slint/api/cpp/include
Tasuku Suzuki f24ad34a03
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Add support for CSS conic-gradient 'from <angle>' syntax (#9830)
* Add support for CSS conic-gradient 'from <angle>' syntax

Implement rotation support for conic gradients by adding the 'from <angle>'
syntax, which rotates the entire gradient by the specified angle.

- Add `from_angle` field to ConicGradient expression
- Parse 'from <angle>' syntax in compiler (defaults to 0deg when omitted)
- Normalize angles to 0-1 range (0.0 = 0°, 1.0 = 360°)
- Add `ConicGradientBrush::rotated_stops()` method that:
  * Applies rotation by adding from_angle to each stop position
  * Adds boundary stops at 0.0 and 1.0 with interpolated colors
  * Handles stops outside [0, 1] range for boundary interpolation
- Update all renderers (Skia, FemtoVG, Qt, Software) to use rotated_stops()

The rotation is applied at render time by the rotated_stops() method,
which ensures all renderers consistently handle the gradient rotation.

* Add screenshot to rotated conic gradient docs example

Wraps the rotated conic gradient example in CodeSnippetMD to automatically
generate and display a visual screenshot of the gradient rotation effect.
This makes it easier for users to understand how the 'from' parameter rotates
the gradient.

* Make ConicGradientBrush fields private

The from_angle and stops fields don't need to be pub since:
- Rust code in the same module can access them without pub
- C++ FFI access works through cbindgen-generated struct (C++ struct members are public by default)

* Optimize ConicGradientBrush::rotated_stops to avoid allocations

- Changed return type from Vec to SharedVector
- When from_angle is zero, returns a clone of internal SharedVector
  (only increments reference count instead of allocating new Vec)
- Removed break from duplicate position separation loop to handle
  all duplicate pairs, not just the first one
- Updated documentation to match actual implementation

* Remove automatic sorting in ConicGradientBrush::new() to match CSS spec

- CSS conic-gradient does not automatically sort color stops
- Stops are processed in the order specified by the user
- Changed boundary stop interpolation logic to use max_by/min_by
  instead of relying on sorted order
- This allows CSS-style hard transitions when stops are out of order

* Move conic gradient rotation processing to construction time

Major changes:
- ConicGradientBrush::new() now applies rotation and boundary stop
  processing immediately, instead of deferring to rotated_stops()
- Removed rotated_stops() method - backends now use stops() directly
- Changed to LinearGradientBrush pattern: store angle in first dummy stop
- Added angle() method to retrieve the stored angle
- Maintained #[repr(transparent)] by removing from_angle field
- All backends updated: rotated_stops() -> stops()
  - Qt backend
  - Skia renderer
  - femtovg renderer
  - Software renderer

C++ API changes:
- Added FFI function slint_conic_gradient_new() for C++ to call Rust's new()
- Updated make_conic_gradient() to call FFI function instead of manually
  constructing SharedVector
- Ensures C++-created gradients get full rotation processing

Benefits:
- Eliminates per-frame rotation calculations
- Reduces memory usage (no from_angle field)
- Consistent with LinearGradientBrush design
- C++ and Rust APIs now produce identical results

* Change ConicGradientBrush::new() from_angle parameter to use degrees

- Changed from_angle parameter from normalized form (0.0-1.0) to degrees
- Matches LinearGradientBrush API convention (angle in degrees)
- Updated internal conversion: from_angle / 360.0 for normalization
- Stores angle as-is in degrees in the first dummy stop
- FFI function slint_conic_gradient_new() passes degrees directly

Example usage:
  ConicGradientBrush::new(90.0, stops)  // 90 degrees
  LinearGradientBrush::new(90.0, stops) // 90 degrees (consistent)

* Fix ConicGradient color transformation methods to preserve angle

Changed brighter(), darker(), transparentize(), and with_alpha() methods
to clone and modify the gradient in-place instead of calling new().

- Clones the existing gradient (preserves angle and rotation)
- Modifies only color stops (skips first stop which contains angle)
- Avoids re-running expensive rotation processing
- Maintains the original angle information

Before: ConicGradientBrush::new(0.0, ...) // Lost angle information
After:  Clone + modify colors in-place     // Preserves angle

* Use premultiplied alpha interpolation for conic gradient colors

- Changed interpolate_color() to use premultiplied RGBA interpolation
- Updated signature to match Color::mix convention (&Color, factor)
- Added documentation explaining why we can't use Color::mix() here
  (Sass algorithm vs CSS gradient color interpolation)
- Reference: https://www.w3.org/TR/css-images-4/#color-interpolation

This ensures correct visual interpolation of semi-transparent colors
in gradient boundaries, following CSS gradient specification.

* Run rustfmt on conic gradient code

* Fix ConicGradientBrush edge cases and add comprehensive tests

- Handle stops that are all below 0.0 or all above 1.0
- Add default transparent gradient when no valid stops remain
- Add 7 unit tests covering basic functionality and edge cases

* Apply clippy suggestion: use retain() instead of filter().collect()

* Fix radial-gradient parsing to allow empty gradients

Allow @radial-gradient(circle) without color stops, fixing syntax test
regression from commit 820ae2b04.

The previous logic required a comma after 'circle', but it should only
error if there's something that is NOT a comma.

* Fix conic-gradient syntax test error markers

Update error markers to match actual compiler error positions.
The 'from 2' case produces two errors:
- One at the @conic-gradient expression level
- One at the literal '2' position

Auto-updated using SLINT_SYNTAX_TEST_UPDATE=1.

* Refactor ConicGradientBrush epsilon adjustment and update tests

- Move epsilon adjustment for first stop into rotation block
  (only needed when rotation is applied)
- Update property_view test to reflect boundary stops added by
  ConicGradientBrush::new()

* Update conic-gradient screenshot reference image

Update the reference screenshot to match the current rendering output.
The small pixel differences (1% different pixels, max color diff 3.46)
are due to minor rounding differences in the conic gradient implementation.

* Fix ConicGradientBrush C++ FFI to avoid C-linkage return type error

Refactored ConicGradientBrush construction to match LinearGradientBrush
pattern, fixing macOS Clang error about returning C++ types from extern "C"
functions.

Changes:
- Rust: Split ConicGradientBrush::new into simple construction + separate
  normalize_stops() and apply_rotation() methods
- Rust: Added FFI functions slint_conic_gradient_normalize_stops() and
  slint_conic_gradient_apply_rotation() that take pointers (no return value)
- C++: Construct SharedVector directly in make_conic_gradient(), then call
  Rust functions via pointer (matching LinearGradientBrush pattern)
- Optimized both methods to only copy when changes are needed

This resolves the macOS Clang error:
"'slint_conic_gradient_new' has C-linkage specified, but returns incomplete
type 'ConicGradientBrush' which could be incompatible with C"

The new approach maintains ABI compatibility while keeping complex gradient
processing logic in Rust.

* Fix C++ header generation to avoid GradientStop redefinition error

Resolves the macOS CI compilation error where GradientStop and
ConicGradientBrush were being defined in multiple headers
(slint_color_internal.h, slint_image_internal.h, and slint_brush_internal.h).

Changes:
- cbindgen.rs: Add ConicGradientBrush and FFI functions to slint_brush_internal.h include list
- cbindgen.rs: Add GradientStop, ConicGradientBrush, and FFI functions to exclude list for other headers
- slint_color.h: Add forward declaration for ConicGradientBrush
- slint_color.h: Add friend declaration for ConicGradientBrush to allow access to Color::inner

Root cause: After adding extern "C" functions in graphics/brush.rs,
cbindgen automatically detects and tries to include them in all headers
that use graphics/brush.rs as a source. The exclude list + filter logic
ensures these types only appear in slint_brush_internal.h.

This fixes the C++ compilation errors:
- "redefinition of 'GradientStop'"
- "ConicGradientBrush does not name a type"
- "Color::inner is private within this context"

* Prepare ConicGradientBrush FFI for Rust 2024 edition

Update FFI functions to use the new `#[unsafe(no_mangle)]` attribute
syntax and safe function signatures in preparation for Rust 2024 edition.

- Add `#![allow(unsafe_code)]` to graphics module for `#[unsafe(no_mangle)]`
- Add `#[cfg(feature = "ffi")]` to conditionally compile FFI functions
- Change from raw pointers to safe references (&mut)
- Remove manual null checks and unsafe blocks
2025-11-13 16:05:16 +01:00
..
slint-interpreter.h Rename "Live Reload" feature to "Live Preview for Rust/C++" 2025-08-28 17:26:01 +02:00
slint-platform.h Fix typos (#8421) 2025-05-12 13:03:59 +02:00
slint-stm32.h Revert "stm32: Fix compilation with newer STM BSPs" 2025-02-08 23:18:08 +01:00
slint-testing.h Add the accessible-id property (#9940) 2025-11-05 10:54:11 +01:00
slint.h !fixup Try to fix the C++ build 2025-08-21 14:29:55 +02:00
slint_brush.h Add support for CSS conic-gradient 'from <angle>' syntax (#9830) 2025-11-13 16:05:16 +01:00
slint_callbacks.h Simplify commercial license (#3063) 2024-05-31 14:06:17 +02:00
slint_color.h Add support for CSS conic-gradient 'from <angle>' syntax (#9830) 2025-11-13 16:05:16 +01:00
slint_config.h Simplify commercial license (#3063) 2024-05-31 14:06:17 +02:00
slint_image.h C++: Fix ABI mismatch with Slice on MSVC AArch64 2025-08-19 15:05:48 +02:00
slint_interpreter.h Simplify commercial license (#3063) 2024-05-31 14:06:17 +02:00
slint_item_tree.h C++: move model code to its own file 2025-03-25 10:37:20 +01:00
slint_live_preview.h C++ live preview: fix getting model in C++ from a defined array in slint 2025-11-05 08:32:19 +01:00
slint_models.h Update slint_models.h 2025-11-13 06:58:22 +01:00
slint_pathdata.h Simplify commercial license (#3063) 2024-05-31 14:06:17 +02:00
slint_point.h infra: Test out mise 2025-03-20 16:33:00 +01:00
slint_properties.h Two ways binding to struct fields with C++ 2025-10-24 17:33:13 +02:00
slint_sharedvector.h Re-run clang-format with version 18 2024-06-10 02:25:40 -07:00
slint_size.h Simplify commercial license (#3063) 2024-05-31 14:06:17 +02:00
slint_string.h C++: Fix ABI mismatch with Slice on MSVC AArch64 2025-08-19 15:05:48 +02:00
slint_tests_helpers.h Simplify commercial license (#3063) 2024-05-31 14:06:17 +02:00
slint_timer.h C++: add asserts that we are in the main thread 2025-05-28 11:29:48 +02:00
slint_window.h More optimization when the scale factor is constant 2025-11-04 14:05:50 +01:00
vtable.h C++: adapt to menu bar API change 2025-07-29 16:53:57 +02:00