1
  2
  3
  4
  5
  6
  7
  8
  9
 10
 11
 12
 13
 14
 15
 16
 17
 18
 19
 20
 21
 22
 23
 24
 25
 26
 27
 28
 29
 30
 31
 32
 33
 34
 35
 36
 37
 38
 39
 40
 41
 42
 43
 44
 45
 46
 47
 48
 49
 50
 51
 52
 53
 54
 55
 56
 57
 58
 59
 60
 61
 62
 63
 64
 65
 66
 67
 68
 69
 70
 71
 72
 73
 74
 75
 76
 77
 78
 79
 80
 81
 82
 83
 84
 85
 86
 87
 88
 89
 90
 91
 92
 93
 94
 95
 96
 97
 98
 99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137

//! Utility to help drawing on a widget in a relm application.
//! Create a DrawHandler, initialize it, and get its context when handling a message (that could be
//! sent from the draw signal).

// TODO: check if clip has the intended behavior.

use std::cell::RefCell;
use std::ops::Deref;
use std::rc::Rc;

use cairo::{
    self,
    Context,
    Format,
    ImageSurface,
};
use gtk::{
    Inhibit,
    WidgetExt,
};

#[derive(Clone)]
struct Surface {
    surface: Rc<RefCell<ImageSurface>>,
}

impl Surface {
    fn new(surface: ImageSurface) -> Self {
        Self {
            surface: Rc::new(RefCell::new(surface)),
        }
    }

    fn get(&self) -> ImageSurface {
        self.surface.borrow().clone()
    }

    fn set(&self, surface: &ImageSurface) {
        *self.surface.borrow_mut() = surface.clone();
    }
}

pub struct DrawContext<W: WidgetExt> {
    context: Context,
    draw_surface: Surface,
    edit_surface: ImageSurface,
    widget: W,
}

impl<W: Clone + WidgetExt> DrawContext<W> {
    fn new(draw_surface: &Surface, edit_surface: &ImageSurface, widget: &W) -> Self {
        Self {
            context: Context::new(&edit_surface),
            draw_surface: draw_surface.clone(),
            edit_surface: edit_surface.clone(),
            widget: widget.clone(),
        }
    }
}

impl<W: WidgetExt> Deref for DrawContext<W> {
    type Target = Context;

    fn deref(&self) -> &Self::Target {
        &self.context
    }
}

impl<W: WidgetExt> Drop for DrawContext<W> {
    fn drop(&mut self) {
        self.draw_surface.set(&self.edit_surface);
        self.widget.queue_draw();
    }
}

/// Manager for drawing operations.
pub struct DrawHandler<W> {
    draw_surface: Surface,
    edit_surface: ImageSurface,
    widget: Option<W>,
}

impl<W: Clone + WidgetExt> DrawHandler<W> {
    /// Create a new DrawHandler.
    pub fn new() -> Result<Self, cairo::Status> {
        Ok(Self {
            draw_surface: Surface::new(ImageSurface::create(Format::ARgb32, 100, 100)?),
            edit_surface: ImageSurface::create(Format::ARgb32, 100, 100)?,
            widget: None,
        })
    }

    /// Get the drawing context to draw on a widget.
    pub fn get_context(&mut self) -> DrawContext<W> {
        if let Some(ref widget) = self.widget {
            let allocation = widget.get_allocation();
            let scale = if cfg!(feature = "hidpi") {
                widget.get_scale_factor()
            } else {
                1
            };
            let width = allocation.width * scale;
            let height = allocation.height * scale;
            if (width, height) != (self.edit_surface.get_width(), self.edit_surface.get_height()) {
                // TODO: also copy the old small surface to the new bigger one?
                match ImageSurface::create(Format::ARgb32, width, height) {
                    Ok(surface) => {
                        {
                            #[cfg(feature = "hidpi")]
                            surface.set_device_scale(scale as f64, scale as f64);
                        }
                        self.edit_surface = surface
                    }
                    Err(error) => eprintln!("Cannot resize image surface: {:?}", error),
                }
            }
            DrawContext::new(&self.draw_surface, &self.edit_surface, widget)
        }
        else {
            panic!("Call DrawHandler::init() before DrawHandler::get_context().");
        }
    }

    /// Initialize the draw handler.
    /// The widget is the one on which drawing will occur.
    pub fn init(&mut self, widget: &W) {
        widget.set_app_paintable(true);
        self.widget = Some(widget.clone());
        let draw_surface = self.draw_surface.clone();
        widget.connect_draw(move |_, context| {
            // TODO: only copy the area that was exposed?
            context.set_source_surface(&draw_surface.get(), 0.0, 0.0);
            context.paint();
            Inhibit(false)
        });
    }
}