2 files changed, 95 insertions, 0 deletions
diff --git a/src/ide/jump.rs b/src/ide/jump.rs
new file mode 100644
index 00000000..1a96fbbe
--- /dev/null
+++ b/src/ide/jump.rs
@@ -0,0 +1,93 @@
+use std::num::NonZeroUsize;
+
+use crate::doc::{Element, Frame, Location};
+use crate::geom::Point;
+use crate::syntax::{LinkedNode, Source, Span, SyntaxKind};
+use crate::World;
+
+/// Find the source file and byte offset for a click position.
+pub fn jump_to_source<'a>(
+    world: &'a dyn World,
+    frame: &Frame,
+    click: Point,
+) -> Option<(&'a Source, usize)> {
+    for (mut pos, element) in frame.elements() {
+        if let Element::Text(text) = element {
+            for glyph in &text.glyphs {
+                if glyph.span.is_detached() {
+                    continue;
+                }
+
+                let width = glyph.x_advance.at(text.size);
+                if pos.x <= click.x
+                    && pos.x + width >= click.x
+                    && pos.y >= click.y
+                    && pos.y - text.size <= click.y
+                {
+                    let source = world.source(glyph.span.source());
+                    let node = source.find(glyph.span);
+                    let pos = if node.kind() == SyntaxKind::Text {
+                        let range = node.range();
+                        (range.start + usize::from(glyph.offset)).min(range.end)
+                    } else {
+                        node.offset()
+                    };
+                    return Some((source, pos));
+                }
+
+                pos.x += width;
+            }
+        }
+
+        if let Element::Group(group) = element {
+            if let Some(span) = jump_to_source(world, &group.frame, click - pos) {
+                return Some(span);
+            }
+        }
+    }
+
+    None
+}
+
+/// Find the output location for a cursor position.
+pub fn jump_to_preview(
+    frames: &[Frame],
+    source: &Source,
+    cursor: usize,
+) -> Option<Location> {
+    let node = LinkedNode::new(source.root()).leaf_at(cursor)?;
+    if node.kind() != SyntaxKind::Text {
+        return None;
+    }
+
+    let span = node.span();
+    for (i, frame) in frames.iter().enumerate() {
+        if let Some(pos) = find_in_frame(frame, span) {
+            return Some(Location { page: NonZeroUsize::new(i + 1).unwrap(), pos });
+        }
+    }
+
+    None
+}
+
+/// Find the position of a span in a frame.
+fn find_in_frame(frame: &Frame, span: Span) -> Option<Point> {
+    for (mut pos, element) in frame.elements() {
+        if let Element::Text(text) = element {
+            for glyph in &text.glyphs {
+                if glyph.span == span {
+                    return Some(pos);
+                }
+                pos.x += glyph.x_advance.at(text.size);
+            }
+        }
+
+        if let Element::Group(group) = element {
+            if let Some(point) = find_in_frame(&group.frame, span) {
+                return Some(point + pos);
+            }
+        }
+    }
+
+    None
+}
diff --git a/src/ide/mod.rs b/src/ide/mod.rs
index 4999da52..bee959cd 100644
--- a/src/ide/mod.rs
+++ b/src/ide/mod.rs
@@ -3,10 +3,12 @@
 mod analyze;
 mod complete;
 mod highlight;
+mod jump;
 mod tooltip;
 
 pub use self::complete::*;
 pub use self::highlight::*;
+pub use self::jump::*;
 pub use self::tooltip::*;
 
 use std::fmt::Write;