Replace statics in headers with inline constants (#15100)

C++ is a very well balanced and reasonable language, which is why
`static` inside classes means "shared between all instances", whereas
`static` outside of classes means "not shared between all .cpp files".

32 years after this problem was written onto parchment it was fixed with
the introduction of inline variables in C++17, which tell the compiler
to deduplicate variables the same way it deduplicates functions.

src/cascadia/TerminalApp/TerminalPage.h

@@ -15,9 +15,6 @@
 
 #define DECLARE_ACTION_HANDLER(action) void _Handle##action(const IInspectable& sender, const Microsoft::Terminal::Settings::Model::ActionEventArgs& args);
 
-static constexpr uint32_t DefaultRowsToScroll{ 3 };
-static constexpr std::wstring_view TabletInputServiceKey{ L"TabletInputService" };
-
 namespace TerminalAppLocalTests
 {
     class TabTests;
@@ -31,6 +28,9 @@ namespace Microsoft::Terminal::Core
 
 namespace winrt::TerminalApp::implementation
 {
+    inline constexpr uint32_t DefaultRowsToScroll{ 3 };
+    inline constexpr std::wstring_view TabletInputServiceKey{ L"TabletInputService" };
+
     enum StartupState : int
     {
         NotInitialized = 0,

src/cascadia/TerminalApp/TerminalTab.h

@@ -7,9 +7,6 @@
 #include "TabBase.h"
 #include "TerminalTab.g.h"
 
-static constexpr double HeaderRenameBoxWidthDefault{ 165 };
-static constexpr double HeaderRenameBoxWidthTitleLength{ std::numeric_limits<double>::infinity() };
-
 // fwdecl unittest classes
 namespace TerminalAppLocalTests
 {
@@ -109,6 +106,9 @@ namespace winrt::TerminalApp::implementation
         TYPED_EVENT(TaskbarProgressChanged, IInspectable, IInspectable);
 
     private:
+        static constexpr double HeaderRenameBoxWidthDefault{ 165 };
+        static constexpr double HeaderRenameBoxWidthTitleLength{ std::numeric_limits<double>::infinity() };
+
         std::shared_ptr<Pane> _rootPane{ nullptr };
         std::shared_ptr<Pane> _activePane{ nullptr };
         std::shared_ptr<Pane> _zoomedPane{ nullptr };

src/cascadia/TerminalConnection/AzureClientID.h

@@ -3,4 +3,4 @@
 
 #pragma once
 
-static constexpr std::wstring_view AzureClientID = L"0";
+inline constexpr std::wstring_view AzureClientID = L"0";

src/cascadia/TerminalCore/Terminal.hpp

@@ -17,8 +17,8 @@
 
 #include <til/ticket_lock.h>
 
-static constexpr std::wstring_view linkPattern{ LR"(\b(https?|ftp|file)://[-A-Za-z0-9+&@#/%?=~_|$!:,.;]*[A-Za-z0-9+&@#/%=~_|$])" };
-static constexpr size_t TaskbarMinProgress{ 10 };
+inline constexpr std::wstring_view linkPattern{ LR"(\b(https?|ftp|file)://[-A-Za-z0-9+&@#/%?=~_|$!:,.;]*[A-Za-z0-9+&@#/%=~_|$])" };
+inline constexpr size_t TaskbarMinProgress{ 10 };
 
 // You have to forward decl the ICoreSettings here, instead of including the header.
 // If you include the header, there will be compilation errors with other

src/cascadia/TerminalSettingsEditor/ColorSchemeViewModel.h

@@ -10,13 +10,13 @@
 
 namespace winrt::Microsoft::Terminal::Settings::Editor::implementation
 {
-    inline static constexpr uint8_t ColorTableDivider{ 8 };
-    inline static constexpr uint8_t ColorTableSize{ 16 };
+    inline constexpr uint8_t ColorTableDivider{ 8 };
+    inline constexpr uint8_t ColorTableSize{ 16 };
 
-    inline static constexpr std::wstring_view ForegroundColorTag{ L"Foreground" };
-    inline static constexpr std::wstring_view BackgroundColorTag{ L"Background" };
-    inline static constexpr std::wstring_view CursorColorTag{ L"CursorColor" };
-    inline static constexpr std::wstring_view SelectionBackgroundColorTag{ L"SelectionBackground" };
+    inline constexpr std::wstring_view ForegroundColorTag{ L"Foreground" };
+    inline constexpr std::wstring_view BackgroundColorTag{ L"Background" };
+    inline constexpr std::wstring_view CursorColorTag{ L"CursorColor" };
+    inline constexpr std::wstring_view SelectionBackgroundColorTag{ L"SelectionBackground" };
 
     struct ColorSchemeViewModel : ColorSchemeViewModelT<ColorSchemeViewModel>, ViewModelHelper<ColorSchemeViewModel>
     {

src/cascadia/TerminalSettingsModel/DynamicProfileUtils.h

@@ -21,6 +21,6 @@ Author(s):
 // will become disconnected from user settings.
 // {2bde4a90-d05f-401c-9492-e40884ead1d8}
 // uuidv5 properties: name format is UTF-16LE bytes
-static constexpr GUID TERMINAL_PROFILE_NAMESPACE_GUID = { 0x2bde4a90, 0xd05f, 0x401c, { 0x94, 0x92, 0xe4, 0x8, 0x84, 0xea, 0xd1, 0xd8 } };
+inline constexpr GUID TERMINAL_PROFILE_NAMESPACE_GUID = { 0x2bde4a90, 0xd05f, 0x401c, { 0x94, 0x92, 0xe4, 0x8, 0x84, 0xea, 0xd1, 0xd8 } };
 
 winrt::com_ptr<winrt::Microsoft::Terminal::Settings::Model::implementation::Profile> CreateDynamicProfile(const std::wstring_view& name);

src/cascadia/TerminalSettingsModel/LegacyProfileGeneratorNamespaces.h

@@ -16,6 +16,6 @@ Author(s):
 
 #pragma once
 
-static constexpr std::wstring_view WslGeneratorNamespace{ L"Windows.Terminal.Wsl" };
-static constexpr std::wstring_view AzureGeneratorNamespace{ L"Windows.Terminal.Azure" };
-static constexpr std::wstring_view PowershellCoreGeneratorNamespace{ L"Windows.Terminal.PowershellCore" };
+inline constexpr std::wstring_view WslGeneratorNamespace{ L"Windows.Terminal.Wsl" };
+inline constexpr std::wstring_view AzureGeneratorNamespace{ L"Windows.Terminal.Azure" };
+inline constexpr std::wstring_view PowershellCoreGeneratorNamespace{ L"Windows.Terminal.PowershellCore" };

src/cascadia/inc/WindowingBehavior.h

@@ -4,11 +4,11 @@ Licensed under the MIT license.
 --*/
 
 #pragma once
-constexpr int32_t WindowingBehaviorUseCurrent{ 0 };
-constexpr int32_t WindowingBehaviorUseNew{ -1 };
-constexpr int32_t WindowingBehaviorUseExisting{ -2 };
-constexpr int32_t WindowingBehaviorUseAnyExisting{ -3 };
-constexpr int32_t WindowingBehaviorUseName{ -4 };
-constexpr int32_t WindowingBehaviorUseNone{ -5 };
+inline constexpr int32_t WindowingBehaviorUseCurrent{ 0 };
+inline constexpr int32_t WindowingBehaviorUseNew{ -1 };
+inline constexpr int32_t WindowingBehaviorUseExisting{ -2 };
+inline constexpr int32_t WindowingBehaviorUseAnyExisting{ -3 };
+inline constexpr int32_t WindowingBehaviorUseName{ -4 };
+inline constexpr int32_t WindowingBehaviorUseNone{ -5 };
 
-static constexpr std::wstring_view QuakeWindowName{ L"_quake" };
+inline constexpr std::wstring_view QuakeWindowName{ L"_quake" };

src/inc/til/spsc.h

@@ -24,9 +24,9 @@ namespace til::spsc
 
     namespace details
     {
-        static constexpr size_type position_mask = std::numeric_limits<size_type>::max() >> 2u; // 0b00111....
-        static constexpr size_type revolution_flag = 1u << (std::numeric_limits<size_type>::digits - 2u); // 0b01000....
-        static constexpr size_type drop_flag = 1u << (std::numeric_limits<size_type>::digits - 1u); // 0b10000....
+        inline constexpr size_type position_mask = std::numeric_limits<size_type>::max() >> 2u; // 0b00111....
+        inline constexpr size_type revolution_flag = 1u << (std::numeric_limits<size_type>::digits - 2u); // 0b01000....
+        inline constexpr size_type drop_flag = 1u << (std::numeric_limits<size_type>::digits - 1u); // 0b10000....
 
         struct block_initially_policy
         {

src/inc/til/string.h

@@ -36,7 +36,7 @@ namespace til // Terminal Implementation Library. Also: "Today I Learned"
         inline constexpr uint8_t F_ = 0b10; // stripped in clean_filename
         inline constexpr uint8_t _P = 0b01; // stripped in clean_path
         inline constexpr uint8_t FP = 0b11; // stripped in clean_filename and clean_path
-        static constexpr std::array<uint8_t, 128> pathFilter{ {
+        inline constexpr std::array<uint8_t, 128> pathFilter{ {
             // clang-format off
             __ /* NUL */, __ /* SOH */, __ /* STX */, __ /* ETX */, __ /* EOT */, __ /* ENQ */, __ /* ACK */, __ /* BEL */, __ /* BS  */, __ /* HT  */, __ /* LF  */, __ /* VT  */, __ /* FF  */, __ /* CR  */, __ /* SO  */, __ /* SI  */,
             __ /* DLE */, __ /* DC1 */, __ /* DC2 */, __ /* DC3 */, __ /* DC4 */, __ /* NAK */, __ /* SYN */, __ /* ETB */, __ /* CAN */, __ /* EM  */, __ /* SUB */, __ /* ESC */, __ /* FS  */, __ /* GS  */, __ /* RS  */, __ /* US  */,

src/renderer/inc/FontInfoBase.hpp

@@ -20,8 +20,8 @@ Author(s):
 
 #include "IFontDefaultList.hpp"
 
-static constexpr wchar_t DEFAULT_TT_FONT_FACENAME[]{ L"__DefaultTTFont__" };
-static constexpr wchar_t DEFAULT_RASTER_FONT_FACENAME[]{ L"Terminal" };
+inline constexpr wchar_t DEFAULT_TT_FONT_FACENAME[]{ L"__DefaultTTFont__" };
+inline constexpr wchar_t DEFAULT_RASTER_FONT_FACENAME[]{ L"Terminal" };
 
 class FontInfoBase
 {