URenderPipeline: Fix rendering being affected by global glShadeModel state

The `glShadeModel` state is initially `GL_SMOOTH`, but other code may
change it to `GL_FLAT` and if it doesn't change it back afterwards,
users of `URenderPipeline` may not get the expected render result (e.g.
trying to draw a gradient will result in a single flat color instead).

The chance of some user of `URenderPipeline` intentionally relying on
this global state leaking in feels sufficiently low, that I don't think
any backwards compatibility needs to be maintained for it.
I don't think it is even necessary to make this behavior configurable,
since we don't allow a single vertex to be shared by multiple
primitives, so anything which could be achieved by using GL_FLAT can
also by achieved by simply using the same data for all vertices of each
primitive. And modern OpenGL doesn't support it anyway.

GitHub: #116

Author: Johni0702

src/main/kotlin/gg/essential/universal/render/ManagedGlState.kt

@@ -23,6 +23,7 @@ internal class ManagedGlState(
     var polygonOffset: Boolean,
     var polygonOffsetFactor: Float,
     var polygonOffsetUnits: Float,
+    var shadeModel: Int,
     var alphaTest: Boolean,
     var alphaTestFunc: Int,
     var alphaTestRef: Float,
@@ -40,6 +41,7 @@ internal class ManagedGlState(
         polygonOffset = other.polygonOffset,
         polygonOffsetFactor = other.polygonOffsetFactor,
         polygonOffsetUnits = other.polygonOffsetUnits,
+        shadeModel = other.shadeModel,
         alphaTest = other.alphaTest,
         alphaTestFunc = other.alphaTestFunc,
         alphaTestRef = other.alphaTestRef,
@@ -160,6 +162,10 @@ internal class ManagedGlState(
         //#if MC>=11700
         //$$ @Suppress("UNUSED_VARIABLE") val unused = org
         //#else
+        if (curr.shadeModel != shadeModel) {
+            curr.shadeModel = shadeModel
+            GlStateManager.shadeModel(shadeModel)
+        }
         if (curr.alphaTest != alphaTest) {
             curr.alphaTest = alphaTest
             //#if MC==11602
@@ -212,10 +218,12 @@ internal class ManagedGlState(
             polygonOffsetFactor = GL11.glGetFloat(GL11.GL_POLYGON_OFFSET_FACTOR),
             polygonOffsetUnits = GL11.glGetFloat(GL11.GL_POLYGON_OFFSET_UNITS),
             //#if MC>=11700
+            //$$ shadeModel = 0,
             //$$ alphaTest = false,
             //$$ alphaTestFunc = 0,
             //$$ alphaTestRef = 0f,
             //#else
+            shadeModel = GL11.glGetInteger(GL11.GL_SHADE_MODEL),
             alphaTest = GL11.glGetBoolean(GL11.GL_ALPHA_TEST),
             alphaTestFunc = GL11.glGetInteger(GL11.GL_ALPHA_TEST_FUNC),
             alphaTestRef = GL11.glGetFloat(GL11.GL_ALPHA_TEST_REF),

src/main/kotlin/gg/essential/universal/render/URenderPipeline.kt

@@ -465,6 +465,7 @@ class URenderPipeline private constructor(
                     polygonOffset = polygonOffset.first != 0f || polygonOffset.second != 0f,
                     polygonOffsetFactor = polygonOffset.first,
                     polygonOffsetUnits = polygonOffset.second,
+                    shadeModel = GL11.GL_SMOOTH,
                     alphaTest = true,
                     alphaTestFunc = GL11.GL_ALWAYS,
                     alphaTestRef = 0f,