Commit 551d459a authored by Neil Roberts's avatar Neil Roberts Committed by Kristian H. Kristensen

Add the EGL_MESA_configless_context extension

This extension provides a way for an application to render to multiple
surfaces with different buffer formats without having to use multiple
contexts. An EGLContext can be created without an EGLConfig by passing
EGL_NO_CONFIG_MESA. In that case there are no restrictions on the surfaces
that can be used with the context apart from that they must be using the same
EGLDisplay.

_mesa_initialze_context can now take a NULL gl_config which will mark the
context as ‘configless’. It will memset the visual to zero in that case.
Previously the i965 and i915 drivers were explicitly creating a zeroed visual
whenever 0 is passed for the EGLConfig. Mesa needs to be aware that the
context is configless because it affects the initial value to use for
glDrawBuffer. The first time the context is bound it will set the initial
value for configless contexts depending on whether the framebuffer used is
double-buffered.
Reviewed-by: Kristian H. Kristensen's avatarKristian Høgsberg <krh@bitplanet.net>
parent 4b17dff3
Name
MESA_configless_context
Name Strings
EGL_MESA_configless_context
Contact
Neil Roberts <neil.s.roberts@intel.com>
Status
Proposal
Version
Version 1, February 28, 2014
Number
EGL Extension #not assigned
Dependencies
Requires EGL 1.4 or later. This extension is written against the
wording of the EGL 1.4 specification.
Overview
This extension provides a means to use a single context to render to
multiple surfaces which have different EGLConfigs. Without this extension
the EGLConfig for every surface used by the context must be compatible
with the one used by the context. The only way to render to surfaces with
different formats would be to create multiple contexts but this is
inefficient with modern GPUs where this restriction is unnecessary.
IP Status
Open-source; freely implementable.
New Procedures and Functions
None.
New Tokens
Accepted as <config> in eglCreateContext
EGL_NO_CONFIG_MESA ((EGLConfig)0)
Additions to the EGL Specification section "2.2 Rendering Contexts and Drawing
Surfaces"
Add the following to the 3rd paragraph:
"EGLContexts can also optionally be created with respect to an EGLConfig
depending on the parameters used at creation time. If a config is provided
then additional restrictions apply on what surfaces can be used with the
context."
Replace the last sentence of the 6th paragraph with:
"In order for a context to be compatible with a surface they both must have
been created with respect to the same EGLDisplay. If the context was
created without respect to an EGLConfig then there are no further
constraints. Otherwise they are only compatible if:"
Remove the last bullet point in the list of constraints.
Additions to the EGL Specification section "3.7.1 Creating Rendering Contexts"
Replace the paragraph starting "If config is not a valid EGLConfig..."
with
"The config argument can either be a valid EGLConfig or EGL_NO_CONFIG_MESA.
If it is neither of these then an EGL_BAD_CONFIG error is generated. If a
valid config is passed then the error will also be generated if the config
does not support the requested client API (this includes requesting
creation of an OpenGL ES 1.x context when the EGL_RENDERABLE_TYPE
attribute of config does not contain EGL_OPENGL_ES_BIT, or creation of an
OpenGL ES 2.x context when the attribute does not contain
EGL_OPENGL_ES2_BIT).
Passing EGL_NO_CONFIG_MESA will create a configless context. When a
configless context is used with the OpenGL API it can be assumed that the
initial values of the context's state will be decided when the context is
first made current. In particular this means that the decision of whether
to use GL_BACK or GL_FRONT for the initial value of the first output in
glDrawBuffers will be decided based on the config of the draw surface when
it is first bound."
Additions to the EGL Specification section "3.7.3 Binding Contexts and
Drawables"
Replace the first bullet point with the following:
"* If draw or read are not compatible with ctx as described in section 2.2,
then an EGL_BAD_MATCH error is generated."
Add a second bullet point after that:
"* If draw and read are not compatible with each other as described in
section 2.2, then an EGL_BAD_MATCH error is generated."
Issues
1. What happens when an OpenGL context with a double-buffered surface and
draw buffer set to GL_BACK is made current with a single-buffered
surface?
NOT RESOLVED: There are a few options here. An implementation can
raise an error, change the drawbuffer state to GL_FRONT or just do
nothing, expecting the application to set GL_FRONT drawbuffer before
drawing. However, this extension deliberately does not specify any
required behavior in this corner case and applications should avoid
mixing single- and double-buffered surfaces with configless contexts.
Future extensions may specify required behavior in this case.
Revision History
Version 1, February 28, 2014
Initial draft (Neil Roberts)
......@@ -165,6 +165,11 @@ typedef EGLBoolean (EGLAPIENTRYP PFNEGLSWAPBUFFERSREGIONNOK) (EGLDisplay dpy, EG
#define EGL_NATIVE_BUFFER_ANDROID 0x3140 /* eglCreateImageKHR target */
#endif
#ifndef EGL_MESA_configless_context
#define EGL_MESA_configless_context 1
#define EGL_NO_CONFIG_MESA ((EGLConfig)0)
#endif
#ifdef __cplusplus
}
#endif
......
......@@ -508,6 +508,7 @@ dri2_setup_screen(_EGLDisplay *disp)
assert(dri2_dpy->dri2 || dri2_dpy->swrast);
disp->Extensions.KHR_surfaceless_context = EGL_TRUE;
disp->Extensions.MESA_configless_context = EGL_TRUE;
if (dri2_dpy->dri2 && dri2_dpy->dri2->base.version >= 3) {
disp->Extensions.KHR_create_context = EGL_TRUE;
......
......@@ -431,7 +431,7 @@ eglCreateContext(EGLDisplay dpy, EGLConfig config, EGLContext share_list,
_EGL_CHECK_DISPLAY(disp, EGL_NO_CONTEXT, drv);
if (!config)
if (!config && !disp->Extensions.MESA_configless_context)
RETURN_EGL_ERROR(disp, EGL_BAD_CONFIG, EGL_NO_CONTEXT);
if (!share && share_list != EGL_NO_CONTEXT)
......
......@@ -523,10 +523,22 @@ _eglCheckMakeCurrent(_EGLContext *ctx, _EGLSurface *draw, _EGLSurface *read)
return _eglError(EGL_BAD_ACCESS, "eglMakeCurrent");
}
/* simply require the configs to be equal */
if ((draw && draw->Config != ctx->Config) ||
(read && read->Config != ctx->Config))
return _eglError(EGL_BAD_MATCH, "eglMakeCurrent");
/* If the context has a config then it must match that of the two
* surfaces */
if (ctx->Config) {
if ((draw && draw->Config != ctx->Config) ||
(read && read->Config != ctx->Config))
return _eglError(EGL_BAD_MATCH, "eglMakeCurrent");
} else {
/* Otherwise we must be using the EGL_MESA_configless_context
* extension */
assert(dpy->Extensions.MESA_configless_context);
/* The extension doesn't permit binding draw and read buffers with
* differing contexts */
if (draw && read && draw->Config != read->Config)
return _eglError(EGL_BAD_MATCH, "eglMakeCurrent");
}
switch (ctx->ClientAPI) {
/* OpenGL and OpenGL ES are conflicting */
......
......@@ -89,6 +89,7 @@ struct _egl_extensions
EGLBoolean MESA_copy_context;
EGLBoolean MESA_drm_display;
EGLBoolean MESA_drm_image;
EGLBoolean MESA_configless_context;
EGLBoolean WL_bind_wayland_display;
EGLBoolean WL_create_wayland_buffer_from_image;
......
......@@ -90,6 +90,7 @@ _eglUpdateExtensionsString(_EGLDisplay *dpy)
_EGL_CHECK_EXTENSION(MESA_copy_context);
_EGL_CHECK_EXTENSION(MESA_drm_display);
_EGL_CHECK_EXTENSION(MESA_drm_image);
_EGL_CHECK_EXTENSION(MESA_configless_context);
_EGL_CHECK_EXTENSION(WL_bind_wayland_display);
_EGL_CHECK_EXTENSION(WL_create_wayland_buffer_from_image);
......
......@@ -410,7 +410,6 @@ intelInitContext(struct intel_context *intel,
__DRIscreen *sPriv = driContextPriv->driScreenPriv;
struct intel_screen *intelScreen = sPriv->driverPrivate;
int bo_reuse_mode;
struct gl_config visual;
/* Can't rely on invalidate events, fall back to glViewport hack */
if (!driContextPriv->driScreenPriv->dri2.useInvalidate)
......@@ -418,11 +417,6 @@ intelInitContext(struct intel_context *intel,
else
functions->Viewport = intel_viewport;
if (mesaVis == NULL) {
memset(&visual, 0, sizeof visual);
mesaVis = &visual;
}
intel->intelScreen = intelScreen;
if (!_mesa_initialize_context(&intel->ctx, api, mesaVis, shareCtx,
......
......@@ -584,7 +584,6 @@ brwCreateContext(gl_api api,
struct intel_screen *screen = sPriv->driverPrivate;
const struct brw_device_info *devinfo = screen->devinfo;
struct dd_function_table functions;
struct gl_config visual;
/* Only allow the __DRI_CTX_FLAG_ROBUST_BUFFER_ACCESS flag if the kernel
* provides us with context reset notifications.
......@@ -651,11 +650,6 @@ brwCreateContext(gl_api api,
struct gl_context *ctx = &brw->ctx;
if (mesaVis == NULL) {
memset(&visual, 0, sizeof visual);
mesaVis = &visual;
}
if (!_mesa_initialize_context(ctx, api, mesaVis, shareCtx, &functions)) {
*dri_ctx_error = __DRI_CTX_ERROR_NO_MEMORY;
fprintf(stderr, "%s: failed to init mesa context\n", __FUNCTION__);
......
......@@ -1013,7 +1013,8 @@ _mesa_initialize_dispatch_tables(struct gl_context *ctx)
*
* \param ctx the context to initialize
* \param api the GL API type to create the context for
* \param visual describes the visual attributes for this context
* \param visual describes the visual attributes for this context or NULL to
* create a configless context
* \param share_list points to context to share textures, display lists,
* etc with, or NULL
* \param driverFunctions table of device driver functions for this context
......@@ -1033,12 +1034,20 @@ _mesa_initialize_context(struct gl_context *ctx,
assert(driverFunctions->FreeTextureImageBuffer);
ctx->API = api;
ctx->Visual = *visual;
ctx->DrawBuffer = NULL;
ctx->ReadBuffer = NULL;
ctx->WinSysDrawBuffer = NULL;
ctx->WinSysReadBuffer = NULL;
if (visual) {
ctx->Visual = *visual;
ctx->HasConfig = GL_TRUE;
}
else {
memset(&ctx->Visual, 0, sizeof ctx->Visual);
ctx->HasConfig = GL_FALSE;
}
if (_mesa_is_desktop_gl(ctx)) {
_mesa_override_gl_version(ctx);
}
......@@ -1145,7 +1154,8 @@ fail:
* the rendering context.
*
* \param api the GL API type to create the context for
* \param visual a struct gl_config pointer (we copy the struct contents)
* \param visual a struct gl_config pointer (we copy the struct contents) or
* NULL to create a configless context
* \param share_list another context to share display lists with or NULL
* \param driverFunctions points to the dd_function_table into which the
* driver has plugged in all its special functions.
......@@ -1160,8 +1170,6 @@ _mesa_create_context(gl_api api,
{
struct gl_context *ctx;
ASSERT(visual);
ctx = calloc(1, sizeof(struct gl_context));
if (!ctx)
return NULL;
......@@ -1475,6 +1483,54 @@ _mesa_check_init_viewport(struct gl_context *ctx, GLuint width, GLuint height)
}
}
static void
handle_first_current(struct gl_context *ctx)
{
GLenum buffer;
GLint bufferIndex;
assert(ctx->Version > 0);
ctx->Extensions.String = _mesa_make_extension_string(ctx);
check_context_limits(ctx);
/* According to GL_MESA_configless_context the default value of
* glDrawBuffers depends on the config of the first surface it is bound to.
* For GLES it is always GL_BACK which has a magic interpretation */
if (!ctx->HasConfig && _mesa_is_desktop_gl(ctx)) {
if (ctx->DrawBuffer != _mesa_get_incomplete_framebuffer()) {
if (ctx->DrawBuffer->Visual.doubleBufferMode)
buffer = GL_BACK;
else
buffer = GL_FRONT;
_mesa_drawbuffers(ctx, 1, &buffer, NULL /* destMask */);
}
if (ctx->ReadBuffer != _mesa_get_incomplete_framebuffer()) {
if (ctx->ReadBuffer->Visual.doubleBufferMode) {
buffer = GL_BACK;
bufferIndex = BUFFER_BACK_LEFT;
}
else {
buffer = GL_FRONT;
bufferIndex = BUFFER_FRONT_LEFT;
}
_mesa_readbuffer(ctx, buffer, bufferIndex);
}
}
/* We can use this to help debug user's problems. Tell them to set
* the MESA_INFO env variable before running their app. Then the
* first time each context is made current we'll print some useful
* information.
*/
if (_mesa_getenv("MESA_INFO")) {
_mesa_print_info(ctx);
}
}
/**
* Bind the given context to the given drawBuffer and readBuffer and
......@@ -1567,21 +1623,7 @@ _mesa_make_current( struct gl_context *newCtx,
}
if (newCtx->FirstTimeCurrent) {
assert(newCtx->Version > 0);
newCtx->Extensions.String = _mesa_make_extension_string(newCtx);
check_context_limits(newCtx);
/* We can use this to help debug user's problems. Tell them to set
* the MESA_INFO env variable before running their app. Then the
* first time each context is made current we'll print some useful
* information.
*/
if (_mesa_getenv("MESA_INFO")) {
_mesa_print_info(newCtx);
}
handle_first_current(newCtx);
newCtx->FirstTimeCurrent = GL_FALSE;
}
}
......
......@@ -4212,6 +4212,12 @@ struct gl_context
GLboolean FirstTimeCurrent;
/*@}*/
/**
* False if this context was created without a config. This is needed
* because the initial state of glDrawBuffers depends on this
*/
GLboolean HasConfig;
/** software compression/decompression supported or not */
GLboolean Mesa_DXTn;
......
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