Screen¶
The bScreen struct generally contains the positions and arrangements of areas and regions within a Window.
A window can contain more than one Screen, but only one is active at a
time. For example, when you have an editor "Maximize Area" it creates
another Screen with just the one
editor, which is closed when you
are done to reveal the previous layout. The list of screens is kept in
the Main database struct.
WorkSpaceLayout has a screen pointer, and each screen also has a
winid that matches that of its parent window's winid.
How Editors are Arranged in Screens¶
bScreen is generally keeping track of where each non-global editor
(ScrArea) is in the screen. Global areas (TopBar and StatusBar) are
tracked in the Window itself - you can find this state with
ED_area_is_global.
Each ScrArea has four pointers (V1 - V4) to ScrVert structs that
live in a list in the bScreen (vertbase), that represent that editor's
four corners. it is important to note that these screen verts are shared
by neighbors. The best way to think about this is that each editor is
not just immediately adjacent to its neighbors, but actually overlap by
a pixel. This way we can move one shared ScrEdge between them when
resizing, for example.
The internal visible part of each editor (ScrArea->totrct) is then
inset from its corners by U.pixelsize in area_calc_totrct. This
results (when the UI scale is 1) in a 1 pixel gap between each editor.
The border we see is actually wider and drawn around each editor,
overlapping each one a bit. This difference is why can sometimes see
inconsistencies in header height as the size of the occluded portion can
vary.
Getting the Active Screen¶
It is a simple call to get the current screen. In most cases you need it for a user-interactive purpose, so you can often avoid having to test the return for NULL. The exception to be aware of is when Blender is run headless from the command-line. You get the current window manager from the Context like this:
If you have a pointer to a window (active or not), you can also get its active screen:
Screen Operations¶
Operations with screens are generally about the arrangement and
locations of editors and regions, and with changing them. For example if
you want to know what region is at a particular location you need to
pass the screen to BKE_screen_find_region_xy. To find the largest
editor in a window you pass one to BKE_screen_find_big_area. You can
iterate over all the screen's editors with ED_screen_areas_iter. You
can also also alter screens by calling screen_area_close to remove
one, area_split to cut one into two, or screen_area_join to
merge one into another's space.
API¶
For more specific information, look at these files:
source/blender/makesdna/DNA_screen_types.h
source/blender/editors/screen/screen_intern.h
source/blender/editors/include/ED_screen.hh
source/blender/editors/screen/screen_draw.cc
source/blender/editors/screen/screen_geometry.cc
source/blender/editors/screen/screen_edit.cc
source/blender/editors/screen/screen_ops.cc