Deprecating AbstractShaderProgram::bind*Location().

Preferred workflow is to specify attribute location explicitly in the
shader. The functions remains here as some old Intel systems don't
support the required extension ARB_explicit_attrib_location (and it's
not in GL 3.0 either). Also updated and fixed the documentation.

Function bindAttribute() was renamed to bindAttributeLocation() to be
consistent with bindFragmentDataLocation().

PhongShader now uses explicit attribute location.

src/AbstractShaderProgram.cpp

@@ -38,7 +38,7 @@ bool AbstractShaderProgram::attachShader(Shader& shader) {
     return true;
 }
 
-void AbstractShaderProgram::bindAttribute(GLuint location, const string& name) {
+void AbstractShaderProgram::bindAttributeLocation(GLuint location, const string& name) {
     CORRADE_ASSERT(state == Initialized, "AbstractShaderProgram: attribute cannot be bound after linking.", )
 
     glBindAttribLocation(program, location, name.c_str());

src/AbstractShaderProgram.h

@@ -30,6 +30,8 @@ namespace Magnum {
 /**
 @brief Base class for shaders
 
+@section AbstractShaderProgramSubclassing Subclassing workflow
+
 This class is designed to be used via subclassing. Subclasses define these
 functions and properties:
  - **Attribute location** typedefs defining locations and types for attribute
@@ -39,19 +41,13 @@ typedef Attribute<0, Vector4> Vertex;
 typedef Attribute<1, Vector3> Normal;
 typedef Attribute<2, Vector2> TextureCoords;
 @endcode
-   See also bindAttribute().
- - **Constructor**, which attaches particular shaders, links the program,
-   binds attribute locations and gets uniform locations, for example:
+ - **Constructor**, which attaches particular shaders, links the program and
+   gets uniform locations, for example:
 @code
 // Load shaders from file and attach them to the program
 attachShader(Shader::fromFile(Shader::Vertex, "PhongShader.vert"));
 attachShader(Shader::fromFile(Shader::Fragment, "PhongShader.frag"));
 
-// Bind attribute names to IDs
-bindAttribute(Vertex::Location, "vertex");
-bindAttribute(Normal::Location, "normal");
-bindAttribute(TextureCoords::Location, "textureCoords");
-
 // Link
 link();
 
@@ -61,28 +57,43 @@ projectionMatrixUniform = uniformLocation("projectionMatrix");
 // more uniforms like light location, colors etc.
 @endcode
  - **Uniform binding functions**, which set shader uniforms using
-   setUniform() and setUniformArray() functions. Example:
+   setUniform() functions. Example:
 @code
 void setTransformationMatrixUniform(const Matrix4& matrix) {
     setUniform(transformationMatrixUniform, matrix);
 }
 @endcode
 
-Basic workflow with AbstractShaderProgram subclasses is: instancing the class
-(once at the beginning), then in every frame calling use(), setting uniforms
-and calling Mesh::draw() (see its documentation for more).
+@subsection AbstractShaderProgramAttributeLocation Binding attribute location
+The preferred workflow is to specify attribute location for vertex shader
+input attributes and fragment shader output attributes explicitly in the
+shader code, e.g.:
+@code
+layout(location = 0) in vec4 vertex;
+layout(location = 1) in vec3 normal;
+layout(location = 2) in vec2 textureCoords;
+@endcode
+@requires_gl33 Extension @extension{ARB,explicit_attrib_location} (for
+    explicit attribute location instead of using bindAttributeLocation())
 
-@section MultipleFragmentOutputs Multiple fragment shader outputs
-If your shader uses multiple fragment outputs, you can use
-bindFragmentDataLocation() *before linking* to bind their names to desired
-location, e.g.:
+If you don't have the required extension, you can use functions bindAttributeLocation()
+and bindFragmentDataLocation() between attaching of shaders and linking the
+program:
 @code
-bindFragmentDataLocation(0, "color");
+// Shaders attached...
+
+bindAttributeLocation(Vertex::Location, "vertex");
+bindAttributeLocation(Normal::Location, "normal");
+bindAttributeLocation(TextureCoords::Location, "textureCoords");
+
+// Link...
 @endcode
 
-You should then clearly state in the documentation which output is on what
-position, so the user can set framebuffer attachments for them using
-Framebuffer::mapForDraw() or Framebuffer::mapDefaultForDraw().
+@section AbstractShaderProgramRenderingWorkflow Rendering workflow
+
+Basic workflow with AbstractShaderProgram subclasses is: instancing the class
+(once at the beginning), then in every frame calling use(), setting uniforms
+and calling Mesh::draw() (see its documentation for more).
 
 @todo Uniform arrays support
 
@@ -152,19 +163,27 @@ class MAGNUM_EXPORT AbstractShaderProgram {
          * @param name          Attribute name
          *
          * Binds attribute to location which is be used later for binding
-         * vertex buffers.
-         * @note This function should be called between loadShader() calls
-         * and link().
+         * vertex buffers. Preferred usage is to
+         * @note This function should be called between attachShader() calls
+         *      and link().
+         * @deprecated Preferred usage is to specify attribute location
+         *      explicitly in the shader instead of using this function. See
+         *      @ref AbstractShaderProgramAttributeLocation "class documentation"
+         *      for more information.
          */
-        void bindAttribute(GLuint location, const std::string& name);
+        void bindAttributeLocation(GLuint location, const std::string& name);
 
         /**
          * @brief Bind fragment data to given location
          * @param location      Location
          * @param name          Fragment output variable name
          *
-         * @note This function should be called between loadShader() calls
-         * and link().
+         * @note This function should be called between attachShader() calls
+         *      and link().
+         * @deprecated Preferred usage is to specify attribute location
+         *      explicitly in the shader instead of using this function. See
+         *      @ref AbstractShaderProgramAttributeLocation "class documentation"
+         *      for more information.
          *
          * @requires_gl30 Extension @extension{EXT,gpu_shader4}
          */
@@ -212,7 +231,6 @@ class MAGNUM_EXPORT AbstractShaderProgram {
             glUniform4fv(location, 1, value.data());
         }
 
-
         /** @copydoc setUniform(GLint, GLfloat) */
         inline void setUniform(GLint location, GLint value) {
             glUniform1i(location, value);

src/Shaders/PhongShader.cpp

@@ -24,9 +24,6 @@ PhongShader::PhongShader() {
     attachShader(Shader::fromData(Shader::Type::Vertex, rs.get("PhongShader.vert")));
     attachShader(Shader::fromData(Shader::Type::Fragment, rs.get("PhongShader.frag")));
 
-    bindAttribute(Vertex::Location, "vertex");
-    bindAttribute(Normal::Location, "normal");
-
     link();
 
     ambientColorUniform = uniformLocation("ambientColor");

src/Shaders/PhongShader.vert

@@ -4,8 +4,8 @@ uniform mat4 transformationMatrix;
 uniform mat4 projectionMatrix;
 uniform vec3 light;
 
-in vec4 vertex;
-in vec3 normal;
+layout(location = 0) in vec4 vertex;
+layout(location = 1) in vec3 normal;
 
 out vec3 transformedNormal;
 out vec3 lightDirection;