Shaders: ability to use RGBA colors with VertexColor shader.

It was just RGB before. In order to avoid breaking current code, the
attribute now requires explicit specification of number of components.
If building with deprecated APIs enabled, there is an additional
deprecated constructor that defaults to RGB so the current code should
keep working as-is.

src/Magnum/DebugTools/ObjectRenderer.cpp

@@ -171,7 +171,7 @@ template<UnsignedInt dimensions> ObjectRenderer<dimensions>::ObjectRenderer(Scen
         .setCount(Renderer<dimensions>::indices.size())
         .addVertexBuffer(*vertexBuffer, 0,
             typename Shaders::VertexColor<dimensions>::Position(),
-            typename Shaders::VertexColor<dimensions>::Color())
+            typename Shaders::VertexColor<dimensions>::Color{Shaders::VertexColor<dimensions>::Color::Components::Four})
         .setIndexBuffer(*indexBuffer, 0, Mesh::IndexType::UnsignedByte, 0, Renderer<dimensions>::positions.size());
     ResourceManager::instance().set<Mesh>(_mesh.key(), mesh, ResourceDataState::Final, ResourcePolicy::Manual);
 }

src/Magnum/Shaders/Generic.h

@@ -70,9 +70,25 @@ template<UnsignedInt dimensions> struct Generic {
     /**
      * @brief Vertex color
      *
-     * @ref Color3.
+     * @ref Color4, however defaults to @ref Color3 if @ref MAGNUM_BUILD_DEPRECATED
+     * is defined. See the constructor documentation for more information.
      */
-    typedef Attribute<3, Color3> Color;
+    struct Color: Attribute<3, Color4> {
+        /**
+         * @brief Constructor
+         * @param components    Component count
+         * @param dataType      Type of passed data
+         * @param dataOptions   Data options
+         */
+        constexpr explicit Color(Components components, DataType dataType = DataType::Float, DataOptions dataOptions = {});
+
+        #ifdef MAGNUM_BUILD_DEPRECATED
+        /** @copybrief Color(Components, DataType, DataOptions)
+         * @deprecated Use @ref Color(Components, DataType, DataOptions) instead.
+         */
+        CORRADE_DEPRECATED("use Color(Components, DataType, DataOptions) instead") constexpr explicit Color(DataType dataType = DataType::Float, DataOptions dataOptions = {});
+        #endif
+    };
 };
 #endif
 
@@ -85,7 +101,14 @@ typedef Generic<3> Generic3D;
 #ifndef DOXYGEN_GENERATING_OUTPUT
 struct BaseGeneric {
     typedef Attribute<1, Vector2> TextureCoordinates;
-    typedef Attribute<3, Color3> Color;
+
+    struct Color: Attribute<3, Color4> {
+        constexpr explicit Color(Components components, DataType dataType = DataType::Float, DataOptions dataOptions = DataOptions()): Attribute<3, Color4>{components, dataType, dataOptions} {}
+
+        #ifdef MAGNUM_BUILD_DEPRECATED
+        CORRADE_DEPRECATED("use Color(Components, DataType, DataOptions) instead") constexpr explicit Color(DataType dataType = DataType::Float, DataOptions dataOptions = DataOptions()): Attribute<3, Color4>{Components::Three, dataType, dataOptions} {}
+        #endif
+    };
 };
 
 template<> struct Generic<2>: BaseGeneric {

src/Magnum/Shaders/VertexColor.frag

@@ -28,12 +28,12 @@
 #define fragmentColor gl_FragColor
 #endif
 
-in lowp vec3 interpolatedColor;
+in lowp vec4 interpolatedColor;
 
 #ifdef NEW_GLSL
 out lowp vec4 fragmentColor;
 #endif
 
 void main() {
-    fragmentColor = vec4(interpolatedColor, 1.0);
+    fragmentColor = interpolatedColor;
 }

src/Magnum/Shaders/VertexColor.h

@@ -51,7 +51,10 @@ attributes in your triangle mesh and call at least
 
 ## Example usage
 
-Common mesh setup:
+Common mesh setup. Note the explicit specification of components for the color
+attribute -- the shader accepts four-component color attribute but, similarly
+to all other attributes, it's possible to supply also three-component colors if
+alpha is not important.
 @code
 struct Vertex {
     Vector3 position;
@@ -65,7 +68,7 @@ vertices.setData(data, BufferUsage::StaticDraw);
 Mesh mesh;
 mesh.addVertexBuffer(vertices, 0,
     Shaders::VertexColor3D::Position{},
-    Shaders::VertexColor3D::Color{});
+    Shaders::VertexColor3D::Color{Shaders::VertexColor3D::Color::Components::Three});
 @endcode
 
 Common rendering setup:
@@ -94,7 +97,9 @@ template<UnsignedInt dimensions> class MAGNUM_SHADERS_EXPORT VertexColor: public
         /**
          * @brief Vertex color
          *
-         * @ref shaders-generic "Generic attribute", @ref Color3.
+         * @ref shaders-generic "Generic attribute", @ref Color4, however
+         * defaults to @ref Color3 if @ref MAGNUM_BUILD_DEPRECATED is defined.
+         * See the @ref Generic::Color for more information.
          */
         typedef typename Generic<dimensions>::Color Color;
 

src/Magnum/Shaders/VertexColor2D.vert

@@ -45,9 +45,9 @@ in highp vec2 position;
 #ifdef EXPLICIT_ATTRIB_LOCATION
 layout(location = 3)
 #endif
-in lowp vec3 color;
+in lowp vec4 color;
 
-out lowp vec3 interpolatedColor;
+out lowp vec4 interpolatedColor;
 
 void main() {
     gl_Position.xywz = vec4(transformationProjectionMatrix*vec3(position, 1.0), 0.0);

src/Magnum/Shaders/VertexColor3D.vert

@@ -40,13 +40,13 @@ uniform highp mat4 transformationProjectionMatrix;
 
 #ifdef EXPLICIT_ATTRIB_LOCATION
 layout(location = POSITION_ATTRIBUTE_LOCATION) in highp vec4 position;
-layout(location = 3) in lowp vec3 color;
+layout(location = 3) in lowp vec4 color;
 #else
 in highp vec4 position;
-in lowp vec3 color;
+in lowp vec4 color;
 #endif
 
-out lowp vec3 interpolatedColor;
+out lowp vec4 interpolatedColor;
 
 void main() {
     gl_Position = transformationProjectionMatrix*position;