Patch will allow range selection similar to outliner.
New function ANIM_animchannel_select_range created for range selection.
Similar to outliner, active fcurve remains unchanged when this operation is called.
New keymap is created to separate extend and extend range functionality.

Old Differential revision: https://archive.blender.org/developer/D17079

@@ -3192,0 +3220,4 @@
+
+    if (cursor->flag & FCURVE_ACTIVE) {
+      cursor->flag |= FCURVE_SELECTED;
+      return;

@@ -3192,0 +3194,4 @@
+  ListBase anim_data = anim_channels_for_selection(ac);
+
+  LISTBASE_FOREACH (bAnimListElem *, ale, &anim_data) {
+    if (ale->type != ANIMTYPE_FCURVE) {

@@ -3192,0 +3198,4 @@
+      continue;
+    }
+
+    FCurve *fcu = (FCurve *)ale->data;

@@ -3192,0 +3205,4 @@
+  ANIM_animdata_freelist(&anim_data);
+}
+
+static void animchannel_select_range(bAnimContext *ac, FCurve *cursor)

@@ -3192,0 +3208,4 @@
+static void animchannel_select_range(bAnimContext *ac, FCurve *cursor)
+{
+  ListBase anim_data = anim_channels_for_selection(ac);
+  bool selected = false;

@@ -3192,0 +3212,4 @@
+
+  LISTBASE_FOREACH (bAnimListElem *, ale, &anim_data) {
+
+    if (ale->type != ANIMTYPE_FCURVE) {

@@ -3192,0 +3218,4 @@
+
+    FCurve *fcu = (FCurve *)ale->data;
+
+    if (cursor->flag & FCURVE_ACTIVE) {

@@ -3526,6 +3583,9 @@ static void ANIM_OT_channels_click(wmOperatorType *ot)
   prop = RNA_def_boolean(ot->srna, "extend", false, "Extend Select", "");
   RNA_def_property_flag(prop, PROP_SKIP_SAVE);
 
+  prop = RNA_def_boolean(ot->srna, "extend_range", false, "Extend Range", "");

@@ -3205,0 +3273,4 @@
+  else if (selectmode == SELECT_EXTEND_RANGE) {
+    animchannel_clear_selection(ac);
+    /* When active channel is being clicked again for range selection, only select the
+     * clicked/active channel. Otherwise call range selection function. */

@@ -3205,0 +3274,4 @@
+    animchannel_clear_selection(ac);
+    /* When active channel is being clicked again for range selection, only select the
+     * clicked/active channel. Otherwise call range selection function. */
+    if ((fcu->flag & FCURVE_ACTIVE) == 0) {

@@ -3280,0 +3361,4 @@
+    animchannel_clear_selection(ac);
+    /* When active channel is being clicked again for range selection, only select the
+     * clicked/active channel. Otherwise call range selection function. */
+    if ((gpl->flag & FCURVE_ACTIVE) == 0) {

@@ -3285,3 +3376,3 @@
 
   /* change active layer, if this is selected (since we must always have an active layer) */
-  if (gpl->flag & GP_LAYER_SELECT) {
+  if ((gpl->flag & GP_LAYER_SELECT) && (selectmode != SELECT_EXTEND_RANGE)) {

@@ -3193,0 +3224,4 @@
+      case ANIMTYPE_FCURVE:
+      case ANIMTYPE_NLACURVE: {
+        FCurve *fcu = (FCurve *)ale->data;
+        FCurve *cursor = (FCurve *)cursor_elem->data;

@@ -3193,0 +3236,4 @@
+        if (in_selection_range) {
+          fcu->flag |= FCURVE_SELECTED;
+        }
+      } break;

@@ -3205,0 +3273,4 @@
+  else if (selectmode == SELECT_EXTEND_RANGE) {
+    animchannel_clear_selection(ac);
+    /* When active channel is being clicked again for range selection, only select the
+     * clicked/active channel. Otherwise call range selection function. */

@@ -3193,0 +3224,4 @@
+      case ANIMTYPE_FCURVE:
+      case ANIMTYPE_NLACURVE: {
+        FCurve *fcu = (FCurve *)ale->data;
+        FCurve *cursor = (FCurve *)cursor_elem->data;

@@ -3205,0 +3273,4 @@
+  else if (selectmode == SELECT_EXTEND_RANGE) {
+    animchannel_clear_selection(ac);
+    /* When active channel is being clicked again for range selection, only select the
+     * clicked/active channel. Otherwise call range selection function. */

@@ -3193,0 +3221,4 @@
+  bool in_selection_range = false;
+
+  LISTBASE_FOREACH (bAnimListElem *, ale, &anim_data) {
+    bool is_cursor_elem = (ale->data == cursor_elem->data);

@@ -215,3 +215,3 @@
 }
 
-static void select_pchan_for_action_group(bAnimContext *ac, bActionGroup *agrp, bAnimListElem *ale)
+static void select_pchan_for_action_group(bAnimContext *ac, bActionGroup *agrp, bAnimListElem *ale, const bool change_active)

@@ -3027,6 +3028,224 @@ static int click_select_channel_scene(bAnimListElem *ale,
   return (ND_ANIMCHAN | NA_SELECTED);
 }
 
+/* Before selecting the range, check if any active element is present. */

@@ -3028,2 +3029,4 @@
 }
 
+/* Before selecting the range, check if any active element is present. */
+static bool animchannel_active_check(bAnimContext *ac, eAnim_ChannelType type)

@@ -3030,0 +3085,4 @@
+        is_active_found |= gpl->flag & GP_LAYER_ACTIVE;
+        break;
+      }
+      default:

@@ -3030,0 +3088,4 @@
+      default:
+        break;
+    }
+  }

@@ -3030,0 +3153,4 @@
+  ANIM_animdata_freelist(&anim_data);
+}
+
+/* Select channels that lies between active channel and last clicked channel. */

@@ -3030,0 +3161,4 @@
+
+  LISTBASE_FOREACH (bAnimListElem *, ale, &anim_data) {
+    bool is_active_elem = false;
+    bool is_selection_allowed = ale->type == cursor_elem->type;

@@ -3030,0 +3162,4 @@
+  LISTBASE_FOREACH (bAnimListElem *, ale, &anim_data) {
+    bool is_active_elem = false;
+    bool is_selection_allowed = ale->type == cursor_elem->type;
+    const bool is_cursor_elem = (ale->data == cursor_elem->data);

@@ -3030,0 +3169,4 @@
+      continue;
+    }
+
+    switch (ale->type) {

@@ -357,7 +357,7 @@ void ED_pose_bone_select_tag_update(struct Object *ob);
 /**
  * Utility method for changing the selection status of a bone.
  */

@@ -358,3 +358,3 @@
  * Utility method for changing the selection status of a bone.
  */
-void ED_pose_bone_select(struct Object *ob, struct bPoseChannel *pchan, bool select);
+void ED_pose_bone_select(struct Object *ob, struct bPoseChannel *pchan, bool select, const bool change_active);

@@ -217,1 +217,3 @@
-static void select_pchan_for_action_group(bAnimContext *ac, bActionGroup *agrp, bAnimListElem *ale)
+bool ANIM_is_active_channel(bAnimListElem *ale)
+{
+  bool is_active_found = false;

@@ -218,0 +263,4 @@
+      is_active_found = gpl->flag & GP_LAYER_ACTIVE;
+      break;
+    }
+      return is_active_found;

@@ -3030,0 +3106,4 @@
+  return is_active_found;
+}
+
+static void animchannel_clear_selection(bAnimContext *ac)

@@ -3030,0 +3172,4 @@
+  LISTBASE_FOREACH (bAnimListElem *, ale, &anim_data) {
+    bool is_active_elem = false;
+    const bool is_selection_allowed = (ale->type == cursor_elem->type);
+    const bool is_cursor_elem = (ale->data == cursor_elem->data);

@@ -3030,0 +3179,4 @@
+      continue;
+    }
+
+    is_active_elem = ANIM_is_active_channel(ale);

@@ -110,3 +110,3 @@
     if (select) {
       pchan->bone->flag |= BONE_SELECTED;
-      arm->act_bone = pchan->bone;
+      arm->act_bone = change_active ? pchan->bone : arm->act_bone;

@@ -218,0 +258,4 @@
+      bGPDlayer *gpl = (bGPDlayer *)ale->data;
+      return gpl->flag & GP_LAYER_ACTIVE;
+    }
+      return false;

@@ -218,0 +258,4 @@
+      bGPDlayer *gpl = (bGPDlayer *)ale->data;
+      return gpl->flag & GP_LAYER_ACTIVE;
+    }
+    /* These channel types do not have active flags. */