Get sizes from FontMetrics

src/render/context.rs

@@ -1,5 +1,3 @@
-use std::ffi::CString;
-
 use pangocairo::FontMap;
 use pango::prelude::*;
 use pango;
@@ -9,31 +7,77 @@ use sys::pango as sys_pango;
 use ui_model::StyledLine;
 
 pub struct Context {
-    pango_context: pango::Context,
+    state: ContextState,
 }
 
 impl Context {
-    pub fn new(font_desc: &pango::FontDescription) -> Self {
-        Context { pango_context: create_pango_context(font_desc) }
+    pub fn new(font_desc: pango::FontDescription) -> Self {
+        Context { state: ContextState::new(font_desc) }
     }
 
-    pub fn update(&mut self, font_desc: &pango::FontDescription) {
-        self.pango_context = create_pango_context(font_desc);
+    pub fn update(&mut self, font_desc: pango::FontDescription) {
+        self.state = ContextState::new(font_desc);
     }
 
     pub fn itemize(&self, line: &StyledLine) -> Vec<sys_pango::Item> {
         sys_pango::pango_itemize(
-            &self.pango_context,
+            &self.state.pango_context,
             line.line_str.trim_right(),
             &line.attr_list,
         )
     }
+
+    #[inline]
+    pub fn font_description(&self) -> &pango::FontDescription {
+        &self.state.font_desc
+    }
+
+    #[inline]
+    pub fn ascent(&self) -> f64 {
+        self.state.cell_metrics.ascent
+    }
+
+    #[inline]
+    pub fn cell_metrics(&self) -> &CellMetrics {
+        &self.state.cell_metrics
+    }
 }
 
-fn create_pango_context(font_desc: &pango::FontDescription) -> pango::Context {
-    let font_map = FontMap::get_default();
-    let pango_context = font_map.create_context().unwrap();
-    pango_context.set_font_description(&font_desc);
-
-    pango_context
+struct ContextState {
+    pango_context: pango::Context,
+    cell_metrics: CellMetrics,
+    font_desc: pango::FontDescription,
+}
+
+impl ContextState {
+    pub fn new(font_desc: pango::FontDescription) -> Self {
+        let font_map = FontMap::get_default();
+        let pango_context = font_map.create_context().unwrap();
+        pango_context.set_font_description(&font_desc);
+
+        let font_metrics = pango_context.get_metrics(None, None).unwrap();
+
+        ContextState {
+            pango_context,
+            cell_metrics: CellMetrics::new(&font_metrics),
+            font_desc,
+        }
+    }
+}
+
+pub struct CellMetrics {
+    pub line_height: f64,
+    pub char_width: f64,
+    pub ascent: f64,
+}
+
+impl CellMetrics {
+    fn new(font_metrics: &pango::FontMetrics) -> Self {
+        CellMetrics {
+            ascent: font_metrics.get_ascent() as f64 / pango::SCALE as f64,
+            line_height: (font_metrics.get_ascent() + font_metrics.get_descent()) as f64 /
+                pango::SCALE as f64,
+            char_width: font_metrics.get_approximate_digit_width() as f64 / pango::SCALE as f64,
+        }
+    }
 }

src/render/mod.rs

@@ -1,6 +1,7 @@
 mod context;
 
 pub use self::context::Context;
+pub use self::context::CellMetrics;
 
 use color;
 use sys::pango::*;
@@ -11,10 +12,9 @@ use ui_model;
 
 pub fn render(
     ctx: &cairo::Context,
+    font_ctx: &context::Context, 
     ui_model: &ui_model::UiModel,
     color_model: &color::ColorModel,
-    line_height: f64,
-    char_width: f64,
 ) {
     ctx.set_source_rgb(
         color_model.bg_color.0,
@@ -23,16 +23,25 @@ pub fn render(
     );
     ctx.paint();
 
-    let mut line_y = line_height;
+    let &CellMetrics {line_height, char_width, ..} = font_ctx.cell_metrics();
+    let mut line_y = 0.0;
+    let ascent = font_ctx.ascent();
 
     for line in ui_model.model() {
         let mut line_x = 0.0;
 
         for i in 0..line.line.len() {
-            ctx.move_to(line_x, line_y);
+            let (bg, fg) = color_model.cell_colors(&line.line[i]);
+
+            if let Some(bg) = bg {
+                ctx.set_source_rgb(bg.0, bg.1, bg.2);
+                ctx.rectangle(line_x, line_y, char_width, line_height);
+                ctx.fill();
+            }
+
             if let Some(item) = line.item_line[i].as_ref() {
                 if let Some(ref glyphs) = item.glyphs {
-                    let (_, fg) = color_model.cell_colors(&line.line[i]);
+                    ctx.move_to(line_x, line_y + ascent);
                     ctx.set_source_rgb(fg.0, fg.1, fg.2);
                     ctx.show_glyph_string(item.font(), glyphs);
                 }