gst-plugin: Properly export external API symbols

We do not install headers from gst-plugin, but still need to export
symbols to compile modules that use plugin provided shared libraries.

src/lib/gst/plugin/gstclappercontexthandler.h

@@ -22,6 +22,8 @@
 #include <gst/gst.h>
 #include <gst/base/gstbasesink.h>
 
+#include "gst/plugin/clapper-gst-visibility.h"
+
 G_BEGIN_DECLS
 
 #define GST_TYPE_CLAPPER_CONTEXT_HANDLER               (gst_clapper_context_handler_get_type())
@@ -53,10 +55,13 @@ struct _GstClapperContextHandlerClass
                                      GstQuery                 *query);
 };
 
+CLAPPER_GST_API
 GType                      gst_clapper_context_handler_get_type              (void);
 
+CLAPPER_GST_API
 gboolean                   gst_clapper_context_handler_handle_context_query  (GstClapperContextHandler *handler, GstBaseSink *bsink, GstQuery *query);
 
+CLAPPER_GST_API
 GstClapperContextHandler * gst_clapper_context_handler_obtain_with_type      (GPtrArray *context_handlers, GType type);
 
 G_END_DECLS

src/lib/gst/plugin/gstclapperimporter.h

@@ -23,6 +23,8 @@
 #include <gst/gst.h>
 #include <gst/video/video.h>
 
+#include "gst/plugin/clapper-gst-visibility.h"
+
 G_BEGIN_DECLS
 
 #define GST_TYPE_CLAPPER_IMPORTER               (gst_clapper_importer_get_type())
@@ -79,6 +81,7 @@ struct _GstClapperImporterClass
                                      GstVideoInfo       *v_info);
 };
 
+CLAPPER_GST_API
 GType           gst_clapper_importer_get_type                (void);
 
 GstBufferPool * gst_clapper_importer_create_pool             (GstClapperImporter *importer, GstStructure **config);

src/lib/gst/plugin/gstgtkutils.h

@@ -26,10 +26,14 @@
 #include <gtk/gtk.h>
 #include <gst/video/video.h>
 
+#include "gst/plugin/clapper-gst-visibility.h"
+
 G_BEGIN_DECLS
 
+CLAPPER_GST_API
 gpointer        gst_gtk_invoke_on_main                (GThreadFunc func, gpointer data);
 
+CLAPPER_GST_API
 GdkTexture *    gst_video_frame_into_gdk_texture      (GstVideoFrame *frame);
 
 void            gst_gtk_get_width_height_for_rotation (gint width, gint height,

src/lib/gst/plugin/handlers/gl/gstclapperglcontexthandler.h

@@ -27,10 +27,13 @@
 #include <gtk/gtk.h>
 
 #include "gst/plugin/gstclappercontexthandler.h"
+#include "gst/plugin/clapper-gst-visibility.h"
 
 G_BEGIN_DECLS
 
 #define GST_TYPE_CLAPPER_GL_CONTEXT_HANDLER (gst_clapper_gl_context_handler_get_type())
+
+CLAPPER_GST_API
 G_DECLARE_FINAL_TYPE (GstClapperGLContextHandler, gst_clapper_gl_context_handler, GST, CLAPPER_GL_CONTEXT_HANDLER, GstClapperContextHandler)
 
 #define GST_CLAPPER_GL_CONTEXT_HANDLER_CAST(obj)        ((GstClapperGLContextHandler *)(obj))
@@ -55,10 +58,13 @@ struct _GstClapperGLContextHandler
   GstGLContext *gst_context;
 };
 
+CLAPPER_GST_API
 void         gst_clapper_gl_context_handler_add_handler            (GPtrArray *context_handlers);
 
+CLAPPER_GST_API
 GstCaps *    gst_clapper_gl_context_handler_make_gdk_gl_caps       (const gchar *features, gboolean only_2d);
 
+CLAPPER_GST_API
 GdkTexture * gst_clapper_gl_context_handler_make_gl_texture        (GstClapperGLContextHandler *handler, GstBuffer *buffer, GstVideoInfo *v_info);
 
 G_END_DECLS

src/lib/gst/plugin/meson.build

@@ -23,11 +23,15 @@ endforeach
 
 gst_clapper_plugin_args = [
   '-DHAVE_CONFIG_H',
+  '-DCLAPPER_GST_COMPILATION',
   '-DGST_USE_UNSTABLE_API',
 ]
 
 if get_option('default_library') == 'static'
-  gst_clapper_plugin_args += ['-DGST_STATIC_COMPILATION']
+  gst_clapper_plugin_args += [
+    '-DGST_STATIC_COMPILATION',
+    '-DCLAPPER_GST_STATIC_COMPILATION',
+  ]
 endif
 
 cdata = configuration_data()
@@ -46,6 +50,20 @@ configure_file(
   output: 'config.h',
   configuration: cdata,
 )
+
+visibility_conf = configuration_data()
+
+visibility_conf.set(
+  'CLAPPER_API',
+  'CLAPPER_GST',
+)
+
+clappergst_visibility_header = configure_file(
+  input: '../../shared/clapper-api-visibility.h.in',
+  output: 'clapper-gst-visibility.h',
+  configuration: visibility_conf,
+)
+
 gst_plugin_conf_inc = [
   include_directories('.'),
   include_directories('..'),