[gtk+] Document new texture api

[Matthias Clasen <matthiasc src gnome org>]

commit e1d81d096cc6115bb7da033b1085ea909d645448
Author: Matthias Clasen <mclasen redhat com>
Date:   Wed Jan 17 21:45:08 2018 -0500

    Document new texture api

 docs/reference/gdk/gdk4-sections.txt |    2 ++
 gdk/gdktexture.c                     |   33 +++++++++++++++++++++++++++++++++
 2 files changed, 35 insertions(+), 0 deletions(-)
---
diff --git a/docs/reference/gdk/gdk4-sections.txt b/docs/reference/gdk/gdk4-sections.txt
index eff5965..d492279 100644
--- a/docs/reference/gdk/gdk4-sections.txt
+++ b/docs/reference/gdk/gdk4-sections.txt
@@ -786,11 +786,13 @@ gdk_event_get_type
 GdkTexture
 gdk_texture_new_for_data
 gdk_texture_new_for_pixbuf
+gdk_texture_new_for_gl
 gdk_texture_new_from_resource
 gdk_texture_new_from_file
 gdk_texture_get_width
 gdk_texture_get_height
 gdk_texture_download
+gdk_texture_release_gl
 
 <SUBSECTION Standard>
 GdkTextureClass
diff --git a/gdk/gdktexture.c b/gdk/gdktexture.c
index f85b096..aefb82c 100644
--- a/gdk/gdktexture.c
+++ b/gdk/gdktexture.c
@@ -541,6 +541,19 @@ gdk_gl_texture_get_id (GdkGLTexture *self)
   return self->id;
 }
 
+/**
+ * gdk_texture_release_gl:
+ * @texture: a #GdkTexture wrapping a GL texture
+ *
+ * Releases the GL resources held by a #GdkTexture that
+ * was created with gdk_texture_new_for_gl().
+ *
+ * The texture contents are still available via the
+ * gdk_texture_download() function, after this function
+ * has been called.
+ *
+ * Since: 3.94
+ */
 void
 gdk_texture_release_gl (GdkTexture *texture)
 {
@@ -676,6 +689,26 @@ gdk_texture_new_from_file (GFile   *file,
   return texture;
 }
 
+/**
+ * gdk_texture_new_for_gl:
+ * @context: a #GdkGLContext
+ * @id: the ID of a texture that was created with @context
+ * @width: the nominal width of the texture
+ * @height: the nominal height of the texture
+ * @destroy: a destroy notify that will be called when the GL resources
+ *           are released
+ * @data: data that gets passed to @destroy
+ *
+ * Creates a new texture for an existing GL texture.
+ *
+ * Note that the GL texture must not be modified until @destroy is called,
+ * which will happen when the GdkTexture object is finalized, or due to
+ * an explicit call of gdk_texture_release_gl().
+ *
+ * Return value: A newly-created #GdkTexture
+ *
+ * Since: 3.94
+ **/
 GdkTexture *
 gdk_texture_new_for_gl (GdkGLContext   *context,
                         int             id,