Wayland: Store and act on XDG decoration mode

Refer to the XDG decoration mode (or the lack of one) directly instead
of setting a boolean in a struct meant for the fallback decorations.

This makes things a bit more verbose but is in preparation for
a refactoring of all decoration paths.

src/wl_platform.h

@@ -251,6 +251,7 @@ typedef struct _GLFWwindowWayland
         struct xdg_surface*     surface;
         struct xdg_toplevel*    toplevel;
         struct zxdg_toplevel_decoration_v1* decoration;
+        uint32_t                decorationMode;
     } xdg;
 
     _GLFWcursor*                currentCursor;
@@ -273,7 +274,6 @@ typedef struct _GLFWwindowWayland
     struct zwp_idle_inhibitor_v1*          idleInhibitor;
 
     struct {
-        GLFWbool                           serverSide;
         struct wl_buffer*                  buffer;
         _GLFWdecorationWayland             top, left, right, bottom;
         int                                focus;

src/wl_window.c

@@ -220,7 +220,7 @@ static void createFallbackDecorations(_GLFWwindow* window)
     unsigned char data[] = { 224, 224, 224, 255 };
     const GLFWimage image = { 1, 1, data };
 
-    if (!_glfw.wl.viewporter || !window->decorated || window->wl.decorations.serverSide)
+    if (!_glfw.wl.viewporter || !window->decorated)
         return;
 
     if (!window->wl.decorations.buffer)
@@ -273,9 +273,9 @@ static void xdgDecorationHandleConfigure(void* userData,
 {
     _GLFWwindow* window = userData;
 
-    window->wl.decorations.serverSide = (mode == ZXDG_TOPLEVEL_DECORATION_V1_MODE_SERVER_SIDE);
+    window->wl.xdg.decorationMode = mode;
 
-    if (!window->wl.decorations.serverSide)
+    if (mode == ZXDG_TOPLEVEL_DECORATION_V1_MODE_CLIENT_SIDE)
         createFallbackDecorations(window);
 }
 
@@ -431,7 +431,7 @@ static void acquireMonitor(_GLFWwindow* window)
 
     setIdleInhibitor(window, GLFW_TRUE);
 
-    if (!window->wl.decorations.serverSide)
+    if (window->wl.decorations.top.surface)
         destroyFallbackDecorations(window);
 }
 
@@ -444,7 +444,7 @@ static void releaseMonitor(_GLFWwindow* window)
 
     setIdleInhibitor(window, GLFW_FALSE);
 
-    if (!_glfw.wl.decorationManager)
+    if (window->wl.xdg.decorationMode != ZXDG_TOPLEVEL_DECORATION_V1_MODE_SERVER_SIDE)
         createFallbackDecorations(window);
 }
 
@@ -635,10 +635,7 @@ static GLFWbool createShellObjects(_GLFWwindow* window)
                 ZXDG_TOPLEVEL_DECORATION_V1_MODE_SERVER_SIDE);
         }
         else
-        {
-            window->wl.decorations.serverSide = GLFW_FALSE;
             createFallbackDecorations(window);
-        }
     }
 
     if (window->minwidth != GLFW_DONT_CARE && window->minheight != GLFW_DONT_CARE)
@@ -689,6 +686,7 @@ static void destroyShellObjects(_GLFWwindow* window)
         xdg_surface_destroy(window->wl.xdg.surface);
 
     window->wl.xdg.decoration = NULL;
+    window->wl.xdg.decorationMode = 0;
     window->wl.xdg.toplevel = NULL;
     window->wl.xdg.surface = NULL;
 }
@@ -1978,7 +1976,7 @@ void _glfwGetWindowFrameSizeWayland(_GLFWwindow* window,
                                     int* left, int* top,
                                     int* right, int* bottom)
 {
-    if (window->decorated && !window->monitor && !window->wl.decorations.serverSide)
+    if (window->decorated && !window->monitor && window->wl.decorations.top.surface)
     {
         if (top)
             *top = GLFW_CAPTION_HEIGHT;