preparation

src/layout/text.rs

@@ -28,6 +28,16 @@ pub struct TextAttrs {
     pub family: Family<'static>,
 }
 
+#[derive(Default)]
+pub enum Cursor {
+    #[default]
+    None,
+    Select {
+        line: usize,
+        idx: usize,
+    },
+}
+
 pub type TextBuffer = Buffer;
 
 impl Default for TextAttrs {
@@ -48,6 +58,7 @@ impl TextData {
         buffer: &mut TextBuffer,
         content: &str,
         attrs: &TextAttrs,
+        cursor: &Cursor,
         textures: &mut Textures,
     ) -> (TextureHandle, TextOffset) {
         buffer.set_metrics(
@@ -67,7 +78,14 @@ impl TextData {
         let mut max_y = 0;
         let c = attrs.color;
         let mut max_width = 0.0f32;
-        for run in buffer.layout_runs() {
+        let mut i = 0;
+        let mut cursor_x = 0;
+        for (run_i, run) in buffer.layout_runs().enumerate() {
+            if let Cursor::Select { line, .. } = cursor
+                && *line == run_i
+            {
+                cursor_x = run.line_w as i32;
+            }
             for glyph in run.glyphs.iter() {
                 let physical_glyph = glyph.physical((0., 0.), 1.0);
 
@@ -76,6 +94,14 @@ impl TextData {
                     None => cosmic_text::Color::rgba(c.r, c.g, c.b, c.a),
                 };
 
+                if let Cursor::Select { idx, line } = cursor
+                    && *line == run_i
+                    && *idx == i
+                {
+                    cursor_x = physical_glyph.x;
+                }
+                i += 1;
+
                 self.swash_cache.with_pixels(
                     &mut self.font_system,
                     physical_glyph.cache_key,
@@ -93,6 +119,11 @@ impl TextData {
             }
             max_width = max_width.max(run.line_w);
         }
+        if let &Cursor::Select { line, .. } = cursor {
+            let y = (attrs.line_height * (line + 1) as f32) as i32 - 1;
+            max_y = max_y.max(y);
+            max_x = max_x.max(cursor_x);
+        }
         let width = (max_x - min_x + 1) as u32;
         let height = (max_y - min_y + 1) as u32;
         let mut image = RgbaImage::new(width, height);
@@ -101,6 +132,15 @@ impl TextData {
             let y = (y - min_y) as u32;
             image.put_pixel(x, y, color);
         }
+        if let &Cursor::Select { line, .. } = cursor {
+            for y in 0..attrs.line_height as u32 {
+                // no clue if this is good or bad for non integer values
+                // depends on how the layouting is actually done
+                let x = (cursor_x - min_x) as u32;
+                let y = (y as f32 + attrs.line_height * line as f32 - min_y as f32) as u32;
+                image.put_pixel(x, y, Rgba(c.as_arr()));
+            }
+        }
         let offset = TextOffset {
             top_left: Vec2::new(min_x as f32, min_y as f32),
             bot_right: Vec2::new(