[libhandy/wip/haecker-felix/flap-widget] Generalize transition allocations

[Alexander Mikhaylenko <alexm src gnome org>]

commit 60e50598fd48268f40d93890144536a4bd6d9b9d
Author: Alexander Mikhaylenko <alexm gnome org>
Date:   Thu Nov 19 02:22:34 2020 +0500

    Generalize transition allocations

 src/hdy-flap.c | 25 +++++++++++++++++++------
 1 file changed, 19 insertions(+), 6 deletions(-)
---
diff --git a/src/hdy-flap.c b/src/hdy-flap.c
index 038761bd..1f579306 100644
--- a/src/hdy-flap.c
+++ b/src/hdy-flap.c
@@ -1,5 +1,6 @@
 /*
  * Copyright (C) 2020 Felix Häcker <haeckerfelix gnome org>
+ * Copyright (C) 2020 Purism SPC
  *
  * SPDX-License-Identifier: LGPL-2.1+
  */
@@ -33,6 +34,8 @@
  */
 
 #define HDY_SWIPE_BORDER 16
+#define FLAP_MOTION_FACTOR 1.0
+#define CONTENT_MOTION_FACTOR 0.0
 
 struct _HdyFlap
 {
@@ -469,6 +472,8 @@ compute_allocation (HdyFlap       *self,
                     GtkAllocation *flap_alloc,
                     GtkAllocation *content_alloc)
 {
+  gint content_offset, flap_offset;
+
   if (!self->flap && !self->content)
     return;
 
@@ -489,18 +494,26 @@ compute_allocation (HdyFlap       *self,
     return;
 
   if (self->orientation == GTK_ORIENTATION_HORIZONTAL) {
+    content_offset = (gint) round (MIN (self->fold_progress, self->reveal_progress) * CONTENT_MOTION_FACTOR 
* flap_alloc->width);
+    flap_offset = (gint) round ((self->reveal_progress - 1) * FLAP_MOTION_FACTOR * flap_alloc->width);
+
     if (self->flap_position == get_start_or_end (self)) {
-      content_alloc->x = alloc->width - content_alloc->width;
-      flap_alloc->x = (self->reveal_progress - 1) * flap_alloc->width;
+      content_alloc->x = alloc->width - content_alloc->width + content_offset;
+      flap_alloc->x = flap_offset;
     } else {
-      flap_alloc->x = alloc->width - self->reveal_progress * flap_alloc->width;
+      content_alloc->x = -content_offset;
+      flap_alloc->x = alloc->width - flap_alloc->width - flap_offset;
     }
   } else {
+    content_offset = (gint) round (MIN (self->fold_progress, self->reveal_progress) * CONTENT_MOTION_FACTOR 
* flap_alloc->height);
+    flap_offset = (gint) round ((self->reveal_progress - 1) * FLAP_MOTION_FACTOR * flap_alloc->height);
+
     if (self->flap_position == GTK_PACK_START) {
-      content_alloc->y = alloc->height - content_alloc->height;
-      flap_alloc->y = (self->reveal_progress - 1) * flap_alloc->height;
+      content_alloc->y = alloc->height - content_alloc->height + content_offset;
+      flap_alloc->y = flap_offset;
     } else {
-      flap_alloc->y = alloc->height - self->reveal_progress * flap_alloc->height;
+      content_alloc->y = -content_offset;
+      flap_alloc->y = alloc->height - flap_alloc->height - flap_offset;
     }
   }
 }