chore: Add example to create mask and use set_mouse_callback
#473
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examples/create_mask.rs
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| /// Converts an `i32` to a `opencv::highgui::MouseEventTypes` | ||
| /// | ||
| /// # Panics | ||
| /// | ||
| /// Panics if the argument less than 0 or greater than 11. | ||
| fn mouse_event_from_i32(value: i32) -> opencv::highgui::MouseEventTypes { | ||
| (value.gt(&(opencv::highgui::MouseEventTypes::EVENT_MOUSEHWHEEL as i32) /* 11 */) | ||
| || (value.lt(&(opencv::highgui::MouseEventTypes::EVENT_MOUSEMOVE as i32) /* 0 */))) | ||
| .then(|| panic!("Invalid cv::highgui::MouseEventTypes value: {}", value)); | ||
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||
| // Safe because of the previous check | ||
| unsafe { std::mem::transmute(value) } | ||
| } |
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Can this function be generated automatically during the build process?
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Definitely! I’ll take a look.
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Thank you!
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With this automatic implementation, we can easily use
highgui::MouseEventTypesenum and pattern matching together to take advantage of exhaustiveness checking, enabling us to discover issues earlier. This approach is preferred over comparing values of type i32 with if-else statements and certain constants(e.g.if event == highgui::EVENT_MOUSEMOVE {}).I think the same principle can be applied to other enums within
opencv::highguimodule, such ashighgui::MouseEventFlags、highgui::QtButtonTypesetc.impl From<i32> for crate::highgui::MouseEventTypes { fn from(v: i32) -> Self { (v.gt(&(crate::highgui::MouseEventTypes::EVENT_MOUSEHWHEEL as i32)) || (v.lt(&(crate::highgui::MouseEventTypes::EVENT_MOUSEMOVE as i32)))) .then(|| panic!("Invalid cv::highgui::MouseEventTypes value: {}", v)); // Safe because of the previous check unsafe { std::mem::transmute(v) } } }
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And the type
MouseCallbackmay can be redefinedpub type MouseCallback = Option<Box<dyn FnMut(i32, i32, i32, i32) + Send + Sync + 'static>>;
to
pub type MouseCallback = Option<Box<dyn FnMut(highgui::MouseEventTypes, i32, i32, highgui::MouseEventFlags) + Send + Sync + 'static>>;
But it will make breaking changes!
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