[unity] Fixed all Tint and TintBlack shader blend behaviour, previous changes by commit d43b7b0 were incorrect in some cases. Closes #1756.

spine-unity/Assets/Spine/Runtime/spine-unity/Shaders/CGIncludes/Spine-Skeleton-Tint-Common.cginc

@@ -1,21 +1,21 @@
 #ifndef SKELETON_TINT_COMMON_INCLUDED
 #define SKELETON_TINT_COMMON_INCLUDED
 
-float4 fragTintedColor(float4 texColor, float3 darkTintColor, float4 lightTintColor, float darkColorAlpha) {
+float4 fragTintedColor(float4 texColor, float3 darkTintColor, float4 lightTintColorPMA, float lightColorAlpha, float darkColorAlpha) {
 
-	float a = texColor.a * lightTintColor.a;
+	float a = texColor.a * lightTintColorPMA.a;
 
 #if !defined(_STRAIGHT_ALPHA_INPUT)
 	float3 texDarkColor = (texColor.a - texColor.rgb);
 #else
 	float3 texDarkColor = (1 - texColor.rgb);
 #endif
-	float3 darkColor = texDarkColor * darkTintColor.rgb;
-	float3 lightColor = texColor.rgb * lightTintColor.rgb;
+	float3 darkColor = texDarkColor * darkTintColor.rgb * lightColorAlpha;
+	float3 lightColor = texColor.rgb * lightTintColorPMA.rgb;
 
 	float4 fragColor = float4(darkColor + lightColor, a);
 #if defined(_STRAIGHT_ALPHA_INPUT)
-	fragColor.rgb *= fragColor.a;
+	fragColor.rgb *= texColor.a;
 #endif
 
 #if defined(_DARK_COLOR_ALPHA_ADDITIVE)

spine-unity/Assets/Spine/Runtime/spine-unity/Shaders/SkeletonGraphic/Spine-SkeletonGraphic-TintBlack.shader

@@ -109,7 +109,7 @@ Shader "Spine/SkeletonGraphic Tint Black"
 				OUT.vertex = UnityObjectToClipPos(OUT.worldPosition);
 				OUT.texcoord = IN.texcoord;
 
-				OUT.color = IN.color * _Color;
+				OUT.color = IN.color;
 				OUT.darkColor = float4(IN.uv1.r, IN.uv1.g, IN.uv2.r, IN.uv2.g);
 				return OUT;
 			}
@@ -125,17 +125,19 @@ Shader "Spine/SkeletonGraphic Tint Black"
 				clip(texColor.a - 0.001);
 				#endif
 
-				float4 vertexColor = IN.color;
+				float4 vertexColor = IN.color * float4(_Color.rgb * _Color.a, _Color.a);
 			#ifdef _CANVAS_GROUP_COMPATIBLE
 				// CanvasGroup alpha multiplies existing vertex color alpha, but
 				// does not premultiply it to rgb components. This causes problems
 				// with additive blending (alpha = 0), which is why we store the
 				// alpha value in uv2.g (darkColor.a).
-				vertexColor.a = IN.darkColor.a;
+				float originalAlpha = IN.darkColor.a;
+				float canvasAlpha = (originalAlpha == 0) ? IN.color.a : IN.color.a / originalAlpha;
+				vertexColor.a = originalAlpha * _Color.a;
 			#endif
-				float4 fragColor = fragTintedColor(texColor, _Black.rgb + IN.darkColor, vertexColor, _Black.a);
+				float4 fragColor = fragTintedColor(texColor, _Black.rgb + IN.darkColor, vertexColor, _Color.a, _Black.a);
 			#ifdef _CANVAS_GROUP_COMPATIBLE
-				fragColor.rgba *= IN.color.a;
+				fragColor.rgba *= canvasAlpha;
 			#endif
 				return fragColor;
 			}

spine-unity/Assets/Spine/Runtime/spine-unity/Shaders/Spine-Skeleton-Tint.shader

@@ -69,7 +69,7 @@ Shader "Spine/Skeleton Tint" {
 				VertexOutput o;
 				o.pos = UnityObjectToClipPos(v.vertex);
 				o.uv = v.uv;
-				o.vertexColor = v.vertexColor * _Color;
+				o.vertexColor = v.vertexColor * float4(_Color.rgb * _Color.a, _Color.a); // Combine a PMA version of _Color with vertexColor.
 				return o;
 			}
 
@@ -77,7 +77,7 @@ Shader "Spine/Skeleton Tint" {
 
 			float4 frag (VertexOutput i) : SV_Target {
 				float4 texColor = tex2D(_MainTex, i.uv);
-				return fragTintedColor(texColor, _Black.rgb, i.vertexColor, _Black.a);
+				return fragTintedColor(texColor, _Black.rgb, i.vertexColor, _Color.a, _Black.a);
 			}
 			ENDCG
 		}

spine-unity/Assets/Spine/Runtime/spine-unity/Shaders/Spine-Skeleton-TintBlack.shader

@@ -75,7 +75,7 @@ Shader "Spine/Skeleton Tint Black" {
 				VertexOutput o;
 				o.pos = UnityObjectToClipPos(v.vertex); // Upgrade NOTE: replaced 'mul(UNITY_MATRIX_MVP,*)' with 'UnityObjectToClipPos(*)'
 				o.uv = v.uv;
-				o.vertexColor = v.vertexColor * _Color;
+				o.vertexColor = v.vertexColor * float4(_Color.rgb * _Color.a, _Color.a); // Combine a PMA version of _Color with vertexColor.
 				o.darkColor = float3(v.uv1.r, v.uv1.g, v.uv2.r);
 				return o;
 			}
@@ -84,7 +84,7 @@ Shader "Spine/Skeleton Tint Black" {
 
 			float4 frag (VertexOutput i) : SV_Target {
 				float4 texColor = tex2D(_MainTex, i.uv);
-				return fragTintedColor(texColor, _Black.rgb + i.darkColor, i.vertexColor, _Black.a);
+				return fragTintedColor(texColor, _Black.rgb + i.darkColor, i.vertexColor, _Color.a, _Black.a);
 			}
 			ENDCG
 		}