VSE: Add precise drag and drop and strip previews

This patch adds the drag and drop strip previews in the VSE.
It also adds two new functions to the drag and drop API.

1. "draw_in_view" for callbacks that wants to draw elements in local viewport coordinates
2. "on_drag_start" that can be used for prefetching data only once at the start of the drag.

Reviewed By: Julian, Campbell

Differential Revision: http://developer.blender.org/D14560

1 files changed, 51 insertions, 4 deletions

diff --git a/source/blender/windowmanager/intern/wm_dragdrop.c b/source/blender/windowmanager/intern/wm_dragdrop.c
index 4970b09c18b..a98ded82a92 100644
--- a/source/blender/windowmanager/intern/wm_dragdrop.c
+++ b/source/blender/windowmanager/intern/wm_dragdrop.c
@@ -17,6 +17,7 @@
 
 #include "BLT_translation.h"
 
+#include "BLI_bitmap.h"
 #include "BLI_blenlib.h"
 #include "BLI_math_color.h"
 
@@ -95,7 +96,7 @@ 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 *),
-                          void (*copy)(wmDrag *, wmDropBox *),
+                          void (*copy)(bContext *, wmDrag *, wmDropBox *),
                           void (*cancel)(struct Main *, wmDrag *, wmDropBox *),
                           WMDropboxTooltipFunc tooltip)
 {
@@ -136,6 +137,44 @@ void wm_dropbox_free(void)
 
 /* *********************************** */
 
+static void wm_dropbox_invoke(bContext *C, wmDrag *drag)
+{
+  wmWindowManager *wm = CTX_wm_manager(C);
+
+  /* Create a bitmap flag matrix of all currently visible region and area types.
+   * Everything that isn't visible in the current window should not prefetch any data. */
+  bool area_region_tag[SPACE_TYPE_NUM][RGN_TYPE_NUM] = {{false}};
+
+  LISTBASE_FOREACH (wmWindow *, win, &wm->windows) {
+    bScreen *screen = WM_window_get_active_screen(win);
+    ED_screen_areas_iter (win, screen, area) {
+      LISTBASE_FOREACH (ARegion *, region, &area->regionbase) {
+        if (region->visible) {
+          BLI_assert(area->spacetype < SPACE_TYPE_NUM);
+          BLI_assert(region->regiontype < RGN_TYPE_NUM);
+          area_region_tag[area->spacetype][region->regiontype] = true;
+        }
+      }
+    }
+  }
+
+  LISTBASE_FOREACH (wmDropBoxMap *, dm, &dropboxes) {
+    if (!area_region_tag[dm->spaceid][dm->regionid]) {
+      continue;
+    }
+    LISTBASE_FOREACH (wmDropBox *, drop, &dm->dropboxes) {
+      if (drag->drop_state.ui_context) {
+        CTX_store_set(C, drag->drop_state.ui_context);
+      }
+
+      if (drop->on_drag_start) {
+        drop->on_drag_start(C, drag);
+      }
+      CTX_store_set(C, NULL);
+    }
+  }
+}
+
 wmDrag *WM_event_start_drag(
     struct bContext *C, int icon, int type, void *poin, double value, unsigned int flags)
 {
@@ -187,6 +226,8 @@ wmDrag *WM_event_start_drag(
   }
   drag->value = value;
 
+  wm_dropbox_invoke(C, drag);
+
   return drag;
 }
 
@@ -416,7 +457,7 @@ void wm_drop_prepare(bContext *C, wmDrag *drag, wmDropBox *drop)
    * operator fails anyway, it might do more than just set properties (e.g.
    * typically import an asset). */
   if (drop->copy && WM_operator_poll_context(C, drop->ot, opcontext)) {
-    drop->copy(drag, drop);
+    drop->copy(C, drag, drop);
   }
 
   wm_drags_exit(CTX_wm_manager(C), CTX_wm_window(C));
@@ -947,10 +988,16 @@ void wm_drags_draw(bContext *C, wmWindow *win)
       CTX_wm_region_set(C, drag->drop_state.region_from);
       CTX_store_set(C, drag->drop_state.ui_context);
 
+      if (region && drag->drop_state.active_dropbox->draw_in_view) {
+        wmViewport(&region->winrct);
+        drag->drop_state.active_dropbox->draw_in_view(C, win, drag, xy);
+        wmWindowViewport(win);
+      }
+
       /* Drawing should be allowed to assume the context from handling and polling (that's why we
        * restore it above). */
-      if (drag->drop_state.active_dropbox->draw) {
-        drag->drop_state.active_dropbox->draw(C, win, drag, xy);
+      if (drag->drop_state.active_dropbox->draw_droptip) {
+        drag->drop_state.active_dropbox->draw_droptip(C, win, drag, xy);
         continue;
       }
     }