FindOpenGL: simplify OS selection code

This was using nested if's, now it uses elseif to flatten that. It also removes
one "if" from the general "else" branch that checks for Apple, as that has it's
own branch anyway and can't be true at this point.

Modules/FindOpenGL.cmake

@@ -28,111 +28,102 @@
 # (To distribute this file outside of CMake, substitute the full
 #  License text for the above reference.)
 
-if (WIN32)
-  if (CYGWIN)
+if (CYGWIN)
 
-    find_path(OPENGL_INCLUDE_DIR GL/gl.h )
+  find_path(OPENGL_INCLUDE_DIR GL/gl.h )
 
-    find_library(OPENGL_gl_LIBRARY opengl32 )
+  find_library(OPENGL_gl_LIBRARY opengl32 )
 
-    find_library(OPENGL_glu_LIBRARY glu32 )
+  find_library(OPENGL_glu_LIBRARY glu32 )
 
-  else ()
+elseif (WIN32)
 
-    if(BORLAND)
-      set (OPENGL_gl_LIBRARY import32 CACHE STRING "OpenGL library for win32")
-      set (OPENGL_glu_LIBRARY import32 CACHE STRING "GLU library for win32")
-    else()
-      set (OPENGL_gl_LIBRARY opengl32 CACHE STRING "OpenGL library for win32")
-      set (OPENGL_glu_LIBRARY glu32 CACHE STRING "GLU library for win32")
-    endif()
-
-  endif ()
-
-else ()
+  if(BORLAND)
+    set (OPENGL_gl_LIBRARY import32 CACHE STRING "OpenGL library for win32")
+    set (OPENGL_glu_LIBRARY import32 CACHE STRING "GLU library for win32")
+  else()
+    set (OPENGL_gl_LIBRARY opengl32 CACHE STRING "OpenGL library for win32")
+    set (OPENGL_glu_LIBRARY glu32 CACHE STRING "GLU library for win32")
+  endif()
 
-  if (APPLE)
+elseif (APPLE)
 
-    find_library(OPENGL_gl_LIBRARY OpenGL DOC "OpenGL lib for OSX")
-    find_library(OPENGL_glu_LIBRARY AGL DOC "AGL lib for OSX")
-    find_path(OPENGL_INCLUDE_DIR OpenGL/gl.h DOC "Include for OpenGL on OSX")
+  find_library(OPENGL_gl_LIBRARY OpenGL DOC "OpenGL lib for OSX")
+  find_library(OPENGL_glu_LIBRARY AGL DOC "AGL lib for OSX")
+  find_path(OPENGL_INCLUDE_DIR OpenGL/gl.h DOC "Include for OpenGL on OSX")
 
-  else()
-    if (CMAKE_SYSTEM_NAME MATCHES "HP-UX")
-      # Handle HP-UX cases where we only want to find OpenGL in either hpux64
-      # or hpux32 depending on if we're doing a 64 bit build.
-      if(CMAKE_SIZEOF_VOID_P EQUAL 4)
-        set(_OPENGL_LIB_PATH
-          /opt/graphics/OpenGL/lib/hpux32/)
-      else()
-        set(_OPENGL_LIB_PATH
-          /opt/graphics/OpenGL/lib/hpux64/
-          /opt/graphics/OpenGL/lib/pa20_64)
-      endif()
-    elseif(CMAKE_SYSTEM_NAME STREQUAL Haiku)
+else()
+  if (CMAKE_SYSTEM_NAME MATCHES "HP-UX")
+    # Handle HP-UX cases where we only want to find OpenGL in either hpux64
+    # or hpux32 depending on if we're doing a 64 bit build.
+    if(CMAKE_SIZEOF_VOID_P EQUAL 4)
+      set(_OPENGL_LIB_PATH
+        /opt/graphics/OpenGL/lib/hpux32/)
+    else()
       set(_OPENGL_LIB_PATH
-        /boot/develop/lib/x86)
-      set(_OPENGL_INCLUDE_PATH
-        /boot/develop/headers/os/opengl)
+        /opt/graphics/OpenGL/lib/hpux64/
+        /opt/graphics/OpenGL/lib/pa20_64)
     endif()
+  elseif(CMAKE_SYSTEM_NAME STREQUAL Haiku)
+    set(_OPENGL_LIB_PATH
+      /boot/develop/lib/x86)
+    set(_OPENGL_INCLUDE_PATH
+      /boot/develop/headers/os/opengl)
+  endif()
 
-    # The first line below is to make sure that the proper headers
-    # are used on a Linux machine with the NVidia drivers installed.
-    # They replace Mesa with NVidia's own library but normally do not
-    # install headers and that causes the linking to
-    # fail since the compiler finds the Mesa headers but NVidia's library.
-    # Make sure the NVIDIA directory comes BEFORE the others.
-    #  - Atanas Georgiev <[email protected]>
-
-    find_path(OPENGL_INCLUDE_DIR GL/gl.h
-      /usr/share/doc/NVIDIA_GLX-1.0/include
-      /usr/openwin/share/include
-      /opt/graphics/OpenGL/include /usr/X11R6/include
-      ${_OPENGL_INCLUDE_PATH}
-    )
-
-    find_path(OPENGL_xmesa_INCLUDE_DIR GL/xmesa.h
-      /usr/share/doc/NVIDIA_GLX-1.0/include
-      /usr/openwin/share/include
-      /opt/graphics/OpenGL/include /usr/X11R6/include
-    )
-
-    find_library(OPENGL_gl_LIBRARY
-      NAMES GL MesaGL
-      PATHS /opt/graphics/OpenGL/lib
-            /usr/openwin/lib
-            /usr/shlib /usr/X11R6/lib
-            ${_OPENGL_LIB_PATH}
-    )
-
-    unset(_OPENGL_INCLUDE_PATH)
-    unset(_OPENGL_LIB_PATH)
-
-    # On Unix OpenGL most certainly always requires X11.
-    # Feel free to tighten up these conditions if you don't
-    # think this is always true.
-    # It's not true on OSX.
-
-    if (OPENGL_gl_LIBRARY)
-      if(NOT X11_FOUND)
-        include(${CMAKE_CURRENT_LIST_DIR}/FindX11.cmake)
-      endif()
-      if (X11_FOUND)
-        if (NOT APPLE)
-          set (OPENGL_LIBRARIES ${X11_LIBRARIES})
-        endif ()
-      endif ()
+  # The first line below is to make sure that the proper headers
+  # are used on a Linux machine with the NVidia drivers installed.
+  # They replace Mesa with NVidia's own library but normally do not
+  # install headers and that causes the linking to
+  # fail since the compiler finds the Mesa headers but NVidia's library.
+  # Make sure the NVIDIA directory comes BEFORE the others.
+  #  - Atanas Georgiev <[email protected]>
+
+  find_path(OPENGL_INCLUDE_DIR GL/gl.h
+    /usr/share/doc/NVIDIA_GLX-1.0/include
+    /usr/openwin/share/include
+    /opt/graphics/OpenGL/include /usr/X11R6/include
+    ${_OPENGL_INCLUDE_PATH}
+  )
+
+  find_path(OPENGL_xmesa_INCLUDE_DIR GL/xmesa.h
+    /usr/share/doc/NVIDIA_GLX-1.0/include
+    /usr/openwin/share/include
+    /opt/graphics/OpenGL/include /usr/X11R6/include
+  )
+
+  find_library(OPENGL_gl_LIBRARY
+    NAMES GL MesaGL
+    PATHS /opt/graphics/OpenGL/lib
+          /usr/openwin/lib
+          /usr/shlib /usr/X11R6/lib
+          ${_OPENGL_LIB_PATH}
+  )
+
+  unset(_OPENGL_INCLUDE_PATH)
+  unset(_OPENGL_LIB_PATH)
+
+  # On Unix OpenGL most certainly always requires X11.
+  # Feel free to tighten up these conditions if you don't
+  # think this is always true.
+
+  if (OPENGL_gl_LIBRARY)
+    if(NOT X11_FOUND)
+      include(${CMAKE_CURRENT_LIST_DIR}/FindX11.cmake)
+    endif()
+    if (X11_FOUND)
+      set (OPENGL_LIBRARIES ${X11_LIBRARIES})
     endif ()
+  endif ()
 
-    find_library(OPENGL_glu_LIBRARY
-      NAMES GLU MesaGLU
-      PATHS ${OPENGL_gl_LIBRARY}
-            /opt/graphics/OpenGL/lib
-            /usr/openwin/lib
-            /usr/shlib /usr/X11R6/lib
-    )
+  find_library(OPENGL_glu_LIBRARY
+    NAMES GLU MesaGLU
+    PATHS ${OPENGL_gl_LIBRARY}
+          /opt/graphics/OpenGL/lib
+          /usr/openwin/lib
+          /usr/shlib /usr/X11R6/lib
+  )
 
-  endif()
 endif ()
 
 if(OPENGL_gl_LIBRARY)