Fix issue emilk#2578

- `row_start_x` tracks a virtual position in the source paragraph (the one that is too long) for which length has already been processed. When creating an empty row, this position should not be updated as no glyphs were consumed from the source paragraph.
- added example that would demonstrate the problem if the line was included, and that is fixed with this commit

Cargo.lock

@@ -4732,6 +4732,14 @@ dependencies = [
  "memchr",
 ]
 
+[[package]]
+name = "wrapping-layout"
+version = "0.1.0"
+dependencies = [
+ "eframe",
+ "tracing-subscriber",
+]
+
 [[package]]
 name = "x11-dl"
 version = "2.21.0"

crates/epaint/src/text/text_layout.rs

@@ -147,6 +147,9 @@ fn layout_section(
         paragraph.empty_paragraph_height = line_height; // TODO(emilk): replace this hack with actually including `\n` in the glyphs?
     }
 
+    // TODO(bu5hm4nn): in a label widget, `leading_space` is used to adjust for existing text in a screen row,
+    // but the comment on `LayoutSection::leading_space` makes it clear it was originally intended for typographical
+    // indentation and not for screen layout
     paragraph.cursor_x += leading_space;
 
     let mut last_glyph_id = None;
@@ -250,15 +253,15 @@ fn line_break(paragraph: &Paragraph, job: &LayoutJob, out_rows: &mut Vec<Row>, e
     let mut first_row_indentation = paragraph.glyphs[0].pos.x;
     let mut row_start_x = 0.0;
     let mut row_start_idx = 0;
+    let mut non_empty_rows = 0;
 
     for i in 0..paragraph.glyphs.len() {
-        if job.wrap.max_rows <= out_rows.len() {
-            *elided = true;
+        let potential_row_width = paragraph.glyphs[i].max_x() - row_start_x - first_row_indentation;
+
+        if job.wrap.max_rows > 0 && non_empty_rows >= job.wrap.max_rows {
             break;
         }
 
-        let potential_row_width = paragraph.glyphs[i].max_x() - row_start_x;
-
         if job.wrap.max_width + wrap_width_margin < potential_row_width {
             // Row break:
 
@@ -303,6 +306,12 @@ fn line_break(paragraph: &Paragraph, job: &LayoutJob, out_rows: &mut Vec<Row>, e
                 row_start_idx = last_kept_index + 1;
                 row_start_x = paragraph.glyphs[row_start_idx].pos.x;
                 row_break_candidates.forget_before_idx(row_start_idx);
+                non_empty_rows += 1;
+
+                // (bu5hm4nn) first row indentation gets consumed the first time it's used
+                if first_row_indentation > 0.0 {
+                    first_row_indentation = 0.0;
+                }
             } else {
                 // Found no place to break, so we have to overrun wrap_width.
             }
@@ -948,6 +957,7 @@ impl RowBreakCandidates {
             .flatten()
     }
 
+    #[allow(dead_code)]
     fn has_good_candidate(&self, break_anywhere: bool) -> bool {
         if break_anywhere {
             self.any.is_some()
@@ -1114,3 +1124,36 @@ mod tests {
         );
     }
 }
+
+#[test]
+fn test_line_break_first_row_not_empty() {
+    let mut fonts = FontsImpl::new(1.0, 1024, super::FontDefinitions::default());
+    let mut layout_job = LayoutJob::single_section(
+        "SomeSuperLongTextThatDoesNotHaveAnyGoodBreakCandidatesButStillNeedsToBeBroken".into(),
+        super::TextFormat::default(),
+    );
+
+    // a small area
+    layout_job.wrap.max_width = 110.0;
+
+    // give the first row a leading space, simulating that there already is
+    // text in this visual row
+    layout_job.sections.first_mut().unwrap().leading_space = 50.0;
+
+    let galley = super::layout(&mut fonts, layout_job.into());
+    assert_eq!(
+        galley
+            .rows
+            .iter()
+            .map(|row| row.glyphs.iter().map(|g| g.chr).collect::<String>())
+            .collect::<Vec<_>>(),
+        vec![
+            "SomeSup",
+            "erLongTextThat",
+            "DoesNotHaveAn",
+            "yGoodBreakCand",
+            "idatesButStillNe",
+            "edsToBeBroken"
+        ]
+    );
+}

examples/wrapping-layout/Cargo.toml

@@ -0,0 +1,12 @@
+[package]
+name = "wrapping-layout"
+version = "0.1.0"
+edition = "2021"
+
+# See more keys and their definitions at https://doc.rust-lang.org/cargo/reference/manifest.html
+
+[dependencies]
+eframe = { path = "../../crates/eframe", features = [
+    "__screenshot", # __screenshot is so we can dump a screenshot using EFRAME_SCREENSHOT_TO
+] }
+tracing-subscriber = "0.3"

examples/wrapping-layout/src/main.rs

@@ -0,0 +1,54 @@
+use eframe::{
+    egui::{self, WidgetText},
+    emath::Align,
+    epaint::Stroke,
+};
+
+fn main() -> Result<(), eframe::Error> {
+    let options = eframe::NativeOptions {
+        initial_window_size: Some(egui::vec2(380.0, 440.0)),
+        ..Default::default()
+    };
+    eframe::run_native(
+        "Horizontal Wrapped Layouts",
+        options,
+        Box::new(|cc| Box::new(MyEguiApp::new(cc))),
+    )
+}
+
+#[derive(Default)]
+struct MyEguiApp {}
+
+impl MyEguiApp {
+    fn new(_cc: &eframe::CreationContext<'_>) -> Self {
+        Self::default()
+    }
+}
+
+impl eframe::App for MyEguiApp {
+    fn update(&mut self, ctx: &egui::Context, _frame: &mut eframe::Frame) {
+        egui::CentralPanel::default().show(ctx, |ui| {
+            ui.horizontal_wrapped(|ui| {
+                ui.hyperlink_to("@npub1vdaeclr2mnntmyw...", "whocares");
+                let text = " LotsOfTextPrecededByASpace5kgqfqqxwhkrkw60stn8aph4gm2h2053xvwvvlvjm3q9eqdpqxycrqvpqd3hhgar9wfujqarfvd4k2arncqzpgxqzz6sp5vfenc5l4uafsky0w069zs329edf608ggpjjveguwxfl3xlswg5vq9qyyssqj46d5x3gsnljffm79eqwszk4mk47lkxywdp8mxum7un3qm0ztwj9jf46cm4lw2un9hk4gttgtjdrk29h27xu4e3ume20sqsna8q7xwspqqkwq7";
+                ui.label(text);
+                ui.style_mut().visuals.widgets.noninteractive.fg_stroke = Stroke::new( 1.0, eframe::epaint::Color32::RED );
+                ui.label("More text followed by two newlines\n\n");
+                ui.style_mut().visuals.widgets.noninteractive.fg_stroke = Stroke::new( 1.0, eframe::epaint::Color32::GREEN );
+                ui.label("more text, no newline");
+                ui.reset_style();
+            });
+            ui.separator();
+            ui.horizontal_wrapped(|ui| {
+                ui.label("Hyperlink no newline:");
+                let url = "https://i.nostrimg.com/c72f5e1a2e162fad2625e15651a654465c06016016f7743b496021cafa2a524e/file.jpeg";
+                ui.hyperlink_to( url, url );
+                ui.end_row();
+                ui.label("Hyperlink break_anywhere=true");
+                let mut job = WidgetText::from(url).into_text_job(ui.style(), egui::FontSelection::Default, Align::LEFT);
+                job.job.wrap.break_anywhere = true;
+                ui.hyperlink_to( job.job, url );
+            });
+       });
+    }
+}