[Cogl] [PATCH 2/2] Use the EGL_KHR_surfacless_context extension
Robert Bragg
robert at sixbynine.org
Fri Jun 13 11:28:23 PDT 2014
Yeah, this sounds like a can of worms to spec and no doubt there will
be driver inconsistencies here, so playing it safe and explicitly
setting the state like this seems like the way to go.
Reviewed-by: Robert Bragg <robert at sixbynine.org>
--
Thanks,
Robert
On Tue, Apr 1, 2014 at 2:54 PM, Neil Roberts <neil at linux.intel.com> wrote:
> The surfaceless context extension can be used to bind a context
> without a surface. We can use this to avoid creating a dummy surface
> when the CoglContext is first created. Otherwise we have to have the
> dummy surface so that we can bind it before the first onscreen is
> created.
>
> The main awkward part of this patch is that theoretically according to
> the GL and GLES spec if you first bind a context without a surface
> then the default state for glDrawBuffers is GL_NONE instead of
> GL_BACK. In practice Mesa doesn't seem to do this but we need to be
> robust against a GL implementation that does. Therefore we track when
> the CoglContext is first used with a CoglOnscreen and force the
> glDrawBuffers state to be GL_BACK.
>
> There is a further awkward part in that GLES2 doesn't actually have a
> glDrawBuffers state but GLES3 does. GLES3 also defaults to GL_NONE in
> this case so if GLES3 is available then we have to be sure to set the
> state to GL_BACK. As far as I can tell that actually makes GLES3
> incompatible with GLES2 because in theory if the application is not
> aware of GLES3 then it should be able to assume the draw buffer is
> always GL_BACK.
> ---
> cogl/cogl-context-private.h | 5 ++
> cogl/driver/gl/cogl-framebuffer-gl.c | 29 +++++++++++
> cogl/gl-prototypes/cogl-all-functions.h | 8 +++
> cogl/winsys/cogl-winsys-egl-feature-functions.h | 6 +++
> cogl/winsys/cogl-winsys-egl-kms.c | 48 +++++++++--------
> cogl/winsys/cogl-winsys-egl-private.h | 3 +-
> cogl/winsys/cogl-winsys-egl-wayland.c | 68 ++++++++++++++++---------
> cogl/winsys/cogl-winsys-egl-x11.c | 58 ++++++++++++---------
> 8 files changed, 154 insertions(+), 71 deletions(-)
>
> diff --git a/cogl/cogl-context-private.h b/cogl/cogl-context-private.h
> index c5a125d..32f2aa2 100644
> --- a/cogl/cogl-context-private.h
> +++ b/cogl/cogl-context-private.h
> @@ -200,6 +200,11 @@ struct _CoglContext
> CoglGLES2Context *current_gles2_context;
> GQueue gles2_context_stack;
>
> + /* This becomes TRUE the first time the context is bound to an
> + * onscreen buffer. This is used by cogl-framebuffer-gl to determine
> + * when to initialise the glDrawBuffer state */
> + CoglBool was_bound_to_onscreen;
> +
> /* Primitives */
> CoglPipeline *stencil_pipeline;
>
> diff --git a/cogl/driver/gl/cogl-framebuffer-gl.c b/cogl/driver/gl/cogl-framebuffer-gl.c
> index ce2b5b5..5ef8486 100644
> --- a/cogl/driver/gl/cogl-framebuffer-gl.c
> +++ b/cogl/driver/gl/cogl-framebuffer-gl.c
> @@ -255,6 +255,35 @@ _cogl_framebuffer_gl_bind (CoglFramebuffer *framebuffer, GLenum target)
> /* glBindFramebuffer is an an extension with OpenGL ES 1.1 */
> if (cogl_has_feature (ctx, COGL_FEATURE_ID_OFFSCREEN))
> GE (ctx, glBindFramebuffer (target, 0));
> +
> + /* Initialise the glDrawBuffer state the first time the context
> + * is bound to the default framebuffer. If the winsys is using a
> + * surfaceless context for the initial make current then the
> + * default draw buffer will be GL_NONE so we need to correct
> + * that. We can't do it any earlier because binding GL_BACK when
> + * there is no default framebuffer won't work */
> + if (!ctx->was_bound_to_onscreen)
> + {
> + if (ctx->glDrawBuffer)
> + {
> + GE (ctx, glDrawBuffer (GL_BACK));
> + }
> + else if (ctx->glDrawBuffers)
> + {
> + /* glDrawBuffer isn't available on GLES 3.0 so we need
> + * to be able to use glDrawBuffers as well. On GLES 2
> + * neither is available but the state should always be
> + * GL_BACK anyway so we don't need to set anything. On
> + * desktop GL this must be GL_BACK_LEFT instead of
> + * GL_BACK but as this code path will only be hit for
> + * GLES we can just use GL_BACK. */
> + static const GLenum buffers[] = { GL_BACK };
> +
> + GE (ctx, glDrawBuffers (G_N_ELEMENTS (buffers), buffers));
> + }
> +
> + ctx->was_bound_to_onscreen = TRUE;
> + }
> }
> }
>
> diff --git a/cogl/gl-prototypes/cogl-all-functions.h b/cogl/gl-prototypes/cogl-all-functions.h
> index b3d7739..a8a6e61 100644
> --- a/cogl/gl-prototypes/cogl-all-functions.h
> +++ b/cogl/gl-prototypes/cogl-all-functions.h
> @@ -318,3 +318,11 @@ COGL_EXT_FUNCTION (void, glDeleteSync,
> (GLsync sync))
> COGL_EXT_END ()
> #endif
> +
> +COGL_EXT_BEGIN (draw_buffers, 2, 0,
> + COGL_EXT_IN_GLES3,
> + "ARB\0EXT\0",
> + "draw_buffers\0")
> +COGL_EXT_FUNCTION (void, glDrawBuffers,
> + (GLsizei n, const GLenum *bufs))
> +COGL_EXT_END ()
> diff --git a/cogl/winsys/cogl-winsys-egl-feature-functions.h b/cogl/winsys/cogl-winsys-egl-feature-functions.h
> index ae2acfe..8433e19 100644
> --- a/cogl/winsys/cogl-winsys-egl-feature-functions.h
> +++ b/cogl/winsys/cogl-winsys-egl-feature-functions.h
> @@ -142,3 +142,9 @@ COGL_WINSYS_FEATURE_FUNCTION (EGLBoolean, eglDestroySync,
> EGLSyncKHR sync))
> COGL_WINSYS_FEATURE_END ()
> #endif
> +
> +COGL_WINSYS_FEATURE_BEGIN (surfaceless_context,
> + "KHR\0",
> + "surfaceless_context\0",
> + COGL_EGL_WINSYS_FEATURE_SURFACELESS_CONTEXT)
> +COGL_WINSYS_FEATURE_END ()
> diff --git a/cogl/winsys/cogl-winsys-egl-kms.c b/cogl/winsys/cogl-winsys-egl-kms.c
> index acd0d0c..dca9be7 100644
> --- a/cogl/winsys/cogl-winsys-egl-kms.c
> +++ b/cogl/winsys/cogl-winsys-egl-kms.c
> @@ -769,29 +769,35 @@ _cogl_winsys_egl_context_created (CoglDisplay *display,
> CoglRendererEGL *egl_renderer = renderer->winsys;
> CoglRendererKMS *kms_renderer = egl_renderer->platform;
>
> - kms_display->dummy_gbm_surface = gbm_surface_create (kms_renderer->gbm,
> - 16, 16,
> - GBM_FORMAT_XRGB8888,
> - GBM_BO_USE_RENDERING);
> - if (!kms_display->dummy_gbm_surface)
> + if ((egl_renderer->private_features &
> + COGL_EGL_WINSYS_FEATURE_SURFACELESS_CONTEXT) == 0)
> {
> - _cogl_set_error (error, COGL_WINSYS_ERROR,
> - COGL_WINSYS_ERROR_CREATE_CONTEXT,
> - "Failed to create dummy GBM surface");
> - return FALSE;
> - }
> + kms_display->dummy_gbm_surface =
> + gbm_surface_create (kms_renderer->gbm,
> + 16, 16,
> + GBM_FORMAT_XRGB8888,
> + GBM_BO_USE_RENDERING);
> + if (!kms_display->dummy_gbm_surface)
> + {
> + _cogl_set_error (error, COGL_WINSYS_ERROR,
> + COGL_WINSYS_ERROR_CREATE_CONTEXT,
> + "Failed to create dummy GBM surface");
> + return FALSE;
> + }
>
> - egl_display->dummy_surface =
> - eglCreateWindowSurface (egl_renderer->edpy,
> - egl_display->egl_config,
> - (NativeWindowType) kms_display->dummy_gbm_surface,
> - NULL);
> - if (egl_display->dummy_surface == EGL_NO_SURFACE)
> - {
> - _cogl_set_error (error, COGL_WINSYS_ERROR,
> - COGL_WINSYS_ERROR_CREATE_CONTEXT,
> - "Failed to create dummy EGL surface");
> - return FALSE;
> + egl_display->dummy_surface =
> + eglCreateWindowSurface (egl_renderer->edpy,
> + egl_display->egl_config,
> + (NativeWindowType)
> + kms_display->dummy_gbm_surface,
> + NULL);
> + if (egl_display->dummy_surface == EGL_NO_SURFACE)
> + {
> + _cogl_set_error (error, COGL_WINSYS_ERROR,
> + COGL_WINSYS_ERROR_CREATE_CONTEXT,
> + "Failed to create dummy EGL surface");
> + return FALSE;
> + }
> }
>
> if (!_cogl_winsys_egl_make_current (display,
> diff --git a/cogl/winsys/cogl-winsys-egl-private.h b/cogl/winsys/cogl-winsys-egl-private.h
> index ff05226..3cee0fc 100644
> --- a/cogl/winsys/cogl-winsys-egl-private.h
> +++ b/cogl/winsys/cogl-winsys-egl-private.h
> @@ -99,7 +99,8 @@ typedef enum _CoglEGLWinsysFeature
> COGL_EGL_WINSYS_FEATURE_EGL_IMAGE_FROM_WAYLAND_BUFFER =1L<<2,
> COGL_EGL_WINSYS_FEATURE_CREATE_CONTEXT =1L<<3,
> COGL_EGL_WINSYS_FEATURE_BUFFER_AGE =1L<<4,
> - COGL_EGL_WINSYS_FEATURE_FENCE_SYNC =1L<<5
> + COGL_EGL_WINSYS_FEATURE_FENCE_SYNC =1L<<5,
> + COGL_EGL_WINSYS_FEATURE_SURFACELESS_CONTEXT =1L<<6
> } CoglEGLWinsysFeature;
>
> typedef struct _CoglRendererEGL
> diff --git a/cogl/winsys/cogl-winsys-egl-wayland.c b/cogl/winsys/cogl-winsys-egl-wayland.c
> index c849797..adc0b28 100644
> --- a/cogl/winsys/cogl-winsys-egl-wayland.c
> +++ b/cogl/winsys/cogl-winsys-egl-wayland.c
> @@ -64,8 +64,8 @@ typedef struct _CoglRendererWayland
>
> typedef struct _CoglDisplayWayland
> {
> - struct wl_surface *wayland_surface;
> - struct wl_egl_window *wayland_egl_native_window;
> + struct wl_surface *dummy_wayland_surface;
> + struct wl_egl_window *dummy_wayland_egl_native_window;
> } CoglDisplayWayland;
>
> typedef struct _CoglOnscreenWayland
> @@ -330,8 +330,8 @@ _cogl_winsys_egl_display_destroy (CoglDisplay *display)
> }
>
> static CoglBool
> -_cogl_winsys_egl_context_created (CoglDisplay *display,
> - CoglError **error)
> +make_dummy_surface (CoglDisplay *display,
> + CoglError **error)
> {
> CoglRenderer *renderer = display->renderer;
> CoglRendererEGL *egl_renderer = renderer->winsys;
> @@ -340,19 +340,19 @@ _cogl_winsys_egl_context_created (CoglDisplay *display,
> CoglDisplayWayland *wayland_display = egl_display->platform;
> const char *error_message;
>
> - wayland_display->wayland_surface =
> + wayland_display->dummy_wayland_surface =
> wl_compositor_create_surface (wayland_renderer->wayland_compositor);
> - if (!wayland_display->wayland_surface)
> + if (!wayland_display->dummy_wayland_surface)
> {
> error_message= "Failed to create a dummy wayland surface";
> goto fail;
> }
>
> - wayland_display->wayland_egl_native_window =
> - wl_egl_window_create (wayland_display->wayland_surface,
> + wayland_display->dummy_wayland_egl_native_window =
> + wl_egl_window_create (wayland_display->dummy_wayland_surface,
> 1,
> 1);
> - if (!wayland_display->wayland_egl_native_window)
> + if (!wayland_display->dummy_wayland_egl_native_window)
> {
> error_message= "Failed to create a dummy wayland native egl surface";
> goto fail;
> @@ -362,7 +362,7 @@ _cogl_winsys_egl_context_created (CoglDisplay *display,
> eglCreateWindowSurface (egl_renderer->edpy,
> egl_display->egl_config,
> (EGLNativeWindowType)
> - wayland_display->wayland_egl_native_window,
> + wayland_display->dummy_wayland_egl_native_window,
> NULL);
> if (egl_display->dummy_surface == EGL_NO_SURFACE)
> {
> @@ -370,22 +370,42 @@ _cogl_winsys_egl_context_created (CoglDisplay *display,
> goto fail;
> }
>
> + return TRUE;
> +
> + fail:
> + _cogl_set_error (error, COGL_WINSYS_ERROR,
> + COGL_WINSYS_ERROR_CREATE_CONTEXT,
> + "%s", error_message);
> +
> + return FALSE;
> +}
> +
> +static CoglBool
> +_cogl_winsys_egl_context_created (CoglDisplay *display,
> + CoglError **error)
> +{
> + CoglRenderer *renderer = display->renderer;
> + CoglRendererEGL *egl_renderer = renderer->winsys;
> + CoglDisplayEGL *egl_display = display->winsys;
> +
> + if ((egl_renderer->private_features &
> + COGL_EGL_WINSYS_FEATURE_SURFACELESS_CONTEXT) == 0 &&
> + !make_dummy_surface(display, error))
> + return FALSE;
> +
> if (!_cogl_winsys_egl_make_current (display,
> egl_display->dummy_surface,
> egl_display->dummy_surface,
> egl_display->egl_context))
> {
> - error_message = "Unable to eglMakeCurrent with dummy surface";
> - goto fail;
> + _cogl_set_error (error,
> + COGL_WINSYS_ERROR,
> + COGL_WINSYS_ERROR_CREATE_CONTEXT,
> + "%s",
> + "Unable to eglMakeCurrent with dummy surface");
> }
>
> return TRUE;
> -
> - fail:
> - _cogl_set_error (error, COGL_WINSYS_ERROR,
> - COGL_WINSYS_ERROR_CREATE_CONTEXT,
> - "%s", error_message);
> - return FALSE;
> }
>
> static void
> @@ -402,16 +422,16 @@ _cogl_winsys_egl_cleanup_context (CoglDisplay *display)
> egl_display->dummy_surface = EGL_NO_SURFACE;
> }
>
> - if (wayland_display->wayland_egl_native_window)
> + if (wayland_display->dummy_wayland_egl_native_window)
> {
> - wl_egl_window_destroy (wayland_display->wayland_egl_native_window);
> - wayland_display->wayland_egl_native_window = NULL;
> + wl_egl_window_destroy (wayland_display->dummy_wayland_egl_native_window);
> + wayland_display->dummy_wayland_egl_native_window = NULL;
> }
>
> - if (wayland_display->wayland_surface)
> + if (wayland_display->dummy_wayland_surface)
> {
> - wl_surface_destroy (wayland_display->wayland_surface);
> - wayland_display->wayland_surface = NULL;
> + wl_surface_destroy (wayland_display->dummy_wayland_surface);
> + wayland_display->dummy_wayland_surface = NULL;
> }
> }
>
> diff --git a/cogl/winsys/cogl-winsys-egl-x11.c b/cogl/winsys/cogl-winsys-egl-x11.c
> index c530fd1..02b54fe 100644
> --- a/cogl/winsys/cogl-winsys-egl-x11.c
> +++ b/cogl/winsys/cogl-winsys-egl-x11.c
> @@ -610,39 +610,47 @@ _cogl_winsys_egl_context_created (CoglDisplay *display,
> AllocNone);
> attrs.border_pixel = 0;
>
> - xlib_display->dummy_xwin =
> - XCreateWindow (xlib_renderer->xdpy,
> - DefaultRootWindow (xlib_renderer->xdpy),
> - -100, -100, 1, 1,
> - 0,
> - xvisinfo->depth,
> - CopyFromParent,
> - xvisinfo->visual,
> - CWOverrideRedirect |
> - CWColormap |
> - CWBorderPixel,
> - &attrs);
> -
> - XFree (xvisinfo);
> -
> - egl_display->dummy_surface =
> - eglCreateWindowSurface (egl_renderer->edpy,
> - egl_display->egl_config,
> - (NativeWindowType) xlib_display->dummy_xwin,
> - NULL);
> -
> - if (egl_display->dummy_surface == EGL_NO_SURFACE)
> + if ((egl_renderer->private_features &
> + COGL_EGL_WINSYS_FEATURE_SURFACELESS_CONTEXT) == 0)
> {
> - error_message = "Unable to create an EGL surface";
> - goto fail;
> + xlib_display->dummy_xwin =
> + XCreateWindow (xlib_renderer->xdpy,
> + DefaultRootWindow (xlib_renderer->xdpy),
> + -100, -100, 1, 1,
> + 0,
> + xvisinfo->depth,
> + CopyFromParent,
> + xvisinfo->visual,
> + CWOverrideRedirect |
> + CWColormap |
> + CWBorderPixel,
> + &attrs);
> +
> + egl_display->dummy_surface =
> + eglCreateWindowSurface (egl_renderer->edpy,
> + egl_display->egl_config,
> + (NativeWindowType) xlib_display->dummy_xwin,
> + NULL);
> +
> + if (egl_display->dummy_surface == EGL_NO_SURFACE)
> + {
> + error_message = "Unable to create an EGL surface";
> + XFree (xvisinfo);
> + goto fail;
> + }
> }
>
> + XFree (xvisinfo);
> +
> if (!_cogl_winsys_egl_make_current (display,
> egl_display->dummy_surface,
> egl_display->dummy_surface,
> egl_display->egl_context))
> {
> - error_message = "Unable to eglMakeCurrent with dummy surface";
> + if (egl_display->dummy_surface == EGL_NO_SURFACE)
> + error_message = "Unable to eglMakeCurrent with no surface";
> + else
> + error_message = "Unable to eglMakeCurrent with dummy surface";
> goto fail;
> }
>
> --
> 1.8.5.3
>
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