feat: commit transaction system

Author: dy-tea

include/Server.h

@@ -14,6 +14,7 @@
 #include "PointerConstraint.h"
 #include "Seat.h"
 #include "Toplevel.h"
+#include "Transaction.h"
 #include "Workspace.h"
 #include "WorkspaceManager.h"
 #include "wlr.h"
@@ -52,6 +53,7 @@ struct Server {
 
     OutputManager *output_manager;
     WorkspaceManager *workspace_manager;
+    TransactionManager *transaction_manager;
 
     struct {
         wlr_scene_tree *background;

include/Toplevel.h

@@ -80,6 +80,9 @@ struct Toplevel {
     wlr_box geometry{};
     wlr_box saved_geometry{};
 
+    bool in_transaction{false};
+    wlr_box pending_transaction_geometry{};
+
     std::string tag{};
 
     Toplevel(Server *server, wlr_xdg_toplevel *wlr_xdg_toplevel);

include/Transaction.h

@@ -0,0 +1,73 @@
+#pragma once
+
+#include "wlr.h"
+#include <vector>
+#include <unordered_set>
+
+struct PendingGeometry {
+    struct Toplevel *toplevel;
+    wlr_box geometry;
+    uint32_t serial;
+    bool committed{false};
+};
+
+struct Transaction {
+    struct Server *server;
+    std::vector<PendingGeometry> pending_changes;
+    std::unordered_set<struct Toplevel *> waiting_for_commit;
+    wl_event_source *timeout_timer{nullptr};
+    bool committed{false};
+
+    wl_listener surface_commit;
+
+    explicit Transaction(struct Server *server);
+    ~Transaction();
+
+    // Add a geometry change to this transaction
+    void add_change(Toplevel *toplevel, const wlr_box &geometry);
+    void add_change(Toplevel *toplevel, int x, int y, int width, int height);
+
+    // Commit the transaction (send configure events and wait for responses)
+    void commit();
+
+    // Apply all changes immediately (called after all surfaces commit or timeout)
+    void apply();
+
+    // Check if a toplevel is part of this transaction
+    bool contains(Toplevel *toplevel) const;
+
+    // Handle surface commit from a toplevel
+    void handle_commit(Toplevel *toplevel);
+    
+    // Remove a toplevel from this transaction (e.g., when it unmaps)
+    void remove_toplevel(Toplevel *toplevel);
+
+private:
+    void setup_timeout();
+    void cleanup();
+    static int on_timeout(void *data);
+};
+
+// Transaction manager handles the active transaction
+struct TransactionManager {
+    Server *server;
+    Transaction *active_transaction{nullptr};
+
+    explicit TransactionManager(Server *server);
+    ~TransactionManager();
+
+    // Start a new transaction (commits any existing one first)
+    Transaction *begin();
+
+    // Get the current active transaction, or nullptr if none
+    Transaction *current() const { return active_transaction; }
+
+    // Check if a transaction is currently active
+    bool is_active() const { return active_transaction != nullptr; }
+
+    // Commit and apply the current transaction
+    void commit();
+    
+    // Remove a toplevel from any active transaction
+    void remove_toplevel(Toplevel *toplevel);
+};

meson.build

@@ -136,6 +136,7 @@ executable(
     'src' / 'InputMethodPopup.cpp',
     'src' / 'TearingController.cpp',
     'src' / 'ActivationToken.cpp',
+    'src' / 'Transaction.cpp',
     protocol_sources,
   ],
   include_directories: include,

src/BSPTree.cpp

@@ -1,5 +1,7 @@
 #include "BSPTree.h"
+#include "Server.h"
 #include "Toplevel.h"
+#include "Transaction.h"
 #include "Workspace.h"
 #include <algorithm>
 #include <functional>
@@ -202,8 +204,14 @@ void BSPTree::apply_layout(const wlr_box &bounds) {
     if (!root)
         return;
 
+    // start transaction for atomic updates
+    workspace->output->server->transaction_manager->begin();
+
     calculate_layout(root.get(), bounds);
     apply_geometries(root.get());
+
+    // Commit the transaction to apply all changes atomically
+    workspace->output->server->transaction_manager->commit();
 }
 
 BSPNode *BSPTree::find_node(Toplevel *toplevel) {

src/Server.cpp

@@ -592,6 +592,9 @@ Server::Server(Config *config) : config(config) {
     // workspace manager
     workspace_manager = new WorkspaceManager(this);
 
+    // transaction manager
+    transaction_manager = new TransactionManager(this);
+
     // scene
     scene = wlr_scene_create();
     scene_layout =
@@ -1389,6 +1392,7 @@ Server::~Server() {
 
     delete output_manager;
     delete workspace_manager;
+    delete transaction_manager;
     delete seat;
     delete cursor;
 

src/Toplevel.cpp

@@ -82,8 +82,10 @@ void Toplevel::map_notify(wl_listener *listener, [[maybe_unused]] void *data) {
         } else {
             wlr_box output_box = output->layout_geometry;
 
-            int32_t x = output_box.x + usable_area.x + (usable_area.width - width) / 2;
-            int32_t y = output_box.y + usable_area.y + (usable_area.height - height) / 2;
+            int32_t x =
+                output_box.x + usable_area.x + (usable_area.width - width) / 2;
+            int32_t y = output_box.y + usable_area.y +
+                        (usable_area.height - height) / 2;
 
             // ensure position falls in bounds
             x = std::max(x, output_box.x + usable_area.x);
@@ -114,12 +116,21 @@ void Toplevel::map_notify(wl_listener *listener, [[maybe_unused]] void *data) {
             if (!xwayland_surface->surface)
                 return;
 
+            // commit if part of transaction
+            if (toplevel->in_transaction) {
+                Transaction *txn =
+                    toplevel->server->transaction_manager->current();
+                if (txn && txn->contains(toplevel))
+                    txn->handle_commit(toplevel);
+            }
+
             wlr_surface_state *state = &xwayland_surface->surface->current;
             wlr_box *current = &toplevel->geometry;
 
             // update size if state differs
-            if (current->width != state->width ||
-                current->height != state->height) {
+            if (!toplevel->in_transaction &&
+                (current->width != state->width ||
+                 current->height != state->height)) {
                 current->width = state->width;
                 current->height = state->height;
                 toplevel->set_position_size(*current);
@@ -159,9 +170,11 @@ void Toplevel::map_notify(wl_listener *listener, [[maybe_unused]] void *data) {
 
             // center the surface to the focused output if zero
             if (!x)
-                x = output->layout_geometry.x + area.x + (area.width - width) / 2;
+                x = output->layout_geometry.x + area.x +
+                    (area.width - width) / 2;
             if (!y)
-                y = output->layout_geometry.y + area.y + (area.height - height) / 2;
+                y = output->layout_geometry.y + area.y +
+                    (area.height - height) / 2;
 
             // send a configure event
             wlr_xwayland_surface_configure(xwayland_surface, x, y, width,
@@ -223,6 +236,12 @@ void Toplevel::unmap_notify(wl_listener *listener,
     Toplevel *toplevel = wl_container_of(listener, toplevel, unmap);
     Server *server = toplevel->server;
 
+    // remove from any active transaction
+    if (toplevel->in_transaction && server->transaction_manager) {
+        server->transaction_manager->remove_toplevel(toplevel);
+        toplevel->in_transaction = false;
+    }
+
     // deactivate
     if (toplevel == server->seat->grabbed_toplevel)
         server->cursor->reset_mode();
@@ -297,6 +316,13 @@ Toplevel::Toplevel(Server *server, wlr_xdg_toplevel *xdg_toplevel)
                     WLR_XDG_TOPLEVEL_WM_CAPABILITIES_MAXIMIZE |
                     WLR_XDG_TOPLEVEL_WM_CAPABILITIES_MINIMIZE);
         }
+
+        // handle commit if part of transaction
+        if (toplevel->in_transaction) {
+            Transaction *txn = toplevel->server->transaction_manager->current();
+            if (txn && txn->contains(toplevel))
+                txn->handle_commit(toplevel);
+        }
     };
     wl_signal_add(&xdg_toplevel->base->surface->events.commit, &commit);
 
@@ -313,6 +339,10 @@ Toplevel::Toplevel(Server *server, wlr_xdg_toplevel *xdg_toplevel)
     // xdg_toplevel_destroy
     destroy.notify = [](wl_listener *listener, [[maybe_unused]] void *data) {
         Toplevel *toplevel = wl_container_of(listener, toplevel, destroy);
+        if (toplevel->in_transaction && toplevel->server->transaction_manager) {
+            toplevel->server->transaction_manager->remove_toplevel(toplevel);
+            toplevel->in_transaction = false;
+        }
         delete toplevel;
     };
     wl_signal_add(&xdg_toplevel->events.destroy, &destroy);
@@ -479,6 +509,10 @@ Toplevel::Toplevel(Server *server, wlr_xwayland_surface *xwayland_surface)
     // destroy
     destroy.notify = [](wl_listener *listener, [[maybe_unused]] void *data) {
         Toplevel *toplevel = wl_container_of(listener, toplevel, destroy);
+        if (toplevel->in_transaction && toplevel->server->transaction_manager) {
+            toplevel->server->transaction_manager->remove_toplevel(toplevel);
+            toplevel->in_transaction = false;
+        }
         delete toplevel;
     };
     wl_signal_add(&xwayland_surface->events.destroy, &destroy);
@@ -812,6 +846,12 @@ void Toplevel::begin_interactive(const CursorMode mode, const uint32_t edges) {
 
 // set the position and size of a toplevel, send a configure
 void Toplevel::set_position_size(double x, double y, int width, int height) {
+    if (Transaction *txn = server->transaction_manager->current()) {
+        txn->add_change(this, static_cast<int>(x), static_cast<int>(y), width,
+                        height);
+        return;
+    }
+
     // xwayland surfaces can call fullscreen and maximize when unmapped so this
     // check is necessary
 #ifdef XWAYLAND