Image sampler set to linear/clamp

[galop1n]

If a Bevy application override the default sampler to repeat, Egui window backgrounds are incorrectly transparent.

[mvlabat]

Hi! Could you provide more details on how to reproduce the issue? A code example with screenshots would be great.
I'm not sure how to confirm the fix atm. Thanks!

P.S. If I merge it after the Bevy 0.10 update release, I'll make a new patch release no problem.

[galop1n]

In side_panel.rs replace the main function with the version below, clearing to red, and setting the default descriptor to Repeat and linear

fn main() {
    App::new()
        .insert_resource(ClearColor(Color::rgb(1.0, 0.0, 0.0)))
        .add_plugins(DefaultPlugins.set(ImagePlugin {
            default_sampler: bevy::render::render_resource::SamplerDescriptor {
                address_mode_u: bevy::render::render_resource::AddressMode::Repeat,
                address_mode_v: bevy::render::render_resource::AddressMode::Repeat,
                anisotropy_clamp: std::num::NonZeroU8::new(8u8),
                ..bevy::render::texture::ImageSampler::linear_descriptor()
            },
        }))
        .add_plugin(EguiPlugin)
        .init_resource::<OccupiedScreenSpace>()
        .add_startup_system(setup_system)
        .add_system(ui_example_system)
        .add_system(update_camera_transform_system)
        .run();
}

This is what it will looks like:

With the PR:

If you look at egui glow backend, you can see the init to clamp : https://github.com/emilk/egui/blob/master/crates/egui_glow/src/painter.rs

 self.gl.tex_parameter_i32(
                glow::TEXTURE_2D,
                glow::TEXTURE_WRAP_S,
                glow::CLAMP_TO_EDGE as i32,
            );
            self.gl.tex_parameter_i32(
                glow::TEXTURE_2D,
                glow::TEXTURE_WRAP_T,
                glow::CLAMP_TO_EDGE as i32,
            );

[mvlabat]

lgtm, thank you for the PR!