fix(borders): properly handle in-viewport borderless panes (#697)

* fix(borders): properly handle in-viewport borderless panes

* style(fmt): make clippy happy

* fix(borders): properly handle panes outside the viewport on startup

* style(fmt): not this time, clippy

* docs(changelog): document change

CHANGELOG.md

@@ -9,6 +9,7 @@ The format is based on [Keep a Changelog](https://keepachangelog.com/en/1.0.0/)
 * Fix bug when in some cases closing a tab would not clear the previous pane's contents (https://github.com/zellij-org/zellij/pull/684)
 * Fix bug where tabs would sometimes be created with the wrong index in their name (https://github.com/zellij-org/zellij/pull/686)
 * Fix bug where wide chars would mess up pane titles (https://github.com/zellij-org/zellij/pull/698)
+* Fix various borderless-frame in viewport bugs (https://github.com/zellij-org/zellij/pull/697)
 
 ## [0.16.0] - 2021-08-31
 * Plugins don't crash zellij anymore on receiving mouse events (https://github.com/zellij-org/zellij/pull/620)

zellij-server/src/panes/terminal_pane.rs

@@ -253,7 +253,9 @@ impl Pane for TerminalPane {
                     color: self.frame_color,
                 };
                 if &frame != last_frame {
-                    vte_output.push_str(&frame.render());
+                    if !self.borderless {
+                        vte_output.push_str(&frame.render());
+                    }
                     self.frame = Some(frame);
                 }
             }

zellij-server/src/tab.rs

@@ -684,22 +684,35 @@ impl Tab {
     }
     pub fn set_pane_frames(&mut self, draw_pane_frames: bool) {
         self.draw_pane_frames = draw_pane_frames;
+        self.should_clear_display_before_rendering = true;
+        let viewport = self.viewport;
         for (pane_id, pane) in self.panes.iter_mut() {
-            pane.set_frame(draw_pane_frames);
-            if draw_pane_frames {
+            if !pane.borderless() {
+                pane.set_frame(draw_pane_frames);
+            }
+
+            #[allow(clippy::if_same_then_else)]
+            if draw_pane_frames & !pane.borderless() {
+                // there's definitely a frame around this pane, offset its contents
                 pane.set_content_offset(Offset::frame(1));
+            } else if draw_pane_frames && pane.borderless() {
+                // there's no frame around this pane, and the tab isn't handling the boundaries
+                // between panes (they each draw their own frames as they please)
+                // this one doesn't - do not offset its content
+                pane.set_content_offset(Offset::default());
+            } else if !is_inside_viewport(&viewport, pane) {
+                // this pane is outside the viewport and has no border - it should not have an offset
+                pane.set_content_offset(Offset::default());
             } else {
+                // no draw_pane_frames and this pane should have a separation to other panes
+                // according to its position in the viewport (eg. no separation if its at the
+                // viewport bottom) - offset its content accordingly
                 let position_and_size = pane.current_geom();
                 let (pane_columns_offset, pane_rows_offset) =
                     pane_content_offset(&position_and_size, &self.viewport);
                 pane.set_content_offset(Offset::shift(pane_rows_offset, pane_columns_offset));
             }
 
-            // FIXME: this should also override the above logic
-            if pane.borderless() {
-                pane.set_content_offset(Offset::default());
-            }
-
             // FIXME: This, and all other `set_terminal_size_using_fd` calls, would be best in
             // `TerminalPane::reflow_lines`
             if let PaneId::Terminal(pid) = pane_id {
@@ -2345,10 +2358,9 @@ impl Tab {
             .unwrap();
     }
     fn is_inside_viewport(&self, pane_id: &PaneId) -> bool {
-        let pane_position_and_size = self.panes.get(pane_id).unwrap().current_geom();
-        pane_position_and_size.y >= self.viewport.y
-            && pane_position_and_size.y + pane_position_and_size.rows.as_usize()
-                <= self.viewport.y + self.viewport.rows
+        // this is mostly separated to an outside function in order to allow us to pass a clone to
+        // it sometimes when we need to get around the borrow checker
+        is_inside_viewport(&self.viewport, self.panes.get(pane_id).unwrap())
     }
     fn offset_viewport(&mut self, position_and_size: &Viewport) {
         if position_and_size.x == self.viewport.x
@@ -2378,6 +2390,14 @@ impl Tab {
     }
 }
 
+#[allow(clippy::borrowed_box)]
+fn is_inside_viewport(viewport: &Viewport, pane: &Box<dyn Pane>) -> bool {
+    let pane_position_and_size = pane.current_geom();
+    pane_position_and_size.y >= viewport.y
+        && pane_position_and_size.y + pane_position_and_size.rows.as_usize()
+            <= viewport.y + viewport.rows
+}
+
 #[cfg(test)]
 #[path = "./unit/tab_tests.rs"]
 mod tab_tests;