@@ -28,9 +28,18 @@ int main()

         "player.vert",

         "player.frag", "lighting.frag",

     });

+

+    // Use.

+    player

+        .validate();

 }

 ```

+All public (non-static) member functions return a reference to the current

+object, allowing [method chaining][].

+

+[method chaining]: https://en.wikipedia.org/wiki/Method_chaining

+

 ### Errors

 Errors are handled by throwing [`std::runtime_error`][] with a [`what()`][]

@@ -100,6 +109,22 @@ a separating `"/"` if non-empty, to all paths (defaults to `""`).

 [shader stage]: https://www.khronos.org/opengl/wiki/Shader#Stages

 [OpenGL / OpenGL ES Reference Compiler]: https://www.khronos.org/opengles/sdk/tools/Reference-Compiler/

+### Validation

+

+By calling `validate()` the shader can be [validate][]d against the current

+OpenGL state to make sure that a subsequent draw call would succeed. An error

+is thrown if a problem is detected.

+

+Additional issues that are not typically detected by [`glValidateProgram`][]

+are checked for.

+

+If the macro [`NDEBUG`][] is defined, the check is optimised out. Therefore, it

+is recommended to always call `validate()` before issuing draw calls.

+

+[validate]: https://www.khronos.org/registry/OpenGL-Refpages/gl4/html/glValidateProgram.xhtml

+[`glValidateProgram`]: https://www.khronos.org/registry/OpenGL-Refpages/gl4/html/glValidateProgram.xhtml

+[`NDEBUG`]: https://en.cppreference.com/w/c/error/assert

+

 ## Dependencies

 Public (interface):

new file mode 100644

@@ -0,0 +1,13 @@

+#version 110

+

+

+uniform sampler1D sampler1;

+uniform sampler2D sampler2;

+

+

+void main()

+{

+    gl_Position =

+        texture1D(sampler1, 0.0) +

+        texture2D(sampler2, vec2(0.0));

+}

@@ -25,14 +25,27 @@ public:

     GLuint program() const;

+    Shader & validate();

+

 protected:

+    void validate_() const;

+

     GLuint             program_;

     std::string        program_name_;

     std::string static root_;

 };

+// Debug macros.

+

+#ifndef NDEBUG

+    #define GLSHADER_DEBUG_(...) __VA_ARGS__

+#else

+    #define GLSHADER_DEBUG_(...)

+#endif // NDEBUG

+

+

 // Inline definitions.

 #define GLSHADER_SET_(TYPE, NAME) \

@@ -47,5 +60,11 @@ inline GLuint Shader::program() const

     return program_;

 }

+inline Shader & Shader::validate()

+{

+    GLSHADER_DEBUG_(validate_();)

+    return *this;

+}

+

 #endif // GLSHADER_SHADER_HPP_

@@ -216,3 +216,17 @@ Shader::~Shader()

     if (program_)

         glDeleteProgram(program_);

 }

+

+

+void Shader::validate_() const

+{

+    // Set error.

+    auto const validate_error = STR("Failed to validate " << program_name_);

+

+    // Validate program.

+    info_log_action_(

+        validate_error,

+        glValidateProgram, program_,

+        GL_VALIDATE_STATUS, glGetProgramiv, glGetProgramInfoLog

+    );

+}

@@ -39,11 +39,21 @@ GLTEST(2, 0, 640, 480, glshader)

         "error: vertex shader does not write to `gl_Position'. \n"

     )

+    // Validate.

+    GLTEST_EXPECT_EXCEPTION(true,

+        Shader({"tests/validate_bad_samplers.vert"}).validate(),

+        "Failed to validate shader program 'tests/validate_bad_samplers.vert':\n"

+        "active samplers with a different type refer to the same texture image unit"

+    )

+

     auto all = Shader({

         "tests/all.vert",

         "tests/all.frag",

     });

+    all

+        .validate();

+

     constexpr auto size = 0.5F;

     glBegin(GL_TRIANGLE_STRIP);

     glVertex3f(-size, -size, 0.0F);