Don't use GL-specific stuff on targets without GL enabled.

CMakeLists.txt

@@ -213,13 +213,15 @@ if(BUILD_STATIC)
 endif()
 
 # Check dependencies
-if(NOT TARGET_GLES OR TARGET_DESKTOP_GLES)
-    set(OpenGL_GL_PREFERENCE GLVND) # since CMake 3.11
-    find_package(OpenGL REQUIRED)
-elseif(TARGET_GLES2)
-    find_package(OpenGLES2 REQUIRED)
-else()
-    find_package(OpenGLES3 REQUIRED)
+if(WITH_GL)
+    if(NOT TARGET_GLES OR TARGET_DESKTOP_GLES)
+        set(OpenGL_GL_PREFERENCE GLVND) # since CMake 3.11
+        find_package(OpenGL REQUIRED)
+    elseif(TARGET_GLES2)
+        find_package(OpenGLES2 REQUIRED)
+    else()
+        find_package(OpenGLES3 REQUIRED)
+    endif()
 endif()
 
 # Configuration variables (saved later to configure.h)

doc/changelog.dox

@@ -285,6 +285,8 @@ See also:
 
 -   There's now a PPA for Ubuntu packages. See @ref building-packages-deb
     for more information.
+-   Fixed various issues preventing to build and use the base libraries with
+    OpenGL support disabled (see [mosra/magnum#255](https://github.com/mosra/magnum/pull/255))
 -   Magnum now links to GLVND on Linux instead of the old libGL ABI if using
     CMake 3.11 and newer
 -   @ref cmake "FindMagnum.cmake" now allows to use the @ref DebugTools library

modules/FindMagnum.cmake

@@ -327,7 +327,7 @@ if(NOT TARGET Magnum::Magnum)
         ${MAGNUM_INCLUDE_DIR})
     # Some deprecated APIs use headers (but not externally defined symbols)
     # from the GL library, link those includes as well
-    if(MAGNUM_BUILD_DEPRECATED)
+    if(MAGNUM_BUILD_DEPRECATED AND MAGNUM_TARGET_GL)
         set_property(TARGET Magnum::Magnum APPEND PROPERTY
             INTERFACE_INCLUDE_DIRECTORIES ${MAGNUM_INCLUDE_DIR}/MagnumExternal/OpenGL)
     endif()

src/Magnum/ImageView.h

@@ -350,7 +350,7 @@ template<UnsignedInt dimensions> class ImageView {
          */
         UnsignedInt formatExtra() const { return _formatExtra; }
 
-        #ifdef MAGNUM_BUILD_DEPRECATED
+        #if defined(MAGNUM_BUILD_DEPRECATED) && defined(MAGNUM_TARGET_GL)
         /**
          * @brief Data type of pixel data
          * @deprecated Cast @ref formatExtra() to @ref GL::PixelType instead.

src/Magnum/Magnum.h

@@ -34,7 +34,7 @@
 #include "Magnum/Types.h"
 #include "Magnum/Math/Math.h"
 
-#ifdef MAGNUM_BUILD_DEPRECATED
+#if defined(MAGNUM_BUILD_DEPRECATED) && defined(MAGNUM_TARGET_GL)
 #include "Magnum/GL/GL.h"
 #endif
 
@@ -761,7 +761,7 @@ enum class SamplerWrapping: UnsignedInt;
 
 class Timeline;
 
-#ifdef MAGNUM_BUILD_DEPRECATED
+#if defined(MAGNUM_BUILD_DEPRECATED) && defined(MAGNUM_TARGET_GL)
 typedef CORRADE_DEPRECATED("use GL::AbstractFramebuffer instead") GL::AbstractFramebuffer AbstractFramebuffer;
 
 #if !(defined(MAGNUM_TARGET_WEBGL) && defined(MAGNUM_TARGET_GLES2))

src/Magnum/PixelFormat.h

@@ -635,7 +635,7 @@ enum class PixelFormat: UnsignedInt {
     #endif
 };
 
-#ifdef MAGNUM_BUILD_DEPRECATED
+#if defined(MAGNUM_BUILD_DEPRECATED) && defined(MAGNUM_TARGET_GL)
 /** @brief @copybrief GL::PixelType
  * @deprecated Use @ref GL::PixelType instead.
  */

src/Magnum/Trade/AbstractImageConverter.h

@@ -33,7 +33,6 @@
 #include <Corrade/PluginManager/AbstractManagingPlugin.h>
 
 #include "Magnum/Magnum.h"
-#include "Magnum/GL/GL.h"
 #include "Magnum/Trade/Trade.h"
 #include "Magnum/Trade/visibility.h"