Added and documented glfwSetGamma value checks.

include/GLFW/glfw3.h

@@ -1424,7 +1424,8 @@ GLFWAPI const GLFWvidmode* glfwGetVideoMode(GLFWmonitor* monitor);
 /*! @brief Generates a gamma ramp and sets it for the specified monitor.
  *
  *  This function generates a 256-element gamma ramp from the specified exponent
- *  and then calls @ref glfwSetGammaRamp with it.
+ *  and then calls @ref glfwSetGammaRamp with it.  The value must be a finite
+ *  number greater than zero.
  *
  *  @param[in] monitor The monitor whose gamma ramp to set.
  *  @param[in] gamma The desired exponent.

src/monitor.c

@@ -28,6 +28,7 @@
 #include "internal.h"
 
 #include <math.h>
+#include <float.h>
 #include <string.h>
 #include <stdlib.h>
 #include <limits.h>
@@ -385,10 +386,9 @@ GLFWAPI void glfwSetGamma(GLFWmonitor* handle, float gamma)
 
     _GLFW_REQUIRE_INIT();
 
-    if (gamma <= 0.f)
+    if (gamma != gamma || gamma <= 0.f || gamma > FLT_MAX)
     {
-        _glfwInputError(GLFW_INVALID_VALUE,
-                        "Gamma value must be greater than zero");
+        _glfwInputError(GLFW_INVALID_VALUE, "Invalid gamma value");
         return;
     }