GHOST: replace multiple functions with a single capabilities flag

Adding checks for platform capabilities involved adding functions
to multiple classes and was too involved.

Replace this with a single GHOST_System::getCapabilities() function.

intern/ghost/GHOST_C-api.h

@@ -924,19 +924,9 @@ extern bool GHOST_setConsoleWindowState(GHOST_TConsoleWindowState action);
 extern bool GHOST_UseNativePixels(void);
 
 /**
- * Warp the cursor, if supported.
+ * Return features which are supported by the GHOST back-end.
  */
-extern bool GHOST_SupportsCursorWarp(void);
-
-/**
- * Support positioning windows (when false `wmWindow.x,y` are meaningless).
- */
-extern bool GHOST_SupportsWindowPosition(void);
-
-/**
- * Support a separate primary clipboard.
- */
-extern bool GHOST_SupportsPrimaryClipboard(void);
+extern GHOST_TCapabilityFlag GHOST_GetCapabilities(void);
 
 /**
  * Assign the callback which generates a back-trace (may be NULL).

intern/ghost/GHOST_ISystem.h

@@ -318,19 +318,11 @@ class GHOST_ISystem {
   virtual bool useNativePixel(void) = 0;
 
   /**
-   * Return true when warping the cursor is supported.
+   * Return features supported by the system back-end.
+   *
+   * The resulting value doesn't change at run-time.
    */
-  virtual bool supportsCursorWarp() = 0;
-
-  /**
-   * Return true getting/setting the window position is supported.
-   */
-  virtual bool supportsWindowPosition() = 0;
-
-  /**
-   * Return true when a separate primary clipboard is supported.
-   */
-  virtual bool supportsPrimaryClipboard() = 0;
+  virtual GHOST_TCapabilityFlag getCapabilities() const = 0;
 
   /**
    * Focus window after opening, or put them in the background.

intern/ghost/GHOST_Types.h

@@ -74,6 +74,37 @@ typedef void *GHOST_TUserDataPtr;
 
 typedef enum { GHOST_kFailure = 0, GHOST_kSuccess } GHOST_TSuccess;
 
+/**
+ * Static flag (relating to the back-ends support for features).
+ *
+ * \note When adding new capabilities, add to #GHOST_CAPABILITY_FLAG_ALL,
+ * then mask out of from the `getCapabilities(..)` callback with an explanation for why
+ * the feature is not supported.
+ */
+typedef enum {
+  /**
+   * Set when warping the cursor is supported (re-positioning the users cursor).
+   */
+  GHOST_kCapabilityCursorWarp = (1 << 0),
+  /**
+   * Set when getting/setting the window position is supported.
+   */
+  GHOST_kCapabilityWindowPosition = (1 << 1),
+  /**
+   * Set when a separate primary clipboard is supported.
+   * This is a convention for X11/WAYLAND, select text & MMB to paste (without an explicit copy).
+   */
+  GHOST_kCapabilityPrimaryClipboard = (1 << 2),
+} GHOST_TCapabilityFlag;
+
+/**
+ * Back-ends should use this, masking out features which are not supported
+ * with notes as to why those features cannot be supported.
+ */
+#define GHOST_CAPABILITY_FLAG_ALL \
+  (GHOST_kCapabilityCursorWarp | GHOST_kCapabilityWindowPosition | \
+   GHOST_kCapabilityPrimaryClipboard)
+
 /* Xtilt and Ytilt represent how much the pen is tilted away from
  * vertically upright in either the X or Y direction, with X and Y the
  * axes of the tablet surface.

intern/ghost/intern/GHOST_C-api.cpp

@@ -895,22 +895,10 @@ bool GHOST_UseNativePixels(void)
   return system->useNativePixel();
 }
 
-bool GHOST_SupportsCursorWarp(void)
+GHOST_TCapabilityFlag GHOST_GetCapabilities(void)
 {
   GHOST_ISystem *system = GHOST_ISystem::getSystem();
-  return system->supportsCursorWarp();
-}
-
-bool GHOST_SupportsWindowPosition(void)
-{
-  GHOST_ISystem *system = GHOST_ISystem::getSystem();
-  return system->supportsWindowPosition();
-}
-
-bool GHOST_SupportsPrimaryClipboard(void)
-{
-  GHOST_ISystem *system = GHOST_ISystem::getSystem();
-  return system->supportsPrimaryClipboard();
+  return system->getCapabilities();
 }
 
 void GHOST_SetBacktraceHandler(GHOST_TBacktraceFn backtrace_fn)

intern/ghost/intern/GHOST_System.cpp

@@ -418,21 +418,6 @@ void GHOST_System::setAutoFocus(const bool auto_focus)
   m_autoFocus = auto_focus;
 }
 
-bool GHOST_System::supportsCursorWarp()
-{
-  return true;
-}
-
-bool GHOST_System::supportsWindowPosition()
-{
-  return true;
-}
-
-bool GHOST_System::supportsPrimaryClipboard()
-{
-  return false;
-}
-
 void GHOST_System::initDebug(GHOST_Debug debug)
 {
   m_is_debug_enabled = debug.flags & GHOST_kDebugDefault;

intern/ghost/intern/GHOST_System.h

@@ -150,10 +150,6 @@ class GHOST_System : public GHOST_ISystem {
   bool useNativePixel(void);
   bool m_nativePixel;
 
-  bool supportsCursorWarp(void);
-  bool supportsWindowPosition(void);
-  bool supportsPrimaryClipboard(void);
-
   /**
    * Focus window after opening, or put them in the background.
    */

intern/ghost/intern/GHOST_SystemCocoa.h

@@ -193,6 +193,8 @@ class GHOST_SystemCocoa : public GHOST_System {
    */
   GHOST_TSuccess getButtons(GHOST_Buttons &buttons) const;
 
+  GHOST_TCapabilityFlag getCapabilities() const;
+
   /**
    * Returns Clipboard data
    * \param selection: Indicate which buffer to return.

intern/ghost/intern/GHOST_SystemCocoa.mm

@@ -900,6 +900,14 @@ GHOST_TSuccess GHOST_SystemCocoa::getButtons(GHOST_Buttons &buttons) const
   return GHOST_kSuccess;
 }
 
+GHOST_TCapabilityFlag GHOST_SystemCocoa::getCapabilities() const
+{
+  return GHOST_TCapabilityFlag(GHOST_CAPABILITY_FLAG_ALL &
+                               ~(
+                                   /* Cocoa has no support for a primary selection clipboard. */
+                                   GHOST_kCapabilityPrimaryClipboard));
+}
+
 #pragma mark Event handlers
 
 /**

intern/ghost/intern/GHOST_SystemHeadless.h

@@ -42,6 +42,13 @@ class GHOST_SystemHeadless : public GHOST_System {
   {
     return GHOST_kSuccess;
   }
+  GHOST_TCapabilityFlag getCapabilities() const override
+  {
+    return GHOST_TCapabilityFlag(GHOST_CAPABILITY_FLAG_ALL &
+                                 /* No windowing functionality supported. */
+                                 ~(GHOST_kCapabilityWindowPosition | GHOST_kCapabilityCursorWarp |
+                                   GHOST_kCapabilityPrimaryClipboard));
+  }
   char *getClipboard(bool /*selection*/) const override
   {
     return nullptr;

intern/ghost/intern/GHOST_SystemSDL.cpp

@@ -751,6 +751,15 @@ GHOST_TSuccess GHOST_SystemSDL::getButtons(GHOST_Buttons &buttons) const
   return GHOST_kSuccess;
 }
 
+GHOST_TCapabilityFlag GHOST_SystemSDL::getCapabilities() const
+{
+  return GHOST_TCapabilityFlag(
+      GHOST_CAPABILITY_FLAG_ALL &
+      ~(
+          /* This SDL back-end has not yet implemented primary clipboard. */
+          GHOST_kCapabilityPrimaryClipboard));
+}
+
 char *GHOST_SystemSDL::getClipboard(bool /*selection*/) const
 {
   return (char *)SDL_GetClipboardText();

intern/ghost/intern/GHOST_SystemSDL.h

@@ -42,6 +42,8 @@ class GHOST_SystemSDL : public GHOST_System {
 
   GHOST_TSuccess getButtons(GHOST_Buttons &buttons) const;
 
+  GHOST_TCapabilityFlag getCapabilities() const;
+
   char *getClipboard(bool selection) const;
 
   void putClipboard(const char *buffer, bool selection) const;

intern/ghost/intern/GHOST_SystemWayland.cpp

@@ -6675,22 +6675,16 @@ GHOST_TSuccess GHOST_SystemWayland::cursor_visibility_set(const bool visible)
   return GHOST_kSuccess;
 }
 
-bool GHOST_SystemWayland::supportsCursorWarp()
+GHOST_TCapabilityFlag GHOST_SystemWayland::getCapabilities() const
 {
-  /* WAYLAND doesn't support setting the cursor position directly,
-   * this is an intentional choice, forcing us to use a software cursor in this case. */
-  return false;
-}
-
-bool GHOST_SystemWayland::supportsWindowPosition()
-{
-  /* WAYLAND doesn't support accessing the window position. */
-  return false;
-}
-
-bool GHOST_SystemWayland::supportsPrimaryClipboard()
-{
-  return true;
+  return GHOST_TCapabilityFlag(
+      GHOST_CAPABILITY_FLAG_ALL &
+      ~(
+          /* WAYLAND doesn't support accessing the window position. */
+          GHOST_kCapabilityWindowPosition |
+          /* WAYLAND doesn't support setting the cursor position directly,
+           * this is an intentional choice, forcing us to use a software cursor in this case. */
+          GHOST_kCapabilityCursorWarp));
 }
 
 bool GHOST_SystemWayland::cursor_grab_use_software_display_get(const GHOST_TGrabCursorMode mode)
@@ -7038,7 +7032,7 @@ bool GHOST_SystemWayland::window_cursor_grab_set(const GHOST_TGrabCursorMode mod
   const struct GWL_SeatStateGrab grab_state_next = seat_grab_state_from_mode(mode,
                                                                              use_software_confine);
 
-  /* Check for wrap as #supportsCursorWarp isn't supported. */
+  /* Check for wrap as #GHOST_kCapabilityCursorWarp isn't supported. */
   const bool use_visible = !(ELEM(mode, GHOST_kGrabHide, GHOST_kGrabWrap) || use_software_confine);
   const bool is_hardware_cursor = !cursor_is_software(mode, use_software_confine);
 

intern/ghost/intern/GHOST_SystemWayland.h

@@ -142,9 +142,7 @@ class GHOST_SystemWayland : public GHOST_System {
                               const bool is_dialog,
                               const GHOST_IWindow *parentWindow) override;
 
-  bool supportsCursorWarp() override;
-  bool supportsWindowPosition() override;
-  bool supportsPrimaryClipboard() override;
+  GHOST_TCapabilityFlag getCapabilities() const override;
 
   /* WAYLAND utility functions (share window/system logic). */
 

intern/ghost/intern/GHOST_SystemWin32.cpp

@@ -496,6 +496,14 @@ GHOST_TSuccess GHOST_SystemWin32::getButtons(GHOST_Buttons &buttons) const
   return GHOST_kSuccess;
 }
 
+GHOST_TCapabilityFlag GHOST_SystemWin32::getCapabilities() const
+{
+  return GHOST_TCapabilityFlag(GHOST_CAPABILITY_FLAG_ALL &
+                               ~(
+                                   /* WIN32 has no support for a primary selection clipboard. */
+                                   GHOST_kCapabilityPrimaryClipboard));
+}
+
 GHOST_TSuccess GHOST_SystemWin32::init()
 {
   GHOST_TSuccess success = GHOST_System::init();

intern/ghost/intern/GHOST_SystemWin32.h

@@ -199,6 +199,8 @@ class GHOST_SystemWin32 : public GHOST_System {
    */
   GHOST_TSuccess getButtons(GHOST_Buttons &buttons) const;
 
+  GHOST_TCapabilityFlag getCapabilities() const;
+
   /**
    * Returns unsigned char from CUT_BUFFER0
    * \param selection: Used by X11 only.

intern/ghost/intern/GHOST_SystemX11.cpp

@@ -1740,9 +1740,9 @@ GHOST_TSuccess GHOST_SystemX11::setCursorPosition(int32_t x, int32_t y)
   return GHOST_kSuccess;
 }
 
-bool GHOST_SystemX11::supportsPrimaryClipboard()
+GHOST_TCapabilityFlag GHOST_SystemX11::getCapabilities() const
 {
-  return true;
+  return GHOST_TCapabilityFlag(GHOST_CAPABILITY_FLAG_ALL);
 }
 
 void GHOST_SystemX11::addDirtyWindow(GHOST_WindowX11 *bad_wind)

intern/ghost/intern/GHOST_SystemX11.h

@@ -168,7 +168,7 @@ class GHOST_SystemX11 : public GHOST_System {
    */
   GHOST_TSuccess getButtons(GHOST_Buttons &buttons) const;
 
-  bool supportsPrimaryClipboard() override;
+  GHOST_TCapabilityFlag getCapabilities() const;
 
   /**
    * Flag a window as dirty. This will

source/blender/windowmanager/intern/wm_draw.c

@@ -179,7 +179,7 @@ struct GrabState {
 static bool wm_software_cursor_needed(void)
 {
   if (UNLIKELY(g_software_cursor.enabled == -1)) {
-    g_software_cursor.enabled = !GHOST_SupportsCursorWarp();
+    g_software_cursor.enabled = !(WM_capabilities_flag() & WM_CAPABILITY_CURSOR_WARP);
   }
   return g_software_cursor.enabled;
 }

source/blender/windowmanager/intern/wm_event_system.cc

@@ -5165,7 +5165,8 @@ static void attach_ndof_data(wmEvent *event, const GHOST_TEventNDOFMotionData *g
 static wmWindow *wm_event_cursor_other_windows(wmWindowManager *wm, wmWindow *win, wmEvent *event)
 {
   /* If GHOST doesn't support window positioning, don't use this feature at all. */
-  const static int8_t supports_window_position = GHOST_SupportsWindowPosition();
+  const static int8_t supports_window_position = (WM_capabilities_flag() &
+                                                  WM_CAPABILITY_WINDOW_POSITION) != 0;
   if (!supports_window_position) {
     return nullptr;
   }

source/blender/windowmanager/intern/wm_window.c

@@ -998,7 +998,11 @@ wmWindow *WM_window_open(bContext *C,
   return NULL;
 }
 
-/* ****************** Operators ****************** */
+/** \} */
+
+/* -------------------------------------------------------------------- */
+/** \name Operators
+ * \{ */
 
 int wm_window_close_exec(bContext *C, wmOperator *UNUSED(op))
 {
@@ -1063,7 +1067,11 @@ int wm_window_fullscreen_toggle_exec(bContext *C, wmOperator *UNUSED(op))
   return OPERATOR_FINISHED;
 }
 
-/* ************ events *************** */
+/** \} */
+
+/* -------------------------------------------------------------------- */
+/** \name Events
+ * \{ */
 
 void wm_cursor_position_from_ghost_client_coords(wmWindow *win, int *x, int *y)
 {
@@ -1827,14 +1835,14 @@ eWM_CapabilitiesFlag WM_capabilities_flag(void)
     return flag;
   }
 
-  flag = 0;
-  if (GHOST_SupportsCursorWarp()) {
+  const GHOST_TCapabilityFlag ghost_flag = GHOST_GetCapabilities();
+  if (ghost_flag & GHOST_kCapabilityCursorWarp) {
     flag |= WM_CAPABILITY_CURSOR_WARP;
   }
-  if (GHOST_SupportsWindowPosition()) {
+  if (ghost_flag & GHOST_kCapabilityWindowPosition) {
     flag |= WM_CAPABILITY_WINDOW_POSITION;
   }
-  if (GHOST_SupportsPrimaryClipboard()) {
+  if (ghost_flag & GHOST_kCapabilityPrimaryClipboard) {
     flag |= WM_CAPABILITY_PRIMARY_CLIPBOARD;
   }