Add support for setting custom bitmap cursors #10270

redstrate · 2025-12-11T16:48:05Z

Right now you can set the mouse cursor shape in a TouchArea to a
pre-defined list of cursor shapes, but sometimes you have your own
custom cursor set for actions that aren't in the CSS spec.

This change introduces new API to set a mouse cursor to an Image, using
the same property (mouse-cursor) and a changeable hotspot.

Example

TouchArea {
    width: parent.width;
    height: parent.height;
    mouse-cursor: custom(@image-url("close.png"), 0, 0);
}

TODO

Clean up the code, obviously
~~Link to existing issue/discussion~~
Check documentation, add docs for custom cursors
Add support for winit (maybe rebasing on top of https://github.com/slint-ui/slint/pull/6923/files and adding the suggestions)
Review the API (should specifying a hotspot be optional, for example)
Add unit tests for cpp/rust code generators and interpreter

redstrate · 2025-12-12T16:14:49Z

internal/backends/testing/testing_backend.rs

    size: Cell<PhysicalSize>,
    pub ime_requests: RefCell<Vec<InputMethodRequest>>,
-    pub mouse_cursor: Cell<i_slint_core::items::MouseCursor>,
+    pub mouse_cursor: RefCell<i_slint_core::items::MouseCursor>,


Not happy about this change (and the sibling one in headless) but it's the only way I got it to work, since MouseCursor is no longer Copy.

This is just for tests anyway so it's fine.
Maybe the tests would be a bit nicer if there was a pub fn mouse_cursor(&self)->MouseCursor { self.mouse_cursor.borrow().clone() } getter function.

(And in headless this isn't even used, so we could just remove it)

redstrate · 2025-12-12T16:26:07Z

There is still some stuff in the TODO like documentation, but now that it works I would like some input on:

Does the API make sense? Should the hotspot x/y be optional? Right now they aren't.
Does the approach make sense? This is my first time doing a major Slint compiler/generator change, so :)

NigelBreslaw · 2025-12-15T09:31:55Z

@redstrate There are quite a few people on vacation at the moment so replies/help might be slow till 2026 rolls around.

Right now you can set the mouse cursor shape in a TouchArea to a pre-defined list of cursor shapes, but sometimes you have your own custom cursor set for actions that aren't in the CSS spec. This change introduces new API to set a mouse cursor to an Image, using the same property (mouse-cursor) and a changeable hotspot.

redstrate · 2025-12-16T14:29:22Z

internal/compiler/tests/syntax/elements/toucharea.slint

+
+    // Custom cursor macro
+    TouchArea {
+        mouse-cursor: MouseCursor.custom(@image-url("cursor.png"), 0, 0);


I noticed something while testing that it won't allow things like:

// Custom cursor macro from image property TouchArea { in property <image> custom-cursor; mouse-cursor: MouseCursor.custom(custom-cursor, 0, 0); }

Maybe this is just a limitation of macros?

this ideally should be allowed. What was the error?

ogoffart

Thanks, this is great work so far.
I'm on vacation at the moment but I just had a look over this PR anyway.

One thing I wonder is what to do with regard to scale factor. Especially when rendering SVG, we should probably take it into account.

ogoffart · 2025-12-18T13:34:43Z

internal/interpreter/api.rs

+    /// A mouse cursor.
+    MouseCursor(i_slint_core::items::MouseCursor) = 15,


The i_slint_core::MouseCursor is still private API so it should have #[doc(hidden)]

ogoffart · 2025-12-18T13:37:11Z

internal/backends/testing/testing_backend.rs

    size: Cell<PhysicalSize>,
    pub ime_requests: RefCell<Vec<InputMethodRequest>>,
-    pub mouse_cursor: Cell<i_slint_core::items::MouseCursor>,
+    pub mouse_cursor: RefCell<i_slint_core::items::MouseCursor>,


This is just for tests anyway so it's fine.
Maybe the tests would be a bit nicer if there was a pub fn mouse_cursor(&self)->MouseCursor { self.mouse_cursor.borrow().clone() } getter function.

(And in headless this isn't even used, so we could just remove it)

ogoffart · 2025-12-18T13:39:37Z

internal/compiler/tests/syntax/elements/toucharea.slint

+
+    // Custom cursor macro
+    TouchArea {
+        mouse-cursor: MouseCursor.custom(@image-url("cursor.png"), 0, 0);


this ideally should be allowed. What was the error?

ogoffart · 2025-12-18T13:42:24Z

internal/compiler/tests/syntax/elements/toucharea.slint

+    TouchArea {
+        mouse-cursor: MouseCursor.custom();
+//                                >    <error{Not enough arguments}
+    }


Also try:
mouse-cursor: MouseCursor.custom; (not called)
mouse-cursor: custom(...) should work without the MouseCursor.
mouse-cursor: custom(@image-url("cursor.png", 0, 0, 0)); too many args.

ogoffart · 2025-12-18T13:44:59Z

internal/core/items/cursor.rs

+    NeswResize,
+    /// Bidirectional resize north-west-south-east.
+    NwseResize,
+    /// Custom cursor from an `Image`.


should document what the hotspot is and relative to what.

ogoffart · 2025-12-18T13:49:32Z

internal/core/items/cursor.rs

+#[non_exhaustive]
+#[repr(C, u32)]
+#[derive(Debug, Clone, PartialEq, Default)]
+pub enum MouseCursor {


when this was in the enums.rs macro, it got also automatic documentation in there: https://docs.slint.dev/latest/docs/slint/reference/gestures/toucharea/#mouse-cursor
Now, the documentation need to be written manually and kept in sync.
I wonder if it wouldn't be good to put that enum in i_slint_common, so it can be enumerated to generate the docs and avoid repetition in lookup.rs.

ogoffart · 2025-12-18T13:57:35Z

internal/compiler/expression_tree.rs

+    NsResize,
+    NeswResize,
+    NwseResize,
+    CustomCursor(ImageReference, i32, i32),


I think this should be Expression so the image and hotspot can be dynamic.

Suggested change

CustomCursor(ImageReference, i32, i32),

CustomCursor{img: Expression, hotspot_x: Expression, hotspot_y: Expression},

ogoffart · 2025-12-18T14:00:27Z

internal/compiler/generator/cpp.rs

                )
            }
        }
+        Expression::MouseCursor(MouseCursor::Default) => {


i think we would used strnum macros to simplify this. (same in rust)

ogoffart · 2025-12-18T14:05:26Z

internal/backends/winit/winitwindowadapter.rs

+            MouseCursor::NwseResize => Some(winit::window::CursorIcon::NwseResize),
+            MouseCursor::CustomCursor { image, hotspot_x, hotspot_y } => {
+                if let Some(rgba8) = image.to_rgba8() {
+                    let rgba_vec = rgba8.as_slice().to_vec();


why allocate a vector if we're going to allocate another vector in the next line?

redstrate force-pushed the work/josh/custom-cursor branch 3 times, most recently from 18350b2 to 80b3462 Compare December 11, 2025 22:24

redstrate mentioned this pull request Dec 12, 2025

Add support for setting custom bitmap cursors #10256

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redstrate force-pushed the work/josh/custom-cursor branch from 80b3462 to 1768401 Compare December 12, 2025 16:13

redstrate commented Dec 12, 2025

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redstrate force-pushed the work/josh/custom-cursor branch from cf4124f to d50c6ac Compare December 12, 2025 16:23

redstrate marked this pull request as ready for review December 12, 2025 16:26

redstrate commented Dec 16, 2025

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redstrate force-pushed the work/josh/custom-cursor branch from d50c6ac to e4c102f Compare December 16, 2025 16:02

ogoffart reviewed Dec 18, 2025

View reviewed changes

		/// A mouse cursor.
		MouseCursor(i_slint_core::items::MouseCursor) = 15,

	CustomCursor(ImageReference, i32, i32),
	CustomCursor{img: Expression, hotspot_x: Expression, hotspot_y: Expression},

Add support for setting custom bitmap cursors #10270

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redstrate commented Dec 11, 2025 • edited Loading Uh oh! There was an error while loading. Please reload this page.

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TODO

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redstrate commented Dec 12, 2025

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redstrate commented Dec 11, 2025 •

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