From 5a5d08080cd6d5030481425b4a323e34e2fe0d8a Mon Sep 17 00:00:00 2001
From: Wez Furlong <wez@wezfurlong.org>
Date: Wed, 3 Mar 2021 23:29:18 -0800
Subject: [PATCH] gui: allow dragging the window by non-tab areas in tab bar

I've only tested this on macos, but it should be cross platform,
with the caveat that Wayland doesn't let a window position itself,
so this won't work there.
---
 wezterm-gui/src/termwindow/mod.rs        |  3 +++
 wezterm-gui/src/termwindow/mouseevent.rs | 30 +++++++++++++++++++++++-
 2 files changed, 32 insertions(+), 1 deletion(-)

diff --git a/wezterm-gui/src/termwindow/mod.rs b/wezterm-gui/src/termwindow/mod.rs
index e3f9fefde..268461c34 100644
--- a/wezterm-gui/src/termwindow/mod.rs
+++ b/wezterm-gui/src/termwindow/mod.rs
@@ -114,6 +114,7 @@ pub struct TermWindow {
     last_mouse_terminal_coords: (usize, StableRowIndex),
     scroll_drag_start: Option<isize>,
     split_drag_start: Option<PositionedSplit>,
+    window_drag_position: Option<MouseEvent>,
     prev_cursor: PrevCursorPos,
     last_scroll_info: RenderableDimensions,
 
@@ -260,6 +261,7 @@ impl WindowCallbacks for TermWindow {
             last_mouse_terminal_coords: self.last_mouse_terminal_coords.clone(),
             scroll_drag_start: self.scroll_drag_start.clone(),
             split_drag_start: self.split_drag_start.clone(),
+            window_drag_position: None,
             prev_cursor: self.prev_cursor.clone(),
             last_scroll_info: self.last_scroll_info.clone(),
             clipboard_contents: Arc::clone(&clipboard_contents),
@@ -474,6 +476,7 @@ impl TermWindow {
                 last_mouse_terminal_coords: (0, 0),
                 scroll_drag_start: None,
                 split_drag_start: None,
+                window_drag_position: None,
                 prev_cursor: PrevCursorPos::new(),
                 last_scroll_info: RenderableDimensions::default(),
                 clipboard_contents: Arc::clone(&clipboard_contents),
diff --git a/wezterm-gui/src/termwindow/mouseevent.rs b/wezterm-gui/src/termwindow/mouseevent.rs
index 5e5f57fd4..508ac74ed 100644
--- a/wezterm-gui/src/termwindow/mouseevent.rs
+++ b/wezterm-gui/src/termwindow/mouseevent.rs
@@ -62,6 +62,10 @@ impl super::TermWindow {
                     // Completed a split drag
                     return;
                 }
+                if press == &MousePress::Left && self.window_drag_position.take().is_some() {
+                    // Completed a window drag
+                    return;
+                }
             }
 
             WMEK::Press(ref press) => {
@@ -96,6 +100,27 @@ impl super::TermWindow {
             }
 
             WMEK::Move => {
+                if let Some(start) = self.window_drag_position.as_ref() {
+                    // Dragging the window
+                    // Compute the distance since the initial event
+                    let delta_x = start.screen_coords.x - event.screen_coords.x;
+                    let delta_y = start.screen_coords.y - event.screen_coords.y;
+
+                    // Now compute a new window position.
+                    // We don't have a direct way to get the position,
+                    // but we can infer it by comparing the mouse coords
+                    // with the screen coords in the initial event.
+                    // This computes the original top_left position,
+                    // and applies the total drag delta to it.
+                    let top_left = ::window::ScreenPoint::new(
+                        (start.screen_coords.x - start.coords.x) - delta_x,
+                        (start.screen_coords.y - start.coords.y) - delta_y,
+                    );
+                    // and now tell the window to go there
+                    context.set_window_position(top_left);
+                    return;
+                }
+
                 let current_viewport = self.get_viewport(pane.pane_id());
                 if let Some(from_top) = self.scroll_drag_start.as_ref() {
                     // Dragging the scroll bar
@@ -171,7 +196,10 @@ impl super::TermWindow {
                 TabBarItem::NewTabButton => {
                     self.spawn_tab(&SpawnTabDomain::CurrentPaneDomain);
                 }
-                TabBarItem::None => {}
+                TabBarItem::None => {
+                    // Potentially starting a drag by the tab bar
+                    self.window_drag_position.replace(event.clone());
+                }
             },
             WMEK::Press(MousePress::Middle) => match self.tab_bar.hit_test(x) {
                 TabBarItem::Tab(tab_idx) => {