UI: Add UILayout.operator_menu_hold

This is an operator button that opens a menu when the button is held.

source/blender/editors/interface/interface.c

@@ -2672,6 +2672,10 @@ static void ui_but_free(const bContext *C, uiBut *but)
 		MEM_freeN(but->tip_argN);
 	}
 
+	if (but->hold_argN) {
+		MEM_freeN(but->hold_argN);
+	}
+
 	if (but->active) {
 		/* XXX solve later, buttons should be free-able without context ideally,
 		 * however they may have open tooltips or popup windows, which need to
@@ -4520,6 +4524,12 @@ void UI_but_focus_on_enter_event(wmWindow *win, uiBut *but)
 	wm_event_add(win, &event);
 }
 
+void UI_but_func_hold_set(uiBut *but, uiButHandleHoldFunc func, void *argN)
+{
+	but->hold_func = func;
+	but->hold_argN = argN;
+}
+
 void UI_but_string_info_get(bContext *C, uiBut *but, ...)
 {
 	va_list args;

source/blender/editors/interface/interface_handlers.c

@@ -304,6 +304,9 @@ typedef struct uiHandleButtonData {
 	bool used_mouse;
 	wmTimer *autoopentimer;
 
+	/* auto open (hold) */
+	wmTimer *hold_action_timer;
+
 	/* text selection/editing */
 	/* size of 'str' (including terminator) */
 	int maxlen;
@@ -7808,6 +7811,15 @@ static void button_activate_state(bContext *C, uiBut *but, uiHandleButtonState s
 		data->flashtimer = NULL;
 	}
 
+	/* add hold timer if it's used */
+	if (state == BUTTON_STATE_WAIT_RELEASE && (but->hold_func != NULL)) {
+		data->hold_action_timer = WM_event_add_timer(data->wm, data->window, TIMER, BUTTON_AUTO_OPEN_THRESH);
+	}
+	else if (data->hold_action_timer) {
+		WM_event_remove_timer(data->wm, data->window, data->hold_action_timer);
+		data->hold_action_timer = NULL;
+	}
+
 	/* add a blocking ui handler at the window handler for blocking, modal states
 	 * but not for popups, because we already have a window level handler*/
 	if (!(but->block->handle && but->block->handle->popup)) {
@@ -8422,6 +8434,25 @@ static int ui_handle_button_event(bContext *C, const wmEvent *event, uiBut *but)
 				button_activate_state(C, but, BUTTON_STATE_EXIT);
 				break;
 
+			case TIMER:
+			{
+				if (event->customdata == data->hold_action_timer) {
+					if (true) {
+						data->cancel = true;
+						button_activate_state(C, but, BUTTON_STATE_EXIT);
+					}
+					else {
+						/* Do this so we can still mouse-up, closing the menu and running the button.
+						 * This is nice to support but there are times when the button gets left pressed.
+						 * Keep disavled for now. */
+						WM_event_remove_timer(data->wm, data->window, data->hold_action_timer);
+						data->hold_action_timer = NULL;
+					}
+					retval = WM_UI_HANDLER_CONTINUE;
+					but->hold_func(C, data->region, but);
+				}
+				break;
+			}
 			case MOUSEMOVE:
 				if (ELEM(but->type, UI_BTYPE_LINK, UI_BTYPE_INLINK)) {
 					but->flag |= UI_SELECT;
@@ -9348,21 +9379,29 @@ static int ui_handle_menu_event(
 			if (inside == 0) {
 				uiSafetyRct *saferct = block->saferct.first;
 
-				if (ELEM(event->type, LEFTMOUSE, MIDDLEMOUSE, RIGHTMOUSE) &&
-				    ELEM(event->val, KM_PRESS, KM_DBL_CLICK))
-				{
-					if ((is_parent_menu == false) && (U.uiflag & USER_MENUOPENAUTO) == 0) {
-						/* for root menus, allow clicking to close */
-						if (block->flag & (UI_BLOCK_OUT_1))
-							menu->menuretval = UI_RETURN_OK;
-						else
-							menu->menuretval = UI_RETURN_OUT;
+				if (ELEM(event->type, LEFTMOUSE, MIDDLEMOUSE, RIGHTMOUSE)) {
+					if (ELEM(event->val, KM_PRESS, KM_DBL_CLICK)) {
+						if ((is_parent_menu == false) && (U.uiflag & USER_MENUOPENAUTO) == 0) {
+							/* for root menus, allow clicking to close */
+							if (block->flag & (UI_BLOCK_OUT_1))
+								menu->menuretval = UI_RETURN_OK;
+							else
+								menu->menuretval = UI_RETURN_OUT;
+						}
+						else if (saferct && !BLI_rctf_isect_pt(&saferct->parent, event->x, event->y)) {
+							if (block->flag & (UI_BLOCK_OUT_1))
+								menu->menuretval = UI_RETURN_OK;
+							else
+								menu->menuretval = UI_RETURN_OUT;
+						}
 					}
-					else if (saferct && !BLI_rctf_isect_pt(&saferct->parent, event->x, event->y)) {
-						if (block->flag & (UI_BLOCK_OUT_1))
-							menu->menuretval = UI_RETURN_OK;
-						else
-							menu->menuretval = UI_RETURN_OUT;
+					else if (ELEM(event->val, KM_RELEASE, KM_CLICK)) {
+						/* For buttons that use a hold function, exit when mouse-up outside the menu. */
+						if (block->flag & UI_BLOCK_POPUP_HOLD) {
+							/* Note, we could check the cursor is over the parent button. */
+							menu->menuretval = UI_RETURN_CANCEL;
+							retval = WM_UI_HANDLER_CONTINUE;
+						}
 					}
 				}
 			}

source/blender/editors/interface/interface_intern.h

@@ -264,6 +264,10 @@ struct uiBut {
 	void *rename_arg1;
 	void *rename_orig;
 
+	/* Run an action when holding the button down. */
+	uiButHandleHoldFunc hold_func;
+	void *hold_argN;
+
 	uiLink *link;
 	short linkto[2];  /* region relative coords */
 	

source/blender/editors/interface/interface_layout.c

@@ -795,7 +795,7 @@ static void ui_item_disabled(uiLayout *layout, const char *name)
  * \param r_opptr: Optional, initialize with operator properties when not NULL.
  * Will always be written to even in the case of errors.
  */
-void uiItemFullO_ptr(
+static uiBut *uiItemFullO_ptr_ex(
         uiLayout *layout, wmOperatorType *ot,
         const char *name, int icon, IDProperty *properties, int context, int flag,
         PointerRNA *r_opptr)
@@ -862,6 +862,50 @@ void uiItemFullO_ptr(
 			*r_opptr = *opptr;
 		}
 	}
+
+	return but;
+}
+
+static void ui_item_hold_menu(struct bContext *C, ARegion *butregion, uiBut *but)
+{
+	uiPopupMenu *pup = UI_popup_menu_begin(C, "", ICON_NONE);
+	uiLayout *layout = UI_popup_menu_layout(pup);
+	uiBlock *block = layout->root->block;
+	UI_popup_menu_but_set(pup, butregion, but);
+
+	block->flag |= UI_BLOCK_POPUP_HOLD;
+
+	const char *menu_id = but->hold_argN;
+	MenuType *mt = WM_menutype_find(menu_id, true);
+	if (mt) {
+		Menu menu = {NULL};
+		menu.layout = layout;
+		menu.type = mt;
+		mt->draw(C, &menu);
+	}
+	else {
+		uiItemL(layout, "Menu Missing:", ICON_NONE);
+		uiItemL(layout, menu_id, ICON_NONE);
+	}
+	UI_popup_menu_end(C, pup);
+}
+
+void uiItemFullO_ptr(
+        uiLayout *layout, wmOperatorType *ot,
+        const char *name, int icon, IDProperty *properties, int context, int flag,
+        PointerRNA *r_opptr)
+{
+	uiItemFullO_ptr_ex(layout, ot, name, icon, properties, context, flag, r_opptr);
+}
+
+void uiItemFullOMenuHold_ptr(
+        uiLayout *layout, wmOperatorType *ot,
+        const char *name, int icon, IDProperty *properties, int context, int flag,
+        const char *menu_id,
+        PointerRNA *r_opptr)
+{
+	uiBut *but = uiItemFullO_ptr_ex(layout, ot, name, icon, properties, context, flag, r_opptr);
+	UI_but_func_hold_set(but, ui_item_hold_menu, BLI_strdup(menu_id));
 }
 
 void uiItemFullO(

source/blender/editors/interface/interface_regions.c

@@ -2627,6 +2627,7 @@ struct uiPopupMenu {
 	uiBlock *block;
 	uiLayout *layout;
 	uiBut *but;
+	ARegion *butregion;
 
 	int mx, my;
 	bool popup, slideout;
@@ -2873,17 +2874,33 @@ uiPopupMenu *UI_popup_menu_begin(bContext *C, const char *title, int icon)
 	return UI_popup_menu_begin_ex(C, title, __func__, icon);
 }
 
+/**
+ * Setting the button makes the popup open from the button instead of the cursor.
+ */
+void UI_popup_menu_but_set(uiPopupMenu *pup, struct ARegion *butregion, uiBut *but)
+{
+	pup->but = but;
+	pup->butregion = butregion;
+}
+
 /* set the whole structure to work */
 void UI_popup_menu_end(bContext *C, uiPopupMenu *pup)
 {
 	wmWindow *window = CTX_wm_window(C);
 	uiPopupBlockHandle *menu;
+	uiBut *but = NULL;
+	ARegion *butregion = NULL;
 	
 	pup->popup = true;
 	pup->mx = window->eventstate->x;
 	pup->my = window->eventstate->y;
-	
-	menu = ui_popup_block_create(C, NULL, NULL, NULL, ui_block_func_POPUP, pup);
+
+	if (pup->but) {
+		but = pup->but;
+		butregion = pup->butregion;
+	}
+
+	menu = ui_popup_block_create(C, butregion, but, NULL, ui_block_func_POPUP, pup);
 	menu->popup = true;
 	
 	UI_popup_handlers_add(C, &window->modalhandlers, menu, 0);

source/blender/editors/interface/interface_widgets.c

@@ -66,6 +66,15 @@
 /* icons are 80% of height of button (16 pixels inside 20 height) */
 #define ICON_SIZE_FROM_BUTRECT(rect) (0.8f * BLI_rcti_size_y(rect))
 
+#define UI_BUT_FLAGS_PUBLIC \
+	(UI_SELECT | UI_SCROLLED | UI_ACTIVE | UI_HAS_ICON | UI_TEXTINPUT | UI_HIDDEN)
+
+/* Bits 0..5 are from UI_SELECT .. etc */
+enum {
+	/* Show that holding the button opens a menu. */
+	UI_STATE_HOLD_ACTION = (1 << 6),
+};
+
 /* ************** widget base functions ************** */
 /**
  * - in: roundbox codes for corner types and radius
@@ -184,6 +193,15 @@ static const unsigned int check_tria_face[4][3] = {
 	{3, 2, 4}, {3, 4, 5}, {1, 0, 3}, {0, 2, 3}
 };
 
+#define OY -0.2 
+#define SC 0.35
+static const unsigned int hold_action_tri_face[2][3] = {{2, 0, 1}, {3, 5, 4}};
+static const float hold_action_tri_vert[6][2] = {
+	{-0.5 + SC, 1.0 + OY},  {0.5, 1.0 + OY},  {0.5, 0.0 + OY + SC},
+};
+#undef OY
+#undef SC
+
 /* ************************************************* */
 
 void ui_draw_anti_tria(float x1, float y1, float x2, float y2, float x3, float y3)
@@ -529,6 +547,14 @@ static void widget_num_tria(uiWidgetTrias *tria, const rcti *rect, float triasiz
 	        num_tria_face, ARRAY_SIZE(num_tria_face));
 }
 
+static void widget_hold_action_tria(uiWidgetTrias *tria, const rcti *rect, float triasize, char where)
+{
+	widget_draw_tria_ex(
+	        tria, rect, triasize, where,
+	        hold_action_tri_vert, ARRAY_SIZE(hold_action_tri_vert),
+	        hold_action_tri_face, ARRAY_SIZE(hold_action_tri_face));
+}
+
 static void widget_scroll_circle(uiWidgetTrias *tria, const rcti *rect, float triasize, char where)
 {
 	widget_draw_tria_ex(
@@ -3347,6 +3373,7 @@ static void widget_but(uiWidgetColors *wcol, rcti *rect, int UNUSED(state), int
 	widgetbase_draw(&wtb, wcol);
 }
 
+#if 0
 static void widget_roundbut(uiWidgetColors *wcol, rcti *rect, int UNUSED(state), int roundboxalign)
 {
 	uiWidgetBase wtb;
@@ -3359,6 +3386,25 @@ static void widget_roundbut(uiWidgetColors *wcol, rcti *rect, int UNUSED(state),
 
 	widgetbase_draw(&wtb, wcol);
 }
+#endif
+
+static void widget_roundbut_exec(uiWidgetColors *wcol, rcti *rect, int state, int roundboxalign)
+{
+	uiWidgetBase wtb;
+	const float rad = 0.25f * U.widget_unit;
+
+	widget_init(&wtb);
+
+	if (state & UI_STATE_HOLD_ACTION) {
+		/* Show that keeping pressed performs another action (typically a menu). */
+		widget_hold_action_tria(&wtb.tria1, rect, 0.75f, 'r');
+	}
+
+	/* half rounded */
+	round_box_edges(&wtb, roundboxalign, rect, rad);
+
+	widgetbase_draw(&wtb, wcol);
+}
 
 static void widget_draw_extra_mask(const bContext *C, uiBut *but, uiWidgetType *wt, rcti *rect)
 {
@@ -3439,7 +3485,7 @@ static uiWidgetType *widget_type(uiWidgetTypeEnum type)
 			
 		case UI_WTYPE_EXEC:
 			wt.wcol_theme = &btheme->tui.wcol_tool;
-			wt.draw = widget_roundbut;
+			wt.draw = widget_roundbut_exec;
 			break;
 
 		case UI_WTYPE_TOOLTIP:
@@ -3849,7 +3895,7 @@ void ui_draw_but(const bContext *C, ARegion *ar, uiStyle *style, uiBut *but, rct
 		
 		roundboxalign = widget_roundbox_set(but, rect);
 
-		state = but->flag;
+		state = but->flag & UI_BUT_FLAGS_PUBLIC;
 
 		if ((but->editstr) ||
 		    (UNLIKELY(but->flag & UI_BUT_DRAG_MULTI) && ui_but_drag_multi_edit_get(but)))
@@ -3857,6 +3903,10 @@ void ui_draw_but(const bContext *C, ARegion *ar, uiStyle *style, uiBut *but, rct
 			state |= UI_TEXTINPUT;
 		}
 
+		if (but->hold_func) {
+			state |= UI_STATE_HOLD_ACTION;
+		}
+
 		if (state & (UI_BUT_DISABLED | UI_BUT_INACTIVE))
 			if (but->dt != UI_EMBOSS_PULLDOWN)
 				disabled = true;