UI: Refactor how dragging onto text buttons works, fixing issues

There was a bunch of special handling to support dropping data-blocks onto
string or search-menu buttons, to change the value of these. This refactor
makes that case use the normal drop-box design, where an operator is executed
on drop that gets input properties set by the drop-box. This should also make
it easier to add support for dragging assets into these buttons.

In addition this fixes an issue: Two tooltips were shown when dragging assets
over text buttons. None should be shown, because this isn't supported.

source/blender/editors/include/UI_interface.h

@@ -788,7 +788,8 @@ void UI_but_drag_set_value(uiBut *but);
 void UI_but_drag_set_image(
     uiBut *but, const char *path, int icon, struct ImBuf *imb, float scale, const bool use_free);
 
-bool UI_but_active_drop_name(struct bContext *C);
+uiBut *UI_but_active_drop_name_button(const struct bContext *C);
+bool UI_but_active_drop_name(const struct bContext *C);
 bool UI_but_active_drop_color(struct bContext *C);
 
 void UI_but_flag_enable(uiBut *but, int flag);

source/blender/editors/interface/interface_dropboxes.cc

@@ -24,6 +24,8 @@
 
 #include "MEM_guardedalloc.h"
 
+#include "RNA_access.h"
+
 #include "WM_api.h"
 
 #include "UI_interface.h"
@@ -59,6 +61,21 @@ static char *ui_tree_view_drop_tooltip(bContext *C,
   return UI_tree_view_item_drop_tooltip(hovered_tree_item, drag);
 }
 
+/* ---------------------------------------------------------------------- */
+
+static bool ui_drop_name_poll(struct bContext *C, wmDrag *drag, const wmEvent *UNUSED(event))
+{
+  return UI_but_active_drop_name(C) && (drag->type == WM_DRAG_ID);
+}
+
+static void ui_drop_name_copy(wmDrag *drag, wmDropBox *drop)
+{
+  const ID *id = WM_drag_get_local_ID(drag, 0);
+  RNA_string_set(drop->ptr, "string", id->name + 2);
+}
+
+/* ---------------------------------------------------------------------- */
+
 void ED_dropboxes_ui()
 {
   ListBase *lb = WM_dropboxmap_find("User Interface", SPACE_EMPTY, 0);
@@ -69,4 +86,10 @@ void ED_dropboxes_ui()
                  nullptr,
                  nullptr,
                  ui_tree_view_drop_tooltip);
+  WM_dropbox_add(lb,
+                 "UI_OT_drop_name",
+                 ui_drop_name_poll,
+                 ui_drop_name_copy,
+                 WM_drag_free_imported_drag_ID,
+                 nullptr);
 }

source/blender/editors/interface/interface_handlers.c

@@ -2442,39 +2442,6 @@ static void ui_apply_but(
 
 /** \} */
 
-/* -------------------------------------------------------------------- */
-/** \name Button Drop Event
- * \{ */
-
-/* only call if event type is EVT_DROP */
-static void ui_but_drop(bContext *C, const wmEvent *event, uiBut *but, uiHandleButtonData *data)
-{
-  ListBase *drags = event->customdata; /* drop event type has listbase customdata by default */
-
-  LISTBASE_FOREACH (wmDrag *, wmd, drags) {
-    /* TODO: asset dropping. */
-    if (wmd->type == WM_DRAG_ID) {
-      /* align these types with UI_but_active_drop_name */
-      if (ELEM(but->type, UI_BTYPE_TEXT, UI_BTYPE_SEARCH_MENU)) {
-        ID *id = WM_drag_get_local_ID(wmd, 0);
-
-        button_activate_state(C, but, BUTTON_STATE_TEXT_EDITING);
-
-        ui_textedit_string_set(but, data, id->name + 2);
-
-        if (ELEM(but->type, UI_BTYPE_SEARCH_MENU)) {
-          but->changed = true;
-          ui_searchbox_update(C, data->searchbox, but, true);
-        }
-
-        button_activate_state(C, but, BUTTON_STATE_EXIT);
-      }
-    }
-  }
-}
-
-/** \} */
-
 /* -------------------------------------------------------------------- */
 /** \name Button Copy & Paste
  * \{ */
@@ -2672,15 +2639,9 @@ static void ui_but_copy_text(uiBut *but, char *output, int output_len_max)
 
 static void ui_but_paste_text(bContext *C, uiBut *but, uiHandleButtonData *data, char *buf_paste)
 {
-  button_activate_state(C, but, BUTTON_STATE_TEXT_EDITING);
-  ui_textedit_string_set(but, but->active, buf_paste);
-
-  if (but->type == UI_BTYPE_SEARCH_MENU) {
-    but->changed = true;
-    ui_searchbox_update(C, data->searchbox, but, true);
-  }
-
-  button_activate_state(C, but, BUTTON_STATE_EXIT);
+  BLI_assert(but->active == data);
+  UNUSED_VARS_NDEBUG(data);
+  ui_but_set_string_interactive(C, but, buf_paste);
 }
 
 static void ui_but_copy_colorband(uiBut *but)
@@ -3024,6 +2985,24 @@ void ui_but_text_password_hide(char password_str[UI_MAX_PASSWORD_STR],
 /** \name Button Text Selection/Editing
  * \{ */
 
+/**
+ * Use handling code to set a string for the button. Handles the case where the string is set for a
+ * search button while the search menu is open, so the results are updated accordingly.
+ * This is basically the same as pasting the string into the button.
+ */
+void ui_but_set_string_interactive(bContext *C, uiBut *but, const char *value)
+{
+  button_activate_state(C, but, BUTTON_STATE_TEXT_EDITING);
+  ui_textedit_string_set(but, but->active, value);
+
+  if (but->type == UI_BTYPE_SEARCH_MENU && but->active) {
+    but->changed = true;
+    ui_searchbox_update(C, but->active->searchbox, but, true);
+  }
+
+  button_activate_state(C, but, BUTTON_STATE_EXIT);
+}
+
 void ui_but_active_string_clear_and_exit(bContext *C, uiBut *but)
 {
   if (!but->active) {
@@ -7949,7 +7928,7 @@ static int ui_do_button(bContext *C, uiBlock *block, uiBut *but, const wmEvent *
   /* Only hard-coded stuff here, button interactions with configurable
    * keymaps are handled using operators (see #ED_keymap_ui). */
 
-  if ((data->state == BUTTON_STATE_HIGHLIGHT) || (event->type == EVT_DROP)) {
+  if (data->state == BUTTON_STATE_HIGHLIGHT) {
 
     /* handle copy and paste */
     bool is_press_ctrl_but_no_shift = event->val == KM_PRESS && IS_EVENT_MOD(event, ctrl, oskey) &&
@@ -7998,11 +7977,6 @@ static int ui_do_button(bContext *C, uiBlock *block, uiBut *but, const wmEvent *
       return WM_UI_HANDLER_BREAK;
     }
 
-    /* handle drop */
-    if (event->type == EVT_DROP) {
-      ui_but_drop(C, event, but, data);
-    }
-
     if ((data->state == BUTTON_STATE_HIGHLIGHT) &&
         ELEM(event->type, LEFTMOUSE, EVT_BUT_OPEN, EVT_PADENTER, EVT_RETKEY) &&
         (event->val == KM_RELEASE) &&
@@ -11716,20 +11690,25 @@ void UI_screen_free_active_but(const bContext *C, bScreen *screen)
   }
 }
 
-/* returns true if highlighted button allows drop of names */
-/* called in region context */
-bool UI_but_active_drop_name(bContext *C)
+uiBut *UI_but_active_drop_name_button(const bContext *C)
 {
   ARegion *region = CTX_wm_region(C);
   uiBut *but = ui_region_find_active_but(region);
 
   if (but) {
     if (ELEM(but->type, UI_BTYPE_TEXT, UI_BTYPE_SEARCH_MENU)) {
-      return true;
+      return but;
     }
   }
 
-  return false;
+  return NULL;
+}
+
+/* returns true if highlighted button allows drop of names */
+/* called in region context */
+bool UI_but_active_drop_name(const bContext *C)
+{
+  return UI_but_active_drop_name_button(C) != NULL;
 }
 
 bool UI_but_active_drop_color(bContext *C)

source/blender/editors/interface/interface_intern.h

@@ -680,6 +680,7 @@ extern bool ui_but_string_eval_number(struct bContext *C,
 extern int ui_but_string_get_max_length(uiBut *but);
 /* Clear & exit the active button's string. */
 extern void ui_but_active_string_clear_and_exit(struct bContext *C, uiBut *but) ATTR_NONNULL();
+extern void ui_but_set_string_interactive(struct bContext *C, uiBut *but, const char *value);
 extern uiBut *ui_but_drag_multi_edit_get(uiBut *but);
 
 void ui_def_but_icon(uiBut *but, const int icon, const int flag);

source/blender/editors/interface/interface_ops.c

@@ -1863,6 +1863,39 @@ static void UI_OT_drop_color(wmOperatorType *ot)
 
 /** \} */
 
+/* -------------------------------------------------------------------- */
+/** \name Drop Name Operator
+ * \{ */
+
+static int drop_name_invoke(bContext *C, wmOperator *op, const wmEvent *UNUSED(event))
+{
+  uiBut *but = UI_but_active_drop_name_button(C);
+  char *str = RNA_string_get_alloc(op->ptr, "string", NULL, 0, NULL);
+
+  if (str) {
+    ui_but_set_string_interactive(C, but, str);
+    MEM_freeN(str);
+  }
+
+  return OPERATOR_FINISHED;
+}
+
+static void UI_OT_drop_name(wmOperatorType *ot)
+{
+  ot->name = "Drop Name";
+  ot->idname = "UI_OT_drop_name";
+  ot->description = "Drop name to button";
+
+  ot->poll = ED_operator_regionactive;
+  ot->invoke = drop_name_invoke;
+  ot->flag = OPTYPE_UNDO | OPTYPE_INTERNAL;
+
+  RNA_def_string(
+      ot->srna, "string", NULL, 0, "String", "The string value to drop into the button");
+}
+
+/** \} */
+
 /* -------------------------------------------------------------------- */
 /** \name UI List Search Operator
  * \{ */
@@ -2025,6 +2058,7 @@ void ED_operatortypes_ui(void)
   WM_operatortype_append(UI_OT_copy_to_selected_button);
   WM_operatortype_append(UI_OT_jump_to_target_button);
   WM_operatortype_append(UI_OT_drop_color);
+  WM_operatortype_append(UI_OT_drop_name);
 #ifdef WITH_PYTHON
   WM_operatortype_append(UI_OT_editsource);
   WM_operatortype_append(UI_OT_edittranslation_init);

source/blender/windowmanager/intern/wm_dragdrop.c

@@ -821,10 +821,7 @@ static void wm_drag_draw_tooltip(bContext *C, wmWindow *win, wmDrag *drag, const
 
   const char *tooltip = NULL;
   bool free_tooltip = false;
-  if (UI_but_active_drop_name(C)) {
-    tooltip = IFACE_("Paste name");
-  }
-  else if (drag->active_dropbox) {
+  if (drag->active_dropbox) {
     tooltip = dropbox_tooltip(C, drag, xy, drag->active_dropbox);
     free_tooltip = true;
   }
@@ -907,7 +904,6 @@ void wm_drags_draw(bContext *C, wmWindow *win)
     xy[1] = win->eventstate->xy[1];
   }
 
-  /* Set a region. It is used in the `UI_but_active_drop_name`. */
   bScreen *screen = CTX_wm_screen(C);
   ScrArea *area = BKE_screen_find_area_xy(screen, SPACE_TYPE_ANY, UNPACK2(xy));
   ARegion *region = BKE_area_find_region_xy(area, RGN_TYPE_ANY, UNPACK2(xy));