bug: fix incorrect text width calculation (#925)

* bug: fix incorrect text calculation

* actual fix, add tests

* appease clippy

* add link to inspiration

7 files changed, 230 insertions, 55 deletions

diff --git a/src/components/data_table/sortable.rs b/src/components/data_table/sortable.rs
index 06f3a86b..28262358 100644
--- a/src/components/data_table/sortable.rs
+++ b/src/components/data_table/sortable.rs
@@ -8,7 +8,7 @@ use super::{
     ColumnHeader, ColumnWidthBounds, DataTable, DataTableColumn, DataTableProps, DataTableState,
     DataTableStyling, DataToCell,
 };
-use crate::utils::gen_util::truncate_text;
+use crate::utils::gen_util::truncate_to_text;
 
 /// Denotes the sort order.
 #[derive(Clone, Copy, Debug, PartialEq, Eq)]
@@ -61,7 +61,7 @@ pub trait SortType: private::Sealed {
             if width == 0 {
                 None
             } else {
-                Some(truncate_text(&c.header(), width))
+                Some(truncate_to_text(&c.header(), width))
             }
         }))
     }
@@ -100,9 +100,9 @@ impl SortType for Sortable {
                             SortOrder::Ascending => UP_ARROW,
                             SortOrder::Descending => DOWN_ARROW,
                         };
-                        Some(truncate_text(&concat_string!(c.header(), arrow), width))
+                        Some(truncate_to_text(&concat_string!(c.header(), arrow), width))
                     } else {
-                        Some(truncate_text(&c.header(), width))
+                        Some(truncate_to_text(&c.header(), width))
                     }
                 }),
         )
diff --git a/src/utils/gen_util.rs b/src/utils/gen_util.rs
index 60311105..02b8bfd4 100644
--- a/src/utils/gen_util.rs
+++ b/src/utils/gen_util.rs
@@ -2,6 +2,7 @@ use std::cmp::Ordering;
 
 use tui::text::{Span, Spans, Text};
 use unicode_segmentation::UnicodeSegmentation;
+use unicode_width::UnicodeWidthStr;
 
 pub const KILO_LIMIT: u64 = 1000;
 pub const MEGA_LIMIT: u64 = 1_000_000;
@@ -96,40 +97,59 @@ pub fn get_decimal_prefix(quantity: u64, unit: &str) -> (f64, String) {
 }
 
 /// Truncates text if it is too long, and adds an ellipsis at the end if needed.
-pub fn truncate_text<'a, U: Into<usize>>(content: &str, width: U) -> Text<'a> {
+pub fn truncate_to_text<'a, U: Into<usize>>(content: &str, width: U) -> Text<'a> {
+    Text {
+        lines: vec![Spans(vec![Span::raw(truncate_str(content, width))])],
+    }
+}
+
+/// Truncates a string with an ellipsis character.
+///
+/// NB: This probably does not handle EVERY case, but I think it handles most cases
+/// we will use this function for fine... hopefully.
+fn truncate_str<U: Into<usize>>(content: &str, width: U) -> String {
     let width = width.into();
-    let mut graphemes = UnicodeSegmentation::graphemes(content, true);
-    let grapheme_len = {
-        let (_, upper) = graphemes.size_hint();
-        match upper {
-            Some(upper) => upper,
-            None => graphemes.clone().count(), // Don't think this ever fires.
-        }
-    };
+    let mut text = String::with_capacity(width);
 
-    let text = if grapheme_len > width {
-        let mut text = String::with_capacity(width);
-        // Truncate with ellipsis.
+    if width > 0 {
+        let mut curr_width = 0;
+        let mut early_break = false;
 
-        // Use a hack to reduce the size to size `width`. Think of it like removing
-        // The last `grapheme_len - width` graphemes, which reduces the length to
-        // `width` long.
-        //
-        // This is a way to get around the currently experimental`advance_back_by`.
-        graphemes.nth_back(grapheme_len - width);
+        // This tracks the length of the last added string - note this does NOT match the grapheme *width*.
+        let mut last_added_str_len = 0;
 
-        text.push_str(graphemes.as_str());
-        text.push('…');
+        // Cases to handle:
+        // - Completes adding the entire string.
+        // - Adds a character up to the boundary, then fails.
+        // - Adds a character not up to the boundary, then fails.
+        // Inspired by https://tomdebruijn.com/posts/rust-string-length-width-calculations/
+        for g in UnicodeSegmentation::graphemes(content, true) {
+            let g_width = if g.contains('\u{200d}') {
+                2
+            } else {
+                UnicodeWidthStr::width(g)
+            };
 
-        text
-    } else {
-        content.to_string()
-    };
+            if curr_width + g_width <= width {
+                curr_width += g_width;
+                last_added_str_len = g.len();
+                text.push_str(g);
+            } else {
+                early_break = true;
+                break;
+            }
+        }
 
-    // TODO: [OPT] maybe add interning here?
-    Text {
-        lines: vec![Spans(vec![Span::raw(text)])],
+        if early_break {
+            if curr_width == width {
+                // Remove the last grapheme cluster added.
+                text.truncate(text.len() - last_added_str_len);
+            }
+            text.push('…');
+        }
     }
+
+    text
 }
 
 #[inline]
@@ -180,7 +200,162 @@ mod test {
     }
 
     #[test]
-    fn test_truncation() {
-        // TODO: Add tests for `truncate_text`
+    fn test_truncate() {
+        let cpu_header = "CPU(c)▲";
+
+        assert_eq!(
+            truncate_str(cpu_header, 8_usize),
+            cpu_header,
+            "should match base string as there is enough room"
+        );
+
+        assert_eq!(
+            truncate_str(cpu_header, 7_usize),
+            cpu_header,
+            "should match base string as there is enough room"
+        );
+
+        assert_eq!(truncate_str(cpu_header, 6_usize), "CPU(c…");
+        assert_eq!(truncate_str(cpu_header, 5_usize), "CPU(…");
+        assert_eq!(truncate_str(cpu_header, 4_usize), "CPU…");
+        assert_eq!(truncate_str(cpu_header, 1_usize), "…");
+        assert_eq!(truncate_str(cpu_header, 0_usize), "");
+    }
+
+    #[test]
+    fn test_truncate_cjk() {
+        let cjk = "施氏食獅史";
+
+        assert_eq!(
+            truncate_str(cjk, 11_usize),
+            cjk,
+            "should match base string as there is enough room"
+        );
+
+        assert_eq!(
+            truncate_str(cjk, 10_usize),
+            cjk,
+            "should match base string as there is enough room"
+        );
+
+        assert_eq!(truncate_str(cjk, 9_usize), "施氏食獅…");
+        assert_eq!(truncate_str(cjk, 8_usize), "施氏食…");
+        assert_eq!(truncate_str(cjk, 2_usize), "…");
+        assert_eq!(truncate_str(cjk, 1_usize), "…");
+        assert_eq!(truncate_str(cjk, 0_usize), "");
+    }
+
+    #[test]
+    fn test_truncate_mixed() {
+        let test = "Test (施氏食獅史) Test";
+
+        assert_eq!(
+            truncate_str(test, 30_usize),
+            test,
+            "should match base string as there is enough room"
+        );
+
+        assert_eq!(
+            truncate_str(test, 22_usize),
+            test,
+            "should match base string as there is just enough room"
+        );
+
+        assert_eq!(
+            truncate_str(test, 21_usize),
+            "Test (施氏食獅史) Te…",
+            "should truncate the t and replace the s with ellipsis"
+        );
+
+        assert_eq!(truncate_str(test, 18_usize), "Test (施氏食獅史)…");
+        assert_eq!(truncate_str(test, 17_usize), "Test (施氏食獅史…");
+        assert_eq!(truncate_str(test, 16_usize), "Test (施氏食獅…");
+        assert_eq!(truncate_str(test, 15_usize), "Test (施氏食獅…");
+        assert_eq!(truncate_str(test, 14_usize), "Test (施氏食…");
+        assert_eq!(truncate_str(test, 13_usize), "Test (施氏食…");
+        assert_eq!(truncate_str(test, 8_usize), "Test (…");
+        assert_eq!(truncate_str(test, 7_usize), "Test (…");
+        assert_eq!(truncate_str(test, 6_usize), "Test …");
+    }
+
+    #[test]
+    fn test_truncate_flags() {
+        let flag = "🇨🇦";
+        assert_eq!(truncate_str(flag, 3_usize), flag);
+        assert_eq!(truncate_str(flag, 2_usize), flag);
+        assert_eq!(truncate_str(flag, 1_usize), "…");
+        assert_eq!(truncate_str(flag, 0_usize), "");
+
+        let flag_text = "oh 🇨🇦";
+        assert_eq!(truncate_str(flag_text, 6_usize), flag_text);
+        assert_eq!(truncate_str(flag_text, 5_usize), flag_text);
+        assert_eq!(truncate_str(flag_text, 4_usize), "oh …");
+
+        let flag_text_wrap = "!🇨🇦!";
+        assert_eq!(truncate_str(flag_text_wrap, 6_usize), flag_text_wrap);
+        assert_eq!(truncate_str(flag_text_wrap, 4_usize), flag_text_wrap);
+        assert_eq!(truncate_str(flag_text_wrap, 3_usize), "!…");
+        assert_eq!(truncate_str(flag_text_wrap, 2_usize), "!…");
+        assert_eq!(truncate_str(flag_text_wrap, 1_usize), "…");
+
+        let flag_cjk = "加拿大🇨🇦";
+        assert_eq!(truncate_str(flag_cjk, 9_usize), flag_cjk);
+        assert_eq!(truncate_str(flag_cjk, 8_usize), flag_cjk);
+        assert_eq!(truncate_str(flag_cjk, 7_usize), "加拿大…");
+        assert_eq!(truncate_str(flag_cjk, 6_usize), "加拿…");
+        assert_eq!(truncate_str(flag_cjk, 5_usize), "加拿…");
+        assert_eq!(truncate_str(flag_cjk, 4_usize), "加…");
+
+        let flag_mix = "🇨🇦加gaa拿naa大daai🇨🇦";
+        assert_eq!(truncate_str(flag_mix, 20_usize), flag_mix);
+        assert_eq!(truncate_str(flag_mix, 19_usize), "🇨🇦加gaa拿naa大daai…");
+        assert_eq!(truncate_str(flag_mix, 18_usize), "🇨🇦加gaa拿naa大daa…");
+        assert_eq!(truncate_str(flag_mix, 17_usize), "🇨🇦加gaa拿naa大da…");
+        assert_eq!(truncate_str(flag_mix, 15_usize), "🇨🇦加gaa拿naa大…");
+        assert_eq!(truncate_str(flag_mix, 14_usize), "🇨🇦加gaa拿naa…");
+        assert_eq!(truncate_str(flag_mix, 13_usize), "🇨🇦加gaa拿naa…");
+        assert_eq!(truncate_str(flag_mix, 3_usize), "🇨🇦…");
+        assert_eq!(truncate_str(flag_mix, 2_usize), "…");
+        assert_eq!(truncate_str(flag_mix, 1_usize), "…");
+        assert_eq!(truncate_str(flag_mix, 0_usize), "");
+    }
+
+    /// This might not be the best way to handle it, but this at least tests that it doesn't crash...
+    #[test]
+    fn test_truncate_hindi() {
+        // cSpell:disable
+        let test = "हिन्दी";
+        assert_eq!(truncate_str(test, 10_usize), test);
+        assert_eq!(truncate_str(test, 6_usize), "हिन्दी");
+        assert_eq!(truncate_str(test, 5_usize), "हिन्दी");
+        assert_eq!(truncate_str(test, 4_usize), "हिन्…");
+        assert_eq!(truncate_str(test, 3_usize), "हि…");
+        assert_eq!(truncate_str(test, 2_usize), "…");
+        assert_eq!(truncate_str(test, 1_usize), "…");
+        assert_eq!(truncate_str(test, 0_usize), "");
+        // cSpell:enable
+    }
+
+    #[test]
+    fn test_truncate_emoji() {
+        let heart = "❤️";
+        assert_eq!(truncate_str(heart, 2_usize), heart);
+        assert_eq!(truncate_str(heart, 1_usize), heart);
+        assert_eq!(truncate_str(heart, 0_usize), "");
+
+        let emote = "💎";
+        assert_eq!(truncate_str(emote, 2_usize), emote);
+        assert_eq!(truncate_str(emote, 1_usize), "…");
+        assert_eq!(truncate_str(emote, 0_usize), "");
+
+        let family = "👨‍👨‍👧‍👦";
+        assert_eq!(truncate_str(family, 2_usize), family);
+        assert_eq!(truncate_str(family, 1_usize), "…");
+        assert_eq!(truncate_str(family, 0_usize), "");
+
+        let scientist = "👩‍🔬";
+        assert_eq!(truncate_str(scientist, 2_usize), scientist);
+        assert_eq!(truncate_str(scientist, 1_usize), "…");
+        assert_eq!(truncate_str(scientist, 0_usize), "");
     }
 }
diff --git a/src/widgets/cpu_graph.rs b/src/widgets/cpu_graph.rs
index 7f0c1495..b3d72c78 100644
--- a/src/widgets/cpu_graph.rs
+++ b/src/widgets/cpu_graph.rs
@@ -11,7 +11,7 @@ use crate::{
         DataToCell,
     },
     data_conversion::CpuWidgetData,
-    utils::gen_util::truncate_text,
+    utils::gen_util::truncate_to_text,
 };
 
 #[derive(Default)]
@@ -88,7 +88,7 @@ impl DataToCell<CpuWidgetColumn> for CpuWidgetTableData {
         // it is too small.
         match &self {
             CpuWidgetTableData::All => match column {
-                CpuWidgetColumn::CPU => Some(truncate_text("All", calculated_width)),
+                CpuWidgetColumn::CPU => Some(truncate_to_text("All", calculated_width)),
                 CpuWidgetColumn::Use => None,
             },
             CpuWidgetTableData::Entry {
@@ -100,13 +100,13 @@ impl DataToCell<CpuWidgetColumn> for CpuWidgetTableData {
                         None
                     } else {
                         match data_type {
-                            CpuDataType::Avg => Some(truncate_text("AVG", calculated_width)),
+                            CpuDataType::Avg => Some(truncate_to_text("AVG", calculated_width)),
                             CpuDataType::Cpu(index) => {
                                 let index_str = index.to_string();
                                 let text = if calculated_width < CPU_HIDE_BREAKPOINT {
-                                    truncate_text(&index_str, calculated_width)
+                                    truncate_to_text(&index_str, calculated_width)
                                 } else {
-                                    truncate_text(
+                                    truncate_to_text(
                                         &concat_string!("CPU", index_str),
                                         calculated_width,
                                     )
@@ -117,7 +117,7 @@ impl DataToCell<CpuWidgetColumn> for CpuWidgetTableData {
                         }
                     }
                 }
-                CpuWidgetColumn::Use => Some(truncate_text(
+                CpuWidgetColumn::Use => Some(truncate_to_text(
                     &format!("{:.0}%", last_entry.round()),
                     calculated_width,
                 )),
diff --git a/src/widgets/disk_table.rs b/src/widgets/disk_table.rs
index 1d4cc604..b2a6db74 100644
--- a/src/widgets/disk_table.rs
+++ b/src/widgets/disk_table.rs
@@ -10,7 +10,7 @@ use crate::{
         ColumnHeader, DataTableColumn, DataTableProps, DataTableStyling, DataToCell, SortColumn,
         SortDataTable, SortDataTableProps, SortOrder, SortsRow,
     },
-    utils::gen_util::{get_decimal_bytes, sort_partial_fn, truncate_text},
+    utils::gen_util::{get_decimal_bytes, sort_partial_fn, truncate_to_text},
 };
 
 #[derive(Clone, Debug)]
@@ -84,13 +84,13 @@ impl ColumnHeader for DiskWidgetColumn {
 impl DataToCell<DiskWidgetColumn> for DiskWidgetData {
     fn to_cell<'a>(&'a self, column: &DiskWidgetColumn, calculated_width: u16) -> Option<Text<'a>> {
         let text = match column {
-            DiskWidgetColumn::Disk => truncate_text(&self.name, calculated_width),
-            DiskWidgetColumn::Mount => truncate_text(&self.mount_point, calculated_width),
-            DiskWidgetColumn::Used => truncate_text(&self.usage(), calculated_width),
-            DiskWidgetColumn::Free => truncate_text(&self.free_space(), calculated_width),
-            DiskWidgetColumn::Total => truncate_text(&self.total_space(), calculated_width),
-            DiskWidgetColumn::IoRead => truncate_text(&self.io_read, calculated_width),
-            DiskWidgetColumn::IoWrite => truncate_text(&self.io_write, calculated_width),
+            DiskWidgetColumn::Disk => truncate_to_text(&self.name, calculated_width),
+            DiskWidgetColumn::Mount => truncate_to_text(&self.mount_point, calculated_width),
+            DiskWidgetColumn::Used => truncate_to_text(&self.usage(), calculated_width),
+            DiskWidgetColumn::Free => truncate_to_text(&self.free_space(), calculated_width),
+            DiskWidgetColumn::Total => truncate_to_text(&self.total_space(), calculated_width),
+            DiskWidgetColumn::IoRead => truncate_to_text(&self.io_read, calculated_width),
+            DiskWidgetColumn::IoWrite => truncate_to_text(&self.io_write, calculated_width),
         };
 
         Some(text)
diff --git a/src/widgets/process_table/proc_widget_data.rs b/src/widgets/process_table/proc_widget_data.rs
index c067f92b..bc61de20 100644
--- a/src/widgets/process_table/proc_widget_data.rs
+++ b/src/widgets/process_table/proc_widget_data.rs
@@ -12,7 +12,7 @@ use crate::{
     canvas::Painter,
     components::data_table::{DataTableColumn, DataToCell},
     data_conversion::{binary_byte_string, dec_bytes_per_second_string, dec_bytes_string},
-    utils::gen_util::truncate_text,
+    utils::gen_util::truncate_to_text,
     Pid,
 };
 
@@ -222,7 +222,7 @@ impl ProcWidgetData {
 impl DataToCell<ProcColumn> for ProcWidgetData {
     fn to_cell<'a>(&'a self, column: &ProcColumn, calculated_width: u16) -> Option<Text<'a>> {
         // TODO: Optimize the string allocations here...
-        Some(truncate_text(
+        Some(truncate_to_text(
             &match column {
                 ProcColumn::CpuPercent => {
                     format!("{:.1}%", self.cpu_usage_percent)
diff --git a/src/widgets/process_table/sort_table.rs b/src/widgets/process_table/sort_table.rs
index 5ace0ecb..24febb29 100644
--- a/src/widgets/process_table/sort_table.rs
+++ b/src/widgets/process_table/sort_table.rs
@@ -4,7 +4,7 @@ use tui::text::Text;
 
 use crate::{
     components::data_table::{ColumnHeader, DataTableColumn, DataToCell},
-    utils::gen_util::truncate_text,
+    utils::gen_util::truncate_to_text,
 };
 
 pub struct SortTableColumn;
@@ -17,7 +17,7 @@ impl ColumnHeader for SortTableColumn {
 
 impl DataToCell<SortTableColumn> for &'static str {
     fn to_cell<'a>(&'a self, _column: &SortTableColumn, calculated_width: u16) -> Option<Text<'a>> {
-        Some(truncate_text(self, calculated_width))
+        Some(truncate_to_text(self, calculated_width))
     }
 
     fn column_widths<C: DataTableColumn<SortTableColumn>>(data: &[Self], _columns: &[C]) -> Vec<u16>
@@ -30,7 +30,7 @@ impl DataToCell<SortTableColumn> for &'static str {
 
 impl DataToCell<SortTableColumn> for Cow<'static, str> {
     fn to_cell<'a>(&'a self, _column: &SortTableColumn, calculated_width: u16) -> Option<Text<'a>> {
-        Some(truncate_text(self, calculated_width))
+        Some(truncate_to_text(self, calculated_width))
     }
 
     fn column_widths<C: DataTableColumn<SortTableColumn>>(data: &[Self], _columns: &[C]) -> Vec<u16>
diff --git a/src/widgets/temperature_table.rs b/src/widgets/temperature_table.rs
index b7ee16a2..42103dd2 100644
--- a/src/widgets/temperature_table.rs
+++ b/src/widgets/temperature_table.rs
@@ -11,7 +11,7 @@ use crate::{
         ColumnHeader, DataTableColumn, DataTableProps, DataTableStyling, DataToCell, SortColumn,
         SortDataTable, SortDataTableProps, SortOrder, SortsRow,
     },
-    utils::gen_util::{sort_partial_fn, truncate_text},
+    utils::gen_util::{sort_partial_fn, truncate_to_text},
 };
 
 #[derive(Clone, Debug)]
@@ -50,8 +50,8 @@ impl TempWidgetData {
 impl DataToCell<TempWidgetColumn> for TempWidgetData {
     fn to_cell<'a>(&'a self, column: &TempWidgetColumn, calculated_width: u16) -> Option<Text<'a>> {
         Some(match column {
-            TempWidgetColumn::Sensor => truncate_text(&self.sensor, calculated_width),
-            TempWidgetColumn::Temp => truncate_text(&self.temperature(), calculated_width),
+            TempWidgetColumn::Sensor => truncate_to_text(&self.sensor, calculated_width),
+            TempWidgetColumn::Temp => truncate_to_text(&self.temperature(), calculated_width),
         })
     }