From b2c52f258757e37a74a95c109431f6af8cda8f91 Mon Sep 17 00:00:00 2001
From: Sophie Herold <sophie@hemio.de>
Date: Wed, 7 Dec 2022 17:42:06 +0100
Subject: [PATCH] carousel: give new child a snap_point immediately

Fixes #457, #597
---
 src/adw-carousel.c | 21 ++++++++++++++++++++-
 1 file changed, 20 insertions(+), 1 deletion(-)

diff --git a/src/adw-carousel.c b/src/adw-carousel.c
index 47ea9475..5a9816f9 100644
--- a/src/adw-carousel.c
+++ b/src/adw-carousel.c
@@ -1207,6 +1207,8 @@ adw_carousel_insert (AdwCarousel *self,
 {
   ChildInfo *info;
   GList *next_link = NULL;
+  double snap_point = 0;
+  GList *children;
 
   g_return_if_fail (ADW_IS_CAROUSEL (self));
   g_return_if_fail (GTK_IS_WIDGET (widget));
@@ -1214,7 +1216,8 @@ adw_carousel_insert (AdwCarousel *self,
 
   info = g_new0 (ChildInfo, 1);
   info->widget = widget;
-  info->size = 0;
+  // set a minimal size to give child it's own snap_point from the beginning
+  info->size = 0.00001;
   info->adding = TRUE;
 
   if (position >= 0)
@@ -1230,6 +1233,22 @@ adw_carousel_insert (AdwCarousel *self,
     gtk_widget_set_parent (widget, GTK_WIDGET (self));
   }
 
+  // work around this usually happening in measure which can be too late
+  for (children = self->children; children; children = children->next) {
+    ChildInfo *child_info = children->data;
+
+    child_info->snap_point = snap_point + child_info->size - 1;
+
+    snap_point += child_info->size;
+
+    if (child_info == self->animation_target_child)
+      adw_spring_animation_set_value_to (ADW_SPRING_ANIMATION (self->animation),
+                                         child_info->snap_point);
+  }
+
+  // start animation from correct size
+  info->size = 0;
+
   gtk_widget_queue_allocate (GTK_WIDGET (self));
 
   animate_child_resize (self, info, 1, self->reveal_duration);
-- 
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