UI: add a preference for the number of samples used for FPS playback

This was hard coded to 8, which can still result in a number that
jitters making the overall FPS difficult to measure.

The default is still 8, but this is now a preference that can be
increased for values that don't jitter as much.

release/datafiles/userdef/userdef_default.c

@@ -108,6 +108,7 @@ const UserDef U_default = {
     .gp_euclideandist = 2,
     .gp_eraser = 25,
     .gp_settings = 0,
+    .playback_fps_samples = 8,
 #ifdef __APPLE__
     .gpu_backend = GPU_BACKEND_METAL,
 #else

scripts/startup/bl_ui/space_userpref.py

@@ -720,6 +720,9 @@ class USERPREF_PT_viewport_display(ViewportPanel, CenterAlignMixIn, Panel):
         col.prop(view, "show_object_info", text="Object Info")
         col.prop(view, "show_view_name", text="View Name")
         col.prop(view, "show_playback_fps", text="Playback Frame Rate (FPS)")
+        row = col.row()
+        row.active = view.show_playback_fps
+        row.prop(view, "playback_fps_samples", text="Frame Rate Samples")
 
         layout.separator()
 

source/blender/blenkernel/BKE_blender_version.h

@@ -29,7 +29,7 @@ extern "C" {
 
 /* Blender file format version. */
 #define BLENDER_FILE_VERSION BLENDER_VERSION
-#define BLENDER_FILE_SUBVERSION 17
+#define BLENDER_FILE_SUBVERSION 18
 
 /* Minimum Blender version that supports reading file written with the current
  * version. Older Blender versions will test this and cancel loading the file, showing a warning to

source/blender/blenloader/intern/versioning_userdef.cc

@@ -852,6 +852,10 @@ void blo_do_versions_userdef(UserDef *userdef)
     userdef->node_preview_res = 120;
   }
 
+  if (!USER_VERSION_ATLEAST(400, 18)) {
+    userdef->playback_fps_samples = 8;
+  }
+
   /**
    * Versioning code until next subversion bump goes here.
    *

source/blender/editors/include/ED_screen_types.hh

@@ -43,20 +43,24 @@ enum {
 
 /* ----------------------------------------------------- */
 
-#define REDRAW_FRAME_AVERAGE 8
-
 /**
  * For playback frame-rate info stored during runtime as `scene->fps_info`.
  */
 struct ScreenFrameRateInfo {
   double redrawtime;
   double lredrawtime;
-  float redrawtimes_fps[REDRAW_FRAME_AVERAGE];
-  short redrawtime_index;
+
   /** The target FPS, use to reset on change. */
   float fps_target;
   /** Final result, ignore when -1.0. */
   float fps_average;
+
+  int redrawtimes_index;
+  int redrawtimes_num;
+  int redrawtimes_num_set;
+
+  /** Over allocate. */
+  float redrawtimes_fps[0];
 };
 
 /* ----------------------------------------------------- */

source/blender/editors/screen/screen_edit.cc

@@ -1694,22 +1694,30 @@ void ED_scene_fps_average_accumulate(Scene *scene, const double ltime)
 
   /* Playback running. */
   const float fps_target = float(FPS);
-  ScreenFrameRateInfo *fpsi = static_cast<ScreenFrameRateInfo *>(scene->fps_info);
 
-  /* Reset when the target FPS changes.
-   * Needed redraw times from when a different FPS was set do not contribute
-   * to an average that is over/under the new target. */
-  if (fpsi && (fpsi->fps_target != fps_target)) {
-    MEM_freeN(fpsi);
-    fpsi = nullptr;
-    scene->fps_info = nullptr;
+  ScreenFrameRateInfo *fpsi = static_cast<ScreenFrameRateInfo *>(scene->fps_info);
+  const int redrawtimes_num = U.playback_fps_samples ? U.playback_fps_samples :
+                                                       max_ii(1, int(ceilf(fps_target)));
+
+  if (fpsi) {
+    /* Reset when the target FPS changes.
+     * Needed redraw times from when a different FPS was set do not contribute
+     * to an average that is over/under the new target. */
+    if ((fpsi->fps_target != fps_target) || (fpsi->redrawtimes_num != redrawtimes_num)) {
+      MEM_freeN(fpsi);
+      fpsi = nullptr;
+      scene->fps_info = nullptr;
+    }
   }
 
   /* If there isn't any info, initialize it first. */
   if (fpsi == nullptr) {
-    fpsi = static_cast<ScreenFrameRateInfo *>(
-        scene->fps_info = MEM_callocN(sizeof(ScreenFrameRateInfo), __func__));
+    scene->fps_info = MEM_callocN(sizeof(ScreenFrameRateInfo) + (sizeof(float) * redrawtimes_num),
+                                  __func__);
+    fpsi = static_cast<ScreenFrameRateInfo *>(scene->fps_info);
     fpsi->fps_target = fps_target;
+    fpsi->redrawtimes_num = redrawtimes_num;
+    fpsi->redrawtimes_num_set = 0;
   }
 
   /* Update the values. */
@@ -1738,22 +1746,23 @@ bool ED_scene_fps_average_calc(const Scene *scene)
     return true;
   }
 
-  fpsi->redrawtimes_fps[fpsi->redrawtime_index] = float(1.0 /
-                                                        (fpsi->lredrawtime - fpsi->redrawtime));
+  if (fpsi->redrawtimes_index >= fpsi->redrawtimes_num) {
+    fpsi->redrawtimes_index = 0;
+  }
 
+  /* Doing an average for a more robust calculation. */
+  fpsi->redrawtimes_fps[fpsi->redrawtimes_index] = float(1.0 /
+                                                         (fpsi->lredrawtime - fpsi->redrawtime));
+  fpsi->redrawtimes_index++;
+  if (fpsi->redrawtimes_index > fpsi->redrawtimes_num_set) {
+    fpsi->redrawtimes_num_set = fpsi->redrawtimes_index;
+  }
+  BLI_assert(fpsi->redrawtimes_num_set > 0);
   float fps = 0.0f;
-  int tot = 0;
-  for (int i = 0; i < REDRAW_FRAME_AVERAGE; i++) {
-    if (fpsi->redrawtimes_fps[i]) {
-      fps += fpsi->redrawtimes_fps[i];
-      tot++;
-    }
+  for (int i = 0; i < fpsi->redrawtimes_num_set; i++) {
+    fps += fpsi->redrawtimes_fps[i];
   }
-  if (tot) {
-    fpsi->redrawtime_index = (fpsi->redrawtime_index + 1) % REDRAW_FRAME_AVERAGE;
-    fps = fps / tot;
-  }
-  fpsi->fps_average = fps;
+  fpsi->fps_average = fps / float(fpsi->redrawtimes_num_set);
   return true;
 }
 

source/blender/makesdna/DNA_userdef_types.h

@@ -923,7 +923,10 @@ typedef struct UserDef {
   /** #eGPUBackendType */
   short gpu_backend;
 
-  char _pad7[4];
+  /** Number of samples for FPS display calculations. */
+  uchar playback_fps_samples;
+
+  char _pad7[3];
 
   /** Private, defaults to 20 for 72 DPI setting. */
   short widget_unit;

source/blender/makesrna/intern/rna_userdef.cc

@@ -4833,6 +4833,16 @@ static void rna_def_userdef_view(BlenderRNA *brna)
                            "overlay while animation is played back");
   RNA_def_property_update(prop, 0, "rna_userdef_update");
 
+  prop = RNA_def_property(srna, "playback_fps_samples", PROP_INT, PROP_NONE);
+  RNA_def_property_int_sdna(prop, nullptr, "playback_fps_samples");
+  RNA_def_property_range(prop, 0, 200);
+  RNA_def_property_ui_text(
+      prop,
+      "FPS Average Samples",
+      "The number of frames to use for calculating FPS average. "
+      "Zero to calculate this automatically, where the number of samples matches the target FPS");
+  RNA_def_property_update(prop, 0, "rna_userdef_update");
+
   USERDEF_TAG_DIRTY_PROPERTY_UPDATE_DISABLE;
   prop = RNA_def_property(srna, "show_addons_enabled_only", PROP_BOOLEAN, PROP_NONE);
   RNA_def_property_boolean_sdna(