Add feature available/implemented errors

This adds two new error codes: GLFW_FEATURE_UNAVAILABLE for when
a GLFW feature cannot be reasonably implemented on that platform, and
GLFW_FEATURE_UNIMPLEMENTED for when it can be but has not been yet.

This replaces the current situation where the Wayland code emitted
GLFW_PLATFORM_ERROR in both cases while the macOS code silently did
nothing.

If your application exits on any GLFW error, these error codes should at
least be easy to filter out from that behavior.

Ideally, GLFW_FEATURE_UNAVAILABLE should be rare and
GLFW_FEATURE_UNIMPLEMENTED should never be emitted at all.

Fixes #1692.

README.md

@@ -124,6 +124,8 @@ information on what to include when reporting a bug.
  - Added `GLFW_RESIZE_EW_CURSOR` alias for `GLFW_HRESIZE_CURSOR` (#427)
  - Added `GLFW_RESIZE_NS_CURSOR` alias for `GLFW_VRESIZE_CURSOR` (#427)
  - Added `GLFW_POINTING_HAND_CURSOR` alias for `GLFW_HAND_CURSOR` (#427)
+ - Added `GLFW_FEATURE_UNAVAILABLE` error for platform limitations (#1692)
+ - Added `GLFW_FEATURE_UNIMPLEMENTED` error for incomplete backends (#1692)
  - Updated the minimum required CMake version to 3.1
  - Disabled tests and examples by default when built as a CMake subdirectory
  - Bugfix: The CMake config-file package used an absolute path and was not

include/GLFW/glfw3.h

@@ -783,6 +783,33 @@ extern "C" {
  *  [custom cursor](@ref cursor_custom).
  */
 #define GLFW_CURSOR_UNAVAILABLE     0x0001000B
+/*! @brief The reuqested feature is not provided by the platform.
+ *
+ *  The requested feature is not provided by the platform, so GLFW is unable to
+ *  implement it.  The documentation for each function notes if it could emit
+ *  this error.
+ *
+ *  @analysis Platform or platform version limitation.  The error can be ignored
+ *  unless the feature is critical to the application.
+ *
+ *  @par
+ *  A function call that emits this error has no effect other than the error and
+ *  updating any existing out parameters.
+ */
+#define GLFW_FEATURE_UNAVAILABLE    0x0001000C
+/*! @brief The requested feature is not implemented for the platform.
+ *
+ *  The requested feature has not yet been implemented in GLFW for this platform.
+ *
+ *  @analysis An incomplete implementation of GLFW for this platform, hopefully
+ *  fixed in a future release.  The error can be ignored unless the feature is
+ *  critical to the application.
+ *
+ *  @par
+ *  A function call that emits this error has no effect other than the error and
+ *  updating any existing out parameters.
+ */
+#define GLFW_FEATURE_UNIMPLEMENTED  0x0001000D
 /*! @} */
 
 /*! @addtogroup window
@@ -2871,21 +2898,21 @@ GLFWAPI void glfwSetWindowTitle(GLFWwindow* window, const char* title);
  *  @param[in] images The images to create the icon from.  This is ignored if
  *  count is zero.
  *
- *  @errors Possible errors include @ref GLFW_NOT_INITIALIZED and @ref
- *  GLFW_PLATFORM_ERROR.
+ *  @errors Possible errors include @ref GLFW_NOT_INITIALIZED, @ref
+ *  GLFW_PLATFORM_ERROR and @ref GLFW_FEATURE_UNAVAILABLE (see remarks).
  *
  *  @pointer_lifetime The specified image data is copied before this function
  *  returns.
  *
- *  @remark @macos The GLFW window has no icon, as it is not a document
- *  window, so this function does nothing.  The dock icon will be the same as
+ *  @remark @macos Regular windows do not have icons on macOS.  This function
+ *  will emit @ref GLFW_FEATURE_UNAVAILABLE.  The dock icon will be the same as
  *  the application bundle's icon.  For more information on bundles, see the
  *  [Bundle Programming Guide](https://developer.apple.com/library/mac/documentation/CoreFoundation/Conceptual/CFBundles/)
  *  in the Mac Developer Library.
  *
  *  @remark @wayland There is no existing protocol to change an icon, the
  *  window will thus inherit the one defined in the application's desktop file.
- *  This function always emits @ref GLFW_PLATFORM_ERROR.
+ *  This function will emit @ref GLFW_FEATURE_UNAVAILABLE.
  *
  *  @thread_safety This function must only be called from the main thread.
  *
@@ -2911,12 +2938,12 @@ GLFWAPI void glfwSetWindowIcon(GLFWwindow* window, int count, const GLFWimage* i
  *  @param[out] ypos Where to store the y-coordinate of the upper-left corner of
  *  the content area, or `NULL`.
  *
- *  @errors Possible errors include @ref GLFW_NOT_INITIALIZED and @ref
- *  GLFW_PLATFORM_ERROR.
+ *  @errors Possible errors include @ref GLFW_NOT_INITIALIZED, @ref
+ *  GLFW_PLATFORM_ERROR and @ref GLFW_FEATURE_UNAVAILABLE (see remarks).
  *
  *  @remark @wayland There is no way for an application to retrieve the global
- *  position of its windows, this function will always emit @ref
- *  GLFW_PLATFORM_ERROR.
+ *  position of its windows.  This function will emit @ref
+ *  GLFW_FEATURE_UNAVAILABLE.
  *
  *  @thread_safety This function must only be called from the main thread.
  *
@@ -2945,12 +2972,12 @@ GLFWAPI void glfwGetWindowPos(GLFWwindow* window, int* xpos, int* ypos);
  *  @param[in] xpos The x-coordinate of the upper-left corner of the content area.
  *  @param[in] ypos The y-coordinate of the upper-left corner of the content area.
  *
- *  @errors Possible errors include @ref GLFW_NOT_INITIALIZED and @ref
- *  GLFW_PLATFORM_ERROR.
+ *  @errors Possible errors include @ref GLFW_NOT_INITIALIZED, @ref
+ *  GLFW_PLATFORM_ERROR and @ref GLFW_FEATURE_UNAVAILABLE (see remarks).
  *
  *  @remark @wayland There is no way for an application to set the global
- *  position of its windows, this function will always emit @ref
- *  GLFW_PLATFORM_ERROR.
+ *  position of its windows.  This function will emit @ref
+ *  GLFW_FEATURE_UNAVAILABLE.
  *
  *  @thread_safety This function must only be called from the main thread.
  *
@@ -3262,8 +3289,11 @@ GLFWAPI float glfwGetWindowOpacity(GLFWwindow* window);
  *  @param[in] window The window to set the opacity for.
  *  @param[in] opacity The desired opacity of the specified window.
  *
- *  @errors Possible errors include @ref GLFW_NOT_INITIALIZED and @ref
- *  GLFW_PLATFORM_ERROR.
+ *  @errors Possible errors include @ref GLFW_NOT_INITIALIZED, @ref
+ *  GLFW_PLATFORM_ERROR and @ref GLFW_FEATURE_UNAVAILABLE (see remarks).
+ *
+ *  @remark @wayland There is no way to set an opacity factor for a window.
+ *  This function will emit @ref GLFW_FEATURE_UNAVAILABLE.
  *
  *  @thread_safety This function must only be called from the main thread.
  *
@@ -3430,11 +3460,11 @@ GLFWAPI void glfwHideWindow(GLFWwindow* window);
  *
  *  @param[in] window The window to give input focus.
  *
- *  @errors Possible errors include @ref GLFW_NOT_INITIALIZED and @ref
- *  GLFW_PLATFORM_ERROR.
+ *  @errors Possible errors include @ref GLFW_NOT_INITIALIZED, @ref
+ *  GLFW_PLATFORM_ERROR and @ref GLFW_FEATURE_UNAVAILABLE (see remarks).
  *
- *  @remark @wayland It is not possible for an application to bring its windows
- *  to front, this function will always emit @ref GLFW_PLATFORM_ERROR.
+ *  @remark @wayland It is not possible for an application to set the input
+ *  focus.  This function will emit @ref GLFW_FEATURE_UNAVAILABLE.
  *
  *  @thread_safety This function must only be called from the main thread.
  *
@@ -4186,7 +4216,7 @@ GLFWAPI int glfwGetInputMode(GLFWwindow* window, int mode);
  *  If the mode is `GLFW_RAW_MOUSE_MOTION`, the value must be either `GLFW_TRUE`
  *  to enable raw (unscaled and unaccelerated) mouse motion when the cursor is
  *  disabled, or `GLFW_FALSE` to disable it.  If raw motion is not supported,
- *  attempting to set this will emit @ref GLFW_PLATFORM_ERROR.  Call @ref
+ *  attempting to set this will emit @ref GLFW_FEATURE_UNAVAILABLE.  Call @ref
  *  glfwRawMouseMotionSupported to check for support.
  *
  *  @param[in] window The window whose input mode to set.
@@ -4196,7 +4226,8 @@ GLFWAPI int glfwGetInputMode(GLFWwindow* window, int mode);
  *  @param[in] value The new value of the specified input mode.
  *
  *  @errors Possible errors include @ref GLFW_NOT_INITIALIZED, @ref
- *  GLFW_INVALID_ENUM and @ref GLFW_PLATFORM_ERROR.
+ *  GLFW_INVALID_ENUM, @ref GLFW_PLATFORM_ERROR and @ref
+ *  GLFW_FEATURE_UNAVAILABLE (see above).
  *
  *  @thread_safety This function must only be called from the main thread.
  *

src/cocoa_window.m

@@ -982,7 +982,8 @@ void _glfwPlatformSetWindowTitle(_GLFWwindow* window, const char* title)
 void _glfwPlatformSetWindowIcon(_GLFWwindow* window,
                                 int count, const GLFWimage* images)
 {
-    // Regular windows do not have icons
+    _glfwInputError(GLFW_FEATURE_UNAVAILABLE,
+                    "Cocoa: Regular windows do not have icons on macOS");
 }
 
 void _glfwPlatformGetWindowPos(_GLFWwindow* window, int* xpos, int* ypos)
@@ -1376,6 +1377,8 @@ void _glfwPlatformSetWindowOpacity(_GLFWwindow* window, float opacity)
 
 void _glfwPlatformSetRawMouseMotion(_GLFWwindow *window, GLFWbool enabled)
 {
+    _glfwInputError(GLFW_FEATURE_UNIMPLEMENTED,
+                    "Cocoa: Raw mouse motion not yet implemented");
 }
 
 GLFWbool _glfwPlatformRawMouseMotionSupported(void)

src/init.c

@@ -191,6 +191,10 @@ void _glfwInputError(int code, const char* format, ...)
             strcpy(description, "The specified window has no context");
         else if (code == GLFW_CURSOR_UNAVAILABLE)
             strcpy(description, "The specified cursor shape is unavailable");
+        else if (code == GLFW_FEATURE_UNAVAILABLE)
+            strcpy(description, "The requested feature cannot be implemented for this platform");
+        else if (code == GLFW_FEATURE_UNIMPLEMENTED)
+            strcpy(description, "The requested feature has not yet been implemented for this platform");
         else
             strcpy(description, "ERROR: UNKNOWN GLFW ERROR");
     }

src/wl_monitor.c

@@ -199,15 +199,15 @@ void _glfwPlatformGetVideoMode(_GLFWmonitor* monitor, GLFWvidmode* mode)
 
 GLFWbool _glfwPlatformGetGammaRamp(_GLFWmonitor* monitor, GLFWgammaramp* ramp)
 {
-    _glfwInputError(GLFW_PLATFORM_ERROR,
+    _glfwInputError(GLFW_FEATURE_UNAVAILABLE,
                     "Wayland: Gamma ramp access is not available");
     return GLFW_FALSE;
 }
 
 void _glfwPlatformSetGammaRamp(_GLFWmonitor* monitor,
                                const GLFWgammaramp* ramp)
 {
-    _glfwInputError(GLFW_PLATFORM_ERROR,
+    _glfwInputError(GLFW_FEATURE_UNAVAILABLE,
                     "Wayland: Gamma ramp access is not available");
 }
 

src/wl_window.c

@@ -883,25 +883,25 @@ void _glfwPlatformSetWindowTitle(_GLFWwindow* window, const char* title)
 void _glfwPlatformSetWindowIcon(_GLFWwindow* window,
                                 int count, const GLFWimage* images)
 {
-    _glfwInputError(GLFW_PLATFORM_ERROR,
-                    "Wayland: Setting window icon not supported");
+    _glfwInputError(GLFW_FEATURE_UNAVAILABLE,
+                    "Wayland: The platform does not support setting the window icon");
 }
 
 void _glfwPlatformGetWindowPos(_GLFWwindow* window, int* xpos, int* ypos)
 {
     // A Wayland client is not aware of its position, so just warn and leave it
     // as (0, 0)
 
-    _glfwInputError(GLFW_PLATFORM_ERROR,
-                    "Wayland: Window position retrieval not supported");
+    _glfwInputError(GLFW_FEATURE_UNAVAILABLE,
+                    "Wayland: The platform does not provide the window position");
 }
 
 void _glfwPlatformSetWindowPos(_GLFWwindow* window, int xpos, int ypos)
 {
     // A Wayland client can not set its position, so just warn
 
-    _glfwInputError(GLFW_PLATFORM_ERROR,
-                    "Wayland: Window position setting not supported");
+    _glfwInputError(GLFW_FEATURE_UNAVAILABLE,
+                    "Wayland: The platform does not support setting the window position");
 }
 
 void _glfwPlatformGetWindowSize(_GLFWwindow* window, int* width, int* height)
@@ -940,6 +940,8 @@ void _glfwPlatformSetWindowAspectRatio(_GLFWwindow* window,
 {
     // TODO: find out how to trigger a resize.
     // The actual limits are checked in the xdg_toplevel::configure handler.
+    _glfwInputError(GLFW_FEATURE_UNIMPLEMENTED,
+                    "Wayland: Window aspect ratio not yet implemented");
 }
 
 void _glfwPlatformGetFramebufferSize(_GLFWwindow* window,
@@ -1030,14 +1032,14 @@ void _glfwPlatformHideWindow(_GLFWwindow* window)
 void _glfwPlatformRequestWindowAttention(_GLFWwindow* window)
 {
     // TODO
-    _glfwInputError(GLFW_PLATFORM_ERROR,
+    _glfwInputError(GLFW_FEATURE_UNIMPLEMENTED,
                     "Wayland: Window attention request not implemented yet");
 }
 
 void _glfwPlatformFocusWindow(_GLFWwindow* window)
 {
-    _glfwInputError(GLFW_PLATFORM_ERROR,
-                    "Wayland: Focusing a window requires user interaction");
+    _glfwInputError(GLFW_FEATURE_UNAVAILABLE,
+                    "Wayland: The platform does not support setting the input focus");
 }
 
 void _glfwPlatformSetWindowMonitor(_GLFWwindow* window,
@@ -1096,7 +1098,7 @@ int _glfwPlatformFramebufferTransparent(_GLFWwindow* window)
 void _glfwPlatformSetWindowResizable(_GLFWwindow* window, GLFWbool enabled)
 {
     // TODO
-    _glfwInputError(GLFW_PLATFORM_ERROR,
+    _glfwInputError(GLFW_FEATURE_UNIMPLEMENTED,
                     "Wayland: Window attribute setting not implemented yet");
 }
 
@@ -1114,7 +1116,7 @@ void _glfwPlatformSetWindowDecorated(_GLFWwindow* window, GLFWbool enabled)
 void _glfwPlatformSetWindowFloating(_GLFWwindow* window, GLFWbool enabled)
 {
     // TODO
-    _glfwInputError(GLFW_PLATFORM_ERROR,
+    _glfwInputError(GLFW_FEATURE_UNIMPLEMENTED,
                     "Wayland: Window attribute setting not implemented yet");
 }
 
@@ -1125,6 +1127,8 @@ float _glfwPlatformGetWindowOpacity(_GLFWwindow* window)
 
 void _glfwPlatformSetWindowOpacity(_GLFWwindow* window, float opacity)
 {
+    _glfwInputError(GLFW_FEATURE_UNAVAILABLE,
+                    "Wayland: The platform does not support setting the window opacity");
 }
 
 void _glfwPlatformSetRawMouseMotion(_GLFWwindow *window, GLFWbool enabled)
@@ -1186,6 +1190,8 @@ void _glfwPlatformSetCursorMode(_GLFWwindow* window, int mode)
 const char* _glfwPlatformGetScancodeName(int scancode)
 {
     // TODO
+    _glfwInputError(GLFW_FEATURE_UNIMPLEMENTED,
+                    "Wayland: Key names not yet implemented");
     return NULL;
 }