[Build] Report ccache skip on Windows explicitly

ccache is a near free win for both clean and incremental rebuilds and
has no effect on systems where it is not installed (find_program
guards the whole block). Aligns the CMake default with the documented
behavior; users can still arch with -DUSE_CCACHE=OFF.

.ci/compile.sh

@@ -149,6 +149,9 @@ if [[ $MAKE_TEST ]]; then
 fi
 if [[ $USE_CCACHE ]]; then
   flags+=("-DUSE_CCACHE=1")
+  # PCH-aware caching is required or ccache refuses to cache any TU that
+  # consumes a precompiled header, silently recompiling everything on every run.
+  ccache --set-config sloppiness=pch_defines,time_macros
   if [[ $CCACHE_SIZE ]]; then
     # note, this setting persists after running the script
     ccache --max-size "$CCACHE_SIZE"

CMakeLists.txt

@@ -5,11 +5,11 @@
 # This file sets all the variables shared between the projects
 # like the installation path, compilation flags etc..
 
-# cmake 3.16 is required if using qt6
-cmake_minimum_required(VERSION 3.10)
+# 3.16 required for Qt6 and target_precompile_headers()
+cmake_minimum_required(VERSION 3.16)
 
 # Use compiler cache (ccache)
-option(USE_CCACHE "Cache the build results with ccache" OFF)
+option(USE_CCACHE "Cache the build results with ccache" ON)
 # Treat warnings as errors (Debug builds only)
 option(WARNING_AS_ERROR "Treat warnings as errors in debug builds" ON)
 # Check for translation updates
@@ -39,13 +39,24 @@ else()
   )
 endif()
 
-if(USE_CCACHE)
+# ccache does not support MSVC and must not auto-engage on Windows
+# (it is installed unintentionally on the Windows CI runner).
+# NOTE: this keys off the target OS, so a mingw/Ninja configuration on Windows
+# also opts out of ccache even though the GNUCXX branch below supports it.
+if(USE_CCACHE AND NOT WIN32)
   find_program(CCACHE_PROGRAM ccache)
   if(CCACHE_PROGRAM)
     # Support Unix Makefiles and Ninja
     set_property(GLOBAL PROPERTY RULE_LAUNCH_COMPILE "${CCACHE_PROGRAM}")
+    # PCH-aware caching, matching .ci/compile.sh: without this ccache refuses
+    # to cache any TU that consumes a precompiled header, so every PCH-backed
+    # target recompiles from scratch on each build.
+    execute_process(COMMAND ${CCACHE_PROGRAM} --set-config sloppiness=pch_defines,time_macros)
     message(STATUS "Found CCache ${CCACHE_PROGRAM}")
   endif()
+elseif(USE_CCACHE AND WIN32)
+  # An explicit opt-in must not disappear silently on Windows.
+  message(STATUS "ccache disabled: not supported for the MSVC toolchain on Windows")
 endif()
 
 if(WIN32 OR USE_VCPKG)
@@ -184,6 +195,9 @@ elseif(CMAKE_COMPILER_IS_GNUCXX)
       set(CMAKE_CXX_FLAGS_DEBUG "${CMAKE_CXX_FLAGS_DEBUG} ${FLAG}")
     endif()
   endforeach()
+
+  # Reduce compiler I/O by using pipes between stages instead of temp files
+  set(CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} -pipe")
 else()
   # other: osx/llvm, bsd/llvm
   set(CMAKE_CXX_FLAGS_RELEASE "-O2")
@@ -192,6 +206,9 @@ else()
   else()
     set(CMAKE_CXX_FLAGS_DEBUG "-g -O0 -Wall -Wextra")
   endif()
+
+  # Reduce compiler I/O by using pipes between stages instead of temp files
+  set(CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} -pipe")
 endif()
 
 # GNU systems need to define the Mersenne exponent for the RNG to compile w/o warning

cmake/pch/qtcore_pch.h

@@ -0,0 +1,24 @@
+/** @file qtcore_pch.h
+ *  @brief Precompiled header for all Qt targets (Qt Core only).
+ *
+ * Safe for every target that links Qt Core, including the headless
+ * Servatrice binary. Keep this header free of any widget/gui types.
+ */
+
+#include <QBasicTimer>
+#include <QByteArray>
+#include <QDateTime>
+#include <QDebug>
+#include <QFile>
+#include <QHash>
+#include <QList>
+#include <QLoggingCategory>
+#include <QMap>
+#include <QMetaObject>
+#include <QObject>
+#include <QRandomGenerator>
+#include <QSharedPointer>
+#include <QString>
+#include <QStringList>
+#include <QTimer>
+#include <QVariant>

cmake/pch/qtwidgets_pch.h

@@ -0,0 +1,30 @@
+/** @file qtwidgets_pch.h
+ *  @brief Precompiled header for GUI targets (Cockatrice client, Oracle).
+ *
+ * Includes the Qt Core precompiled header plus the heavy Gui, Widgets and
+ * Network layers that virtually every client translation unit re-parses.
+ * Do not use on Servatrice (headless, QT_DONT_USE_QTGUI).
+ */
+
+#include "qtcore_pch.h"
+
+#include <QAction>
+#include <QApplication>
+#include <QFrame>
+#include <QGraphicsItem>
+#include <QGraphicsScene>
+#include <QGraphicsView>
+#include <QImage>
+#include <QLabel>
+#include <QLayout>
+#include <QMainWindow>
+#include <QMenu>
+#include <QNetworkAccessManager>
+#include <QNetworkReply>
+#include <QPainter>
+#include <QPushButton>
+#include <QScrollArea>
+#include <QTabWidget>
+#include <QToolBar>
+#include <QTreeWidget>
+#include <QWidget>

cockatrice/CMakeLists.txt

@@ -516,6 +516,8 @@ qt6_add_executable(
   MANUAL_FINALIZATION
 )
 
+target_precompile_headers(cockatrice PRIVATE "${CMAKE_SOURCE_DIR}/cmake/pch/qtwidgets_pch.h")
+
 qt6_add_shaders(
   cockatrice
   "onboarding_shaders"

cockatrice/src/interface/widgets/tabs/tab_supervisor.cpp

@@ -116,9 +116,10 @@ void CloseButton::paintEvent(QPaintEvent * /*event*/)
 }
 
 TabSupervisor::TabSupervisor(AbstractClient *_client, QMenu *tabsMenu, QWidget *parent)
-    : QTabWidget(parent), userInfo(nullptr), client(_client), tabsMenu(tabsMenu), tabVisualDeckStorage(nullptr),
-      tabServer(nullptr), tabAccount(nullptr), tabDeckStorage(nullptr), tabReplays(nullptr), tabAdmin(nullptr),
-      tabLog(nullptr), tabReport(nullptr), tabModeration(nullptr), isLocalGame(false)
+    : QTabWidget(parent), userInfo(nullptr), client(_client), tabsMenu(tabsMenu), tabHome(nullptr),
+      tabVisualDeckStorage(nullptr), tabServer(nullptr), tabAccount(nullptr), tabDeckStorage(nullptr),
+      tabReplays(nullptr), tabAdmin(nullptr), tabCardArtRules(nullptr), tabLog(nullptr), tabReport(nullptr),
+      tabModeration(nullptr), isLocalGame(false)
 {
     setElideMode(Qt::ElideRight);
     setMovable(true);

format.sh

@@ -18,6 +18,7 @@ include=("cockatrice/src" \
 libcockatrice_* \
 "oracle/src" \
 "servatrice/src" \
+"cmake/pch" \
 "tests")
 exclude=("libcockatrice_rng/libcockatrice/rng/sfmt/" \
 "libcockatrice_utility/libcockatrice/utility/peglib.h" \

libcockatrice_protocol/libcockatrice/protocol/pb/CMakeLists.txt

@@ -90,7 +90,6 @@ set(PROTO_FILES
     event_game_log_notice.proto
     event_game_say.proto
     event_game_state_changed.proto
-    event_game_state_changed.proto
     event_join.proto
     event_join_room.proto
     event_kicked.proto

oracle/CMakeLists.txt

@@ -113,6 +113,8 @@ qt6_add_executable(
   MANUAL_FINALIZATION
 )
 
+target_precompile_headers(oracle PRIVATE "${CMAKE_SOURCE_DIR}/cmake/pch/qtwidgets_pch.h")
+
 # ------------------------
 # Link libraries
 # ------------------------

servatrice/CMakeLists.txt

@@ -95,6 +95,8 @@ set(DESKTOPDIR
 # Build servatrice binary and link it
 add_executable(servatrice MACOSX_BUNDLE ${servatrice_MOC_SRCS} ${servatrice_RESOURCES_RCC} ${servatrice_SOURCES})
 
+target_precompile_headers(servatrice PRIVATE "${CMAKE_SOURCE_DIR}/cmake/pch/qtcore_pch.h")
+
 if(CMAKE_HOST_SYSTEM MATCHES "FreeBSD")
   target_link_libraries(
     servatrice libcockatrice_deck_list libcockatrice_network_server_remote Threads::Threads ${SERVATRICE_QT_MODULES}