UI: add UILayout.prop_popover_enum function

Support for RNA enum buttons that activate popovers when clicked.

This means we get useful tooltips, shortcuts and Ctrl-Wheel cycling
over enum items.

It also avoids inconvenient & slow access of enum values currently done
via RNA type lookups on the type to get the name & icon to use for a
regular popover button.

Resolves T57738

4 files changed, 67 insertions, 6 deletions

diff --git a/source/blender/editors/interface/interface.c b/source/blender/editors/interface/interface.c
index 48a3e08cbd4..45a41ed418d 100644
--- a/source/blender/editors/interface/interface.c
+++ b/source/blender/editors/interface/interface.c
@@ -85,6 +85,7 @@
 /* prototypes. */
 static void ui_but_to_pixelrect(struct rcti *rect, const struct ARegion *ar, struct uiBlock *block, struct uiBut *but);
 static void ui_def_but_rna__menu(bContext *UNUSED(C), uiLayout *layout, void *but_p);
+static void ui_def_but_rna__popover(bContext *UNUSED(C), uiLayout *layout, void *but_p);
 
 /* avoid unneeded calls to ui_but_value_get */
 #define UI_BUT_VALUE_UNSET DBL_MAX
@@ -1149,7 +1150,7 @@ static bool ui_but_event_property_operator_string(
 		if ((but->type == UI_BTYPE_BUT_MENU) &&
 		    (but_parent && but_parent->rnaprop) &&
 		    (RNA_property_type(but_parent->rnaprop) == PROP_ENUM) &&
-		    (but_parent->menu_create_func == ui_def_but_rna__menu))
+		    ELEM(but_parent->menu_create_func, ui_def_but_rna__menu, ui_def_but_rna__popover))
 		{
 			prop_enum_value = (int)but->hardmin;
 			ptr = &but_parent->rnapoin;
@@ -3831,6 +3832,35 @@ static void ui_def_but_rna__menu(bContext *UNUSED(C), uiLayout *layout, void *bu
 	block->flag |= UI_BLOCK_IS_FLIP;
 }
 
+static void ui_def_but_rna__popover(bContext *C, uiLayout *layout, void *but_p)
+{
+	uiBut *but = but_p;
+	const char *panel_type = but->func_argN;
+	PanelType *pt = WM_paneltype_find(panel_type, true);
+	if (pt) {
+		ui_item_paneltype_func(C, layout, pt);
+	}
+	else {
+		char msg[256];
+		SNPRINTF(msg, "Missing Panel: %s", panel_type);
+		uiItemL(layout, msg, ICON_NONE);
+	}
+}
+
+void ui_but_rna_menu_convert_to_popover(uiBut *but, const char *panel_type)
+{
+	BLI_assert(but->type == UI_BTYPE_MENU);
+	BLI_assert(but->menu_create_func == ui_def_but_rna__menu);
+	BLI_assert((void *)but->poin == but);
+	but->menu_create_func = ui_def_but_rna__popover;
+	but->func_argN = BLI_strdup(panel_type);
+}
+
+bool ui_but_menu_draw_as_popover(const uiBut *but)
+{
+	return (but->menu_create_func == ui_def_but_rna__popover);
+}
+
 static void ui_but_submenu_enable(uiBlock *block, uiBut *but)
 {
 	but->flag |= UI_BUT_ICON_SUBMENU;
diff --git a/source/blender/editors/interface/interface_handlers.c b/source/blender/editors/interface/interface_handlers.c
index 6474ccc7794..968d41d9795 100644
--- a/source/blender/editors/interface/interface_handlers.c
+++ b/source/blender/editors/interface/interface_handlers.c
@@ -3725,13 +3725,14 @@ static void ui_block_open_begin(bContext *C, uiBut *but, uiHandleButtonData *dat
 			}
 			break;
 		case UI_BTYPE_MENU:
-			BLI_assert(but->menu_create_func);
-			menufunc = but->menu_create_func;
-			arg = but->poin;
-			break;
 		case UI_BTYPE_POPOVER:
 			BLI_assert(but->menu_create_func);
-			popoverfunc = but->menu_create_func;
+			if ((but->type == UI_BTYPE_POPOVER) || ui_but_menu_draw_as_popover(but)) {
+				popoverfunc = but->menu_create_func;
+			}
+			else {
+				menufunc = but->menu_create_func;
+			}
 			arg = but->poin;
 			break;
 		case UI_BTYPE_COLOR:
diff --git a/source/blender/editors/interface/interface_intern.h b/source/blender/editors/interface/interface_intern.h
index eefed26ef55..930eb72d912 100644
--- a/source/blender/editors/interface/interface_intern.h
+++ b/source/blender/editors/interface/interface_intern.h
@@ -485,6 +485,9 @@ extern uiButExtraIconType ui_but_icon_extra_get(uiBut *but);
 
 extern void ui_but_default_set(struct bContext *C, const bool all, const bool use_afterfunc);
 
+extern void ui_but_rna_menu_convert_to_popover(struct uiBut *but, const char *panel_type);
+extern bool ui_but_menu_draw_as_popover(const uiBut *but);
+
 extern void ui_but_update(uiBut *but);
 extern void ui_but_update_edited(uiBut *but);
 extern bool ui_but_is_float(const uiBut *but) ATTR_WARN_UNUSED_RESULT;
diff --git a/source/blender/editors/interface/interface_layout.c b/source/blender/editors/interface/interface_layout.c
index 160b12526b8..14ce7edf7a8 100644
--- a/source/blender/editors/interface/interface_layout.c
+++ b/source/blender/editors/interface/interface_layout.c
@@ -1990,6 +1990,33 @@ void uiItemR(uiLayout *layout, PointerRNA *ptr, const char *propname, int flag,
 	uiItemFullR(layout, ptr, prop, RNA_NO_INDEX, 0, flag, name, icon);
 }
 
+/**
+ * Use a wrapper function since re-implementing all the logic in this function would be messy.
+ */
+void uiItemFullR_with_popover(
+        uiLayout *layout, PointerRNA *ptr, PropertyRNA *prop, int index, int value, int flag, const char *name, int icon,
+        const char *panel_type)
+{
+	uiBlock *block = layout->root->block;
+	uiBut *but = block->buttons.last;
+	uiItemFullR(layout, ptr, prop, index, value, flag, name, icon);
+	but = but->next;
+	while (but) {
+		if (but->rnaprop == prop && but->type == UI_BTYPE_MENU) {
+			ui_but_rna_menu_convert_to_popover(but, panel_type);
+			break;
+		}
+		but = but->next;
+	}
+	if (but) {
+		const char *propname = RNA_property_identifier(prop);
+		ui_item_disabled(layout, panel_type);
+		RNA_warning(
+		        "property could not use a popover: %s.%s (%s)",
+		        RNA_struct_identifier(ptr->type), propname, panel_type);
+	}
+}
+
 void uiItemEnumR_prop(uiLayout *layout, const char *name, int icon, struct PointerRNA *ptr, PropertyRNA *prop, int value)
 {
 	if (RNA_property_type(prop) != PROP_ENUM) {