- renamed FTexture's UseType flags and gave them a dedicated type.

This was done mainly to reduce the amount of occurences of the word FTexture but it immediately helped detect two small and mostly harmless bugs that were found due to the stricter type checks.

src/polyrenderer/scene/poly_decal.cpp

@@ -50,7 +50,7 @@ void RenderPolyDecal::Render(PolyRenderThread *thread, const TriMatrix &worldToC
 		return;
 
 	FTexture *tex = TexMan(decal->PicNum, true);
-	if (tex == nullptr || tex->UseType == FTexture::TEX_Null)
+	if (tex == nullptr || tex->UseType == ETextureType::Null)
 		return;
 
 	sector_t *front, *back;

src/polyrenderer/scene/poly_plane.cpp

@@ -67,7 +67,7 @@ void RenderPolyPlane::RenderNormal(PolyRenderThread *thread, const TriMatrix &wo
 	if (picnum != skyflatnum)
 	{
 		FTexture *tex = TexMan(picnum);
-		if (!tex || tex->UseType == FTexture::TEX_Null)
+		if (!tex || tex->UseType == ETextureType::Null)
 			return;
 
 		PolyPlaneUVTransform transform = PolyPlaneUVTransform(ceiling ? fakeflat.FrontSector->planes[sector_t::ceiling].xform : fakeflat.FrontSector->planes[sector_t::floor].xform, tex);
@@ -516,7 +516,7 @@ void Render3DFloorPlane::Render(PolyRenderThread *thread, const TriMatrix &world
 {
 	FTextureID picnum = ceiling ? *fakeFloor->bottom.texture : *fakeFloor->top.texture;
 	FTexture *tex = TexMan(picnum);
-	if (tex->UseType == FTexture::TEX_Null)
+	if (tex->UseType == ETextureType::Null)
 		return;
 
 	PolyCameraLight *cameraLight = PolyCameraLight::Instance();

src/polyrenderer/scene/poly_playersprite.cpp

@@ -224,7 +224,7 @@ void RenderPolyPlayerSprites::RenderSprite(PolyRenderThread *thread, DPSprite *p
 	flip = sprframe->Flip & 1;
 	tex = TexMan(picnum);
 
-	if (tex->UseType == FTexture::TEX_Null)
+	if (tex->UseType == ETextureType::Null)
 		return;
 
 	if (pspr->firstTic)

src/polyrenderer/scene/poly_sky.cpp

@@ -342,7 +342,7 @@ void PolySkySetup::Update()
 		}
 
 		frontskytex = TexMan(s->GetTexture(pos), true);
-		if (frontskytex == nullptr || frontskytex->UseType == FTexture::TEX_Null)
+		if (frontskytex == nullptr || frontskytex->UseType == ETextureType::Null)
 		{ // [RH] The blank texture: Use normal sky instead.
 			goto sky1;
 		}

src/polyrenderer/scene/poly_sprite.cpp

@@ -104,7 +104,7 @@ void RenderPolySprite::Render(PolyRenderThread *thread, const TriMatrix &worldTo
 
 	bool flipTextureX = false;
 	FTexture *tex = GetSpriteTexture(thing, flipTextureX);
-	if (tex == nullptr || tex->UseType == FTexture::TEX_Null)
+	if (tex == nullptr || tex->UseType == ETextureType::Null)
 		return;
 
 	double thingyscalemul = thing->Scale.Y / tex->Scale.Y;
@@ -315,7 +315,7 @@ FTexture *RenderPolySprite::GetSpriteTexture(AActor *thing, /*out*/ bool &flipX)
 	if (thing->picnum.isValid())
 	{
 		FTexture *tex = TexMan(thing->picnum);
-		if (tex->UseType == FTexture::TEX_Null)
+		if (tex->UseType == ETextureType::Null)
 		{
 			return nullptr;
 		}

src/polyrenderer/scene/poly_wall.cpp

@@ -173,7 +173,7 @@ bool RenderPolyWall::RenderLine(PolyRenderThread *thread, const TriMatrix &world
 			wall.FogBoundary = IsFogBoundary(frontsector, backsector);
 
 			FTexture *midtex = TexMan(line->sidedef->GetTexture(side_t::mid), true);
-			if ((midtex && midtex->UseType != FTexture::TEX_Null) || wall.FogBoundary)
+			if ((midtex && midtex->UseType != ETextureType::Null) || wall.FogBoundary)
 				translucentWallsOutput.push_back(thread->FrameMemory->NewObject<PolyTranslucentWall>(wall));
 
 			if (polyportal)
@@ -519,7 +519,7 @@ void RenderPolyWall::ClampHeight(TriVertex &v1, TriVertex &v2)
 FTexture *RenderPolyWall::GetTexture(const line_t *line, const side_t *side, side_t::ETexpart texpart)
 {
 	FTexture *tex = TexMan(side->GetTexture(texpart), true);
-	if (tex == nullptr || tex->UseType == FTexture::TEX_Null)
+	if (tex == nullptr || tex->UseType == ETextureType::Null)
 	{
 		// Mapping error. Doom floodfills this with a plane.
 		// This code doesn't do that, but at least it uses the "right" texture..
@@ -539,7 +539,7 @@ FTexture *RenderPolyWall::GetTexture(const line_t *line, const side_t *side, sid
 				tex = TexMan(line->frontsector->GetTexture(sector_t::floor), true);
 		}
 
-		if (tex == nullptr || tex->UseType == FTexture::TEX_Null)
+		if (tex == nullptr || tex->UseType == ETextureType::Null)
 			return nullptr;
 	}
 	return tex;

src/polyrenderer/scene/poly_wallsprite.cpp

@@ -41,7 +41,7 @@ void RenderPolyWallSprite::Render(PolyRenderThread *thread, const TriMatrix &wor
 
 	bool flipTextureX = false;
 	FTexture *tex = RenderPolySprite::GetSpriteTexture(thing, flipTextureX);
-	if (tex == nullptr || tex->UseType == FTexture::TEX_Null)
+	if (tex == nullptr || tex->UseType == ETextureType::Null)
 		return;
 
 	DVector2 spriteScale = thing->Scale;