[gtksourceview/wip/minimap] minimap: add some documentation on private struct fields

[Christian Hergert <chergert src gnome org>]

commit 104cfd9607c6e11204859d49e05b54e7e9dc8ee3
Author: Christian Hergert <christian hergert me>
Date:   Thu May 7 12:59:05 2015 -0700

    minimap: add some documentation on private struct fields
    
    Just some more background information on the current implementation.

 gtksourceview/gtksourcemap.c |   29 +++++++++++++++++++++++++++++
 1 files changed, 29 insertions(+), 0 deletions(-)
---
diff --git a/gtksourceview/gtksourcemap.c b/gtksourceview/gtksourcemap.c
index d92374f..b3c9543 100644
--- a/gtksourceview/gtksourcemap.c
+++ b/gtksourceview/gtksourcemap.c
@@ -100,12 +100,41 @@ typedef struct
 {
        PangoFontDescription *font_desc;
 
+       /*
+        * We use a separate CSS provider for the view (controlling the font)
+        * and the overlay box due to the inability to get both styled
+        * correctly from the same CSS provider. If someone can determine
+        * the cause of this, we should merge them into a single provider.
+        */
        GtkCssProvider *view_css_provider;
        GtkCssProvider *box_css_provider;
 
+       /*
+        * We use an overlay to place the scrubber above the source view.
+        * Doing so allows us to composite the two widgets together instead
+        * invalidating the child_view's pixel cache by rendering during its
+        * draw_layer() vfunc.
+        */
        GtkOverlay *overlay;
+
+       /*
+        * This is our minimap widget. We adjust the font to be a 1pt font
+        * but otherwise try to render things as close to the same as the
+        * view we are providing a map of. We do not render the background
+        * grid as it requires a lot of cpu time and isn't visible anyway.
+        * The width of the view is controlled by "right-margin-position"
+        * multiplied by the size of a single character. Content that wraps
+        * beyond right-margin-position is not displayed.
+        */
        GtkSourceView *child_view;
+
+       /*
+        * overlay_box is our scrubber widget. It is the translucent overlay
+        * that the user can grab and drag to perform an accelerated scroll.
+        */
        GtkEventBox *overlay_box;
+
+       /* The GtkSourceView we are providing a map of */
        GtkSourceView *view;
 
        gboolean in_press : 1;