WindowManager: Support Dynamic tooltips when dragging.

Originally the operator name was drawn next to the dragging content.
After that there was an option to add custom, static text with the
dragging content. This patch allows dynamic text to be drawn.

The custom text was implemented as out parameter of the poll function
what made the code unclear. This patch introduces a tooltip function
that separates tooltip generation from the poll function.

NOTE: the text should always be returned in its own memory block. This
block will be freed after it is copied in the drag struct.

Reviewed By: Severin

Differential Revision: https://developer.blender.org/D12104

4 files changed, 63 insertions, 45 deletions

diff --git a/source/blender/windowmanager/WM_api.h b/source/blender/windowmanager/WM_api.h
index c0d408be2e0..136c639caea 100644
--- a/source/blender/windowmanager/WM_api.h
+++ b/source/blender/windowmanager/WM_api.h
@@ -34,6 +34,7 @@
 #include "BLI_sys_types.h"
 #include "DNA_windowmanager_types.h"
 #include "WM_keymap.h"
+#include "WM_types.h"
 
 #ifdef __cplusplus
 extern "C" {
@@ -705,13 +706,13 @@ void WM_event_drag_image(struct wmDrag *, struct ImBuf *, float scale, int sx, i
 void WM_drag_free(struct wmDrag *drag);
 void WM_drag_data_free(int dragtype, void *poin);
 void WM_drag_free_list(struct ListBase *lb);
-
 struct wmDropBox *WM_dropbox_add(
     ListBase *lb,
     const char *idname,
-    bool (*poll)(struct bContext *, struct wmDrag *, const struct wmEvent *event, const char **),
+    bool (*poll)(struct bContext *, struct wmDrag *, const struct wmEvent *event),
     void (*copy)(struct wmDrag *, struct wmDropBox *),
-    void (*cancel)(struct Main *, struct wmDrag *, struct wmDropBox *));
+    void (*cancel)(struct Main *, struct wmDrag *, struct wmDropBox *),
+    WMDropboxTooltipFunc tooltip);
 ListBase *WM_dropboxmap_find(const char *idname, int spaceid, int regionid);
 
 /* ID drag and drop */
diff --git a/source/blender/windowmanager/WM_types.h b/source/blender/windowmanager/WM_types.h
index 4ead0b2699c..4d6cb941347 100644
--- a/source/blender/windowmanager/WM_types.h
+++ b/source/blender/windowmanager/WM_types.h
@@ -114,6 +114,7 @@ struct bContext;
 struct wmEvent;
 struct wmOperator;
 struct wmWindowManager;
+struct wmDrag;
 
 #include "BLI_compiler_attrs.h"
 #include "DNA_listBase.h"
@@ -934,6 +935,10 @@ typedef struct wmDragAsset {
   int import_type; /* eFileAssetImportType */
 } wmDragAsset;
 
+typedef char *(*WMDropboxTooltipFunc)(struct bContext *,
+                                      struct wmDrag *,
+                                      const struct wmEvent *event);
+
 typedef struct wmDrag {
   struct wmDrag *next, *prev;
 
@@ -949,8 +954,8 @@ typedef struct wmDrag {
   float scale;
   int sx, sy;
 
-  /** If set, draws operator name. */
-  char opname[200];
+  /** If filled, draws operator tooltip/operator name. */
+  char tooltip[200];
   unsigned int flags;
 
   /** List of wmDragIDs, all are guaranteed to have the same ID type. */
@@ -964,8 +969,8 @@ typedef struct wmDrag {
 typedef struct wmDropBox {
   struct wmDropBox *next, *prev;
 
-  /** Test if the dropbox is active, then can print optype name. */
-  bool (*poll)(struct bContext *, struct wmDrag *, const wmEvent *, const char **);
+  /** Test if the dropbox is active. */
+  bool (*poll)(struct bContext *, struct wmDrag *, const wmEvent *);
 
   /** Before exec, this copies drag info to #wmDrop properties. */
   void (*copy)(struct wmDrag *, struct wmDropBox *);
@@ -976,6 +981,9 @@ typedef struct wmDropBox {
    */
   void (*cancel)(struct Main *, struct wmDrag *, struct wmDropBox *);
 
+  /** Custom tooltip shown during dragging. */
+  WMDropboxTooltipFunc tooltip;
+
   /**
    * If poll succeeds, operator is called.
    * Not saved in file, so can be pointer.
diff --git a/source/blender/windowmanager/intern/wm_dragdrop.c b/source/blender/windowmanager/intern/wm_dragdrop.c
index db72dd2a819..c58d3c53e03 100644
--- a/source/blender/windowmanager/intern/wm_dragdrop.c
+++ b/source/blender/windowmanager/intern/wm_dragdrop.c
@@ -96,14 +96,16 @@ ListBase *WM_dropboxmap_find(const char *idname, int spaceid, int regionid)
 
 wmDropBox *WM_dropbox_add(ListBase *lb,
                           const char *idname,
-                          bool (*poll)(bContext *, wmDrag *, const wmEvent *, const char **),
+                          bool (*poll)(bContext *, wmDrag *, const wmEvent *),
                           void (*copy)(wmDrag *, wmDropBox *),
-                          void (*cancel)(struct Main *, wmDrag *, wmDropBox *))
+                          void (*cancel)(struct Main *, wmDrag *, wmDropBox *),
+                          WMDropboxTooltipFunc tooltip)
 {
   wmDropBox *drop = MEM_callocN(sizeof(wmDropBox), "wmDropBox");
   drop->poll = poll;
   drop->copy = copy;
   drop->cancel = cancel;
+  drop->tooltip = tooltip;
   drop->ot = WM_operatortype_find(idname, 0);
   drop->opcontext = WM_OP_INVOKE_DEFAULT;
 
@@ -218,22 +220,36 @@ void WM_drag_free_list(struct ListBase *lb)
   }
 }
 
-static const char *dropbox_active(bContext *C,
-                                  ListBase *handlers,
-                                  wmDrag *drag,
-                                  const wmEvent *event)
+static char *dropbox_tooltip(bContext *C,
+                             wmDrag *drag,
+                             const wmEvent *event,
+                             const wmDropBox *drop)
+{
+  char *tooltip = NULL;
+  if (drop->tooltip) {
+    tooltip = drop->tooltip(C, drag, event);
+  }
+  if (!tooltip) {
+    tooltip = BLI_strdup(WM_operatortype_name(drop->ot, drop->ptr));
+  }
+  /* XXX Doing translation here might not be ideal, but later we have no more
+   *     access to ot (and hence op context)... */
+  return tooltip;
+}
+
+static wmDropBox *dropbox_active(bContext *C,
+                                 ListBase *handlers,
+                                 wmDrag *drag,
+                                 const wmEvent *event)
 {
   LISTBASE_FOREACH (wmEventHandler *, handler_base, handlers) {
     if (handler_base->type == WM_HANDLER_TYPE_DROPBOX) {
       wmEventHandler_Dropbox *handler = (wmEventHandler_Dropbox *)handler_base;
       if (handler->dropboxes) {
         LISTBASE_FOREACH (wmDropBox *, drop, handler->dropboxes) {
-          const char *tooltip = NULL;
-          if (drop->poll(C, drag, event, &tooltip) &&
+          if (drop->poll(C, drag, event) &&
               WM_operator_poll_context(C, drop->ot, drop->opcontext)) {
-            /* XXX Doing translation here might not be ideal, but later we have no more
-             *     access to ot (and hence op context)... */
-            return (tooltip) ? tooltip : WM_operatortype_name(drop->ot, drop->ptr);
+            return drop;
           }
         }
       }
@@ -242,29 +258,22 @@ static const char *dropbox_active(bContext *C,
   return NULL;
 }
 
-/* return active operator name when mouse is in box */
-static const char *wm_dropbox_active(bContext *C, wmDrag *drag, const wmEvent *event)
+/* return active operator tooltip/name when mouse is in box */
+static char *wm_dropbox_active(bContext *C, wmDrag *drag, const wmEvent *event)
 {
   wmWindow *win = CTX_wm_window(C);
-  ScrArea *area = CTX_wm_area(C);
-  ARegion *region = CTX_wm_region(C);
-  const char *name;
-
-  name = dropbox_active(C, &win->handlers, drag, event);
-  if (name) {
-    return name;
+  wmDropBox *drop = dropbox_active(C, &win->handlers, drag, event);
+  if (!drop) {
+    ScrArea *area = CTX_wm_area(C);
+    drop = dropbox_active(C, &area->handlers, drag, event);
   }
-
-  name = dropbox_active(C, &area->handlers, drag, event);
-  if (name) {
-    return name;
+  if (!drop) {
+    ARegion *region = CTX_wm_region(C);
+    drop = dropbox_active(C, &region->handlers, drag, event);
   }
-
-  name = dropbox_active(C, &region->handlers, drag, event);
-  if (name) {
-    return name;
+  if (drop) {
+    return dropbox_tooltip(C, drag, event, drop);
   }
-
   return NULL;
 }
 
@@ -279,17 +288,18 @@ static void wm_drop_operator_options(bContext *C, wmDrag *drag, const wmEvent *e
     return;
   }
 
-  drag->opname[0] = 0;
+  drag->tooltip[0] = 0;
 
   /* check buttons (XXX todo rna and value) */
   if (UI_but_active_drop_name(C)) {
-    BLI_strncpy(drag->opname, IFACE_("Paste name"), sizeof(drag->opname));
+    BLI_strncpy(drag->tooltip, IFACE_("Paste name"), sizeof(drag->tooltip));
   }
   else {
-    const char *opname = wm_dropbox_active(C, drag, event);
+    char *tooltip = wm_dropbox_active(C, drag, event);
 
-    if (opname) {
-      BLI_strncpy(drag->opname, opname, sizeof(drag->opname));
+    if (tooltip) {
+      BLI_strncpy(drag->tooltip, tooltip, sizeof(drag->tooltip));
+      MEM_freeN(tooltip);
       // WM_cursor_modal_set(win, WM_CURSOR_COPY);
     }
     // else
@@ -584,7 +594,7 @@ void wm_drags_draw(bContext *C, wmWindow *win, rcti *rect)
     }
 
     /* operator name with roundbox */
-    if (drag->opname[0]) {
+    if (drag->tooltip[0]) {
       if (drag->imb) {
         x = cursorx - drag->sx / 2;
 
@@ -611,7 +621,7 @@ void wm_drags_draw(bContext *C, wmWindow *win, rcti *rect)
         drag_rect_minmax(rect, x, y, x + w, y + iconsize);
       }
       else {
-        wm_drop_operator_draw(drag->opname, x, y);
+        wm_drop_operator_draw(drag->tooltip, x, y);
       }
     }
   }
diff --git a/source/blender/windowmanager/intern/wm_event_system.c b/source/blender/windowmanager/intern/wm_event_system.c
index 5e29a22304c..5cc361fc1bd 100644
--- a/source/blender/windowmanager/intern/wm_event_system.c
+++ b/source/blender/windowmanager/intern/wm_event_system.c
@@ -2851,8 +2851,7 @@ static int wm_handlers_do_intern(bContext *C, wmEvent *event, ListBase *handlers
             if (event->custom == EVT_DATA_DRAGDROP) {
               ListBase *lb = (ListBase *)event->customdata;
               LISTBASE_FOREACH (wmDrag *, drag, lb) {
-                const char *tooltip = NULL;
-                if (drop->poll(C, drag, event, &tooltip)) {
+                if (drop->poll(C, drag, event)) {
                   /* Optionally copy drag information to operator properties. Don't call it if the
                    * operator fails anyway, it might do more than just set properties (e.g.
                    * typically import an asset). */