glValidateProgram

Name

glValidateProgram Validates a program object

C Specification

void glValidateProgram(GLuint program)

Parameters

program	Specifies the handle of the program object to be validated.

Description

glValidateProgram checks to see whether the executables contained in program can execute given the current OpenGL state. The information generated by the validation process is stored in program's information log. The validation information may consist of an empty string, or it may be a string containing information about how the current program object interacts with the rest of current OpenGL state. This function provides a way for OpenGL implementors to convey more information about why the current program is inefficient, suboptimal, failing to execute, and so on.

The status of the validation operation is stored as part of the program object's state. This value is set to GL_TRUE if the validation succeeded, and GL_FALSE otherwise. It can be queried by calling glGetProgram with arguments program and GL_VALIDATE_STATUS. If validation is successful, program is guaranteed to execute given the current state. Otherwise, program is guaranteed to not execute.

This function is typically useful only during application development. The informational string stored in the information log is completely implementation dependent; therefore, different OpenGL implementations cannot be expected to produce identical information strings.

Notes

glValidateProgram is available only if the GL version is 2.0 or greater.

This function mimics the validation operation that OpenGL implementations must perform when rendering commands are issued while programmable shaders are part of current state. The error GL_INVALID_OPERATION is generated by glBegin, glRasterPos, or any command that performs an implicit call to glBegin if

• any two active samplers in the current program object are of different types but refer to the same texture image unit;

• any active sampler in the current program object refers to a texture image unit in which fixed function fragment processing accesses a texture target that does not match the sampler type; or

• the sum of the number of active samplers in the program and the number of texture image units enabled for fixed function fragment processing exceeds the combined limit on the total number of texture image units allowed.

Difficulties or performance degradation may occur if applications try to catch these errors when issuing rendering commands. Therefore, applications are advised to make calls to glValidateProgram to detect these issues during application development.

Errors

GL_INVALID_VALUE is generated if program is not a value generated by OpenGL.

GL_INVALID_OPERATION is generated if program is not a program object.

GL_INVALID_OPERATION is generated if glValidateProgram is executed between the execution of glBegin and the corresponding execution of glEnd.

Associated Gets

glGetProgram with arguments program and GL_VALIDATE_STATUS

glGetProgramInfoLog with argument program

glIsProgram

See Also

glLinkProgram, glUseProgram