clutter/stage: Cleanup the capture_view code

Reuse capture's rect parameter instead of passing a new one, and support the
case where there are no returned areas.

https://gitlab.gnome.org/GNOME/mutter/merge_requests/3

clutter/clutter/clutter-stage.c

@@ -4757,7 +4757,6 @@ static void
 capture_view (ClutterStage          *stage,
               gboolean               paint,
               ClutterStageView      *view,
-              cairo_rectangle_int_t *rect,
               ClutterCapture        *capture)
 {
   CoglFramebuffer *framebuffer;
@@ -4768,10 +4767,12 @@ capture_view (ClutterStage          *stage,
   int stride;
   CoglBitmap *bitmap;
   cairo_rectangle_int_t view_layout;
+  cairo_rectangle_int_t *rect;
   float view_scale;
   float texture_width;
   float texture_height;
 
+  rect = &capture->rect;
   framebuffer = clutter_stage_view_get_framebuffer (view);
 
   if (paint)
@@ -4809,7 +4810,6 @@ capture_view (ClutterStage          *stage,
   if (paint)
     cogl_pop_framebuffer ();
 
-  capture->rect = *rect;
   capture->image = image;
 
   cairo_surface_mark_dirty (capture->image);
@@ -4829,34 +4829,91 @@ clutter_stage_capture (ClutterStage          *stage,
   ClutterCapture *captures;
   int n_captures;
 
+  g_return_val_if_fail (CLUTTER_IS_STAGE (stage), FALSE);
+
   captures = g_new0 (ClutterCapture, g_list_length (views));
   n_captures = 0;
 
   for (l = views; l; l = l->next)
     {
       ClutterStageView *view = l->data;
+      ClutterCapture *capture;
       cairo_rectangle_int_t view_layout;
       cairo_region_t *region;
-      cairo_rectangle_int_t view_capture_rect;
 
       clutter_stage_view_get_layout (view, &view_layout);
       region = cairo_region_create_rectangle (&view_layout);
       cairo_region_intersect_rectangle (region, rect);
-      cairo_region_get_extents (region, &view_capture_rect);
+
+      capture = &captures[n_captures];
+      cairo_region_get_extents (region, &capture->rect);
       cairo_region_destroy (region);
 
-      if (view_capture_rect.width == 0 || view_capture_rect.height == 0)
+      if (capture->rect.width == 0 || capture->rect.height == 0)
         continue;
 
-      capture_view (stage, paint, view, &view_capture_rect,
-                    &captures[n_captures]);
+      capture_view (stage, paint, view, capture);
 
       n_captures++;
     }
 
+  if (n_captures == 0)
+    g_clear_pointer (&captures, g_free);
+
   *out_captures = captures;
   *out_n_captures = n_captures;
 
+  return n_captures > 0;
+}
+
+gboolean
+clutter_stage_get_capture_final_size (ClutterStage          *stage,
+                                      cairo_rectangle_int_t *rect,
+                                      int                   *out_width,
+                                      int                   *out_height,
+                                      float                 *out_scale)
+{
+  float max_scale;
+
+  g_return_val_if_fail (CLUTTER_IS_STAGE (stage), FALSE);
+
+  if (rect)
+    {
+      ClutterRect capture_rect;
+
+      _clutter_util_rect_from_rectangle (rect, &capture_rect);
+      if (!_clutter_stage_get_max_view_scale_factor_for_rect (stage,
+                                                              &capture_rect,
+                                                              &max_scale))
+        return FALSE;
+
+      if (out_width)
+        *out_width = (gint) roundf (rect->width * max_scale);
+
+      if (out_height)
+        *out_height = (gint) roundf (rect->height * max_scale);
+    }
+  else
+    {
+      ClutterActorBox alloc;
+      float stage_width, stage_height;
+
+      clutter_actor_get_allocation_box (CLUTTER_ACTOR (stage), &alloc);
+      clutter_actor_box_get_size (&alloc, &stage_width, &stage_height);
+      if (!_clutter_actor_get_real_resource_scale (CLUTTER_ACTOR (stage),
+                                                   &max_scale))
+        return FALSE;
+
+      if (out_width)
+        *out_width = (gint) roundf (stage_width * max_scale);
+
+      if (out_height)
+        *out_height = (gint) roundf (stage_height * max_scale);
+    }
+
+  if (out_scale)
+    *out_scale = max_scale;
+
   return TRUE;
 }
 
@@ -4874,6 +4931,8 @@ capture_view_into (ClutterStage          *stage,
   CoglBitmap *bitmap;
   cairo_rectangle_int_t view_layout;
 
+  g_return_if_fail (CLUTTER_IS_STAGE (stage));
+
   framebuffer = clutter_stage_view_get_framebuffer (view);
 
   if (paint)

clutter/clutter/clutter-stage.h

@@ -261,6 +261,13 @@ CLUTTER_EXPORT
 void            clutter_stage_skip_sync_delay                   (ClutterStage          *stage);
 #endif
 
+CLUTTER_EXPORT
+gboolean clutter_stage_get_capture_final_size (ClutterStage          *stage,
+                                               cairo_rectangle_int_t *rect,
+                                               int                   *width,
+                                               int                   *height,
+                                               float                 *scale);
+
 CLUTTER_EXPORT
 gboolean clutter_stage_capture (ClutterStage          *stage,
                                 gboolean               paint,