[mutter/gnome-3-36] clutter/stage: Make paint_to_buffer use the correct texture/buffer size

[Georges Basile Stavracas Neto <gbsneto src gnome org>]

commit 81deb99435fc92a36231144fd3099d9e57485d7e
Author: Sebastian Keller <skeller gnome org>
Date:   Wed Jun 17 13:32:54 2020 +0000

    clutter/stage: Make paint_to_buffer use the correct texture/buffer size
    
    The size of the buffer the texture will be written to by
    paint_to_buffer() is determined based on
    meta_screen_cast_area_stream_src_get_specs() which uses roundf() to
    calculate the width and height after scaling. Because the size of the
    texture to be written to that buffer is calculated using ceilf(), it
    might exceed the allocated buffer when using fractional scaling.
    
    In 3.36 paint_to_buffer() is used from capture_view() which also uses
    roundf() to allocate its buffer. Here this leads to a memory corruption
    resulting in a crash when taking screenshots of an area.
    
    Fixes https://gitlab.gnome.org/GNOME/gnome-shell/-/issues/2842
    
    https://gitlab.gnome.org/GNOME/mutter/-/merge_requests/1320
    
    
    (cherry picked from commit e216d9c6ad377ba5ed51d0edf9805ca7c73a7e63)

 clutter/clutter/clutter-stage.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)
---
diff --git a/clutter/clutter/clutter-stage.c b/clutter/clutter/clutter-stage.c
index 82565c6b57..e2b63e7fe6 100644
--- a/clutter/clutter/clutter-stage.c
+++ b/clutter/clutter/clutter-stage.c
@@ -4526,8 +4526,8 @@ clutter_stage_paint_to_buffer (ClutterStage                 *stage,
   CoglFramebuffer *framebuffer;
   CoglBitmap *bitmap;
 
-  texture_width = (int) ceilf (rect->width * scale);
-  texture_height = (int) ceilf (rect->height * scale);
+  texture_width = (int) roundf (rect->width * scale);
+  texture_height = (int) roundf (rect->height * scale);
   texture = cogl_texture_2d_new_with_size (cogl_context,
                                            texture_width,
                                            texture_height);