Allow resize on one both or no axis.

[hydra]

• Note: the original API accepted a Vec2b, but didn't use the x/y properties independently, thus this is a non-breaking change and should probably be considered a bug-fix.

Video:

https://github.com/user-attachments/assets/b92c1828-2304-432b-b567-1d48feadfd3b

• [x] I have followed the instructions in the PR template

[hydra]

Here's a video of the Resize control in combination with a table, using taffy for layout:

https://github.com/user-attachments/assets/51a2396d-65a8-42e1-9c0f-9543650fcbc1

source: https://github.com/MakerPnP/makerpnp/blob/b26be8c4bc73bae1cd06011e6f4a30b793fe0f29/crates/planner_gui_egui/src/project/unit_assignments_tab.rs

This video also highlights a usability issue, where it's hard to resize a table due to the scrollbars. It's hard to find the resize handle; you have to hover around until you see the pointer change. not all of the visible area of the resize handle actually works for resizing.

[michalsustr]

A nice cool improvement would be also to change the cursor to be only horizontal/vertical/diagonal based on the available x/y/x&y

[github-actions[bot]]

Preview available at https://egui-pr-preview.github.io/pr/7047-resize-improvements-1 Note that it might take a couple seconds for the update to show up after the preview_build workflow has completed.

[hydra]

Sorry for late response to your question (https://github.com/emilk/egui/pull/7047#discussion_r2094489365)

Rebased on 0.32.0, fix is still required, video added to original comment.

[hydra]

@emilk I just discovered this PR has unintended consequences, I'm not sure of the correct direction to go.

when this PR is enabled, a resize inside a container works as per the demo, however Windows themselves are no-longer resizable, probably this is because the resize for the window is being created with a Resize::resizable member set to [false, false] instead of [true, true] since the old code didn't check the value of the Resize::resizable field and just blindly overwrote ressizable with the user_requested_size.

I feel this PR is the correct fix, but that other fixes are also required.

Guidance appreciated.

[hydra]

The smoking gun is this, in Window::show_dyn.

let resize = resize.resizable(false); // We resize it manually

Going to investigate a little more...

I found this hack in Window::resize_response()

    if resize_interaction.any_dragged() {
        if let Some(mut state) = resize::State::load(ctx, resize_id) {
            state.requested_size = Some(new_rect.size() - margins);
            state.store(ctx, resize_id);
        }
    }

It really doesn't feel right that the Window is loading the state from Resize and fiddling with it, IMHO that should be the sole responsibility of the code in the resize resize.rs via an API.

So, basically, even though there is a resize that has resizable = [false, false] the hack comes along and updates the internal state of the window's resize. when the hack in Window is combined with the fix in this PR to the resize for windows is thus broken.

AFAICT this code path is only hit by Window

it turns out that is NOT the case, there are two things that update the user_requested_size, a) the window, by the hack above. b) the corner handle, by this chunk of code in Resize::begin.

        let mut user_requested_size = state.requested_size.take();

        let corner_id = self.resizable.any().then(|| id.with("__resize_corner"));

        if let Some(corner_id) = corner_id {
            if let Some(corner_response) = ui.ctx().read_response(corner_id) {
                if let Some(pointer_pos) = corner_response.interact_pointer_pos() {
                    // Respond to the interaction early to avoid frame delay.
                    user_requested_size =
                        Some(pointer_pos - position + 0.5 * corner_response.rect.size()); <-- this line
                }
            }
        }

[hydra]

I added a commit, which avoid the can-of-worms Resize <-> Window state issue which seems to work. I made a short video about the issue, my thoughts on the Resize <-> Window state, the new approach taken in the latest commit and shows the egui_demo_app and updated resize demo in action along with verification that windows resize correctly still too.

https://www.youtube.com/watch?v=p_QwInM-D4o