[Bf-blender-cvs] [54ac90625f7] modifier-panels-ui: UI: Fix last panel dragging affecting region scroll

[Hans Goudey]

Commit: 54ac90625f7c88333dc0529b53ada026e975f66f
Author: Hans Goudey
Date:   Fri Apr 17 12:01:50 2020 -0500
Branches: modifier-panels-ui
https://developer.blender.org/rB54ac90625f7c88333dc0529b53ada026e975f66f

UI: Fix last panel dragging affecting region scroll

When finding the total height of the region's panels for scrolling, we
should use starting position of the drag, because a drag and drop doesn't
change the resulting height of the region.

===================================================================

M	source/blender/editors/interface/interface_panel.c

===================================================================

diff --git a/source/blender/editors/interface/interface_panel.c b/source/blender/editors/interface/interface_panel.c
index b8f87a4300c..8141e17f3d5 100644
--- a/source/blender/editors/interface/interface_panel.c
+++ b/source/blender/editors/interface/interface_panel.c
@@ -853,15 +853,28 @@ int UI_panel_size_y(const Panel *panel)
   return get_panel_real_size_y(panel);
 }
 
-/* this function is needed because uiBlock and Panel itself don't
- * change sizey or location when closed */
-static int get_panel_real_ofsy(Panel *panel)
+/**
+ * Return the offset of the panel, checking if the panel is opened or closed. This function is
+ * needed because the #uiBlock and #Panel don't change sizey or location when closed.
+ *
+ * \param include_drag: When finding the total height of the region's panels for scrolling, we
+ * should use starting position of the drag, because a drag and drop doesn't change the resulting
+ * height of the region. This enables that behavior.
+ */
+static int get_panel_real_ofsy(Panel *panel, bool include_drag)
 {
+  int offset = panel->ofsy;
+  if (!include_drag) {
+    uiHandlePanelData *data = panel->activedata;
+    if (data && data->state == PANEL_STATE_DRAG) {
+      offset = data->startofsy;
+    }
+  }
   if (panel->flag & PNL_CLOSEDY) {
-    return panel->ofsy + panel->sizey;
+    return offset + panel->sizey;
   }
   else {
-    return panel->ofsy;
+    return offset;
   }
 }
 
@@ -1046,7 +1059,7 @@ static bool uiAlignPanelStep(ScrArea *area, ARegion *region, const float fac, co
 
     if (align == BUT_VERTICAL) {
       psnext->panel->ofsx = ps->panel->ofsx;
-      psnext->panel->ofsy = get_panel_real_ofsy(ps->panel) - get_panel_size_y(psnext->panel);
+      psnext->panel->ofsy = get_panel_real_ofsy(ps->panel, true) - get_panel_size_y(psnext->panel);
     }
     else {
       psnext->panel->ofsx = get_panel_real_ofsx(ps->panel);
@@ -1102,7 +1115,7 @@ static void ui_panels_size(ScrArea *area, ARegion *region, int *r_x, int *r_y)
 
       if (align == BUT_VERTICAL) {
         pa_sizex = panel->ofsx + panel->sizex;
-        pa_sizey = get_panel_real_ofsy(panel);
+        pa_sizey = get_panel_real_ofsy(panel, false);
       }
       else {
         pa_sizex = get_panel_real_ofsx(panel) + panel->sizex;