glIsEnabled

glIsEnabled is an OpenGL function used to query whether a specific capability is currently enabled in the active OpenGL context. It helps programs determine the current state of a feature without altering it.

Syntax and parameters

GLboolean glIsEnabled(GLenum cap);

cap is a symbolic constant that identifies a capability. Valid values are the same enumerants accepted by glEnable and glDisable, such as GL_DEPTH_TEST, GL_BLEND, GL_CULL_FACE, GL_DITHER, and related capabilities. If cap is not a valid capability for the current context, the error GL_INVALID_ENUM may be generated.

Return value

The function returns GL_TRUE if the specified capability is enabled, and GL_FALSE otherwise. The result reflects the state of the capability in the current context but does not indicate the intensity or effectiveness of its action; other state and hardware factors may influence the actual rendering outcome.

Behavior notes

glIsEnabled only reports the enabled/disabled state of a capability. It does not modify server state. It is commonly used to avoid redundant state changes, enabling code to conditionally call glEnable or glDisable based on the current setting.

Examples of usage

If (glIsEnabled(GL_DEPTH_TEST)) { /* depth testing is already on */ } else { glEnable(GL_DEPTH_TEST); }

See also

glEnable, glDisable, and related capability enumerants. References to state queries in OpenGL specifications describe the error behavior and the supported set of capabilities for different contexts.