app: Add some comment documentation to code

app/core/gimp-units.c

@@ -18,6 +18,10 @@
  * along with this program.  If not, see <http://www.gnu.org/licenses/>.
  */
 
+/* This file contains functions to load & save the file containing the
+ * user-defined size units, when the application starts/finished.
+ */
+
 #include "config.h"
 
 #include <glib-object.h>

app/core/gimp-user-install.c

@@ -18,6 +18,10 @@
  * along with this program.  If not, see <http://www.gnu.org/licenses/>.
  */
 
+/* This file contains functions to help migrate the settings from a
+ * previous GIMP version to be used with the current (newer) version.
+ */
+
 #include "config.h"
 
 #include <errno.h>

app/core/gimpimagemap.c

@@ -15,6 +15,22 @@
  * along with this program.  If not, see <http://www.gnu.org/licenses/>.
  */
 
+/* This file contains the code necessary for generating on canvas
+ * previews, either by connecting a function to process the pixels or
+ * by connecting a specified GEGL operation to do the processing. It
+ * keeps an undo buffer to allow direct modification of the pixel data
+ * (so that it will show up in the projection) and it will restore the
+ * source in case the mapping procedure was cancelled.
+ *
+ * To create a tool that uses this, see /tools/gimpimagemaptool.c for
+ * the interface and /tools/gimpcolorbalancetool.c for an example of
+ * using that interface.
+ *
+ * Note that when talking about on canvas preview, we are speaking
+ * about non destructive image editing where the operation is previewd
+ * before being applied.
+ */
+
 #include "config.h"
 
 #include <glib-object.h>

app/core/gimppickable.c

@@ -18,6 +18,12 @@
  * along with this program.  If not, see <http://www.gnu.org/licenses/>.
  */
 
+/* This file contains an interface for pixel objects that their color at
+ * a given position can be picked. Also included is a utility for
+ * sampling an average area (which uses the implemented picking
+ * functions).
+ */
+
 #include "config.h"
 
 #include <gegl.h>

app/core/gimptemplate.c

@@ -18,6 +18,9 @@
  * along with this program.  If not, see <http://www.gnu.org/licenses/>.
  */
 
+/* This file contains the definition of the image template objects.
+ */
+
 #include "config.h"
 
 #include <gegl.h>

app/core/gimpunit.c

@@ -18,6 +18,10 @@
  * along with this program.  If not, see <http://www.gnu.org/licenses/>.
  */
 
+/* This file contains the definition of the size unit objects. The
+ * factor of the units is relative to inches (which have a factor of 1).
+ */
+
 #include "config.h"
 
 #include <glib-object.h>

app/tools/gimpimagemaptool.c

@@ -15,6 +15,13 @@
  * along with this program.  If not, see <http://www.gnu.org/licenses/>.
  */
 
+/* This file contains a base class for tools that implement on canvas
+ * preview for non destructive editing. The processing of the pixels can
+ * be done either by a gegl op or by a C function (apply_func).
+ *
+ * For the core side of this, please see /app/core/gimpimagemap.c.
+ */
+
 #include "config.h"
 
 #include <string.h>