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BackendBuilder: move creating renderer into own function #11203

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24f87c1
move creating renderer into own function
Murmele Mar 31, 2026
cee5d00
remove not needed specifier
Murmele Mar 31, 2026
bfb19ab
fix wording
Murmele Mar 31, 2026
2d04223
cleanup
Murmele Mar 31, 2026
654ec9d
Update internal/backends/winit/lib.rs
Murmele Mar 31, 2026
0ba96b7
[autofix.ci] apply automated fixes
autofix-ci[bot] Mar 31, 2026
d890467
fix variable name
Murmele Mar 31, 2026
4f2f433
Fix unreachable-code warning
Murmele Mar 31, 2026
b6ebcda
fix clippy
Murmele Mar 31, 2026
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290 changes: 150 additions & 140 deletions internal/backends/winit/lib.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -248,6 +248,7 @@ pub trait CustomApplicationHandler {
/// Create the builder using [`Backend::builder()`], then configure it for example with [`Self::with_renderer_name`],
/// and build the backend using [`Self::build`].
pub struct BackendBuilder {
/// Allow fallback if the desired renderer is not found
allow_fallback: bool,
requested_graphics_api: Option<RequestedGraphicsAPI>,
window_attributes_hook:
Expand Down Expand Up @@ -369,146 +370,12 @@ impl BackendBuilder {

let shared_data = Rc::new(SharedBackendData::new(
event_loop_builder,
self.renderer_name,
self.requested_graphics_api.clone(),
self.allow_fallback,
)?);

let renderer_factory_fn = match (
self.renderer_name.as_deref(),
self.requested_graphics_api.as_ref(),
) {
#[cfg(all(feature = "renderer-femtovg", supports_opengl))]
(Some("gl"), maybe_graphics_api) | (Some("femtovg"), maybe_graphics_api) => {
// If a graphics API was requested, double check that it's GL. FemtoVG doesn't support Metal, etc.
if let Some(api) = maybe_graphics_api {
i_slint_core::graphics::RequestedOpenGLVersion::try_from(api)?;
}
renderer::femtovg::GlutinFemtoVGRenderer::new_suspended
}
#[cfg(feature = "renderer-femtovg-wgpu")]
(Some("femtovg-wgpu"), maybe_graphics_api) => {
if let Some(_api) = maybe_graphics_api {
#[cfg(feature = "unstable-wgpu-28")]
if !matches!(_api, RequestedGraphicsAPI::WGPU28(..)) {
return Err(
"The FemtoVG WGPU renderer only supports the WGPU28 graphics API selection"
.into(),
);
}
}
renderer::femtovg::WGPUFemtoVGRenderer::new_suspended
}
#[cfg(enable_skia_renderer)]
(Some("skia"), maybe_graphics_api) => {
renderer::skia::WinitSkiaRenderer::factory_for_graphics_api(maybe_graphics_api)?
}
#[cfg(all(enable_skia_renderer, supports_opengl))]
(Some("skia-opengl"), maybe_graphics_api) => {
// If a graphics API was requested, double check that it's GL.
if let Some(api) = maybe_graphics_api {
i_slint_core::graphics::RequestedOpenGLVersion::try_from(api)?;
}
renderer::skia::WinitSkiaRenderer::new_opengl_suspended
}
#[cfg(all(
enable_skia_renderer,
any(feature = "unstable-wgpu-27", feature = "unstable-wgpu-28")
))]
(Some("skia-wgpu"), maybe_graphics_api) => {
if let Some(factory) = maybe_graphics_api.map_or_else(
|| {
cfg_if::cfg_if!(
if #[cfg(feature = "unstable-wgpu-28")]
{
let result = Some(
renderer::skia::WinitSkiaRenderer::new_wgpu_28_suspended
as RendererFactoryFn,
);
} else {
let result = Some(
renderer::skia::WinitSkiaRenderer::new_wgpu_27_suspended
as RendererFactoryFn,
);
}
);
result
},
|api| {
#[cfg(feature = "unstable-wgpu-27")]
if matches!(api, RequestedGraphicsAPI::WGPU27(..)) {
return Some(
renderer::skia::WinitSkiaRenderer::new_wgpu_27_suspended
as RendererFactoryFn,
);
}
#[cfg(feature = "unstable-wgpu-28")]
if matches!(api, RequestedGraphicsAPI::WGPU28(..)) {
return Some(
renderer::skia::WinitSkiaRenderer::new_wgpu_28_suspended
as RendererFactoryFn,
);
}
None
},
) {
factory
} else {
return Err("Skia with WGPU doesn't support non-WGPU graphics API"
.to_string()
.into());
}
}
#[cfg(all(enable_skia_renderer, not(target_os = "android")))]
(Some("skia-software"), None) => {
renderer::skia::WinitSkiaRenderer::new_software_suspended
}
#[cfg(feature = "renderer-software")]
(Some("sw"), None) | (Some("software"), None) => {
renderer::sw::WinitSoftwareRenderer::new_suspended
}
(None, None) => default_renderer_factory,
(Some(renderer_name), _) => {
if self.allow_fallback {
eprintln!(
"slint winit: unrecognized renderer {renderer_name}, falling back to {DEFAULT_RENDERER_NAME}"
);
default_renderer_factory
} else {
return Err(PlatformError::NoPlatform);
}
}
#[cfg(feature = "unstable-wgpu-28")]
(None, Some(RequestedGraphicsAPI::WGPU28(..))) => {
cfg_if::cfg_if! {
if #[cfg(enable_skia_renderer)] {
renderer::skia::WinitSkiaRenderer::new_wgpu_28_suspended
} else if #[cfg(feature = "renderer-femtovg-wgpu")] {
renderer::femtovg::WGPUFemtoVGRenderer::new_suspended
} else {
return Err("unstable-wgpu-28 was enabled but no renderer was selected. Please select either renderer-skia* or renderer-femtovg-wgpu".into())
}
}
}
#[cfg(all(enable_skia_renderer, feature = "unstable-wgpu-27"))]
(None, Some(RequestedGraphicsAPI::WGPU27(..))) => {
renderer::skia::WinitSkiaRenderer::new_wgpu_27_suspended
}
(None, Some(_requested_graphics_api)) => {
cfg_if::cfg_if! {
if #[cfg(enable_skia_renderer)] {
renderer::skia::WinitSkiaRenderer::factory_for_graphics_api(Some(_requested_graphics_api))?
} else if #[cfg(all(feature = "renderer-femtovg", supports_opengl))] {
// If a graphics API was requested, double check that it's GL. FemtoVG doesn't support Metal, etc.
i_slint_core::graphics::RequestedOpenGLVersion::try_from(_requested_graphics_api)?;
renderer::femtovg::GlutinFemtoVGRenderer::new_suspended
} else {
return Err(format!("Graphics API use requested by the compile-time enabled renderers don't support that").into())
}
}
}
};

Ok(Backend {
renderer_factory_fn,
event_loop_state: Default::default(),
window_attributes_hook: self.window_attributes_hook,
shared_data,
Expand All @@ -522,7 +389,10 @@ impl BackendBuilder {
}

pub(crate) struct SharedBackendData {
_requested_graphics_api: Option<RequestedGraphicsAPI>,
/// Allow fallback if the desired renderer is not found
allow_fallback: bool,
renderer_name: Option<String>,
requested_graphics_api: Option<RequestedGraphicsAPI>,
#[cfg(enable_skia_renderer)]
skia_context: i_slint_renderer_skia::SkiaSharedContext,
active_windows: Rc<RefCell<HashMap<winit::window::WindowId, Weak<WinitWindowAdapter>>>>,
Expand All @@ -545,7 +415,9 @@ pub(crate) struct SharedBackendData {
impl SharedBackendData {
fn new(
mut builder: EventLoopBuilder,
renderer_name: Option<String>,
requested_graphics_api: Option<RequestedGraphicsAPI>,
allow_fallback: bool,
) -> Result<Self, PlatformError> {
#[cfg(not(target_arch = "wasm32"))]
use raw_window_handle::HasDisplayHandle;
Expand Down Expand Up @@ -606,7 +478,9 @@ impl SharedBackendData {
.map_err(|display_err| PlatformError::OtherError(display_err.into()))?,
);
Ok(Self {
_requested_graphics_api: requested_graphics_api,
allow_fallback,
renderer_name,
requested_graphics_api,
#[cfg(enable_skia_renderer)]
skia_context: i_slint_renderer_skia::SkiaSharedContext::default(),
active_windows,
Expand Down Expand Up @@ -680,7 +554,6 @@ type RendererFactoryFn =
/// slint::platform::set_platform(Box::new(Backend::new().unwrap()));
/// ```
pub struct Backend {
renderer_factory_fn: RendererFactoryFn,
event_loop_state: RefCell<Option<crate::event_loop::EventLoopState>>,
shared_data: Rc<SharedBackendData>,
custom_application_handler: RefCell<Option<Box<dyn crate::CustomApplicationHandler>>>,
Expand Down Expand Up @@ -757,7 +630,7 @@ impl i_slint_core::platform::Platform for Backend {
attrs = hook(attrs);
}

let adapter = (self.renderer_factory_fn)(&self.shared_data).map_or_else(
let adapter = create_renderer(&self.shared_data).map_or_else(
|e| {
try_create_window_with_fallback_renderer(
&self.shared_data,
Expand Down Expand Up @@ -1036,6 +909,143 @@ impl WinitWindowAccessor for i_slint_core::api::Window {
}
}

/// Creates a new renderer from the backend properties in `shared_data`
fn create_renderer(
shared_data: &Rc<SharedBackendData>,
) -> Result<Box<dyn WinitCompatibleRenderer>, PlatformError> {
match (shared_data.renderer_name.as_deref(), shared_data.requested_graphics_api.as_ref()) {
#[cfg(all(feature = "renderer-femtovg", supports_opengl))]
(Some("gl"), maybe_graphics_api) | (Some("femtovg"), maybe_graphics_api) => {
// If a graphics API was requested, double check that it's GL. FemtoVG doesn't support Metal, etc.
if let Some(api) = maybe_graphics_api {
i_slint_core::graphics::RequestedOpenGLVersion::try_from(api)?;
}
renderer::femtovg::GlutinFemtoVGRenderer::new_suspended(shared_data)
}
#[cfg(feature = "renderer-femtovg-wgpu")]
(Some("femtovg-wgpu"), maybe_graphics_api) => {
if let Some(_api) = maybe_graphics_api {
#[cfg(feature = "unstable-wgpu-28")]
if !matches!(_api, RequestedGraphicsAPI::WGPU28(..)) {
return Err(
"The FemtoVG WGPU renderer only supports the WGPU28 graphics API selection"
.into(),
);
}
}
renderer::femtovg::WGPUFemtoVGRenderer::new_suspended(shared_data)
}
#[cfg(enable_skia_renderer)]
(Some("skia"), maybe_graphics_api) => {
(renderer::skia::WinitSkiaRenderer::factory_for_graphics_api(maybe_graphics_api)?)(
&shared_data,
)
}
#[cfg(all(enable_skia_renderer, supports_opengl))]
(Some("skia-opengl"), maybe_graphics_api) => {
// If a graphics API was requested, double check that it's GL.
if let Some(api) = maybe_graphics_api {
i_slint_core::graphics::RequestedOpenGLVersion::try_from(api)?;
}
renderer::skia::WinitSkiaRenderer::new_opengl_suspended(shared_data)
}
#[cfg(all(
enable_skia_renderer,
any(feature = "unstable-wgpu-27", feature = "unstable-wgpu-28")
))]
(Some("skia-wgpu"), maybe_graphics_api) => {
if let Some(factory) = maybe_graphics_api.map_or_else(
|| {
cfg_if::cfg_if!(
if #[cfg(feature = "unstable-wgpu-28")]
{
let result = Some(
(renderer::skia::WinitSkiaRenderer::new_wgpu_28_suspended
as RendererFactoryFn)(shared_data),
);
} else {
let result = Some(
(renderer::skia::WinitSkiaRenderer::new_wgpu_27_suspended
as RendererFactoryFn)(shared_data),
);
}
);
result
},
|api| {
#[cfg(feature = "unstable-wgpu-27")]
if matches!(api, RequestedGraphicsAPI::WGPU27(..)) {
return Some((renderer::skia::WinitSkiaRenderer::new_wgpu_27_suspended
as RendererFactoryFn)(
&shared_data
));
}
#[cfg(feature = "unstable-wgpu-28")]
if matches!(api, RequestedGraphicsAPI::WGPU28(..)) {
return Some((renderer::skia::WinitSkiaRenderer::new_wgpu_28_suspended
as RendererFactoryFn)(
&shared_data
));
}
None
},
) {
factory
} else {
return Err("Skia with WGPU doesn't support non-WGPU graphics API"
.to_string()
.into());
}
}
#[cfg(all(enable_skia_renderer, not(target_os = "android")))]
(Some("skia-software"), None) => renderer::skia::WinitSkiaRenderer::new_software_suspended,
#[cfg(feature = "renderer-software")]
(Some("sw"), None) | (Some("software"), None) => {
renderer::sw::WinitSoftwareRenderer::new_suspended(shared_data)
}
(None, None) => default_renderer_factory(shared_data),
(Some(renderer_name), _) => {
if shared_data.allow_fallback {
eprintln!(
"slint winit: unrecognized renderer {renderer_name}, falling back to {DEFAULT_RENDERER_NAME}"
);
default_renderer_factory(shared_data)
} else {
return Err(PlatformError::NoPlatform);
}
}
#[cfg(feature = "unstable-wgpu-28")]
(None, Some(RequestedGraphicsAPI::WGPU28(..))) => {
cfg_if::cfg_if! {
if #[cfg(enable_skia_renderer)] {
renderer::skia::WinitSkiaRenderer::new_wgpu_28_suspended(shared_data)
} else if #[cfg(feature = "renderer-femtovg-wgpu")] {
renderer::femtovg::WGPUFemtoVGRenderer::new_suspended(shared_data)
} else {
return Err("unstable-wgpu-28 was enabled but no renderer was selected. Please select either renderer-skia* or renderer-femtovg-wgpu".into())
}
}
}
#[cfg(all(enable_skia_renderer, feature = "unstable-wgpu-27"))]
(None, Some(RequestedGraphicsAPI::WGPU27(..))) => {
renderer::skia::WinitSkiaRenderer::new_wgpu_27_suspended(shared_data)
}
(None, Some(_requested_graphics_api)) => {
cfg_if::cfg_if! {
if #[cfg(enable_skia_renderer)] {
renderer::skia::WinitSkiaRenderer::factory_for_graphics_api(Some(_requested_graphics_api))?(shared_data)
} else if #[cfg(all(feature = "renderer-femtovg", supports_opengl))] {
// If a graphics API was requested, double check that it's GL. FemtoVG doesn't support Metal, etc.
i_slint_core::graphics::RequestedOpenGLVersion::try_from(_requested_graphics_api)?;
renderer::femtovg::GlutinFemtoVGRenderer::new_suspended(shared_data)
} else {
return Err(format!("Graphics API use requested by the compile-time enabled renderers don't support that").into())
}
}
}
}
}

impl private::WinitWindowAccessorSealed for i_slint_core::api::Window {}

#[cfg(test)]
Expand Down
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