rat_widget/

view.rs

//! A view allows scrolling of on or more widgets without builtin
//! support for scrolling.
//!
//! ```rust
//! # use rat_scrolled::Scroll;
//! use rat_widget::paragraph::{Paragraph, ParagraphState};
//! # use rat_widget::view::{View, ViewState};
//! # use ratatui::prelude::*;
//! #
//! # let l2 = [Rect::ZERO, Rect::ZERO];
//! # struct State {
//! #      view: ViewState,
//! #      first: ParagraphState,
//! #  }
//! # let mut state = State {
//! #     view: Default::default(),
//! #     first: Default::default(),
//! # };
//! # let mut buf = Buffer::default();
//!
//! ///
//! /// Create the view and set the layout area
//! /// for the buffer.
//! ///
//!
//! let mut view_buf = View::new()
//!     .layout(Rect::new(0, 0, 400, 400))
//!     .vscroll(Scroll::new())
//!     .hscroll(Scroll::new())
//!     .into_buffer(l2[1], &mut state.view);
//!
//! ///
//! /// Render the widgets to the view buffer.
//! ///
//! view_buf.render_stateful(
//!     Paragraph::new("Paragraph\nParagraph\n..."),
//!     Rect::new(0, 0, 40, 15),
//!     &mut state.first,
//! );
//!
//! ///
//! /// Render the finished buffer.
//! ///
//! view_buf
//!     .into_widget()
//!     .render(l2[1], &mut buf, &mut state.view);
//!
//! ```

use std::cmp::{max, min};

use crate::_private::NonExhaustive;
use crate::event::ScrollOutcome;
use rat_event::{HandleEvent, MouseOnly, Outcome, Regular};
use rat_reloc::RelocatableState;
use rat_scrolled::{Scroll, ScrollArea, ScrollAreaState, ScrollState, ScrollStyle};
use ratatui::buffer::Buffer;
use ratatui::layout::{Position, Rect, Size};
use ratatui::style::Style;
use ratatui::widgets::Block;
use ratatui::widgets::{StatefulWidget, Widget};

/// Configure the view.
#[derive(Debug, Default, Clone)]
pub struct View<'a> {
    layout: Rect,
    view_size: Option<Size>,
    style: Style,
    block: Option<Block<'a>>,
    hscroll: Option<Scroll<'a>>,
    vscroll: Option<Scroll<'a>>,
}

/// Render to the temp buffer.
///
/// * It maps your widget area from layout coordinates
///   to screen coordinates before rendering.
/// * It helps with cleanup of the widget state if your
///   widget is currently invisible.
#[derive(Debug)]
pub struct ViewBuffer<'a> {
    // page layout
    layout: Rect,

    // Scroll offset into the view.
    offset: Position,
    buffer: Buffer,

    // inner area that will finally be rendered.
    widget_area: Rect,

    style: Style,
    block: Option<Block<'a>>,
    hscroll: Option<Scroll<'a>>,
    vscroll: Option<Scroll<'a>>,
}

/// Clips and copies the temp buffer to the frame buffer.
#[derive(Debug)]
pub struct ViewWidget<'a> {
    // Scroll offset into the view.
    offset: Position,
    buffer: Buffer,

    style: Style,
    block: Option<Block<'a>>,
    hscroll: Option<Scroll<'a>>,
    vscroll: Option<Scroll<'a>>,
}

/// All styles for a view.
#[derive(Debug)]
pub struct ViewStyle {
    pub style: Style,
    pub block: Option<Block<'static>>,
    pub scroll: Option<ScrollStyle>,
    pub non_exhaustive: NonExhaustive,
}

/// View state.
#[derive(Debug, Default, Clone)]
pub struct ViewState {
    /// Full area for the widget.
    /// __read only__ renewed for each render.
    pub area: Rect,
    /// Area inside the border.
    /// __read only__ renewed for each render.
    pub widget_area: Rect,

    /// The layout of the temp buffer uses.
    /// __read only__ renewed for each render.
    pub layout: Rect,

    /// Horizontal scroll
    /// __read+write__
    pub hscroll: ScrollState,
    /// Vertical scroll
    /// __read+write__
    pub vscroll: ScrollState,

    /// For the buffer to survive render()
    buffer: Option<Buffer>,
}

impl<'a> View<'a> {
    /// New View.
    pub fn new() -> Self {
        Self::default()
    }

    /// Area for the temp buffer.
    pub fn layout(mut self, area: Rect) -> Self {
        self.layout = area;
        self
    }

    /// Area used for the scrollbars. Maybe bigger then the layout area.
    /// Uses the area if not set.
    pub fn view_size(mut self, view: Size) -> Self {
        self.view_size = Some(view);
        self
    }

    /// Base style.
    pub fn style(mut self, style: Style) -> Self {
        self.style = style;
        self.block = self.block.map(|v| v.style(style));
        self
    }

    /// Block for border
    pub fn block(mut self, block: Block<'a>) -> Self {
        self.block = Some(block);
        self
    }

    /// Scroll support.
    pub fn scroll(mut self, scroll: Scroll<'a>) -> Self {
        self.hscroll = Some(scroll.clone().override_horizontal());
        self.vscroll = Some(scroll.override_vertical());
        self
    }

    /// Horizontal scroll support.
    pub fn hscroll(mut self, scroll: Scroll<'a>) -> Self {
        self.hscroll = Some(scroll.override_horizontal());
        self
    }

    /// Vertical scroll support.
    pub fn vscroll(mut self, scroll: Scroll<'a>) -> Self {
        self.vscroll = Some(scroll.override_vertical());
        self
    }

    /// Combined style.
    pub fn styles(mut self, styles: ViewStyle) -> Self {
        self.style = styles.style;
        if styles.block.is_some() {
            self.block = styles.block;
        }
        if let Some(styles) = styles.scroll {
            self.hscroll = self.hscroll.map(|v| v.styles(styles.clone()));
            self.vscroll = self.vscroll.map(|v| v.styles(styles.clone()));
        }
        self.block = self.block.map(|v| v.style(styles.style));
        self
    }

    /// Calculate the layout width.
    pub fn layout_width(&self, area: Rect, state: &ViewState) -> u16 {
        self.inner(area, state).width
    }

    /// Calculate the view area.
    pub fn inner(&self, area: Rect, state: &ViewState) -> Rect {
        let sa = ScrollArea::new()
            .block(self.block.as_ref())
            .h_scroll(self.hscroll.as_ref())
            .v_scroll(self.vscroll.as_ref());
        sa.inner(area, Some(&state.hscroll), Some(&state.vscroll))
    }

    /// Calculates the layout and creates a temporary buffer.
    pub fn into_buffer(self, area: Rect, state: &mut ViewState) -> ViewBuffer<'a> {
        state.area = area;
        state.layout = self.layout;

        let sa = ScrollArea::new()
            .block(self.block.as_ref())
            .h_scroll(self.hscroll.as_ref())
            .v_scroll(self.vscroll.as_ref());
        state.widget_area = sa.inner(area, Some(&state.hscroll), Some(&state.vscroll));

        let max_x = if let Some(view_size) = self.view_size {
            max(state.layout.right(), view_size.width)
        } else {
            state.layout.right()
        };
        let max_y = if let Some(view_size) = self.view_size {
            max(state.layout.bottom(), view_size.height)
        } else {
            state.layout.bottom()
        };

        state
            .hscroll
            .set_max_offset(max_x.saturating_sub(state.widget_area.width) as usize);
        state.hscroll.set_page_len(state.widget_area.width as usize);
        state
            .vscroll
            .set_page_len(state.widget_area.height as usize);
        state
            .vscroll
            .set_max_offset(max_y.saturating_sub(state.widget_area.height) as usize);

        // offset is in layout coordinates.
        // internal buffer starts at (view.x,view.y)
        let offset = Position::new(state.hscroll.offset as u16, state.vscroll.offset as u16);

        // resize buffer to fit the layout.
        let buffer_area = state.layout;
        let mut buffer = if let Some(mut buffer) = state.buffer.take() {
            buffer.reset();
            buffer.resize(buffer_area);
            buffer
        } else {
            Buffer::empty(buffer_area)
        };
        buffer.set_style(buffer_area, self.style);

        ViewBuffer {
            layout: self.layout,
            offset,
            buffer,
            widget_area: state.widget_area,
            style: self.style,
            block: self.block,
            hscroll: self.hscroll,
            vscroll: self.vscroll,
        }
    }
}

impl<'a> ViewBuffer<'a> {
    /// Render a widget to the temp buffer.
    #[inline(always)]
    pub fn render_widget<W>(&mut self, widget: W, area: Rect)
    where
        W: Widget,
    {
        if area.intersects(self.buffer.area) {
            // render the actual widget.
            widget.render(area, self.buffer());
        }
    }

    /// Render a widget to the temp buffer.
    /// This expects that the state is a [RelocatableState].
    #[inline(always)]
    pub fn render_stateful<W, S>(&mut self, widget: W, area: Rect, state: &mut S)
    where
        W: StatefulWidget<State = S>,
        S: RelocatableState,
    {
        if area.intersects(self.buffer.area) {
            // render the actual widget.
            widget.render(area, self.buffer(), state);
            // shift and clip the output areas.
            self.relocate(state);
        } else {
            self.hidden(state);
        }
    }

    /// Return the buffer layout.
    pub fn layout(&self) -> Rect {
        self.layout
    }

    /// Is the given area visible?
    pub fn is_visible_area(&self, area: Rect) -> bool {
        area.intersects(self.buffer.area)
    }

    /// Calculate the necessary shift from view to screen.
    pub fn shift(&self) -> (i16, i16) {
        (
            self.widget_area.x as i16 - self.offset.x as i16,
            self.widget_area.y as i16 - self.offset.y as i16,
        )
    }

    /// Does nothing for view.
    /// Only exists to match [Clipper](crate::clipper::Clipper).
    pub fn locate_area(&self, area: Rect) -> Rect {
        area
    }

    /// After rendering the widget to the buffer it may have
    /// stored areas in its state. These will be in buffer
    /// coordinates instead of screen coordinates.
    ///
    /// Call this function to correct this after rendering.
    pub fn relocate<S>(&self, state: &mut S)
    where
        S: RelocatableState,
    {
        state.relocate(self.shift(), self.widget_area);
    }

    /// If a widget is not rendered because it is out of
    /// the buffer area, it may still have left over areas
    /// in its state.
    ///
    /// This uses the mechanism for [relocate](Self::relocate) to zero them out.
    pub fn hidden<S>(&self, state: &mut S)
    where
        S: RelocatableState,
    {
        state.relocate((0, 0), Rect::default())
    }

    /// Access the temporary buffer.
    ///
    /// __Note__
    /// Use of render_widget is preferred.
    pub fn buffer(&mut self) -> &mut Buffer {
        &mut self.buffer
    }

    /// Rendering the content is finished.
    ///
    /// Convert to the output widget that can be rendered in the target area.
    pub fn into_widget(self) -> ViewWidget<'a> {
        ViewWidget {
            block: self.block,
            hscroll: self.hscroll,
            vscroll: self.vscroll,
            offset: self.offset,
            buffer: self.buffer,
            style: self.style,
        }
    }
}

impl StatefulWidget for ViewWidget<'_> {
    type State = ViewState;

    fn render(self, area: Rect, buf: &mut Buffer, state: &mut Self::State) {
        assert_eq!(area, state.area);

        ScrollArea::new()
            .style(self.style)
            .block(self.block.as_ref())
            .h_scroll(self.hscroll.as_ref())
            .v_scroll(self.vscroll.as_ref())
            .render(
                area,
                buf,
                &mut ScrollAreaState::new()
                    .h_scroll(&mut state.hscroll)
                    .v_scroll(&mut state.vscroll),
            );

        let src_area = self.buffer.area;
        let tgt_area = state.widget_area;
        let offset = self.offset;

        // extra offset due to buffer starts right of offset.
        let off_x0 = src_area.x.saturating_sub(offset.x);
        let off_y0 = src_area.y.saturating_sub(offset.y);
        // cut source buffer due to start left of offset.
        let cut_x0 = offset.x.saturating_sub(src_area.x);
        let cut_y0 = offset.y.saturating_sub(src_area.y);

        // length to copy
        let len_src = src_area.width.saturating_sub(cut_x0);
        let len_tgt = tgt_area.width.saturating_sub(off_x0);
        let len = min(len_src, len_tgt);

        // area height to copy
        let height_src = src_area.height.saturating_sub(cut_y0);
        let height_tgt = tgt_area.height.saturating_sub(off_y0);
        let height = min(height_src, height_tgt);

        // ** slow version **
        // for y in 0..height {
        //     for x in 0..len {
        //         let src_pos = Position::new(src_area.x + cut_x0 + x, src_area.y + cut_y0 + y);
        //         let src_cell = self.buffer.cell(src_pos).expect("src-cell");
        //
        //         let tgt_pos = Position::new(tgt_area.x + off_x0 + x, tgt_area.y + off_y0 + y);
        //         let tgt_cell = buf.cell_mut(tgt_pos).expect("tgt_cell");
        //
        //         *tgt_cell = src_cell.clone();
        //     }
        // }

        for y in 0..height {
            let src_0 = self
                .buffer
                .index_of(src_area.x + cut_x0, src_area.y + cut_y0 + y);
            let tgt_0 = buf.index_of(tgt_area.x + off_x0, tgt_area.y + off_y0 + y);

            let src = &self.buffer.content[src_0..src_0 + len as usize];
            let tgt = &mut buf.content[tgt_0..tgt_0 + len as usize];
            tgt.clone_from_slice(src);
        }

        // keep buffer
        state.buffer = Some(self.buffer);
    }
}

impl Default for ViewStyle {
    fn default() -> Self {
        Self {
            style: Default::default(),
            block: None,
            scroll: None,
            non_exhaustive: NonExhaustive,
        }
    }
}

impl ViewState {
    pub fn new() -> Self {
        Self::default()
    }

    /// Show this rect.
    pub fn show_area(&mut self, area: Rect) {
        self.hscroll.scroll_to_pos(area.x as usize);
        self.vscroll.scroll_to_pos(area.y as usize);
    }
}

impl ViewState {
    pub fn vertical_offset(&self) -> usize {
        self.vscroll.offset()
    }

    pub fn set_vertical_offset(&mut self, offset: usize) -> bool {
        let old = self.vscroll.offset();
        self.vscroll.set_offset(offset);
        old != self.vscroll.offset()
    }

    pub fn vertical_page_len(&self) -> usize {
        self.vscroll.page_len()
    }

    pub fn horizontal_offset(&self) -> usize {
        self.hscroll.offset()
    }

    pub fn set_horizontal_offset(&mut self, offset: usize) -> bool {
        let old = self.hscroll.offset();
        self.hscroll.set_offset(offset);
        old != self.hscroll.offset()
    }

    pub fn horizontal_page_len(&self) -> usize {
        self.hscroll.page_len()
    }

    pub fn horizontal_scroll_to(&mut self, pos: usize) -> bool {
        self.hscroll.scroll_to_pos(pos)
    }

    pub fn vertical_scroll_to(&mut self, pos: usize) -> bool {
        self.vscroll.scroll_to_pos(pos)
    }

    pub fn scroll_up(&mut self, delta: usize) -> bool {
        self.vscroll.scroll_up(delta)
    }

    pub fn scroll_down(&mut self, delta: usize) -> bool {
        self.vscroll.scroll_down(delta)
    }

    pub fn scroll_left(&mut self, delta: usize) -> bool {
        self.hscroll.scroll_left(delta)
    }

    pub fn scroll_right(&mut self, delta: usize) -> bool {
        self.hscroll.scroll_right(delta)
    }
}

impl HandleEvent<crossterm::event::Event, Regular, Outcome> for ViewState {
    fn handle(&mut self, event: &crossterm::event::Event, _qualifier: Regular) -> Outcome {
        self.handle(event, MouseOnly)
    }
}

impl HandleEvent<crossterm::event::Event, MouseOnly, Outcome> for ViewState {
    fn handle(&mut self, event: &crossterm::event::Event, _qualifier: MouseOnly) -> Outcome {
        let mut sas = ScrollAreaState::new()
            .area(self.widget_area)
            .h_scroll(&mut self.hscroll)
            .v_scroll(&mut self.vscroll);
        match sas.handle(event, MouseOnly) {
            ScrollOutcome::Up(v) => self.scroll_up(v).into(),
            ScrollOutcome::Down(v) => self.scroll_down(v).into(),
            ScrollOutcome::VPos(v) => self.set_vertical_offset(v).into(),
            ScrollOutcome::Left(v) => self.scroll_left(v).into(),
            ScrollOutcome::Right(v) => self.scroll_right(v).into(),
            ScrollOutcome::HPos(v) => self.set_horizontal_offset(v).into(),
            r => r.into(),
        }
    }
}