context: Improve doc (#1842)

library/public/context.h

@@ -28,33 +28,38 @@ class F3D_EXPORT context
   /**
    * Create a GLX context function.
    * Only supported on Linux.
+   * Throw a loading_exception if it fails.
    */
   [[nodiscard]] static function glx();
 
   /**
    * Create a WGL context function.
    * Only supported on Windows.
+   * Throw a loading_exception if it fails.
    */
   [[nodiscard]] static function wgl();
 
   /**
    * Create a COCOA context function.
    * This is usually required when using a headless context and a GPU device.
    * Only supported on macOS.
+   * Throw a loading_exception if it fails.
    */
   [[nodiscard]] static function cocoa();
 
   /**
    * Create a EGL context function.
    * This is usually required when using a headless context and a GPU device.
    * Only supported on Linux and Windows.
+   * Throw a loading_exception if it fails.
    */
   [[nodiscard]] static function egl();
 
   /**
    * Create a OSMesa context function.
    * This is usually required when using a headless context and no GPU device.
    * Only supported on Linux and Windows.
+   * Throw a loading_exception if it fails.
    */
   [[nodiscard]] static function osmesa();
 
@@ -63,6 +68,8 @@ class F3D_EXPORT context
    * The library name must be specified without its prefix and extension.
    * For example, `getSymbol("EGL", "eglGetProcAddress")` looks for the symbol
    * `eglGetProcAddress` in the library `libEGL.so` on Linux.
+   * Throw a loading_exception if it fails to find the library or a symbol_exception
+   * if the lib does not contains the expected symbol.
    */
   [[nodiscard]] static function getSymbol(std::string_view lib, std::string_view func);