From c1c72e23a3b6c978fadc9a75f506feeb4ca0a498 Mon Sep 17 00:00:00 2001
From: Isaac Freund <mail@isaacfreund.com>
Date: Wed, 1 Mar 2023 12:16:53 +0100
Subject: Root: fix more fullscreen bugs

Moving fullscreen views between outputs now works properly.
A case in which we did not inform the client that it is no longer
fullscreen has been fixed as well.
---
 river/Output.zig |  3 +++
 river/Root.zig   | 64 +++++++++++++++++++++++++++++++-------------------------
 2 files changed, 39 insertions(+), 28 deletions(-)

diff --git a/river/Output.zig b/river/Output.zig
index e300598..a297bc9 100644
--- a/river/Output.zig
+++ b/river/Output.zig
@@ -119,6 +119,9 @@ pending: struct {
     ///
     /// This includes both floating/fullscreen views and those arranged in the layout.
     wm_stack: wl.list.Head(View, .pending_wm_stack_link),
+    /// The view to be made fullscreen, if any.
+    /// This state should only be read/written inside Root.applyPending()
+    fullscreen: ?*View = null,
 },
 
 /// The state most recently sent to the layout generator and clients.
diff --git a/river/Root.zig b/river/Root.zig
index 7603705..6223b0a 100644
--- a/river/Root.zig
+++ b/river/Root.zig
@@ -391,7 +391,7 @@ pub fn applyPending(root: *Self) void {
 
             // Iterate the focus stack in order to ensure the currently focused/most
             // recently focused view that requests fullscreen is given fullscreen.
-            var fullscreen_found = false;
+            output.pending.fullscreen = null;
             {
                 var it = output.pending.focus_stack.iterator(.forward);
                 while (it.next()) |view| {
@@ -405,33 +405,10 @@ pub fn applyPending(root: *Self) void {
                         view.pending.box = view.float_box;
                     }
 
-                    if (!fullscreen_found and view.pending.fullscreen and
+                    if (output.pending.fullscreen == null and view.pending.fullscreen and
                         view.pending.tags & output.pending.tags != 0)
                     {
-                        fullscreen_found = true;
-                        if (output.inflight.fullscreen != view) {
-                            if (output.inflight.fullscreen) |old| {
-                                old.setFullscreen(false);
-                                old.pending.box = old.post_fullscreen_box;
-                                old.inflight.box = old.pending.box;
-                            }
-
-                            output.inflight.fullscreen = view;
-
-                            view.setFullscreen(true);
-                            view.post_fullscreen_box = view.pending.box;
-                            view.pending.box = .{
-                                .x = 0,
-                                .y = 0,
-                                .width = undefined,
-                                .height = undefined,
-                            };
-                            output.wlr_output.effectiveResolution(
-                                &view.pending.box.width,
-                                &view.pending.box.height,
-                            );
-                            view.inflight.box = view.pending.box;
-                        }
+                        output.pending.fullscreen = view;
                     }
 
                     view.inflight_focus_stack_link.remove();
@@ -440,8 +417,12 @@ pub fn applyPending(root: *Self) void {
                     view.inflight = view.pending;
                 }
             }
-            if (!fullscreen_found) {
-                output.inflight.fullscreen = null;
+            if (output.pending.fullscreen != output.inflight.fullscreen) {
+                if (output.inflight.fullscreen) |view| {
+                    view.setFullscreen(false);
+                    view.pending.box = view.post_fullscreen_box;
+                    view.inflight.box = view.pending.box;
+                }
             }
 
             {
@@ -456,6 +437,33 @@ pub fn applyPending(root: *Self) void {
         }
     }
 
+    {
+        // This must be done after the original loop completes to handle the
+        // case where a fullscreen is moved between outputs.
+        var output_it = root.outputs.first;
+        while (output_it) |node| : (output_it = node.next) {
+            const output = &node.data;
+            if (output.pending.fullscreen != output.inflight.fullscreen) {
+                if (output.pending.fullscreen) |view| {
+                    view.setFullscreen(true);
+                    view.post_fullscreen_box = view.pending.box;
+                    view.pending.box = .{
+                        .x = 0,
+                        .y = 0,
+                        .width = undefined,
+                        .height = undefined,
+                    };
+                    output.wlr_output.effectiveResolution(
+                        &view.pending.box.width,
+                        &view.pending.box.height,
+                    );
+                    view.inflight.box = view.pending.box;
+                }
+                output.inflight.fullscreen = output.pending.fullscreen;
+            }
+        }
+    }
+
     {
         // Layout demands can't be sent until after the inflight stacks of
         // all outputs have been updated.
-- 
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