Better ability to create portable shaders.

Now the #version string is added from Shader class itself, making it
possible to do workarounds for older versions more conveniently. As a
consequence, #version must not be part of shader source anymore.

src/AbstractShaderProgram.h

@@ -66,8 +66,8 @@ static const GLint SpecularTextureUniform = 3;
 @code
 MyShader() {
     // Load shaders from file and attach them to the program
-    attachShader(Shader::fromFile(Shader::Type::Vertex, "PhongShader.vert"));
-    attachShader(Shader::fromFile(Shader::Type::Fragment, "PhongShader.frag"));
+    attachShader(Shader::fromFile(Version::430, Shader::Type::Vertex, "PhongShader.vert"));
+    attachShader(Shader::fromFile(Version::430, Shader::Type::Fragment, "PhongShader.frag"));
 
     // Link
     link();

src/Shader.cpp

@@ -29,6 +29,29 @@ using namespace std;
 
 namespace Magnum {
 
+Shader::Shader(Version version, Type type): _type(type), _state(State::Initialized), shader(0) {
+    shader = glCreateShader(static_cast<GLenum>(_type));
+
+    switch(version) {
+        #ifndef MAGNUM_TARGET_GLES
+        case Version::GL210: addSource("#version 120\n"); break;
+        case Version::GL300: addSource("#version 130\n"); break;
+        case Version::GL310: addSource("#version 140\n"); break;
+        case Version::GL320: addSource("#version 150\n"); break;
+        case Version::GL330: addSource("#version 330\n"); break;
+        case Version::GL400: addSource("#version 400\n"); break;
+        case Version::GL410: addSource("#version 410\n"); break;
+        case Version::GL420: addSource("#version 420\n"); break;
+        case Version::GL430: addSource("#version 430\n"); break;
+        #else
+        case Version::GLES200: addSource("#version 100\n"); break;
+        case Version::GLES300: addSource("#version 300\n"); break;
+        #endif
+
+        default: break;
+    }
+}
+
 Shader::Shader(Shader&& other): _type(other._type), _state(other._state), sources(other.sources), shader(other.shader) {
     other.shader = 0;
 }

src/Shader.h

@@ -23,6 +23,7 @@
 #include <string>
 
 #include "Magnum.h"
+#include "Context.h"
 
 #include "magnumVisibility.h"
 
@@ -86,54 +87,56 @@ class MAGNUM_EXPORT Shader {
 
         /**
          * @brief Load shader from source
+         * @param version   Target version
          * @param type      %Shader type
          * @param source    %Shader source
          * @return Shader instance
          *
          * Loads the shader from one source. Shorthand for
          * @code
-         * Shader s(type);
+         * Shader s(version, type);
          * s.addData(data);
          * @endcode
          * Note that it is also possible to create shader from more than one
          * source.
          */
-        inline static Shader fromData(Type type, const std::string& source) {
-            Shader s(type);
+        inline static Shader fromData(Version version, Type type, const std::string& source) {
+            Shader s(version, type);
             s.addSource(source);
             return s;
         }
 
         /**
          * @brief Load shader from file
+         * @param version   Target version
          * @param type      %Shader type
-         * @param filename  %Source filename
+         * @param filename  Source filename
          * @return Shader instance
          *
          * Loads the shader from from one file. Shorthand for
          * @code
-         * Shader s(type);
+         * Shader s(version, type);
          * s.addFile(filename);
          * @endcode
          * Note that it is also possible to create shader from more than one
          * source.
          */
-        inline static Shader fromFile(Type type, const char* filename) {
-            Shader s(type);
+        inline static Shader fromFile(Version version, Type type, const char* filename) {
+            Shader s(version, type);
             s.addFile(filename);
             return s;
         }
 
         /**
          * @brief Constructor
+         * @param version   Target version
+         * @param type      %Shader type
          *
-         * Creates empty OpenGL shader. Sources can be added with addSource()
-         * or addFile().
+         * Creates empty OpenGL shader and adds @c \#version directive at the
+         * beginning. Sources can be added with addSource() or addFile().
          * @see fromData(), fromFile(), @fn_gl{CreateShader}
          */
-        inline Shader(Type type): _type(type), _state(State::Initialized), shader(0) {
-            shader = glCreateShader(static_cast<GLenum>(_type));
-        }
+        Shader(Version version, Type type);
 
         /**
          * @brief Destructor

src/Shaders/PhongShader.cpp

@@ -23,8 +23,8 @@ namespace Magnum { namespace Shaders {
 
 PhongShader::PhongShader() {
     Corrade::Utility::Resource rs("MagnumShaders");
-    attachShader(Shader::fromData(Shader::Type::Vertex, rs.get("PhongShader.vert")));
-    attachShader(Shader::fromData(Shader::Type::Fragment, rs.get("PhongShader.frag")));
+    attachShader(Shader::fromData(Version::GL330, Shader::Type::Vertex, rs.get("PhongShader.vert")));
+    attachShader(Shader::fromData(Version::GL330, Shader::Type::Fragment, rs.get("PhongShader.frag")));
 
     link();
 

src/Shaders/PhongShader.frag

@@ -1,5 +1,3 @@
-#version 330
-
 uniform vec3 ambientColor = vec3(0.0, 0.0, 0.0);
 uniform vec3 diffuseColor;
 uniform vec3 specularColor = vec3(1.0, 1.0, 1.0);

src/Shaders/PhongShader.vert

@@ -1,5 +1,3 @@
-#version 330
-
 uniform mat4 transformationMatrix;
 uniform mat4 projectionMatrix;
 uniform vec3 light;