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, 73 insertions, 0 deletions

diff --git a/source/blender/editors/space_graph/graph_draw.c b/source/blender/editors/space_graph/graph_draw.c
index af7a7d9a4de..c6acc8260b7 100644
--- a/source/blender/editors/space_graph/graph_draw.c
+++ b/source/blender/editors/space_graph/graph_draw.c
@@ -211,6 +211,32 @@ static void draw_fcurve_selected_keyframe_vertices(
   immEnd();
 }
 
+/**
+ * Draw the extra indicator for the active point.
+ */
+static void draw_fcurve_active_vertex(const FCurve *fcu, const View2D *v2d, const uint pos)
+{
+  const int active_keyframe_index = BKE_fcurve_active_keyframe_index(fcu);
+  if (!(fcu->flag & FCURVE_ACTIVE) || active_keyframe_index == FCURVE_ACTIVE_KEYFRAME_NONE) {
+    return;
+  }
+
+  const float fac = 0.05f * BLI_rctf_size_x(&v2d->cur);
+  const BezTriple *bezt = &fcu->bezt[active_keyframe_index];
+
+  if (!IN_RANGE(bezt->vec[1][0], (v2d->cur.xmin - fac), (v2d->cur.xmax + fac))) {
+    return;
+  }
+  if (!(bezt->f2 & SELECT)) {
+    return;
+  }
+
+  immBegin(GPU_PRIM_POINTS, 1);
+  immUniformThemeColor(TH_VERTEX_ACTIVE);
+  immVertex2fv(pos, bezt->vec[1]);
+  immEnd();
+}
+
 /* helper func - draw keyframe vertices only for an F-Curve */
 static void draw_fcurve_keyframe_vertices(FCurve *fcu, View2D *v2d, bool edit, uint pos)
 {
@@ -220,6 +246,7 @@ static void draw_fcurve_keyframe_vertices(FCurve *fcu, View2D *v2d, bool edit, u
 
   draw_fcurve_selected_keyframe_vertices(fcu, v2d, edit, false, pos);
   draw_fcurve_selected_keyframe_vertices(fcu, v2d, edit, true, pos);
+  draw_fcurve_active_vertex(fcu, v2d, pos);
 
   immUnbindProgram();
 }
@@ -270,6 +297,39 @@ static void draw_fcurve_selected_handle_vertices(
   immEnd();
 }
 
+/**
+ * Draw the extra handles for the active point.
+ */
+static void draw_fcurve_active_handle_vertices(const FCurve *fcu,
+                                               const bool sel_handle_only,
+                                               const uint pos)
+{
+  const int active_keyframe_index = BKE_fcurve_active_keyframe_index(fcu);
+  if (!(fcu->flag & FCURVE_ACTIVE) || active_keyframe_index == FCURVE_ACTIVE_KEYFRAME_NONE) {
+    return;
+  }
+
+  const BezTriple *bezt = &fcu->bezt[active_keyframe_index];
+
+  if (sel_handle_only && !BEZT_ISSEL_ANY(bezt)) {
+    return;
+  }
+
+  float active_col[4];
+  UI_GetThemeColor4fv(TH_VERTEX_ACTIVE, active_col);
+  immUniform4fv("outlineColor", active_col);
+  immUniformColor3fvAlpha(active_col, 0.01f); /* Almost invisible - only keep for smoothness. */
+  immBeginAtMost(GPU_PRIM_POINTS, 2);
+
+  if ((bezt->f1 & SELECT)) {
+    immVertex2fv(pos, bezt->vec[0]);
+  }
+  if ((bezt->f3 & SELECT)) {
+    immVertex2fv(pos, bezt->vec[2]);
+  }
+  immEnd();
+}
+
 /* helper func - draw handle vertices only for an F-Curve (if it is not protected) */
 static void draw_fcurve_handle_vertices(FCurve *fcu, View2D *v2d, bool sel_handle_only, uint pos)
 {
@@ -282,6 +342,7 @@ static void draw_fcurve_handle_vertices(FCurve *fcu, View2D *v2d, bool sel_handl
 
   draw_fcurve_selected_handle_vertices(fcu, v2d, false, sel_handle_only, pos);
   draw_fcurve_selected_handle_vertices(fcu, v2d, true, sel_handle_only, pos);
+  draw_fcurve_active_handle_vertices(fcu, sel_handle_only, pos);
 
   immUnbindProgram();
 }
@@ -1224,10 +1285,22 @@ void graph_draw_curves(bAnimContext *ac, SpaceGraph *sipo, ARegion *region, shor
    * draw curve, then handle-lines, and finally vertices in this order so that
    * the data will be layered correctly
    */
+  bAnimListElem *ale_active_fcurve = NULL;
   for (ale = anim_data.first; ale; ale = ale->next) {
+    const FCurve *fcu = (FCurve *)ale->key_data;
+    if (fcu->flag & FCURVE_ACTIVE) {
+      ale_active_fcurve = ale;
+      continue;
+    }
     draw_fcurve(ac, sipo, region, ale);
   }
 
+  /* Draw the active FCurve last so that it (especially the active keyframe)
+   * shows on top of the other curves. */
+  if (ale_active_fcurve != NULL) {
+    draw_fcurve(ac, sipo, region, ale_active_fcurve);
+  }
+
   /* free list of curves */
   ANIM_animdata_freelist(&anim_data);
 }