Fix T76595: Indicate the Active Keyframe in Graph Editor

In the graph editor there is a panel that says "Active Keyframe" for
numerically editing a keyframe's values, but in the code there is no
concept of the "active keyframe." Since this is a useful concept to
have for some other features anyway, this commit adds an active
keyframe index value to FCurves. It also displays it with a theme
color for the active vertex (which didn't exist before) if the
FCurve is active.

The active keyframe in the graph editor is treated similarly to the
active vertex in the 3D view. It is the keyframe most recently selected
with a single click, and it is always selected.

For now, the only real functional change is that the active keyframe
appears in white and it should be more predictable which keyframe is
being edited in the sidebar panel.

Differential Revision: https://developer.blender.org/D7737

1 files changed, 9 insertions, 1 deletions

diff --git a/source/blender/makesdna/DNA_anim_types.h b/source/blender/makesdna/DNA_anim_types.h
index 7cb9978f768..a13ed0b2924 100644
--- a/source/blender/makesdna/DNA_anim_types.h
+++ b/source/blender/makesdna/DNA_anim_types.h
@@ -550,6 +550,9 @@ typedef enum eDriver_Flags {
 
 /* F-Curves -------------------------------------- */
 
+/** When #active_keyframe_index is set to this, the FCurve does not have an active keyframe. */
+#define FCURVE_ACTIVE_KEYFRAME_NONE -1
+
 /**
  * FPoint (fpt)
  *
@@ -587,10 +590,15 @@ typedef struct FCurve {
   /** Total number of points which define the curve (i.e. size of arrays in FPoints). */
   unsigned int totvert;
 
+  /**
+   * Index of active keyframe in #bezt for numerical editing in the interface. A value of
+   * #FCURVE_ACTIVE_KEYFRAME_NONE indicates that the FCurve has no active keyframe.
+   */
+  int active_keyframe_index;
+
   /* value cache + settings */
   /** Value stored from last time curve was evaluated (not threadsafe, debug display only!). */
   float curval;
-  char _pad2[4];
   /** User-editable settings for this curve. */
   short flag;
   /** Value-extending mode for this curve (does not cover). */