Use pango for text layout

Cargo.lock

@@ -909,6 +909,58 @@ version = "1.8.0"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "692fcb63b64b1758029e0a96ee63e049ce8c5948587f2f7208df04625e5f6b56"
 
+[[package]]
+name = "pango"
+version = "0.14.8"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "546fd59801e5ca735af82839007edd226fe7d3bb06433ec48072be4439c28581"
+dependencies = [
+ "bitflags",
+ "glib",
+ "libc",
+ "once_cell",
+ "pango-sys",
+]
+
+[[package]]
+name = "pango-sys"
+version = "0.14.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "2367099ca5e761546ba1d501955079f097caa186bb53ce0f718dca99ac1942fe"
+dependencies = [
+ "glib-sys",
+ "gobject-sys",
+ "libc",
+ "system-deps",
+]
+
+[[package]]
+name = "pangocairo"
+version = "0.14.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "f03ac1e8d456f8f436168aeac41201f0bf49d1dc6c8d01bfb04de2cca25df631"
+dependencies = [
+ "bitflags",
+ "cairo-rs",
+ "glib",
+ "libc",
+ "pango",
+ "pangocairo-sys",
+]
+
+[[package]]
+name = "pangocairo-sys"
+version = "0.14.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "f3b9b679ad5c8503e3e533ce06e1619d033274b246e977a6fa1655a6c6ef2b51"
+dependencies = [
+ "cairo-sys-rs",
+ "glib-sys",
+ "libc",
+ "pango-sys",
+ "system-deps",
+]
+
 [[package]]
 name = "parking_lot"
 version = "0.11.2"
@@ -1099,6 +1151,7 @@ dependencies = [
  "log",
  "mlua",
  "nix 0.23.0",
+ "pangocairo",
  "rayon",
  "walkdir",
  "winit",

Cargo.toml

@@ -13,6 +13,7 @@ rayon = "1.5.1"
 winit = {git="https://github.com/rust-windowing/winit"}
 cairo-rs = {version = "0.14.0", features = ["xcb"]}
 cairo-sys-rs = {version = "0.14.0", features = ["xcb"]}
+pangocairo = "0.14.0"
 xcb = "0.9.0"
 xcb-util = {version = "0.3.0", features = ["ewmh", "icccm"]}
 

src/ui/painter.rs

@@ -64,7 +64,7 @@ impl<'a> Painter<'a> {
         ctx.fill().unwrap();
 
         // draw text
-        ctx.move_to(x + 0.2, y + 0.8);
+        ctx.move_to(x + 0.2, y+0.8);
         ctx.theme_text(&input, false, &[], &self.theme);
     }
 

src/ui/theme.rs

@@ -1,8 +1,11 @@
+use log::debug;
+use pangocairo::pango::{self, AttrList, Attribute, FontDescription};
+
 // (r,g,b,a)
 #[derive(Clone, Copy)]
 pub struct Color(f64, f64, f64, f64);
 // (name, size)
-pub struct Font(String, f64);
+pub struct Font(String, i32);
 
 struct ColorScheme {
     base: Color,
@@ -44,7 +47,7 @@ impl Default for Theme {
 
         Theme {
             colors,
-            font: Font("sans".into(), 17.0),
+            font: Font("Sans Regular".into(), 13),
 
             border: 2.0,
             divider: 3.0
@@ -94,27 +97,40 @@ impl ThemedContextExt for cairo::Context {
     }
 
     fn theme_text(&self, text: &str, selected: bool, indices: &[usize], theme: &Theme) {
+        self.save().unwrap();
+
+        self.identity_matrix(); // this is extremely important otherwise pango
+                                // gets totally confused by active cairo transformations
+                                // which then messes with font size, size of attributes, etc
+
         let Color(r,g,b,a) = if selected { theme.colors.text_highlight }
                              else        { theme.colors.text };
         self.set_source_rgba(r,g,b,a);
 
-        let font_size = self.device_to_user_point(theme.font.1);
+        let layout = pangocairo::create_layout(self).unwrap();
-        self.set_font_size(font_size);
+        pangocairo::update_layout(self, &layout);
 
-        for i in 0..text.len() {
+        let attrlist = AttrList::new();
-            if indices.contains(&i) {
+        for i in indices {
-                self.select_font_face(&theme.font.0,
+            let (start, end) = ((*i as u32), (*i as u32)+1);
-                                      cairo::FontSlant::Italic,
+            let mut attr = Attribute::new_underline(pangocairo::pango::Underline::Single);
-                                      cairo::FontWeight::Normal);
+            attr.set_start_index(start);
-            } else {
+            attr.set_end_index(end);
-                self.select_font_face(&theme.font.0,
+            attrlist.insert(attr);
-                                      cairo::FontSlant::Normal,
-                                      cairo::FontWeight::Normal);
-            }
-
-            self.show_text(&text[i..i+1])
-                .expect("Could not draw themed text");
         }
+        layout.set_attributes(Some(&attrlist));
+
+        let mut font = FontDescription::default();
+        font.set_family(&theme.font.0);
+        font.set_size(theme.font.1*pango::SCALE);
+        layout.set_font_description(Some(&font));
+
+        layout.set_text(text);
+
+        let (_width,height) = layout.size();
+        self.rel_move_to(0.0, -(height as f64)/(pango::SCALE as f64));
+        pangocairo::show_layout(self, &layout);
+        self.restore().unwrap();
     }
 
     fn device_to_user_point(&self, point: f64) -> f64 {