CoglDisplay: Setup a display pipeline

CoglDisplay: Setup a display pipeline — Common aspects of a display pipeline

Synopsis

                    CoglDisplay;
CoglBool            cogl_is_display                     (void *object);

CoglDisplay *       cogl_display_new                    (CoglRenderer *renderer,
                                                         CoglOnscreenTemplate *onscreen_template);
CoglRenderer *      cogl_display_get_renderer           (CoglDisplay *display);
CoglBool            cogl_display_setup                  (CoglDisplay *display,
                                                         CoglError **error);

void                cogl_gdl_display_set_plane          (CoglDisplay *display,
                                                         gdl_plane_id_t plane);

void                cogl_wayland_display_set_compositor_display
                                                        (CoglDisplay *display,
                                                         struct wl_display *wayland_display);

Description

The basic intention for this object is to let the application configure common display preferences before creating a context, and there are a few different aspects to this...

Firstly there are options directly relating to the physical display pipeline that is currently being used including the digital to analogue conversion hardware and the screens the user sees.

Another aspect is that display options may constrain or affect how onscreen framebuffers should later be configured. The original rationale for the display object in fact was to let us handle GLX and EGLs requirements that framebuffers must be "compatible" with the config associated with the current context meaning we have to force the user to describe how they would like to create their onscreen windows before we can choose a suitable fbconfig and create a GLContext.

Details

CoglDisplay

typedef struct _CoglDisplay CoglDisplay;

cogl_is_display ()

CoglBool            cogl_is_display                     (void *object);

Gets whether the given object references a CoglDisplay.

object :

A CoglObject pointer

Returns :

TRUE if the object references a CoglDisplay and FALSE otherwise.

Since 1.10

Stability Level: Unstable


cogl_display_new ()

CoglDisplay *       cogl_display_new                    (CoglRenderer *renderer,
                                                         CoglOnscreenTemplate *onscreen_template);

Explicitly allocates a new CoglDisplay object to encapsulate the common state of the display pipeline that applies to the whole application.

Note

Many applications don't need to explicitly use cogl_display_new() and can just jump straight to cogl_context_new() and pass a NULL display argument so Cogl will automatically connect and setup a renderer and display.

A display can only be made for a specific choice of renderer which is why this takes the renderer argument.

A common use for explicitly allocating a display object is to define a template for allocating onscreen framebuffers which is what the onscreen_template argument is for, or alternatively you can use cogl_display_set_onscreen_template().

When a display is first allocated via cogl_display_new() it is in a mutable configuration mode. It's designed this way so we can extend the apis available for configuring a display without requiring huge numbers of constructor arguments.

When you have finished configuring a display object you can optionally call cogl_display_setup() to explicitly apply the configuration and check for errors. Alternaitvely you can pass the display to cogl_context_new() and Cogl will implicitly apply your configuration but if there are errors then the application will abort with a message. For simple applications with no fallback options then relying on the implicit setup can be fine.

renderer :

A CoglRenderer

onscreen_template :

A CoglOnscreenTemplate

Returns :

A newly allocated CoglDisplay object in a mutable configuration mode.

Since 1.10

Stability Level: Unstable


cogl_display_get_renderer ()

CoglRenderer *      cogl_display_get_renderer           (CoglDisplay *display);

Queries the CoglRenderer associated with the given display.

display :

a CoglDisplay

Since 1.10

Stability Level: Unstable


cogl_display_setup ()

CoglBool            cogl_display_setup                  (CoglDisplay *display,
                                                         CoglError **error);

Explicitly sets up the given display object. Use of this api is optional since Cogl will internally setup the display if not done explicitly.

When a display is first allocated via cogl_display_new() it is in a mutable configuration mode. This allows us to extend the apis available for configuring a display without requiring huge numbers of constructor arguments.

Its possible to request a configuration that might not be supportable on the current system and so this api provides a means to apply the configuration explicitly but if it fails then an exception will be returned so you can handle the error gracefully and perhaps fall back to an alternative configuration.

If you instead rely on Cogl implicitly calling cogl_display_setup() for you then if there is an error with the configuration you won't get an opportunity to handle that and the application may abort with a message. For simple applications that don't have any fallback options this behaviour may be fine.

display :

a CoglDisplay

error :

return location for a CoglError

Returns :

Returns TRUE if there was no error, else it returns FALSE and returns an exception via error.

Since 1.10

Stability Level: Unstable


cogl_gdl_display_set_plane ()

void                cogl_gdl_display_set_plane          (CoglDisplay *display,
                                                         gdl_plane_id_t plane);

Request that Cogl output to a specific GDL overlay plane.

display :

a CoglDisplay

plane :

the GDL plane id

Since 1.10

Stability Level: Unstable


cogl_wayland_display_set_compositor_display ()

void                cogl_wayland_display_set_compositor_display
                                                        (CoglDisplay *display,
                                                         struct wl_display *wayland_display);

Informs Cogl of a compositor's Wayland display pointer. This enables Cogl to register private wayland extensions required to pass buffers between the clients and compositor.

display :

a CoglDisplay

wayland_display :

A compositor's Wayland display pointer

Since 1.10

Stability Level: Unstable