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egl: Fallback if EGL_KHR_display_reference not supported
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libglvnd reports client extensions if at least one vendor supports them.
This might lead to display creation failure when a vendor library reports support but
fails to create a display for another reason (like when the nvidia egl implementation is installed but no nvidia card is available).
To work around this issue retry creation without EGL_KHR_display_reference.
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@Molytho
Molytho committed Oct 10, 2023
1 parent 2b77be5 commit 6a03553
Showing 1 changed file with 114 additions and 38 deletions.
152 changes: 114 additions & 38 deletions glutin/src/api/egl/display.rs
View file
Original file line number Diff line number Diff line change
Expand Up @@ -127,28 +127,52 @@ impl Display {

let mut attrs = Vec::<EGLint>::with_capacity(3);

if extensions.contains("EGL_KHR_display_reference") {
attrs.push(egl::TRACK_REFERENCES_KHR as _);
attrs.push(egl::TRUE as _);
}

// TODO: Some extensions exist like EGL_EXT_device_drm which allow specifying
// which DRM master fd to use under the hood by the implementation. This would
// mean there would need to be an unsafe equivalent to this function.

// Push at the end so we can pop it on failure
let has_display_reference = extensions.contains("EGL_KHR_display_reference");
if has_display_reference {
attrs.push(egl::TRACK_REFERENCES_KHR as _);
attrs.push(egl::TRUE as _);
}

// Push `egl::NONE` to terminate the list.
attrs.push(egl::NONE as EGLint);

let display = Self::check_display_error(unsafe {
egl.GetPlatformDisplayEXT(
egl::PLATFORM_DEVICE_EXT,
device.raw_device() as *mut _,
attrs.as_ptr(),
)
})
// NOTE: This fallback is needed because libglvnd advertises client extensions
// if at least one vendor library supports them. This leads to creation
// failures for the vendor libraries not supporting
// EGL_KHR_display_reference. Also according to the spec creation is allowed
// to fail with EGL_KHR_display_reference set to EGL_TRUE even if
// EGL_KHR_display_reference is advertised in the client extension
// string, so just always try creation without EGL_KHR_display_reference
// if it failed using it.
let mut retry_on_failure = has_display_reference;
let platform_display = loop {
let platform_display = Self::check_display_error(unsafe {
egl.GetPlatformDisplayEXT(
egl::PLATFORM_DEVICE_EXT,
device.raw_device() as *mut _,
attrs.as_ptr(),
)
});

if platform_display.is_err() && retry_on_failure {
attrs.pop();
attrs.pop();
attrs.pop();
attrs.push(egl::NONE as EGLint);
retry_on_failure = false;
continue;
}

break platform_display;
}
.map(EglDisplay::Ext)?;

Self::initialize_display(egl, display, None)
Self::initialize_display(egl, platform_display, None)
}

/// Get the [`Device`] the display is using.
Expand Down Expand Up @@ -244,23 +268,48 @@ impl Display {
},
};

if extensions.contains("EGL_KHR_display_reference") {
attrs.push(egl::TRACK_REFERENCES_KHR as _);
attrs.push(egl::TRUE as _);
}

// Be explicit here.
if display.is_null() {
display = egl::DEFAULT_DISPLAY as *mut _;
}

// Push at the end so we can pop it on failure
let has_display_reference = extensions.contains("EGL_KHR_display_reference");
if has_display_reference {
attrs.push(egl::TRACK_REFERENCES_KHR as _);
attrs.push(egl::TRUE as _);
}

// Push `egl::NONE` to terminate the list.
attrs.push(egl::NONE as EGLAttrib);

let display =
unsafe { egl.GetPlatformDisplay(platform, display as *mut _, attrs.as_ptr()) };
// NOTE: This fallback is needed because libglvnd advertises client extensions
// if at least one vendor library supports them. This leads to creation
// failures for the vendor libraries not supporting
// EGL_KHR_display_reference. Also according to the spec creation is allowed
// to fail with EGL_KHR_display_reference set to EGL_TRUE even if
// EGL_KHR_display_reference is advertised in the client extension
// string, so just always try creation without EGL_KHR_display_reference
// if it failed using it.
let mut retry_on_failure = has_display_reference;
let platform_display = loop {
let platform_display = Self::check_display_error(unsafe {
egl.GetPlatformDisplay(platform, display as *mut _, attrs.as_ptr())
});

if platform_display.is_err() && retry_on_failure {
attrs.pop();
attrs.pop();
attrs.pop();
attrs.push(egl::NONE as EGLAttrib);
retry_on_failure = false;
continue;
}

Self::check_display_error(display).map(EglDisplay::Khr)
break platform_display;
};

platform_display.map(EglDisplay::Khr)
}

fn get_platform_display_ext(egl: &Egl, display: RawDisplayHandle) -> Result<EglDisplay> {
Expand Down Expand Up @@ -309,23 +358,48 @@ impl Display {
},
};

if extensions.contains("EGL_KHR_display_reference") {
attrs.push(egl::TRACK_REFERENCES_KHR as _);
attrs.push(egl::TRUE as _);
}

// Be explicit here.
if display.is_null() {
display = egl::DEFAULT_DISPLAY as *mut _;
}

// Push at the end so we can pop it on failure
let has_display_reference = extensions.contains("EGL_KHR_display_reference");
if has_display_reference {
attrs.push(egl::TRACK_REFERENCES_KHR as _);
attrs.push(egl::TRUE as _);
}

// Push `egl::NONE` to terminate the list.
attrs.push(egl::NONE as EGLint);

let display =
unsafe { egl.GetPlatformDisplayEXT(platform, display as *mut _, attrs.as_ptr()) };
// NOTE: This fallback is needed because libglvnd advertises client extensions
// if at least one vendor library supports them. This leads to creation
// failures for the vendor libraries not supporting
// EGL_KHR_display_reference. Also according to the spec creation is allowed
// to fail with EGL_KHR_display_reference set to EGL_TRUE even if
// EGL_KHR_display_reference is advertised in the client extension
// string, so just always try creation without EGL_KHR_display_reference
// if it failed using it.
let mut retry_on_failure = has_display_reference;
let platform_display = loop {
let platform_display = Self::check_display_error(unsafe {
egl.GetPlatformDisplayEXT(platform, display as *mut _, attrs.as_ptr())
});

if platform_display.is_err() && retry_on_failure {
attrs.pop();
attrs.pop();
attrs.pop();
attrs.push(egl::NONE as EGLint);
retry_on_failure = false;
continue;
}

break platform_display;
};

Self::check_display_error(display).map(|display| {
platform_display.map(|display| {
if legacy {
// NOTE: For angle we use the Legacy code path, as that uses CreateWindowSurface
// instead of CreatePlatformWindowSurface*. The latter somehow
Expand Down Expand Up @@ -536,21 +610,23 @@ impl DisplayInner {
// terminate the display without worry for the instance being
// reused elsewhere.
let mut track_references = MaybeUninit::<EGLAttrib>::uninit();
unsafe {
(match self.raw {
EglDisplay::Khr(khr) => self.egl.QueryDisplayAttribKHR(
(match self.raw {
EglDisplay::Khr(khr) => unsafe {
self.egl.QueryDisplayAttribKHR(
khr,
egl::TRACK_REFERENCES_KHR as _,
track_references.as_mut_ptr(),
),
EglDisplay::Ext(ext) => self.egl.QueryDisplayAttribEXT(
)
},
EglDisplay::Ext(ext) => unsafe {
self.egl.QueryDisplayAttribEXT(
ext,
egl::TRACK_REFERENCES_KHR as _,
track_references.as_mut_ptr(),
),
EglDisplay::Legacy(_) => egl::FALSE,
} == egl::TRUE)
}
)
},
EglDisplay::Legacy(_) => egl::FALSE,
} == egl::TRUE)
}
}

Expand Down

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