Adds disposal mailing units (again) (#7630)

Content.Client/Disposal/UI/PressureBar.cs

@@ -0,0 +1,54 @@
+using Content.Shared.Disposal;
+using Robust.Client.Graphics;
+using Robust.Client.UserInterface.Controls;
+using Robust.Shared.Timing;
+
+namespace Content.Client.Disposal.UI;
+
+public sealed class PressureBar : ProgressBar
+{
+    public bool UpdatePressure(TimeSpan fullTime)
+    {
+        var currentTime = IoCManager.Resolve<IGameTiming>().CurTime;
+        var pressure = (float) Math.Min(1.0f, 1.0f - (fullTime.TotalSeconds - currentTime.TotalSeconds) * SharedDisposalUnitSystem.PressurePerSecond);
+        UpdatePressureBar(pressure);
+        return pressure >= 1.0f;
+    }
+
+    private void UpdatePressureBar(float pressure)
+    {
+        Value = pressure;
+
+        var normalized = pressure / MaxValue;
+
+        const float leftHue = 0.0f; // Red
+        const float middleHue = 0.066f; // Orange
+        const float rightHue = 0.33f; // Green
+        const float saturation = 1.0f; // Uniform saturation
+        const float value = 0.8f; // Uniform value / brightness
+        const float alpha = 1.0f; // Uniform alpha
+
+        // These should add up to 1.0 or your transition won't be smooth
+        const float leftSideSize = 0.5f; // Fraction of _chargeBar lerped from leftHue to middleHue
+        const float rightSideSize = 0.5f; // Fraction of _chargeBar lerped from middleHue to rightHue
+
+        float finalHue;
+        if (normalized <= leftSideSize)
+        {
+            normalized /= leftSideSize; // Adjust range to 0.0 to 1.0
+            finalHue = MathHelper.Lerp(leftHue, middleHue, normalized);
+        }
+        else
+        {
+            normalized = (normalized - leftSideSize) / rightSideSize; // Adjust range to 0.0 to 1.0.
+            finalHue = MathHelper.Lerp(middleHue, rightHue, normalized);
+        }
+
+        // Check if null first to avoid repeatedly creating this.
+        ForegroundStyleBoxOverride ??= new StyleBoxFlat();
+
+        var foregroundStyleBoxOverride = (StyleBoxFlat) ForegroundStyleBoxOverride;
+        foregroundStyleBoxOverride.BackgroundColor =
+            Color.FromHsv(new Vector4(finalHue, saturation, value, alpha));
+    }
+}