value / precision -- convert back to display space
-	if displayPrecision then value = round(value, displayPrecision) end -- presentation
+	if displayPrecision then value = roundSymmetric(value, displayPrecision) end -- presentation
 	if displayPrecision and not ifRequired then -- whitespace is needed
 		return string.format("%"..displayPrecision.."f", value)
 	elseif displayPrecision then
-		return tostring(round(value, displayPrecision))
+		return tostring(roundSymmetric(value, displayPrecision))
 	else
-		return tostring(round(value,  precision and m_min(2, m_floor(math.log(precision, 10))) or 2)) -- max decimals ingame is 2 
+		return tostring(roundSymmetric(value,  precision and m_min(2, m_floor(math.log(precision, 10))) or 2)) -- max decimals ingame is 2 
 	end
 end