added changing the extending / extrapolation type of the IPO curves of selected actions in the action editor (to the menu - code to handle hotkey (to rise a popup) is there too but unused & untested now).

source/blender/include/BIF_editaction.h

@@ -38,6 +38,12 @@
 #define SET_IPO_LINEAR   2
 #define SET_IPO_BEZIER   3
 
+#define SET_EXTEND_POPUP    0
+#define SET_EXTEND_CONSTANT 1
+#define SET_EXTEND_EXTRAPOLATION  2
+#define SET_EXTEND_CYCLIC   3
+#define SET_EXTEND_CYCLICEXTRAPOLATION   4
+
 #define	CHANNELHEIGHT	16
 #define	CHANNELSKIP		2
 #define NAMEWIDTH      128

source/blender/src/editaction.c

@@ -1743,6 +1743,67 @@ void set_ipotype_actionchannels(int ipotype)
 	allqueue(REDRAWNLA, 0);
 }
 
+void set_extendtype_actionchannels(int extendtype)
+{
+	bAction *act; 
+	bActionChannel *chan;
+	short event;
+
+	/* Get the selected action, exit if none are selected 
+	 */
+	act = G.saction->action;
+	if (!act)
+		return;
+
+	if (extendtype == SET_EXTEND_POPUP) {
+		/* Present a popup menu asking the user what type
+		 * of IPO curve he/she/GreenBTH wants. ;)
+		 */
+		event
+			=  pupmenu("Channel Extending Type %t|"
+					   "Constant %x1|"
+					   "Extrapolation %x2|"
+					   "Cyclic %x3|"
+					   "Cyclic extrapolation %x4");
+		if(event < 1) return;
+		extendtype = event;
+	}
+	
+	/* Loop through the channels and for the selected ones set
+	 * the type for each Ipo curve in the channel Ipo (based on
+	 * the value from the popup).
+	 */
+	for (chan = act->chanbase.first; chan; chan=chan->next){
+		if (chan->flag & ACHAN_SELECTED) {
+			if (chan->ipo) {
+				switch (extendtype) {
+				case SET_EXTEND_CONSTANT:
+					setexprap_ipoloop(chan->ipo, IPO_HORIZ);
+					break;
+				case SET_EXTEND_EXTRAPOLATION:
+					setexprap_ipoloop(chan->ipo, IPO_DIR);
+					break;
+				case SET_EXTEND_CYCLIC:
+					setexprap_ipoloop(chan->ipo, IPO_CYCL);
+					break;
+				case SET_EXTEND_CYCLICEXTRAPOLATION:
+					setexprap_ipoloop(chan->ipo, IPO_CYCLX);
+					break;
+				}
+			}
+		}
+	}
+
+	/* Clean up and redraw stuff
+	 */
+	remake_action_ipos (act);
+	BIF_undo_push("Set Ipo type Action channel");
+	allspace(REMAKEIPO, 0);
+	allqueue(REDRAWACTION, 0);
+	allqueue(REDRAWIPO, 0);
+	allqueue(REDRAWNLA, 0);
+}
+
 void set_snap_actionchannels(void) 
 {
 	

source/blender/src/editipo_mods.c

@@ -669,6 +669,16 @@ void setipotype_ipo(Ipo *ipo, int code)
 	}
 }
 
+void setexprap_ipoloop(Ipo *ipo, int code)
+{
+	IpoCurve *icu;
+
+    	/* Loop through each curve in the Ipo
+     	*/
+    	for (icu=ipo->curve.first; icu; icu=icu->next)
+        	icu->extrap= code;
+}
+
 void set_ipotype(void)
 {
 	EditIpo *ei;
@@ -1121,5 +1131,3 @@ void set_exprap_ipo(int mode)
 	editipo_changed(G.sipo, 1);
 	BIF_undo_push("Set extrapolation Ipo");
 }
-
-

source/blender/src/header_action.c

@@ -106,6 +106,11 @@
 #define ACTMENU_KEY_INTERP_LINEAR 1
 #define ACTMENU_KEY_INTERP_BEZIER 2
 
+#define ACTMENU_KEY_EXTEND_CONST 0
+#define ACTMENU_KEY_EXTEND_EXTRAPOLATION 1
+#define ACTMENU_KEY_EXTEND_CYCLIC 2
+#define ACTMENU_KEY_EXTEND_CYCLICEXTRAPOLATION 3
+
 void do_action_buttons(unsigned short event)
 {
 	Object *ob= OBACT;
@@ -587,6 +592,84 @@ static uiBlock *action_keymenu_intpolmenu(void *arg_unused)
 	return block;
 }
 
+static void do_action_keymenu_extendmenu(void *arg, int event)
+{
+	Key *key;
+
+	key = get_action_mesh_key();
+
+	switch(event)
+	{
+		case ACTMENU_KEY_EXTEND_CONST:
+			if (key) {
+				/* to do */
+			}
+			else {
+				set_extendtype_actionchannels(SET_EXTEND_CONSTANT);
+			}
+			break;
+		case ACTMENU_KEY_EXTEND_EXTRAPOLATION:
+			if (key) {
+				/* to do */
+			}
+			else {
+				set_extendtype_actionchannels(SET_EXTEND_EXTRAPOLATION);
+			}
+			break;
+		case ACTMENU_KEY_EXTEND_CYCLIC:
+			if (key) {
+				/* to do */
+			}
+			else {
+				set_extendtype_actionchannels(SET_EXTEND_CYCLIC);
+			}
+			break;
+		case ACTMENU_KEY_EXTEND_CYCLICEXTRAPOLATION:
+			if (key) {
+				/* to do */
+			}
+			else {
+				set_extendtype_actionchannels(SET_EXTEND_CYCLICEXTRAPOLATION);
+			}
+			break;
+	}
+
+	scrarea_queue_winredraw(curarea);
+}
+
+static uiBlock *action_keymenu_extendmenu(void *arg_unused)
+{
+	uiBlock *block;
+	short yco= 0, menuwidth=120;
+
+	block= uiNewBlock(&curarea->uiblocks, "action_keymenu_extendmenu", 
+					  UI_EMBOSSP, UI_HELV, G.curscreen->mainwin);
+	uiBlockSetButmFunc(block, do_action_keymenu_extendmenu, NULL);
+
+	uiDefIconTextBut(block, BUTM, 1, ICON_BLANK1, 
+					 "Constant", 0, yco-=20, 
+					 menuwidth, 19, NULL, 0.0, 0.0, 0, 
+					 ACTMENU_KEY_EXTEND_CONST, "");
+	uiDefIconTextBut(block, BUTM, 1, ICON_BLANK1, 
+					 "Extrapolation", 0, yco-=20, 
+					 menuwidth, 19, NULL, 0.0, 0.0, 0, 
+					 ACTMENU_KEY_EXTEND_EXTRAPOLATION, "");
+	uiDefIconTextBut(block, BUTM, 1, ICON_BLANK1, 
+					 "Cyclic", 0, yco-=20, 
+					 menuwidth, 19, NULL, 0.0, 0.0, 0, 
+					 ACTMENU_KEY_EXTEND_CYCLIC, "");
+	uiDefIconTextBut(block, BUTM, 1, ICON_BLANK1, 
+					 "Cyclic Extrapolation", 0, yco-=20, 
+					 menuwidth, 19, NULL, 0.0, 0.0, 0, 
+					 ACTMENU_KEY_EXTEND_CYCLICEXTRAPOLATION, "");
+
+	uiBlockSetDirection(block, UI_RIGHT);
+	uiTextBoundsBlock(block, 60);
+
+	return block;
+}
+
+
 static void do_action_keymenu(void *arg, int event)
 {	
 	SpaceAction *saction;
@@ -669,6 +752,9 @@ static uiBlock *action_keymenu(void *arg_unused)
 	uiDefBut(block, SEPR, 0, "", 0, yco-=6, 
 			 menuwidth, 6, NULL, 0.0, 0.0, 0, 0, "");
 
+	uiDefIconTextBlockBut(block, action_keymenu_extendmenu, 
+						  NULL, ICON_RIGHTARROW_THIN, 
+						  "Extend Mode", 0, yco-=20, 120, 20, "");
 	uiDefIconTextBlockBut(block, action_keymenu_intpolmenu, 
 						  NULL, ICON_RIGHTARROW_THIN, 
 						  "Interpolation Mode", 0, yco-=20, 120, 20, "");