Implement flex and box layouting 📏

1 files changed, 62 insertions, 0 deletions

diff --git a/src/layout/text.rs b/src/layout/text.rs
new file mode 100644
index 00000000..8aa76c4c
--- /dev/null
+++ b/src/layout/text.rs
@@ -0,0 +1,62 @@
+//! Layouting of text into boxes.
+
+use crate::doc::TextAction;
+use crate::font::FontQuery;
+use crate::size::{Size, Size2D};
+use super::*;
+
+
+/// The context for text layouting.
+#[derive(Debug, Clone)]
+pub struct TextContext<'a, 'p> {
+    /// Loads fonts matching queries.
+    pub loader: &'a FontLoader<'p>,
+    /// Base style to set text with.
+    pub style: TextStyle,
+}
+
+/// Layout one piece of text without any breaks as one continous box.
+pub fn layout(text: &str, ctx: &TextContext) -> LayoutResult<BoxLayout> {
+    let mut actions = Vec::new();
+    let mut active_font = std::usize::MAX;
+    let mut buffer = String::new();
+    let mut width = Size::zero();
+
+    // Walk the characters.
+    for character in text.chars() {
+        // Retrieve the best font for this character.
+        let (index, font) = ctx.loader.get(FontQuery {
+            families: ctx.style.font_families.clone(),
+            italic: ctx.style.italic,
+            bold: ctx.style.bold,
+            character,
+        }).ok_or_else(|| LayoutError::NoSuitableFont(character))?;
+
+        // Add the char width to the total box width.
+        let char_width = font.widths[font.map(character) as usize] * ctx.style.font_size;
+        width += char_width;
+
+        // Change the font if necessary.
+        if active_font != index {
+            if !buffer.is_empty() {
+                actions.push(TextAction::WriteText(buffer));
+                buffer = String::new();
+            }
+
+            actions.push(TextAction::SetFont(index, ctx.style.font_size));
+            active_font = index;
+        }
+
+        buffer.push(character);
+    }
+
+    // Write the remaining characters.
+    if !buffer.is_empty() {
+        actions.push(TextAction::WriteText(buffer));
+    }
+
+    Ok(BoxLayout {
+        dimensions: Size2D::new(width, Size::points(ctx.style.font_size)),
+        actions,
+    })
+}