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我想更新 DrawingArea 内的 cairo 绘图。我试图通过调用DrawingArea::connect_draw(...)一个新函数作为参数来实现这一点。我的问题是它不会替换原始绘图功能，而是在显示窗口时调用两者。这是一个例子

extern crate cairo;
extern crate gio;
extern crate gtk;

use gio::prelude::*;
use gtk::prelude::*;

fn main() {
    let application = gtk::Application::new(Some("com.example"), Default::default())
        .expect("Initialization failed...");

    application.connect_activate(|app| {
        build_ui(app);
    });

    application.run(&vec![]);
}

fn build_ui(application: &gtk::Application) {
    let window = get_window(application);
    let drawing_area = Box::new(gtk::DrawingArea::new)();

    // Set drawing function
    drawing_area.connect_draw(|_, ctx| draw(ctx, 0.5, 2.0));
    // Change drawing function
    drawing_area.connect_draw(|_, ctx| draw(ctx, 0.9, 1.0)); // <-- Why is this not working as expected?

    window.add(&drawing_area);
    window.show_all();
}

fn get_window(application: &gtk::Application) -> gtk::ApplicationWindow {
    let window = gtk::ApplicationWindow::new(application);
    window.set_default_size(500i32, 500i32);

    // Set transparency
    set_visual(&window, None);
    window.connect_screen_changed(set_visual);
    window.set_app_paintable(true);

    window
}

fn draw(ctx: &cairo::Context, param1: f64, param2: f64) -> gtk::Inhibit {
    ctx.scale(500f64, 500f64);

    ctx.set_source_rgba(1.0, 0.2, 0.2, param1);
    ctx.arc(0.5, 0.5, 0.2, 0.0, 3.1414 * param2);
    ctx.fill();

    Inhibit(false)
}

fn set_visual(window: &gtk::ApplicationWindow, _screen: Option<&gdk::Screen>) {
    if let Some(screen) = window.get_screen() {
        if let Some(ref visual) = screen.get_rgba_visual() {
            window.set_visual(Some(visual));
        }
    }
}

我希望显示半个圆圈。然而，即使我尝试替换 connect_draw，旧的完整圆圈仍然存在。我该如何正确替换它？

4

1 回答 1

1

使用该connect_draw函数附加另一个信号处理程序，但不会替换现有处理程序。但是，该函数返回 a SignalHandlerId，然后您应该能够使用该signal_handler_disconnect函数断开原始信号处理程序（请参阅https://gtk-rs.org/docs/glib/signal/fn.signal_handler_disconnect.html）。

于 2019-10-12T20:37:36.827 回答