Expose background job info to Python

Add `bpy.app.is_job_running(job_type)` as high-level indicator. Job
types currently exposed are `WM_JOB_TYPE_RENDER`,
`WM_JOB_TYPE_RENDER_PREVIEW`, and `WM_JOB_TYPE_OBJECT_BAKE`, as strings
with the `WM_JOB_TYPE_` prefix removed. The functions can be polled by
Python code to determine whether such background work is still ongoing
or not.

Furthermore, new app handles are added for
`object_bake_{pre,complete,canceled}`, which are called respectively
before an object baking job starts, completes sucessfully, and stops due
to a cancellation.

Motivation: There are various cases where Python can trigger the
execution of a background job, without getting notification that that
background job is done. As a result, it's hard to do things like
cleanups, or auto-quitting Blender after the work is done.

The approach in this commit can easily be extended with other job types,
when the need arises. The rendering of asset previews is one that's
likely to be added sooner than later, as there have already been
requests about this.

Reviewed By: campbellbarton

Differential Revision: https://developer.blender.org/D14587

source/blender/blenkernel/BKE_callbacks.h

@@ -97,6 +97,9 @@ typedef enum {
   BKE_CB_EVT_XR_SESSION_START_PRE,
   BKE_CB_EVT_ANNOTATION_PRE,
   BKE_CB_EVT_ANNOTATION_POST,
+  BKE_CB_EVT_OBJECT_BAKE_PRE,
+  BKE_CB_EVT_OBJECT_BAKE_COMPLETE,
+  BKE_CB_EVT_OBJECT_BAKE_CANCEL,
   BKE_CB_EVT_TOT,
 } eCbEvent;
 

source/blender/editors/object/object_bake_api.c

@@ -21,6 +21,7 @@
 #include "BLI_path_util.h"
 #include "BLI_string.h"
 
+#include "BKE_callbacks.h"
 #include "BKE_context.h"
 #include "BKE_global.h"
 #include "BKE_image.h"
@@ -1806,6 +1807,17 @@ static void bake_startjob(void *bkv, short *UNUSED(stop), short *do_update, floa
   RE_SetReports(bkr->render, NULL);
 }
 
+static void bake_job_complete(void *bkv)
+{
+  BakeAPIRender *bkr = (BakeAPIRender *)bkv;
+  BKE_callback_exec_id(bkr->main, &bkr->ob->id, BKE_CB_EVT_OBJECT_BAKE_COMPLETE);
+}
+static void bake_job_canceled(void *bkv)
+{
+  BakeAPIRender *bkr = (BakeAPIRender *)bkv;
+  BKE_callback_exec_id(bkr->main, &bkr->ob->id, BKE_CB_EVT_OBJECT_BAKE_CANCEL);
+}
+
 static void bake_freejob(void *bkv)
 {
   BakeAPIRender *bkr = (BakeAPIRender *)bkv;
@@ -1941,6 +1953,7 @@ static int bake_invoke(bContext *C, wmOperator *op, const wmEvent *UNUSED(event)
 
   /* init bake render */
   bake_init_api_data(op, C, bkr);
+  BKE_callback_exec_id(CTX_data_main(C), &bkr->ob->id, BKE_CB_EVT_OBJECT_BAKE_PRE);
   re = bkr->render;
 
   /* setup new render */
@@ -1958,7 +1971,8 @@ static int bake_invoke(bContext *C, wmOperator *op, const wmEvent *UNUSED(event)
   /* TODO: only draw bake image, can we enforce this. */
   WM_jobs_timer(
       wm_job, 0.5, (bkr->target == R_BAKE_TARGET_VERTEX_COLORS) ? NC_GEOM | ND_DATA : NC_IMAGE, 0);
-  WM_jobs_callbacks(wm_job, bake_startjob, NULL, NULL, NULL);
+  WM_jobs_callbacks_ex(
+      wm_job, bake_startjob, NULL, NULL, NULL, bake_job_complete, bake_job_canceled);
 
   G.is_break = false;
   G.is_rendering = true;

source/blender/makesrna/RNA_enum_items.h

@@ -147,6 +147,7 @@ DEF_ENUM(rna_enum_keymap_propvalue_items)
 DEF_ENUM(rna_enum_operator_context_items)
 
 DEF_ENUM(rna_enum_wm_report_items)
+DEF_ENUM(rna_enum_wm_job_type_items)
 
 DEF_ENUM(rna_enum_property_type_items)
 DEF_ENUM(rna_enum_property_subtype_items)

source/blender/makesrna/intern/rna_wm.c

@@ -24,6 +24,7 @@
 
 #include "rna_internal.h"
 
+#include "WM_api.h"
 #include "WM_types.h"
 
 #ifdef RNA_RUNTIME
@@ -123,6 +124,22 @@ static const EnumPropertyItem event_ndof_type_items[] = {
 };
 #endif /* RNA_RUNTIME */
 
+/**
+ * Job types for use in the `bpy.app.is_job_running(job_type)` call.
+ *
+ * This is a subset of the `WM_JOB_TYPE_...` anonymous enum defined in `WM_api.h`. It is
+ * intentionally kept as a subset, such that by default how jobs are handled is kept as an
+ * "internal implementation detail" of Blender, rather than a public, reliable part of the API.
+ *
+ * This array can be expanded on a case-by-case basis, when there is a clear and testable use case.
+ */
+const EnumPropertyItem rna_enum_wm_job_type_items[] = {
+    {WM_JOB_TYPE_RENDER, "RENDER", 0, "Regular rendering", ""},
+    {WM_JOB_TYPE_RENDER_PREVIEW, "RENDER_PREVIEW", 0, "Rendering previews", ""},
+    {WM_JOB_TYPE_OBJECT_BAKE, "OBJECT_BAKE", 0, "Object Baking", ""},
+    {0, NULL, 0, NULL, NULL},
+};
+
 const EnumPropertyItem rna_enum_event_type_items[] = {
     /* - Note we abuse 'tooltip' message here to store a 'compact' form of some (too) long names.
      * - Intentionally excluded: #CAPSLOCKKEY, #UNKNOWNKEY.

source/blender/makesrna/intern/rna_wm_api.c

@@ -23,6 +23,7 @@
 #include "wm_cursors.h"
 #include "wm_event_types.h"
 
+#include "WM_api.h"
 #include "WM_types.h"
 
 #include "rna_internal.h" /* own include */

source/blender/python/intern/bpy_app.c

@@ -36,15 +36,19 @@
 #include "BKE_appdir.h"
 #include "BKE_blender_version.h"
 #include "BKE_global.h"
+#include "BKE_main.h"
 
 #include "DNA_ID.h"
 
 #include "UI_interface_icons.h"
 
+#include "RNA_enum_types.h" /* For `rna_enum_wm_job_type_items`. */
+
 /* for notifiers */
 #include "WM_api.h"
 #include "WM_types.h"
 
+#include "../generic/py_capi_rna.h"
 #include "../generic/py_capi_utils.h"
 #include "../generic/python_utildefines.h"
 
@@ -450,6 +454,44 @@ static PyGetSetDef bpy_app_getsets[] = {
     {NULL, NULL, NULL, NULL, NULL},
 };
 
+PyDoc_STRVAR(bpy_app_is_job_running_doc,
+             ".. staticmethod:: is_job_running(job_type)\n"
+             "\n"
+             "   Check whether a job of the given type is running.\n"
+             "\n"
+             "   :arg job_type: job type in ['RENDER', 'RENDER_PREVIEW', OBJECT_BAKE]."
+             "   :type job_type: str\n"
+             "   :return: Whether a job of the given type is currently running.\n"
+             "   :rtype: bool.\n");
+static PyObject *bpy_app_is_job_running(PyObject *UNUSED(self), PyObject *args, PyObject *kwds)
+{
+  struct BPy_EnumProperty_Parse job_type_enum = {
+      .items = rna_enum_wm_job_type_items,
+      .value = 0,
+  };
+  static const char *_keywords[] = {"job_type", NULL};
+  static _PyArg_Parser _parser = {
+      "O&" /* `job_type` */
+      ":is_job_running",
+      _keywords,
+      0,
+  };
+  if (!_PyArg_ParseTupleAndKeywordsFast(
+          args, kwds, &_parser, pyrna_enum_value_parse_string, &job_type_enum)) {
+    return NULL;
+  }
+  wmWindowManager *wm = G_MAIN->wm.first;
+  return PyBool_FromLong(WM_jobs_has_running_type(wm, job_type_enum.value));
+}
+
+static struct PyMethodDef bpy_app_methods[] = {
+    {"is_job_running",
+     (PyCFunction)bpy_app_is_job_running,
+     METH_VARARGS | METH_KEYWORDS | METH_STATIC,
+     bpy_app_is_job_running_doc},
+    {NULL, NULL, 0, NULL},
+};
+
 static void py_struct_seq_getset_init(void)
 {
   /* tricky dynamic members, not to py-spec! */
@@ -459,6 +501,17 @@ static void py_struct_seq_getset_init(void)
     Py_DECREF(item);
   }
 }
+
+static void py_struct_seq_method_init(void)
+{
+  for (PyMethodDef *method = bpy_app_methods; method->ml_name; method++) {
+    BLI_assert_msg(method->ml_flags & METH_STATIC, "Only static methods make sense for 'bpy.app'");
+    PyObject *item = PyCFunction_New(method, NULL);
+    PyDict_SetItemString(BlenderAppType.tp_dict, method->ml_name, item);
+    Py_DECREF(item);
+  }
+}
+
 /* end dynamic bpy.app */
 
 PyObject *BPY_app_struct(void)
@@ -477,6 +530,7 @@ PyObject *BPY_app_struct(void)
 
   /* kindof a hack ontop of PyStructSequence */
   py_struct_seq_getset_init();
+  py_struct_seq_method_init();
 
   return ret;
 }

source/blender/python/intern/bpy_app_handlers.c

@@ -67,6 +67,10 @@ static PyStructSequence_Field app_cb_info_fields[] = {
     {"annotation_pre", "on drawing an annotation (before)"},
     {"annotation_post", "on drawing an annotation (after)"},
 
+    {"object_bake_pre", "before starting a bake job"},
+    {"object_bake_complete", "on completing a bake job; will be called in the main thread"},
+    {"object_bake_cancel", "on canceling a bake job; will be called in the main thread"},
+
 /* sets the permanent tag */
 #define APP_CB_OTHER_FIELDS 1
     {"persistent",

source/blender/windowmanager/WM_api.h

@@ -1400,6 +1400,14 @@ void WM_jobs_callbacks(struct wmJob *,
                        void (*update)(void *),
                        void (*endjob)(void *));
 
+void WM_jobs_callbacks_ex(wmJob *wm_job,
+                          wm_jobs_start_callback startjob,
+                          void (*initjob)(void *),
+                          void (*update)(void *),
+                          void (*endjob)(void *),
+                          void (*completed)(void *),
+                          void (*canceled)(void *));
+
 /**
  * If job running, the same owner gave it a new job.
  * if different owner starts existing startjob, it suspends itself
@@ -1426,6 +1434,7 @@ void WM_jobs_kill_all_except(struct wmWindowManager *wm, const void *owner);
 void WM_jobs_kill_type(struct wmWindowManager *wm, const void *owner, int job_type);
 
 bool WM_jobs_has_running(const struct wmWindowManager *wm);
+bool WM_jobs_has_running_type(const struct wmWindowManager *wm, int job_type);
 
 void WM_job_main_thread_lock_acquire(struct wmJob *job);
 void WM_job_main_thread_lock_release(struct wmJob *job);

source/blender/windowmanager/intern/wm_jobs.c

@@ -87,6 +87,16 @@ struct wmJob {
    * Executed in main thread.
    */
   void (*endjob)(void *);
+  /**
+   * Called when job is stopped normally, i.e. by simply completing the startjob function.
+   * Executed in main thread.
+   */
+  void (*completed)(void *);
+  /**
+   * Called when job is stopped abnormally, i.e. when stop=true but ready=false.
+   * Executed in main thread.
+   */
+  void (*canceled)(void *);
 
   /** Running jobs each have own timer */
   double timestep;
@@ -343,11 +353,24 @@ void WM_jobs_callbacks(wmJob *wm_job,
                        void (*initjob)(void *),
                        void (*update)(void *),
                        void (*endjob)(void *))
+{
+  WM_jobs_callbacks_ex(wm_job, startjob, initjob, update, endjob, NULL, NULL);
+}
+
+void WM_jobs_callbacks_ex(wmJob *wm_job,
+                          wm_jobs_start_callback startjob,
+                          void (*initjob)(void *),
+                          void (*update)(void *),
+                          void (*endjob)(void *),
+                          void (*completed)(void *),
+                          void (*canceled)(void *))
 {
   wm_job->startjob = startjob;
   wm_job->initjob = initjob;
   wm_job->update = update;
   wm_job->endjob = endjob;
+  wm_job->completed = completed;
+  wm_job->canceled = canceled;
 }
 
 static void *do_job_thread(void *job_v)
@@ -465,6 +488,25 @@ void WM_jobs_start(wmWindowManager *wm, wmJob *wm_job)
   }
 }
 
+static void wm_job_end(wmJob *wm_job)
+{
+  BLI_assert_msg(BLI_thread_is_main(), "wm_job_end should only be called from the main thread");
+  if (wm_job->endjob) {
+    wm_job->endjob(wm_job->run_customdata);
+  }
+
+  /* Do the final callback based on whether the job was run to completion or not.
+   * Not all jobs have the same way of signalling cancellation (f.e. rendering
+   * stops when G.is_break=true, but doesn't set any wm_job properties to cancel
+   * the WM job). */
+  const bool was_canceled = wm_job->stop || G.is_break;
+  void (*final_callback)(void *) = (wm_job->ready && !was_canceled) ? wm_job->completed :
+                                                                      wm_job->canceled;
+  if (final_callback) {
+    final_callback(wm_job->run_customdata);
+  }
+}
+
 static void wm_job_free(wmWindowManager *wm, wmJob *wm_job)
 {
   BLI_remlink(&wm->jobs, wm_job);
@@ -485,10 +527,7 @@ static void wm_jobs_kill_job(wmWindowManager *wm, wmJob *wm_job)
     WM_job_main_thread_lock_release(wm_job);
     BLI_threadpool_end(&wm_job->threads);
     WM_job_main_thread_lock_acquire(wm_job);
-
-    if (wm_job->endjob) {
-      wm_job->endjob(wm_job->run_customdata);
-    }
+    wm_job_end(wm_job);
   }
 
   if (wm_job->wt) {
@@ -600,9 +639,7 @@ void wm_jobs_timer(wmWindowManager *wm, wmTimer *wt)
         }
 
         if (wm_job->ready) {
-          if (wm_job->endjob) {
-            wm_job->endjob(wm_job->run_customdata);
-          }
+          wm_job_end(wm_job);
 
           /* free own data */
           wm_job->run_free(wm_job->run_customdata);
@@ -670,3 +707,13 @@ bool WM_jobs_has_running(const wmWindowManager *wm)
 
   return false;
 }
+
+bool WM_jobs_has_running_type(const struct wmWindowManager *wm, int job_type)
+{
+  LISTBASE_FOREACH (wmJob *, wm_job, &wm->jobs) {
+    if (wm_job->running && wm_job->job_type == job_type) {
+      return true;
+    }
+  }
+  return false;
+}