Perform clear and buffer swap before showing window

This should fill window with background color while it is offscreen instead of
showing it with uninitilized surface and then performing `clear`. So, the new
behavior should prevent glitches during startup. e.g. content of the windows
below, garbage from drivers and so on.

CHANGELOG.md

@@ -16,6 +16,7 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 - Text Cursor position when scrolling
 - Performance issues while resizing Alacritty
 - First unfullscreen action ignored on window launched in fullscreen mode
+- The window is now filled with the background color before displaying
 
 ## 0.3.3
 

alacritty_terminal/src/display.rs

@@ -224,6 +224,32 @@ impl Display {
             api.clear(background_color);
         });
 
+        // We should call `clear` when window is offscreen, so when `window.show()` happens it
+        // would be with background color instead of uninitialized surface.
+        window.swap_buffers()?;
+
+        window.show();
+
+        // Set window position
+        //
+        // TODO: replace `set_position` with `with_position` once available
+        // Upstream issue: https://github.com/tomaka/winit/issues/806
+        if let Some(position) = config.window.position {
+            let physical = PhysicalPosition::from((position.x, position.y));
+            let logical = physical.to_logical(window.hidpi_factor());
+            window.set_position(logical);
+        }
+
+        #[allow(clippy::single_match)]
+        match config.window.startup_mode() {
+            StartupMode::Fullscreen => window.set_fullscreen(true),
+            #[cfg(target_os = "macos")]
+            StartupMode::SimpleFullscreen => window.set_simple_fullscreen(true),
+            #[cfg(not(any(target_os = "macos", windows)))]
+            StartupMode::Maximized if window.is_x11() => window.set_maximized(true),
+            _ => (),
+        }
+
         Ok(Display {
             window,
             renderer,

alacritty_terminal/src/window.rs

@@ -17,7 +17,7 @@ use std::ffi::c_void;
 use std::fmt::Display;
 
 use crate::gl;
-use glutin::dpi::{LogicalPosition, LogicalSize, PhysicalPosition, PhysicalSize};
+use glutin::dpi::{LogicalPosition, LogicalSize, PhysicalSize};
 #[cfg(target_os = "macos")]
 use glutin::os::macos::WindowExt;
 #[cfg(not(any(target_os = "macos", windows)))]
@@ -158,38 +158,6 @@ impl Window {
             create_gl_window(window_builder.clone(), &event_loop, false, dimensions)
                 .or_else(|_| create_gl_window(window_builder, &event_loop, true, dimensions))?;
         let window = windowed_context.window();
-        window.show();
-
-        // Maximize window after mapping in X11
-        #[cfg(not(any(target_os = "macos", windows)))]
-        {
-            if event_loop.is_x11() && config.window.startup_mode() == StartupMode::Maximized {
-                window.set_maximized(true);
-            }
-        }
-
-        // Set window position
-        //
-        // TODO: replace `set_position` with `with_position` once available
-        // Upstream issue: https://github.com/tomaka/winit/issues/806
-        if let Some(position) = config.window.position {
-            let physical = PhysicalPosition::from((position.x, position.y));
-            let logical = physical.to_logical(window.get_hidpi_factor());
-            window.set_position(logical);
-        }
-
-        if let StartupMode::Fullscreen = config.window.startup_mode() {
-            let current_monitor = window.get_current_monitor();
-            window.set_fullscreen(Some(current_monitor));
-        }
-
-        #[cfg(target_os = "macos")]
-        {
-            if let StartupMode::SimpleFullscreen = config.window.startup_mode() {
-                use glutin::os::macos::WindowExt;
-                window.set_simple_fullscreen(true);
-            }
-        }
 
         // Text cursor
         window.set_cursor(MouseCursor::Text);
@@ -250,6 +218,12 @@ impl Window {
         self.windowed_context.resize(size);
     }
 
+    /// Show window
+    #[inline]
+    pub fn show(&self) {
+        self.window().show();
+    }
+
     /// Block waiting for events
     #[inline]
     pub fn wait_events<F>(&mut self, func: F)
@@ -379,6 +353,10 @@ impl Window {
         self.window().set_ime_spot(pos);
     }
 
+    pub fn set_position(&self, pos: LogicalPosition) {
+        self.window().set_position(pos);
+    }
+
     #[cfg(not(any(target_os = "macos", target_os = "windows")))]
     pub fn get_window_id(&self) -> Option<usize> {
         match self.window().get_xlib_window() {
@@ -387,6 +365,11 @@ impl Window {
         }
     }
 
+    #[cfg(not(any(target_os = "macos", target_os = "windows")))]
+    pub fn is_x11(&self) -> bool {
+        self.event_loop.is_x11()
+    }
+
     #[cfg(any(target_os = "macos", target_os = "windows"))]
     pub fn get_window_id(&self) -> Option<usize> {
         None
@@ -408,6 +391,10 @@ impl Window {
         }
     }
 
+    pub fn set_maximized(&self, maximized: bool) {
+        self.window().set_maximized(maximized);
+    }
+
     #[cfg(target_os = "macos")]
     pub fn set_simple_fullscreen(&self, fullscreen: bool) {
         use glutin::os::macos::WindowExt;