[gtksourceview] map: improve slider position calculation and snapshotting

[Christian Hergert <chergert src gnome org>]

commit 0bd327cadacdb4537c3acd9bbf8c4d889445cb5e
Author: Christian Hergert <chergert redhat com>
Date:   Thu Oct 14 16:49:23 2021 -0700

    map: improve slider position calculation and snapshotting
    
    We get lots of warnings when using the overlay feature from GtkTextView
    and it also requires doing more work than necessary. Instead, we can just
    manage the child widget manually and update it on size requests to avoid
    extra cycles on allocations (as well as errors about snapshotting without
    an allocation).
    
    Furthermore, we can simplify how we calculate the position.

 gtksourceview/gtksourcemap.c | 121 ++++++++++++++++++++++++++++---------------
 1 file changed, 78 insertions(+), 43 deletions(-)
---
diff --git a/gtksourceview/gtksourcemap.c b/gtksourceview/gtksourcemap.c
index 48bea6d8..82eed216 100644
--- a/gtksourceview/gtksourcemap.c
+++ b/gtksourceview/gtksourcemap.c
@@ -261,57 +261,46 @@ load_override_font (GtkSourceMap *map)
 #endif
 
 static void
-update_slider_position (GtkSourceMap *map)
+get_slider_position (GtkSourceMap *map,
+                     int           width,
+                     int           height,
+                     GdkRectangle *slider_area)
 {
        GtkSourceMapPrivate *priv = gtk_source_map_get_instance_private (map);
-       GdkRectangle them_visible_rect;
-       GdkRectangle us_alloc;
-       GdkRectangle slider_area;
-       GtkStyleContext *style_context;
-       GtkTextBuffer *buffer;
-       GtkTextIter end_iter;
-       GdkRectangle end_rect;
-       GtkBorder border;
-       int us_height;
-       int them_height;
+       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;
 
        if (priv->view == NULL)
        {
                return;
        }
 
-       gtk_widget_get_allocation (GTK_WIDGET (map), &us_alloc);
+       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);
 
-       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_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_iter_location (GTK_TEXT_VIEW (map), &top, &top_rect);
+       gtk_text_view_get_iter_location (GTK_TEXT_VIEW (map), &bottom, &bottom_rect);
 
-       gtk_text_view_get_visible_rect (GTK_TEXT_VIEW (priv->view), &them_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;
+       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);
 
-       if (memcmp (&slider_area, &priv->slider_area, sizeof slider_area) != 0)
-       {
-               priv->slider_area = slider_area;
-               gtk_widget_set_size_request (GTK_WIDGET (priv->slider),
-                                            MAX (0, slider_area.width),
-                                            MAX (0, slider_area.height));
-               gtk_text_view_move_overlay (GTK_TEXT_VIEW (map),
-                                           GTK_WIDGET (priv->slider),
-                                           slider_area.x,
-                                           slider_area.y);
-               gtk_widget_queue_allocate (GTK_WIDGET (map));
-       }
+       slider_area->y = top_y;
+       slider_area->height = bottom_y - top_y;
 }
 
 static void
@@ -501,7 +490,7 @@ view_vadj_value_changed (GtkSourceMap  *map,
                          GtkAdjustment *vadj)
 {
        update_child_vadjustment (map);
-       update_slider_position (map);
+       gtk_widget_queue_allocate (GTK_WIDGET (map));
 }
 
 static void
@@ -509,7 +498,7 @@ view_vadj_notify_upper (GtkSourceMap  *map,
                         GParamSpec    *pspec,
                         GtkAdjustment *vadj)
 {
-       update_slider_position (map);
+       gtk_widget_queue_allocate (GTK_WIDGET (map));
 }
 
 static void
@@ -855,6 +844,12 @@ gtk_source_map_dispose (GObject *object)
        g_clear_object (&priv->css_provider);
        g_clear_pointer (&priv->font_desc, pango_font_description_free);
 
+       if (priv->slider)
+       {
+               gtk_widget_unparent (GTK_WIDGET (priv->slider));
+               priv->slider = NULL;
+       }
+
        G_OBJECT_CLASS (gtk_source_map_parent_class)->dispose (object);
 }
 
@@ -1146,6 +1141,44 @@ gtk_source_map_css_changed (GtkWidget         *widget,
 #endif
 }
 
+static void
+gtk_source_map_size_allocate (GtkWidget *widget,
+                              int        width,
+                              int        height,
+                              int        baseline)
+{
+       GtkSourceMap *map = (GtkSourceMap *)widget;
+       GtkSourceMapPrivate *priv = gtk_source_map_get_instance_private (map);
+       GdkRectangle area;
+       int min, nat;
+
+       g_assert (GTK_SOURCE_IS_MAP (map));
+
+       GTK_WIDGET_CLASS (gtk_source_map_parent_class)->size_allocate (widget, width, height, baseline);
+
+       get_slider_position (map, width, height, &area);
+       gtk_widget_measure (GTK_WIDGET (priv->slider),
+                           GTK_ORIENTATION_VERTICAL,
+                           width, &min, &nat, NULL, NULL);
+       area.height = MAX (nat, area.height);
+       gtk_widget_size_allocate (GTK_WIDGET (priv->slider), &area, -1);
+}
+
+static void
+gtk_source_map_snapshot (GtkWidget   *widget,
+                         GtkSnapshot *snapshot)
+{
+       GtkSourceMap *map = (GtkSourceMap *)widget;
+       GtkSourceMapPrivate *priv = gtk_source_map_get_instance_private (map);
+
+       g_assert (GTK_IS_WIDGET (widget));
+       g_assert (GTK_IS_SNAPSHOT (snapshot));
+
+       GTK_WIDGET_CLASS (gtk_source_map_parent_class)->snapshot (widget, snapshot);
+
+       gtk_widget_snapshot_child (GTK_WIDGET (map), GTK_WIDGET (priv->slider), snapshot);
+}
+
 static void
 gtk_source_map_constructed (GObject *object)
 {
@@ -1174,6 +1207,8 @@ gtk_source_map_class_init (GtkSourceMapClass *klass)
        widget_class->state_flags_changed = gtk_source_map_state_flags_changed;
        widget_class->realize = gtk_source_map_realize;
        widget_class->css_changed = gtk_source_map_css_changed;
+       widget_class->size_allocate = gtk_source_map_size_allocate;
+       widget_class->snapshot = gtk_source_map_snapshot;
 
        text_view_class->snapshot_layer = gtk_source_map_snapshot_layer;
 
@@ -1210,7 +1245,7 @@ gtk_source_map_init (GtkSourceMap *map)
                                     "width-request", 1,
                                     "height-request", 1,
                                     NULL);
-        gtk_text_view_add_overlay (GTK_TEXT_VIEW (map), GTK_WIDGET (priv->slider), 0, 0);
+       gtk_widget_set_parent (GTK_WIDGET (priv->slider), GTK_WIDGET (map));
 
        gtk_style_context_add_provider (gtk_widget_get_style_context (GTK_WIDGET (map)),
                                        GTK_STYLE_PROVIDER (priv->css_provider),