Trade: clearer asserts for "packable" textures.

In these cases there can be more than one attribute, so complaining that
just one particular attribute is not found is misleading.

src/Magnum/Trade/PbrMetallicRoughnessMaterialData.cpp

@@ -152,6 +152,10 @@ Float PbrMetallicRoughnessMaterialData::metalness() const {
 }
 
 UnsignedInt PbrMetallicRoughnessMaterialData::metalnessTexture() const {
+    /* Explicit assertion because printing  that MetalnessTexture isn't found
+       would be misleading as it can be also MetallicRoughnessTexture */
+    CORRADE_ASSERT(hasMetalnessTexture(),
+        "Trade::PbrMetallicRoughnessMaterialData::metalnessTexture(): the material doesn't have a metalness texture", {});
     if(Containers::Optional<UnsignedInt> value = tryAttribute<UnsignedInt>(MaterialAttribute::MetallicRoughnessTexture))
         return *value;
     return attribute<UnsignedInt>(MaterialAttribute::MetalnessTexture);
@@ -186,6 +190,10 @@ Float PbrMetallicRoughnessMaterialData::roughness() const {
 }
 
 UnsignedInt PbrMetallicRoughnessMaterialData::roughnessTexture() const {
+    /* Explicit assertion because printing that RoughnessTexture isn't found
+       would be misleading as it can be also MetallicRoughnessTexture */
+    CORRADE_ASSERT(hasRoughnessTexture(),
+        "Trade::PbrMetallicRoughnessMaterialData::roughnessTexture(): the material doesn't have a roughness texture", {});
     if(Containers::Optional<UnsignedInt> value = tryAttribute<UnsignedInt>(MaterialAttribute::MetallicRoughnessTexture))
         return *value;
     return attribute<UnsignedInt>(MaterialAttribute::RoughnessTexture);

src/Magnum/Trade/PbrSpecularGlossinessMaterialData.cpp

@@ -101,6 +101,10 @@ Color4 PbrSpecularGlossinessMaterialData::specularColor() const {
 }
 
 UnsignedInt PbrSpecularGlossinessMaterialData::specularTexture() const {
+    /* Explicit assertion because printing that SpecularTexture isn't found
+       would be misleading as it can be also SpecularGlossinessTexture */
+    CORRADE_ASSERT(hasSpecularTexture(),
+        "Trade::PbrSpecularGlossinessMaterialData::specularTexture(): the material doesn't have a specular texture", {});
     if(Containers::Optional<UnsignedInt> value = tryAttribute<UnsignedInt>(MaterialAttribute::SpecularGlossinessTexture))
         return *value;
     return attribute<UnsignedInt>(MaterialAttribute::SpecularTexture);
@@ -135,6 +139,10 @@ Float PbrSpecularGlossinessMaterialData::glossiness() const {
 }
 
 UnsignedInt PbrSpecularGlossinessMaterialData::glossinessTexture() const {
+    /* Explicit assertion because printing that GlossinessTexture isn't found
+       would be misleading as it can be also SpecularGlossinessTexture */
+    CORRADE_ASSERT(hasGlossinessTexture(),
+        "Trade::PbrSpecularGlossinessMaterialData::glossinessTexture(): the material doesn't have a glossiness texture", {});
     if(Containers::Optional<UnsignedInt> value = tryAttribute<UnsignedInt>(MaterialAttribute::SpecularGlossinessTexture))
         return *value;
     return attribute<UnsignedInt>(MaterialAttribute::GlossinessTexture);

src/Magnum/Trade/PhongMaterialData.cpp

@@ -204,6 +204,10 @@ Color4 PhongMaterialData::specularColor() const {
 }
 
 UnsignedInt PhongMaterialData::specularTexture() const {
+    /* Explicit assertion because printing that SpecularTexture isn't found
+       would be misleading as it can be also SpecularGlossinessTexture */
+    CORRADE_ASSERT(hasSpecularTexture(),
+        "Trade::PhongMaterialData::specularTexture(): the material doesn't have a specular texture", {});
     if(Containers::Optional<UnsignedInt> value = tryAttribute<UnsignedInt>(MaterialAttribute::SpecularGlossinessTexture))
         return *value;
     return attribute<UnsignedInt>(MaterialAttribute::SpecularTexture);

src/Magnum/Trade/Test/MaterialDataTest.cpp

@@ -2782,11 +2782,11 @@ void MaterialDataTest::pbrMetallicRoughnessAccessInvalidTextures() {
         "Trade::MaterialData::attribute(): attribute BaseColorTexture not found in layer 0\n"
         "Trade::PbrMetallicRoughnessMaterialData::baseColorTextureMatrix(): the material doesn't have a base color texture\n"
         "Trade::PbrMetallicRoughnessMaterialData::baseColorTextureCoordinates(): the material doesn't have a base color texture\n"
-        "Trade::MaterialData::attribute(): attribute MetalnessTexture not found in layer 0\n"
+        "Trade::PbrMetallicRoughnessMaterialData::metalnessTexture(): the material doesn't have a metalness texture\n"
         "Trade::PbrMetallicRoughnessMaterialData::metalnessTextureSwizzle(): the material doesn't have a metalness texture\n"
         "Trade::PbrMetallicRoughnessMaterialData::metalnessTextureMatrix(): the material doesn't have a metalness texture\n"
         "Trade::PbrMetallicRoughnessMaterialData::metalnessTextureCoordinates(): the material doesn't have a metalness texture\n"
-        "Trade::MaterialData::attribute(): attribute RoughnessTexture not found in layer 0\n"
+        "Trade::PbrMetallicRoughnessMaterialData::roughnessTexture(): the material doesn't have a roughness texture\n"
         "Trade::PbrMetallicRoughnessMaterialData::roughnessTextureSwizzle(): the material doesn't have a roughness texture\n"
         "Trade::PbrMetallicRoughnessMaterialData::roughnessTextureMatrix(): the material doesn't have a roughness texture\n"
         "Trade::PbrMetallicRoughnessMaterialData::roughnessTextureCoordinates(): the material doesn't have a roughness texture\n"
@@ -3164,11 +3164,11 @@ void MaterialDataTest::pbrSpecularGlossinessAccessInvalidTextures() {
         "Trade::MaterialData::attribute(): attribute DiffuseTexture not found in layer 0\n"
         "Trade::PbrSpecularGlossinessMaterialData::diffuseTextureMatrix(): the material doesn't have a diffuse texture\n"
         "Trade::PbrSpecularGlossinessMaterialData::diffuseTextureCoordinates(): the material doesn't have a diffuse texture\n"
-        "Trade::MaterialData::attribute(): attribute SpecularTexture not found in layer 0\n"
+        "Trade::PbrSpecularGlossinessMaterialData::specularTexture(): the material doesn't have a specular texture\n"
         "Trade::PbrSpecularGlossinessMaterialData::specularTextureSwizzle(): the material doesn't have a specular texture\n"
         "Trade::PbrSpecularGlossinessMaterialData::specularTextureMatrix(): the material doesn't have a specular texture\n"
         "Trade::PbrSpecularGlossinessMaterialData::specularTextureCoordinates(): the material doesn't have a specular texture\n"
-        "Trade::MaterialData::attribute(): attribute GlossinessTexture not found in layer 0\n"
+        "Trade::PbrSpecularGlossinessMaterialData::glossinessTexture(): the material doesn't have a glossiness texture\n"
         "Trade::PbrSpecularGlossinessMaterialData::glossinessTextureSwizzle(): the material doesn't have a glossiness texture\n"
         "Trade::PbrSpecularGlossinessMaterialData::glossinessTextureMatrix(): the material doesn't have a glossiness texture\n"
         "Trade::PbrSpecularGlossinessMaterialData::glossinessTextureCoordinates(): the material doesn't have a glossiness texture\n"
@@ -3379,7 +3379,7 @@ void MaterialDataTest::phongAccessInvalidTextures() {
         "Trade::MaterialData::attribute(): attribute DiffuseTexture not found in layer 0\n"
         "Trade::PhongMaterialData::diffuseTextureMatrix(): the material doesn't have a diffuse texture\n"
         "Trade::PhongMaterialData::diffuseTextureCoordinates(): the material doesn't have a diffuse texture\n"
-        "Trade::MaterialData::attribute(): attribute SpecularTexture not found in layer 0\n"
+        "Trade::PhongMaterialData::specularTexture(): the material doesn't have a specular texture\n"
         "Trade::PhongMaterialData::specularTextureSwizzle(): the material doesn't have a specular texture\n"
         "Trade::PhongMaterialData::specularTextureMatrix(): the material doesn't have a specular texture\n"
         "Trade::PhongMaterialData::specularTextureCoordinates(): the material doesn't have a specular texture\n"