Draw Manager: Implement render info for external engines

This can be used by any engine actually. For example to give feedback
regarding probe caching in Eevee, ....

Unline master, we try to conciliate both the original viewport info
(FPS, view name) and the render info.

Note: I had to split the function in two because the camera alpha
passepartout is handled inside the view3d_draw_region_info function.

Review: Campbell Barton and Clement Foucault.

Thanks to Sergey Sharybin and Pablo Vazquez for some of the design
discussions.

2 files changed, 6 insertions, 3 deletions

diff --git a/source/blender/editors/space_view3d/view3d_draw.c b/source/blender/editors/space_view3d/view3d_draw.c
index ceb8f69acaf..b54681dfde4 100644
--- a/source/blender/editors/space_view3d/view3d_draw.c
+++ b/source/blender/editors/space_view3d/view3d_draw.c
@@ -2311,7 +2311,7 @@ static void view3d_draw_manipulators(const bContext *C, const ARegion *ar)
 /**
 * Information drawn on top of the solid plates and composed data
 */
-void view3d_draw_region_info(const bContext *C, ARegion *ar)
+void view3d_draw_region_info(const bContext *C, ARegion *ar, const int offset)
 {
 	RegionView3D *rv3d = ar->regiondata;
 	View3D *v3d = CTX_wm_view3d(C);
@@ -2325,6 +2325,9 @@ void view3d_draw_region_info(const bContext *C, ARegion *ar)
 	rcti rect;
 	ED_region_visible_rect(ar, &rect);
 
+	/* Leave room for previously drawn info. */
+	rect.ymax -= offset;
+
 	view3d_draw_border(C, ar);
 	view3d_draw_grease_pencil(C);
 
@@ -2400,7 +2403,7 @@ static void view3d_draw_view(const bContext *C, ARegion *ar, DrawData *draw_data
 
 	glDisable(GL_DEPTH_TEST);
 
-	view3d_draw_region_info(C, ar);
+	view3d_draw_region_info(C, ar, 0);
 
 #if VIEW3D_DRAW_DEBUG
 	view3d_draw_debug(C, ar, draw_data);
diff --git a/source/blender/editors/space_view3d/view3d_intern.h b/source/blender/editors/space_view3d/view3d_intern.h
index 8c306176eff..27d03f81109 100644
--- a/source/blender/editors/space_view3d/view3d_intern.h
+++ b/source/blender/editors/space_view3d/view3d_intern.h
@@ -209,7 +209,7 @@ void draw_sim_debug_data(Scene *scene, View3D *v3d, ARegion *ar);
 
 /* view3d_draw.c */
 void view3d_main_region_draw(const struct bContext *C, struct ARegion *ar);
-void view3d_draw_region_info(const struct bContext *C, struct ARegion *ar);
+void view3d_draw_region_info(const struct bContext *C, struct ARegion *ar, const int offset);
 
 void ED_view3d_draw_depth(
         struct Depsgraph *graph,