Animation: allow manually setting the intended playback range for actions.

Some operations, e.g. adding a new action strip to NLA, require
knowing the active frame range of an action. However, currently it
can only be deduced by scanning the keyframes of the curves within
it. This is not ideal if e.g. curves are staggered for overlap.

As suggested by Nathan Vegdahl in comments to T54724, this patch adds
Action properties that allow manually specifying its active frame range.
The settings are exposed via a panel in the Dopesheet and Action Editor.
When enabled, the range is highlighted in the background using a striped
fill to distinguish it from the solid filled regular playback range.

When set, the frame range is used when adding or updating NLA tracks,
and by add-ons using `Action.frame_range`, e.g. FBX exporter.

Differential Revision: https://developer.blender.org/D11803

3 files changed, 65 insertions, 1 deletions

diff --git a/source/blender/editors/space_action/action_data.c b/source/blender/editors/space_action/action_data.c
index 9ff46d96207..57f9138ec3a 100644
--- a/source/blender/editors/space_action/action_data.c
+++ b/source/blender/editors/space_action/action_data.c
@@ -71,7 +71,7 @@
 /* ACTION CREATION */
 
 /* Helper function to find the active AnimData block from the Action Editor context */
-AnimData *ED_actedit_animdata_from_context(bContext *C, ID **r_adt_id_owner)
+AnimData *ED_actedit_animdata_from_context(const bContext *C, ID **r_adt_id_owner)
 {
   SpaceAction *saction = (SpaceAction *)CTX_wm_space_data(C);
   Object *ob = CTX_data_active_object(C);
diff --git a/source/blender/editors/space_action/action_draw.c b/source/blender/editors/space_action/action_draw.c
index 6f1a90e56a5..bc13b7f2b1b 100644
--- a/source/blender/editors/space_action/action_draw.c
+++ b/source/blender/editors/space_action/action_draw.c
@@ -131,6 +131,54 @@ void draw_channel_names(bContext *C, bAnimContext *ac, ARegion *region)
 /* extra padding for lengths (to go under scrollers) */
 #define EXTRA_SCROLL_PAD 100.0f
 
+/* Draw manually set intended playback frame ranges for actions. */
+static void draw_channel_action_ranges(bAnimContext *ac, ListBase *anim_data, View2D *v2d)
+{
+  /* Variables for coalescing the Y region of one action. */
+  bAction *cur_action = NULL;
+  AnimData *cur_adt = NULL;
+  float cur_ymax;
+
+  /* Walk through channels, grouping contiguous spans referencing the same action. */
+  float ymax = ACHANNEL_FIRST_TOP(ac) + ACHANNEL_SKIP / 2;
+  float ystep = ACHANNEL_STEP(ac);
+  float ymin = ymax - ystep;
+
+  for (bAnimListElem *ale = anim_data->first; ale; ale = ale->next, ymax = ymin, ymin -= ystep) {
+    bAction *action = NULL;
+    AnimData *adt = NULL;
+
+    /* check if visible */
+    if (IN_RANGE(ymin, v2d->cur.ymin, v2d->cur.ymax) ||
+        IN_RANGE(ymax, v2d->cur.ymin, v2d->cur.ymax)) {
+      /* check if anything to show for this channel */
+      if (ale->datatype != ALE_NONE) {
+        action = ANIM_channel_action_get(ale);
+
+        if (action) {
+          adt = ale->adt;
+        }
+      }
+    }
+
+    /* Extend the current region, or flush and restart. */
+    if (action != cur_action || adt != cur_adt) {
+      if (cur_action) {
+        ANIM_draw_action_framerange(cur_adt, cur_action, v2d, ymax, cur_ymax);
+      }
+
+      cur_action = action;
+      cur_adt = adt;
+      cur_ymax = ymax;
+    }
+  }
+
+  /* Flush the last region. */
+  if (cur_action) {
+    ANIM_draw_action_framerange(cur_adt, cur_action, v2d, ymax, cur_ymax);
+  }
+}
+
 /* draw keyframes in each channel */
 void draw_channel_strips(bAnimContext *ac, SpaceAction *saction, ARegion *region)
 {
@@ -166,6 +214,13 @@ void draw_channel_strips(bAnimContext *ac, SpaceAction *saction, ARegion *region
   int height = ACHANNEL_TOT_HEIGHT(ac, items);
   v2d->tot.ymin = -height;
 
+  /* Draw the manual frame ranges for actions in the background of the dopesheet.
+   * The action editor has already drawn the range for its action so it's not needed. */
+  if (ac->datatype == ANIMCONT_DOPESHEET) {
+    draw_channel_action_ranges(ac, &anim_data, v2d);
+  }
+
+  /* Draw the background strips. */
   GPUVertFormat *format = immVertexFormat();
   uint pos = GPU_vertformat_attr_add(format, "pos", GPU_COMP_F32, 2, GPU_FETCH_FLOAT);
 
diff --git a/source/blender/editors/space_action/space_action.c b/source/blender/editors/space_action/space_action.c
index 738eeb21e2e..ebb28f3a208 100644
--- a/source/blender/editors/space_action/space_action.c
+++ b/source/blender/editors/space_action/space_action.c
@@ -25,6 +25,7 @@
 #include <string.h>
 
 #include "DNA_action_types.h"
+#include "DNA_anim_types.h"
 #include "DNA_collection_types.h"
 #include "DNA_object_types.h"
 #include "DNA_scene_types.h"
@@ -35,6 +36,7 @@
 #include "BLI_utildefines.h"
 
 #include "BKE_context.h"
+#include "BKE_nla.h"
 #include "BKE_screen.h"
 
 #include "RNA_access.h"
@@ -204,6 +206,13 @@ static void action_main_region_draw(const bContext *C, ARegion *region)
   /* start and end frame */
   ANIM_draw_framerange(scene, v2d);
 
+  /* Draw the manually set intended playback frame range highlight in the Action editor. */
+  if (ELEM(saction->mode, SACTCONT_ACTION, SACTCONT_SHAPEKEY) && saction->action) {
+    AnimData *adt = ED_actedit_animdata_from_context(C, NULL);
+
+    ANIM_draw_action_framerange(adt, saction->action, v2d, -FLT_MAX, FLT_MAX);
+  }
+
   /* data */
   if (ANIM_animdata_get_context(C, &ac)) {
     draw_channel_strips(&ac, saction, region);