glGetShaderiv — return a parameter from a shader object
void glGetShaderiv( | GLuint shader, |
GLenum pname, | |
GLint *params) ; |
shader
Specifies the shader object to be queried.
pname
Specifies the object parameter. Accepted symbolic names are GL_SHADER_TYPE
, GL_DELETE_STATUS
, GL_COMPILE_STATUS
, GL_INFO_LOG_LENGTH
, GL_SHADER_SOURCE_LENGTH
.
params
Returns the requested object parameter.
glGetShaderiv
returns in params
the value of a parameter for a specific shader object. The following parameters are defined:
GL_SHADER_TYPE
params
returns GL_VERTEX_SHADER
if shader
is a vertex shader object, and GL_FRAGMENT_SHADER
if shader
is a fragment shader object.
GL_DELETE_STATUS
params
returns GL_TRUE
if shader
is currently flagged for deletion, and GL_FALSE
otherwise.
GL_COMPILE_STATUS
For implementations that support a shader compiler, params
returns GL_TRUE
if the last compile operation on shader
was successful, and GL_FALSE
otherwise.
GL_INFO_LOG_LENGTH
For implementations that support a shader compiler, params
returns the number of characters in the information log for shader
including the null termination character (i.e., the size of the character buffer required to store the information log). If shader
has no information log, a value of 0 is returned.
GL_SHADER_SOURCE_LENGTH
For implementations that support a shader compiler, params
returns the length of the concatenation of the source strings that make up the shader source for the shader
, including the null termination character. (i.e., the size of the character buffer required to store the shader source). If no source code exists, 0 is returned.
Shader compiler support is optional, and thus must be queried before use by calling glGet with argument GL_SHADER_COMPILER
. glShaderSource, glCompileShader, glGetShaderPrecisionFormat, and glReleaseShaderCompiler will each generate GL_INVALID_OPERATION
on implementations that do not support a shader compiler, as will glGetShaderiv
queries of GL_COMPILE_STATUS
, GL_INFO_LOG_LENGTH
, and GL_SHADER_SOURCE_LENGTH
. Such implementations instead offer the glShaderBinary alternative for supplying a pre-compiled shader binary.
If an error is generated, no change is made to the contents of params
.
GL_INVALID_ENUM
is generated if pname
is not an accepted value.
GL_INVALID_VALUE
is generated if shader
is not a value generated by OpenGL.
GL_INVALID_OPERATION
is generated if pname
is GL_COMPILE_STATUS
, GL_INFO_LOG_LENGTH
, or GL_SHADER_SOURCE_LENGTH
but a shader compiler is not supported.
GL_INVALID_OPERATION
is generated if shader
does not refer to a shader object.
glGet with argument GL_SHADER_COMPILER
glGetShaderInfoLog with argument shader
glGetShaderSource with argument shader
GLuint vshader = glCreateShader(GL_VERTEX_SHADER); glShaderSource(vshader, 1, &vertex_shader_source, NULL); // vertex_shader_source is a GLchar* containing glsl shader source code glCompileShader(vshader); GLint vertex_compiled; glGetShaderiv(vshader, GL_COMPILE_STATUS, &vertex_compiled); if (vertex_compiled != GL_TRUE) { GLsizei log_length = 0; GLchar message[1024]; glGetShaderInfoLog(vshader, 1024, &log_length, message); // Write the error to a log } GLuint fshader = glCreateShader(GL_FRAGMENT_SHADER); glShaderSource(fshader, 1, &fragment_shader_source, NULL); // fragment_shader_source is a GLchar* containing glsl shader source code glCompileShader(fshader); GLint fragment_compiled; glGetShaderiv(fshader, GL_COMPILE_STATUS, &fragment_compiled); if (fragment_compiled != GL_TRUE) { GLsizei log_length = 0; GLchar message[1024]; glGetShaderInfoLog(fshader, 1024, &log_length, message); // Write the error to a log } GLuint program = glCreateProgram(); // This step is unnecessary if you use the location specifier in your shader // e.g. layout (location = 0) in vec3 position; glBindAttribLocation(program, 0, "position"); // The index passed into glBindAttribLocation is glBindAttribLocation(program, 1, "texcoord"); // used by glEnableVertexAttribArray. "position" glBindAttribLocation(program, 2, "normal"); // "texcoord" "normal" and "color" are the names of the glBindAttribLocation(program, 3, "color"); // respective inputs in your fragment shader. glAttachShader(program, vshader); glAttachShader(program, fshader); glLinkProgram(program); GLint program_linked; glGetProgramiv(program, GL_LINK_STATUS, &program_linked); if (program_linked != GL_TRUE) { GLsizei log_length = 0; GLchar message[1024]; glGetProgramInfoLog(program, 1024, &log_length, message); // Write the error to a log }
glCompileShader, glCreateShader, glDeleteShader, glGetProgramiv, glShaderSource, glShaderBinary
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