[gtksourceview] map: improve slider position again

[Christian Hergert <chergert src gnome org>]

commit 5f0be0143e7068f1d33d8ff23f332a7d70b4e747
Author: Christian Hergert <chergert redhat com>
Date:   Thu Oct 14 17:55:56 2021 -0700

    map: improve slider position again
    
    Sort of a revert of the other changes because it would grow/shrink too
    much as we moved. This is slightly off, but much nicer from the standpoint
    of being stable.

 gtksourceview/gtksourcemap.c | 53 +++++++++++++++++++++++---------------------
 1 file changed, 28 insertions(+), 25 deletions(-)
---
diff --git a/gtksourceview/gtksourcemap.c b/gtksourceview/gtksourcemap.c
index 2f1fdcc8..b741d9e5 100644
--- a/gtksourceview/gtksourcemap.c
+++ b/gtksourceview/gtksourcemap.c
@@ -266,40 +266,43 @@ get_slider_position (GtkSourceMap *map,
                      GdkRectangle *slider_area)
 {
        GtkSourceMapPrivate *priv = gtk_source_map_get_instance_private (map);
-       GdkRectangle visible_rect, top_rect, bottom_rect;
-       GtkTextIter top, bottom;
-       int top_y, bottom_y;
-
-       g_assert (GTK_SOURCE_IS_MAP (map));
-
-       slider_area->x = 0;
-       slider_area->y = 0;
-       slider_area->width = width;
-       slider_area->height = 0;
+       GdkRectangle them_visible_rect, us_visible_rect;
+       GdkRectangle us_alloc;
+       GtkStyleContext *style_context;
+       GtkTextBuffer *buffer;
+       GtkTextIter end_iter;
+       GdkRectangle end_rect;
+       GtkBorder border;
+       int us_height;
+       int them_height;
 
        if (priv->view == NULL)
        {
                return;
        }
 
-       gtk_text_view_get_visible_rect (GTK_TEXT_VIEW (priv->view), &visible_rect);
-       gtk_text_view_get_iter_at_location (GTK_TEXT_VIEW (priv->view), &top, 0, visible_rect.y);
-       gtk_text_view_get_iter_at_location (GTK_TEXT_VIEW (priv->view), &bottom, 0, visible_rect.y + 
visible_rect.height);
+       gtk_widget_get_allocation (GTK_WIDGET (map), &us_alloc);
 
-       gtk_text_view_get_iter_location (GTK_TEXT_VIEW (map), &top, &top_rect);
-       gtk_text_view_get_iter_location (GTK_TEXT_VIEW (map), &bottom, &bottom_rect);
+       buffer = gtk_text_view_get_buffer (GTK_TEXT_VIEW (map));
+       style_context = gtk_widget_get_style_context (GTK_WIDGET (map));
+       gtk_style_context_get_border (style_context, &border);
 
-       gtk_text_view_buffer_to_window_coords (GTK_TEXT_VIEW (map),
-                                              GTK_TEXT_WINDOW_WIDGET,
-                                              0, top_rect.y,
-                                              NULL, &top_y);
-       gtk_text_view_buffer_to_window_coords (GTK_TEXT_VIEW (map),
-                                              GTK_TEXT_WINDOW_WIDGET,
-                                              0, bottom_rect.y + bottom_rect.height,
-                                              NULL, &bottom_y);
+       gtk_text_buffer_get_end_iter (buffer, &end_iter);
+       gtk_text_view_get_iter_location (GTK_TEXT_VIEW (map), &end_iter, &end_rect);
+       us_height = end_rect.y + end_rect.height;
+       gtk_text_view_get_iter_location (GTK_TEXT_VIEW (priv->view), &end_iter, &end_rect);
+       them_height = end_rect.y + end_rect.height;
+
+       gtk_text_view_get_visible_rect (GTK_TEXT_VIEW (priv->view), &them_visible_rect);
+       gtk_text_view_get_visible_rect (GTK_TEXT_VIEW (map), &us_visible_rect);
+
+       slider_area->x = 0;
+       slider_area->width = us_alloc.width - border.left - border.right;
+       slider_area->height = 100;
+       slider_area->y = (double)them_visible_rect.y / (double)them_height * (double)us_height;
+       slider_area->height = ((double)(them_visible_rect.y + them_visible_rect.height) / (double)them_height 
* (double)us_height) - slider_area->y;
 
-       slider_area->y = top_y;
-       slider_area->height = bottom_y - top_y;
+       slider_area->y -= us_visible_rect.y;
 }
 
 static void