From bd02d33bf5f65fc2bc3918866e38f82b52b1d29a Mon Sep 17 00:00:00 2001
From: Wez Furlong <wez@wezfurlong.org>
Date: Fri, 1 Apr 2022 09:31:59 -0700
Subject: [PATCH] tab bar: constrain to constant height

The tab bar height could vary by a couple of pixels depending on the
text shown inside it, which results in visual jitter as the title bar
changes.

Avoid that: always return our constant reserved amount of space for the
tab bar, even if it means that there are a couple of pixels "wasted".

cc: @davidrios
---
 wezterm-gui/src/termwindow/mod.rs    |  2 +-
 wezterm-gui/src/termwindow/render.rs | 21 +++++----------------
 2 files changed, 6 insertions(+), 17 deletions(-)

diff --git a/wezterm-gui/src/termwindow/mod.rs b/wezterm-gui/src/termwindow/mod.rs
index a0caa3ede..dd72e42df 100644
--- a/wezterm-gui/src/termwindow/mod.rs
+++ b/wezterm-gui/src/termwindow/mod.rs
@@ -639,7 +639,7 @@ impl TermWindow {
         // for the tab bar state.
         let show_tab_bar = config.enable_tab_bar && !config.hide_tab_bar_if_only_one_tab;
         let tab_bar_height = if show_tab_bar {
-            Self::tab_bar_pixel_height_impl(&config, &fontconfig, &render_metrics, None)? as usize
+            Self::tab_bar_pixel_height_impl(&config, &fontconfig, &render_metrics)? as usize
         } else {
             0
         };
diff --git a/wezterm-gui/src/termwindow/render.rs b/wezterm-gui/src/termwindow/render.rs
index 0e702eeea..1eacb8668 100644
--- a/wezterm-gui/src/termwindow/render.rs
+++ b/wezterm-gui/src/termwindow/render.rs
@@ -442,29 +442,17 @@ impl super::TermWindow {
         config: &ConfigHandle,
         fontconfig: &wezterm_font::FontConfiguration,
         render_metrics: &RenderMetrics,
-        fancy_tab_bar_height: Option<f32>,
     ) -> anyhow::Result<f32> {
         if config.use_fancy_tab_bar {
-            if let Some(tab_bar_height) = fancy_tab_bar_height {
-                Ok(tab_bar_height)
-            } else {
-                let font = fontconfig.title_font()?;
-                Ok((font.metrics().cell_height.get() as f32 * 1.75).ceil())
-            }
+            let font = fontconfig.title_font()?;
+            Ok((font.metrics().cell_height.get() as f32 * 1.75).ceil())
         } else {
             Ok(render_metrics.cell_size.height as f32)
         }
     }
 
     pub fn tab_bar_pixel_height(&self) -> anyhow::Result<f32> {
-        Self::tab_bar_pixel_height_impl(
-            &self.config,
-            &self.fonts,
-            &self.render_metrics,
-            self.fancy_tab_bar
-                .as_ref()
-                .map(|elem| elem.content_rect.size.height),
-        )
+        Self::tab_bar_pixel_height_impl(&self.config, &self.fonts, &self.render_metrics)
     }
 
     pub fn invalidate_fancy_tab_bar(&mut self) {
@@ -472,6 +460,7 @@ impl super::TermWindow {
     }
 
     pub fn build_fancy_tab_bar(&self, palette: &ColorPalette) -> anyhow::Result<ComputedElement> {
+        let tab_bar_height = self.tab_bar_pixel_height()?;
         let font = self.fonts.title_font()?;
         let metrics = RenderMetrics::with_font_metrics(&font.metrics());
         let items = self.tab_bar.items();
@@ -807,7 +796,7 @@ impl super::TermWindow {
                     border.left.get() as f32,
                     0.,
                     self.dimensions.pixel_width as f32 - (border.left + border.right).get() as f32,
-                    self.dimensions.pixel_height as f32 - (border.top + border.bottom).get() as f32,
+                    tab_bar_height,
                 ),
                 metrics: &metrics,
                 gl_state: self.render_state.as_ref().unwrap(),