Wayland: Fix crash if mouse connected after init

The cursor theme was only loaded if the chosen seat had a mouse
(wl_pointer) during initialization.  If a mouse was connected only after
glfwInit, there would be no cursor theme but the rest of the cursor
related code assumed one had already been loaded.

This also moves the details of cursor theme loading out into a separate
function to declutter platform init.

Because the original cursor theme loading code checked whether we got
a wl_shm, and because the rest of the code just assumes we have
a wl_shm, initialization will now fail if there isn't one.

Fixes #1450

CONTRIBUTORS.md

@@ -187,6 +187,7 @@ video tutorials.
  - Philip Rideout
  - Eddie Ringle
  - Max Risuhin
+ - Joe Roback
  - Jorge Rodriguez
  - Jari Ronkainen
  - Luca Rood

README.md

@@ -372,6 +372,7 @@ information on what to include when reporting a bug.
    wlroots compositors (#1268)
  - [Wayland] Bugfix: `GLFW_DECORATED` was ignored when showing a window with XDG
    decorations
+ - [Wayland] Bugfix: Connecting a mouse after `glfwInit` would segfault (#1450)
  - [POSIX] Removed use of deprecated function `gettimeofday`
  - [POSIX] Bugfix: `CLOCK_MONOTONIC` was not correctly tested for or enabled
  - [Linux] Bugfix: Joysticks without buttons were ignored (#2042,#2043)

src/wl_init.c

@@ -335,6 +335,41 @@ static void createKeyTables(void)
     }
 }
 
+static GLFWbool loadCursorTheme(void)
+{
+    const char* cursorTheme;
+    const char* cursorSizeStr;
+    char* cursorSizeEnd;
+    long cursorSizeLong;
+    int cursorSize;
+
+    cursorTheme = getenv("XCURSOR_THEME");
+    cursorSizeStr = getenv("XCURSOR_SIZE");
+    cursorSize = 32;
+    if (cursorSizeStr)
+    {
+        errno = 0;
+        cursorSizeLong = strtol(cursorSizeStr, &cursorSizeEnd, 10);
+        if (!*cursorSizeEnd && !errno && cursorSizeLong > 0 && cursorSizeLong <= INT_MAX)
+            cursorSize = (int)cursorSizeLong;
+    }
+    _glfw.wl.cursorTheme =
+        wl_cursor_theme_load(cursorTheme, cursorSize, _glfw.wl.shm);
+    if (!_glfw.wl.cursorTheme)
+    {
+        _glfwInputError(GLFW_PLATFORM_ERROR,
+                        "Wayland: Failed to load default cursor theme");
+        return GLFW_FALSE;
+    }
+    // If this happens to be NULL, we just fallback to the scale=1 version.
+    _glfw.wl.cursorThemeHiDPI =
+        wl_cursor_theme_load(cursorTheme, 2 * cursorSize, _glfw.wl.shm);
+    _glfw.wl.cursorSurface =
+        wl_compositor_create_surface(_glfw.wl.compositor);
+    _glfw.wl.cursorTimerfd = timerfd_create(CLOCK_MONOTONIC, TFD_CLOEXEC | TFD_NONBLOCK);
+    return GLFW_TRUE;
+}
+
 
 //////////////////////////////////////////////////////////////////////////
 //////                       GLFW platform API                      //////
@@ -471,12 +506,6 @@ GLFWbool _glfwConnectWayland(int platformID, _GLFWplatform* platform)
 
 int _glfwInitWayland(void)
 {
-    const char* cursorTheme;
-    const char* cursorSizeStr;
-    char* cursorSizeEnd;
-    long cursorSizeLong;
-    int cursorSize;
-
     // These must be set before any failure checks
     _glfw.wl.keyRepeatTimerfd = -1;
     _glfw.wl.cursorTimerfd = -1;
@@ -652,34 +681,16 @@ int _glfwInitWayland(void)
         return GLFW_FALSE;
     }
 
-    if (_glfw.wl.pointer && _glfw.wl.shm)
+    if (!_glfw.wl.shm)
     {
-        cursorTheme = getenv("XCURSOR_THEME");
-        cursorSizeStr = getenv("XCURSOR_SIZE");
-        cursorSize = 32;
-        if (cursorSizeStr)
-        {
-            errno = 0;
-            cursorSizeLong = strtol(cursorSizeStr, &cursorSizeEnd, 10);
-            if (!*cursorSizeEnd && !errno && cursorSizeLong > 0 && cursorSizeLong <= INT_MAX)
-                cursorSize = (int)cursorSizeLong;
-        }
-        _glfw.wl.cursorTheme =
-            wl_cursor_theme_load(cursorTheme, cursorSize, _glfw.wl.shm);
-        if (!_glfw.wl.cursorTheme)
-        {
-            _glfwInputError(GLFW_PLATFORM_ERROR,
-                            "Wayland: Failed to load default cursor theme");
-            return GLFW_FALSE;
-        }
-        // If this happens to be NULL, we just fallback to the scale=1 version.
-        _glfw.wl.cursorThemeHiDPI =
-            wl_cursor_theme_load(cursorTheme, 2 * cursorSize, _glfw.wl.shm);
-        _glfw.wl.cursorSurface =
-            wl_compositor_create_surface(_glfw.wl.compositor);
-        _glfw.wl.cursorTimerfd = timerfd_create(CLOCK_MONOTONIC, TFD_CLOEXEC | TFD_NONBLOCK);
+        _glfwInputError(GLFW_PLATFORM_ERROR,
+                        "Wayland: Failed to find wl_shm in your compositor");
+        return GLFW_FALSE;
     }
 
+    if (!loadCursorTheme())
+        return GLFW_FALSE;
+
     if (_glfw.wl.seat && _glfw.wl.dataDeviceManager)
     {
         _glfw.wl.dataDevice =