Cleanup: Refactor button-group code

* Split generic button-group code from specific application
* Move button-group API to interface.c.
* Avoid struct abuse by using wrapper structs
* Naming, comments, etc.

5 files changed, 189 insertions, 135 deletions

diff --git a/source/blender/blenkernel/BKE_screen.h b/source/blender/blenkernel/BKE_screen.h
index b1777cb77d7..3f3eca7d34b 100644
--- a/source/blender/blenkernel/BKE_screen.h
+++ b/source/blender/blenkernel/BKE_screen.h
@@ -259,7 +259,7 @@ typedef struct uiListType {
 } uiListType;
 
 typedef bool (*uiButtonGroupIdentifyFunc)(struct uiButtonGroup *, void *);
-typedef void (*uiButtonGroupItemsFunc)(struct uiButtonGroup *, void *, ListBase *);
+typedef void (*uiButtonGroupItemsFunc)(void *, ListBase *);
 typedef void (*uiButtonGroupItemDrawFunc)(struct uiBlock *, void *, struct uiButtonGroupItemInfo *);
 
 typedef struct uiButtonGroupType {
diff --git a/source/blender/editors/include/UI_interface.h b/source/blender/editors/include/UI_interface.h
index 7fef72b7484..946c1822da3 100644
--- a/source/blender/editors/include/UI_interface.h
+++ b/source/blender/editors/include/UI_interface.h
@@ -810,6 +810,9 @@ void UI_but_focus_on_enter_event(struct wmWindow *win, uiBut *but);
 
 void UI_but_func_hold_set(uiBut *but, uiButHandleHoldFunc func, void *argN);
 
+struct uiButtonGroup *UI_button_group_ensure(struct ARegion *region, const char *name, void *custom_data);
+void UI_button_group_add_sorted_items(struct uiButtonGroup *group, uiBlock *block, void *custom_data);
+void UI_button_group_item_add(void *data, ListBase *items);
 void UI_block_button_group_begin(uiBlock *block, struct uiButtonGroup *group);
 void UI_block_button_group_end(uiBlock *block);
 
diff --git a/source/blender/editors/interface/interface.c b/source/blender/editors/interface/interface.c
index 3eb8f3d6bb5..5673bc2535c 100644
--- a/source/blender/editors/interface/interface.c
+++ b/source/blender/editors/interface/interface.c
@@ -4756,6 +4756,157 @@ void UI_but_string_info_get(bContext *C, uiBut *but, ...)
 	}
 }
 
+
+/* -------------------------------------------------------------------- */
+/**
+ * \name Button Group
+ * \brief Generate buttons with custom, storable order.
+ *
+ * Button groups have the following key characteristics:
+ * * Sortable: Contained buttons can be sorted.
+ * * Generates: They in fact do not contain buttons, but manage info on how to
+ *   create and sort buttons on runtime.
+ * * Storable: The mapping for custom sorting is written into files, alongside
+ *   an identifier for this specific group. That way the group can be
+ *   identified and the custom sorting re-applied after reading files.
+ *
+ * Maybe button group is a bit of a misleading term, since it doesn't actually
+ * store the buttons itself.
+ * Via a callback a button-group gathers information from which another
+ * callback can create the buttons then. In-between those two callbacks the
+ * items are sorted in a customizable way.
+ *
+ * \{ */
+
+uiButtonGroup *UI_button_group_ensure(ARegion *region, const char *name, void *custom_data)
+{
+	uiButtonGroup *group;
+
+	for (group = region->button_groups.first; group; group = group->next) {
+		if (STREQ(group->type->idname, name) && group->type->identify(group, custom_data)) {
+			return group;
+		}
+	}
+
+	group = MEM_callocN(sizeof(*group), __func__);
+	group->type = WM_uibuttongrouptype_find(name, false);
+	BLI_addtail(&region->button_groups, group);
+
+	return group;
+}
+
+typedef struct SortedButtonGroupItemInfo {
+	struct SortedButtonGroupItemInfo *next, *prev;
+
+	uiButtonGroupItemInfo *item;
+	int new_position_index;
+} SortedButtonGroupItemInfo;
+
+static int ui_button_group_items_cmp(const void *a, const void *b)
+{
+	const SortedButtonGroupItemInfo *item_a = a, *item_b = b;
+	return item_a->new_position_index > item_b->new_position_index ? 1 : 0;
+}
+
+static void ui_button_group_sort(
+        const uiButtonGroup *group, const ListBase *items,
+        ListBase *r_sorted_items)
+{
+	int i = 0;
+	for (uiButtonGroupItemInfo *item = items->first; item; item = item->next, i++) {
+		SortedButtonGroupItemInfo *sort_item = MEM_callocN(sizeof(*sort_item), __func__);
+
+		sort_item->item = item;
+		sort_item->new_position_index = group->reordered_indices[i];
+		BLI_addtail(r_sorted_items, sort_item);
+	}
+	BLI_listbase_sort(r_sorted_items, ui_button_group_items_cmp);
+}
+
+static void ui_button_group_find_added_items(
+        const uiButtonGroup *group, const ListBase *items,
+        const int prev_tot_items,
+        ListBase *r_added_items)
+{
+	const int difference = group->tot_items - prev_tot_items;
+
+	if (difference == 0) {
+		return;
+	}
+
+	if (difference > 0) {
+		for (uiButtonGroupItemInfo *item = items->first; item; item = item->next) {
+			const bool has_item = BLI_findptr(&group->items, item->data,
+			                                  offsetof(uiButtonGroupItemInfo, data)) != NULL;
+			if (!has_item) {
+				uiButtonGroupItemInfo *item_new = MEM_dupallocN(item);
+				BLI_addtail(r_added_items, item_new);
+			}
+		}
+	}
+}
+
+static void ui_button_group_handle_added_or_removed_items(
+        uiButtonGroup *group, const ListBase *new_items,
+        int old_tot_items)
+{
+	ListBase added_items = {NULL, NULL};
+
+	group->reordered_indices = MEM_recallocN(
+	                               group->reordered_indices, sizeof(*group->reordered_indices) * group->tot_items);
+	ui_button_group_find_added_items(group, new_items, old_tot_items, &added_items);
+
+	/* Add new items at the end of the list. */
+	const int tot_new_items = group->tot_items - old_tot_items;
+
+	BLI_assert(BLI_listbase_count(&added_items) == tot_new_items);
+	int i = 0;
+	for (uiButtonGroupItemInfo *new_item = added_items.first; new_item; new_item = new_item->next, i++) {
+		for (int j = group->tot_items - tot_new_items + i; j > new_item->position_index; j--) {
+			group->reordered_indices[j] = group->reordered_indices[j - 1];
+		}
+		group->reordered_indices[new_item->position_index] = group->tot_items - tot_new_items + i;
+	}
+	BLI_freelistN(&added_items);
+
+	/* TODO support removing items */
+}
+
+void UI_button_group_add_sorted_items(uiButtonGroup *group, uiBlock *block, void *custom_data)
+{
+	const int old_tot_items = group->tot_items;
+	ListBase new_items = {NULL, NULL};
+	ListBase sorted_items = {NULL, NULL};
+
+	group->type->items(custom_data, &new_items);
+	group->tot_items = BLI_listbase_count(&new_items);
+
+	if (!group->reordered_indices || (group->tot_items != old_tot_items)) {
+		ui_button_group_handle_added_or_removed_items(group, &new_items, old_tot_items);
+	}
+
+	ui_button_group_sort(group, &new_items, &sorted_items);
+
+	UI_block_button_group_begin(block, group);
+	for (SortedButtonGroupItemInfo *sorted_item = sorted_items.first; sorted_item; sorted_item = sorted_item->next) {
+		group->type->item_draw(block, custom_data, sorted_item->item);
+	}
+	UI_block_button_group_end(block);
+
+	BLI_freelistN(&sorted_items);
+	BLI_freelistN(&group->items);
+	group->items = new_items;
+}
+
+void UI_button_group_item_add(void *data, ListBase *items)
+{
+	uiButtonGroupItemInfo *item = MEM_callocN(sizeof(*item), __func__);
+
+	BLI_addtail(items, item);
+	item->data = data;
+	item->position_index = item->prev ? ((uiButtonGroupItemInfo *)item->prev)->position_index + 1 : 0;
+}
+
 void UI_block_button_group_begin(uiBlock *block, uiButtonGroup *group)
 {
 	BLI_assert(block->current_group == NULL);
diff --git a/source/blender/editors/interface/interface_templates.c b/source/blender/editors/interface/interface_templates.c
index b890e8b38b0..b70468dd508 100644
--- a/source/blender/editors/interface/interface_templates.c
+++ b/source/blender/editors/interface/interface_templates.c
@@ -103,14 +103,10 @@ void UI_template_fix_linking(void)
 {
 }
 
-
 typedef struct TemplateID {
 	PointerRNA ptr;
 	PropertyRNA *prop;
 
-	wmOperatorType *unlink_ot; // XXX tmp!
-	PointerRNA active_ptr;
-
 	ListBase *idlb;
 	short idcode;
 	short filter;
@@ -118,123 +114,13 @@ typedef struct TemplateID {
 	bool preview;
 } TemplateID;
 
-static uiButtonGroup *ui_button_group_ensure(ARegion *region, const char *name, void *custom_data)
-{
-	uiButtonGroup *group;
-
-	for (group = region->button_groups.first; group; group = group->next) {
-		if (STREQ(group->type->idname, name) && group->type->identify(group, custom_data)) {
-			return group;
-		}
-	}
-
-	group = MEM_callocN(sizeof(uiButtonGroup), __func__);
-	group->type = WM_uibuttongrouptype_find(name, false);
-	BLI_addtail(&region->button_groups, group);
-
-	return group;
-}
-
-static int ui_button_group_items_cmp(const void *a, const void *b)
-{
-	const uiButtonGroupItemInfo *item_a = a, *item_b = b;
-	return item_a->position_index > item_b->position_index ? 1 : 0;
-}
-
-static void ui_button_group_sort(
-        const uiButtonGroup *group, const ListBase *items,
-        ListBase *r_sorted_items)
-{
-	int i = 0;
-	for (uiButtonGroupItemInfo *item = items->first; item; item = item->next, i++) {
-		uiButtonGroupItemInfo *sort_item = MEM_dupallocN(item);
-
-		sort_item->position_index = group->reordered_indices[i];
-		BLI_addtail(r_sorted_items, sort_item);
-	}
-	BLI_listbase_sort(r_sorted_items, ui_button_group_items_cmp);
-}
-
-static void ui_button_group_find_new_items(
-        const uiButtonGroup *group, const ListBase *current_items, const int prev_tot_items,
-        ListBase *r_new_items)
-{
-	const int difference = group->tot_items - prev_tot_items;
-
-	if (difference == 0) {
-		return;
-	}
-
-	if (difference > 0) {
-		for (uiButtonGroupItemInfo *item = current_items->first; item; item = item->next) {
-			const bool has_item = BLI_findptr(&group->items, item->data,
-			                                  offsetof(uiButtonGroupItemInfo, data)) != NULL;
-			if (!has_item) {
-				uiButtonGroupItemInfo *item_new = MEM_dupallocN(item);
-				BLI_addtail(r_new_items, item_new);
-			}
-		}
-	}
-}
-
+typedef struct SortableIDTabsData {
+	TemplateID *template_id;
 
-/* XXX split this up into generic and sortable_id_tabs functions */
-static void ui_template_sortable_id_tabs(
-        ARegion *region, uiBlock *block, TemplateID *template_ui, wmOperatorType *unlink_ot)
-{
-	uiButtonGroup *group = ui_button_group_ensure(region, "UI_BGT_sortable_id_tabs", template_ui);
-	const int old_tot_items = group->tot_items;
-	ListBase items = {NULL, NULL};
-
-	template_ui->unlink_ot = unlink_ot;
-	template_ui->active_ptr = RNA_property_pointer_get(&template_ui->ptr, template_ui->prop);
-
-	group->type->items(group, template_ui, &items);
-
-	if (!group->reordered_indices || (group->tot_items != old_tot_items)) {
-		ListBase new_items = {NULL, NULL};
-
-		group->reordered_indices = MEM_recallocN(
-		                               group->reordered_indices, sizeof(*group->reordered_indices) * group->tot_items);
-		ui_button_group_find_new_items(group, &items, old_tot_items, &new_items);
-
-		/* Add new items at the end of the list. */
-		const int tot_new_items = group->tot_items - old_tot_items;
-
-		BLI_assert(BLI_listbase_count(&new_items) == tot_new_items);
-		int i = 0;
-		for (uiButtonGroupItemInfo *new_item = new_items.first; new_item; new_item = new_item->next, i++) {
-			for (int j = group->tot_items - tot_new_items + i; j > new_item->position_index; j--) {
-				group->reordered_indices[j] = group->reordered_indices[j - 1];
-			}
-			group->reordered_indices[new_item->position_index] = group->tot_items - tot_new_items + i;
-		}
-		BLI_freelistN(&new_items);
-
-		/* TODO support removing items */
-	}
-
-	ListBase sorted_items = {NULL, NULL};
-	ui_button_group_sort(group, &items, &sorted_items);
-
-	UI_block_button_group_begin(block, group);
-	for (uiButtonGroupItemInfo *item = sorted_items.first; item; item = item->next) {
-		group->type->item_draw(block, template_ui, item);
-	}
-	UI_block_button_group_end(block);
+	wmOperatorType *unlink_ot;
+	PointerRNA active_ptr;
+} SortableIDTabsData;
 
-	BLI_freelistN(&sorted_items);
-	BLI_freelistN(&group->items);
-	group->items = items;
-}
-
-static void ui_buttong_group_item_add(void *data, ListBase *items)
-{
-	uiButtonGroupItemInfo *item = MEM_callocN(sizeof(*item), __func__);
-	BLI_addtail(items, item);
-	item->data = data;
-	item->position_index = item->prev ? ((uiButtonGroupItemInfo *)item->prev)->position_index + 1 : 0;
-}
 
 /* TODO After file read, we need to be able to identify button groups. That's what should later happen here. */
 static bool ui_sortable_id_tabs_button_group_identify(uiButtonGroup *group, void *UNUSED(custom_data))
@@ -247,29 +133,25 @@ static bool ui_sortable_id_tabs_button_group_identify(uiButtonGroup *group, void
 	return false;
 }
 
-static void ui_sortable_id_tabs_items(
-        uiButtonGroup *group, void *custom_data,
-        ListBase *r_items)
+static void ui_sortable_id_tabs_items(void *custom_data, ListBase *r_items)
 {
-	TemplateID *template_ui = custom_data;
-
-	group->tot_items = BLI_listbase_count(template_ui->idlb);
+	SortableIDTabsData *data = custom_data;
 
-	for (ID *id = template_ui->idlb->first; id; id = id->next) {
-		ui_buttong_group_item_add(id, r_items);
+	for (ID *id = data->template_id->idlb->first; id; id = id->next) {
+		UI_button_group_item_add(id, r_items);
 	}
 }
 
 static void template_ID_set_property_cb(bContext *C, void *arg_template, void *item);
 
-static void ui_sortable_id_tab_draw(
+static void ui_sortable_id_tab_item_draw(
         uiBlock *block, void *custom_data, uiButtonGroupItemInfo *item)
 {
+	SortableIDTabsData *data = custom_data;
 	ID *id = item->data;
-	TemplateID *template_ui = custom_data;
 
 	uiStyle *style = UI_style_get_dpi();
-	const bool is_active = template_ui->active_ptr.data == id;
+	const bool is_active = data->active_ptr.data == id;
 	const unsigned int but_width = UI_fontstyle_string_width(&style->widgetlabel, id->name + 2) + UI_UNIT_X +
 	                               (is_active ? ICON_DEFAULT_WIDTH_SCALE : 0);
 //	const int but_align = (region->alignment == RGN_ALIGN_TOP) ? UI_BUT_ALIGN_DOWN : UI_BUT_ALIGN_TOP;
@@ -277,13 +159,13 @@ static void ui_sortable_id_tab_draw(
 
 	uiButTab *tab = (uiButTab *)uiDefButR_prop(
 	                    block, UI_BTYPE_TAB, 0, "", 0, 0, but_width, UI_UNIT_Y,
-	                    &template_ui->ptr, template_ui->prop, 0, 0.0f,
+	                    &data->template_id->ptr, data->template_id->prop, 0, 0.0f,
 	                    sizeof(id->name) - 2, 0.0f, 0.0f, "");
-	UI_but_funcN_set(&tab->but, template_ID_set_property_cb, MEM_dupallocN(template_ui), id);
+	UI_but_funcN_set(&tab->but, template_ID_set_property_cb, MEM_dupallocN(data->template_id), id);
 	UI_but_drawflag_enable(&tab->but, UI_BUT_ALIGN_DOWN); /* TODO fixed alignment - should be based on region alignment */
 	UI_but_drag_set_reorder(&tab->but);
 	tab->but.custom_data = (void *)id;
-	tab->unlink_ot = template_ui->unlink_ot;
+	tab->unlink_ot = data->unlink_ot;
 	if (is_active) {
 		UI_but_flag_enable(&tab->but, UI_BUT_VALUE_CLEAR);
 	}
@@ -296,11 +178,24 @@ uiButtonGroupType *UI_BGT_sortable_id_tabs(void)
 	group_type->idname = "UI_BGT_sortable_id_tabs"; // TODO not needed?
 	group_type->identify = ui_sortable_id_tabs_button_group_identify;
 	group_type->items = ui_sortable_id_tabs_items;
-	group_type->item_draw = ui_sortable_id_tab_draw;
+	group_type->item_draw = ui_sortable_id_tab_item_draw;
 
 	return group_type;
 }
 
+static void ui_template_sortable_id_tabs(
+        ARegion *region, uiBlock *block, TemplateID *template_ui, wmOperatorType *unlink_ot)
+{
+	uiButtonGroup *group = UI_button_group_ensure(region, "UI_BGT_sortable_id_tabs", template_ui);
+	SortableIDTabsData data;
+
+	data.template_id = template_ui;
+	data.unlink_ot = unlink_ot;
+	data.active_ptr = RNA_property_pointer_get(&template_ui->ptr, template_ui->prop);
+
+	UI_button_group_add_sorted_items(group, block, &data);
+}
+
 
 /**
  * Add a block button for the search menu for templateID and templateSearch.
diff --git a/source/blender/makesdna/DNA_screen_types.h b/source/blender/makesdna/DNA_screen_types.h
index 0034b88eec8..56d1dd57b89 100644
--- a/source/blender/makesdna/DNA_screen_types.h
+++ b/source/blender/makesdna/DNA_screen_types.h
@@ -225,6 +225,11 @@ typedef struct uiButtonGroupItemInfo {
 	void *data;
 } uiButtonGroupItemInfo;
 
+/* TODO Better name for this? Alternatives:
+ * * uiSortedButtonGenerator
+ * * uiButtonGroupGenerator
+ * * uiStorableItems
+ */
 typedef struct uiButtonGroup {
 	struct uiButtonGroup *next, *prev;