Eliminate more transient allocations: Titles and invalid rectangles a…

…nd bitmap runs and utf8 conversions (#8621)

## References
* See also #8617 

## PR Checklist
* [x] Supports #3075
* [x] I work here.
* [x] Manual test.

## Detailed Description of the Pull Request / Additional comments

### Window Title Generation
Every time the renderer checks the title, it's doing two bad things that
I've fixed:
1. It's assembling the prefix to the full title doing a concatenation.
   No one ever gets just the prefix ever after it is set besides the
   concat. So instead of storing prefix and the title, I store the
   assembled prefix + title and the bare title.
2. A copy must be made because it was returning `std::wstring` instead
   of `std::wstring&`. Now it returns the ref.

### Dirty Area Return
Every time the renderer checks the dirty area, which is sometimes
multiple times per pass (regular text printing, again for selection,
etc.), a vector is created off the heap to return the rectangles. The
consumers only ever iterate this data. Now we return a span over a
rectangle or rectangles that the engine must store itself.
1. For some renderers, it's always a constant 1 element. They update
   that 1 element when dirty is queried and return it in the span with a
   span size of 1.
2. For other renderers with more complex behavior, they're already
   holding a cached vector of rectangles. Now it's effectively giving
   out the ref to those in the span for iteration.

### Bitmap Runs
The `til::bitmap` used a `std::optional<std::vector<til::rectangle>>`
inside itself to cache its runs and would clear the optional when the
runs became invalidated. Unfortunately doing `.reset()` to clear the
optional will destroy the underlying vector and have it release its
memory. We know it's about to get reallocated again, so we're just going
to make it a `std::pmr::vector` and give it a memory pool. 

The alternative solution here was to use a `bool` and
`std::vector<til::rectangle>` and just flag when the vector was invalid,
but that was honestly more code changes and I love excuses to try out
PMR now.

Also, instead of returning the ref to the vector... I'm just returning a
span now. Everyone just iterates it anyway, may as well not share the
implementation detail.

### UTF-8 conversions
When testing with Terminal and looking at the `conhost.exe`'s PTY
renderer, it spends a TON of allocation time on converting all the
UTF-16 stuff inside to UTF-8 before it sends it out the PTY. This was
because `ConvertToA` was allocating a string inside itself and returning
it just to have it freed after printing and looping back around again...
as a PTY does.

The change here is to use `til::u16u8` that accepts a buffer out
parameter so the caller can just hold onto it.

## Validation Steps Performed
- [x] `big.txt` in conhost.exe (GDI renderer)
- [x] `big.txt` in Terminal (DX, PTY renderer)
- [x] Ensure WDDM and BGFX build under Razzle with this change.

src/cascadia/TerminalCore/Terminal.hpp

@@ -182,7 +182,7 @@ class Microsoft::Terminal::Core::Terminal final :
     void SelectNewRegion(const COORD coordStart, const COORD coordEnd) override;
     const COORD GetSelectionAnchor() const noexcept override;
     const COORD GetSelectionEnd() const noexcept override;
-    const std::wstring GetConsoleTitle() const noexcept override;
+    const std::wstring_view GetConsoleTitle() const noexcept override;
     void ColorSelection(const COORD coordSelectionStart, const COORD coordSelectionEnd, const TextAttribute) override;
 #pragma endregion
 

src/cascadia/TerminalCore/terminalrenderdata.cpp

@@ -215,7 +215,7 @@ void Terminal::SelectNewRegion(const COORD coordStart, const COORD coordEnd)
     SetSelectionEnd(realCoordEnd, SelectionExpansionMode::Cell);
 }
 
-const std::wstring Terminal::GetConsoleTitle() const noexcept
+const std::wstring_view Terminal::GetConsoleTitle() const noexcept
 try
 {
     if (_title.has_value())

src/host/consoleInformation.cpp

@@ -24,6 +24,8 @@ CONSOLE_INFORMATION::CONSOLE_INFORMATION() :
     // ExeAliasList initialized below
     _OriginalTitle(),
     _Title(),
+    _Prefix(),
+    _TitleAndPrefix(),
     _LinkTitle(),
     Flags(0),
     PopupCount(0),
@@ -115,7 +117,12 @@ ULONG CONSOLE_INFORMATION::GetCSRecursionCount()
     try
     {
         gci.SetTitle(title);
-        gci.SetOriginalTitle(std::wstring(TranslateConsoleTitle(gci.GetTitle().c_str(), TRUE, FALSE)));
+
+        // TranslateConsoleTitle must have a null terminated string.
+        // This should only happen once on startup so the copy shouldn't be costly
+        // but could be eliminated by rewriting TranslateConsoleTitle.
+        const std::wstring nullTerminatedTitle{ gci.GetTitle() };
+        gci.SetOriginalTitle(std::wstring(TranslateConsoleTitle(nullTerminatedTitle.c_str(), TRUE, FALSE)));
     }
     catch (...)
     {
@@ -269,6 +276,7 @@ std::pair<COLORREF, COLORREF> CONSOLE_INFORMATION::LookupAttributeColors(const T
 void CONSOLE_INFORMATION::SetTitle(const std::wstring_view newTitle)
 {
     _Title = std::wstring{ newTitle.begin(), newTitle.end() };
+    _TitleAndPrefix = _Prefix + _Title;
 
     auto* const pRender = ServiceLocator::LocateGlobals().pRender;
     if (pRender)
@@ -284,9 +292,10 @@ void CONSOLE_INFORMATION::SetTitle(const std::wstring_view newTitle)
 // - newTitlePrefix: The new value to use for the title prefix
 // Return Value:
 // - <none>
-void CONSOLE_INFORMATION::SetTitlePrefix(const std::wstring& newTitlePrefix)
+void CONSOLE_INFORMATION::SetTitlePrefix(const std::wstring_view newTitlePrefix)
 {
-    _TitlePrefix = newTitlePrefix;
+    _Prefix = newTitlePrefix;
+    _TitleAndPrefix = _Prefix + _Title;
 
     auto* const pRender = ServiceLocator::LocateGlobals().pRender;
     if (pRender)
@@ -302,7 +311,7 @@ void CONSOLE_INFORMATION::SetTitlePrefix(const std::wstring& newTitlePrefix)
 // - originalTitle: The new value to use for the console's original title
 // Return Value:
 // - <none>
-void CONSOLE_INFORMATION::SetOriginalTitle(const std::wstring& originalTitle)
+void CONSOLE_INFORMATION::SetOriginalTitle(const std::wstring_view originalTitle)
 {
     _OriginalTitle = originalTitle;
 }
@@ -314,7 +323,7 @@ void CONSOLE_INFORMATION::SetOriginalTitle(const std::wstring& originalTitle)
 // - linkTitle: The new value to use for the console's link title
 // Return Value:
 // - <none>
-void CONSOLE_INFORMATION::SetLinkTitle(const std::wstring& linkTitle)
+void CONSOLE_INFORMATION::SetLinkTitle(const std::wstring_view linkTitle)
 {
     _LinkTitle = linkTitle;
 }
@@ -324,8 +333,8 @@ void CONSOLE_INFORMATION::SetLinkTitle(const std::wstring& linkTitle)
 // Arguments:
 // - <none>
 // Return Value:
-// - a reference to the console's title.
-const std::wstring& CONSOLE_INFORMATION::GetTitle() const noexcept
+// - the console's title.
+const std::wstring_view CONSOLE_INFORMATION::GetTitle() const noexcept
 {
     return _Title;
 }
@@ -336,19 +345,19 @@ const std::wstring& CONSOLE_INFORMATION::GetTitle() const noexcept
 // Arguments:
 // - <none>
 // Return Value:
-// - a new wstring containing the combined prefix and title.
-const std::wstring CONSOLE_INFORMATION::GetTitleAndPrefix() const
+// - the combined prefix and title.
+const std::wstring_view CONSOLE_INFORMATION::GetTitleAndPrefix() const
 {
-    return _TitlePrefix + _Title;
+    return _TitleAndPrefix;
 }
 
 // Method Description:
 // - return a reference to the console's original title.
 // Arguments:
 // - <none>
 // Return Value:
-// - a reference to the console's original title.
-const std::wstring& CONSOLE_INFORMATION::GetOriginalTitle() const noexcept
+// - the console's original title.
+const std::wstring_view CONSOLE_INFORMATION::GetOriginalTitle() const noexcept
 {
     return _OriginalTitle;
 }
@@ -358,8 +367,8 @@ const std::wstring& CONSOLE_INFORMATION::GetOriginalTitle() const noexcept
 // Arguments:
 // - <none>
 // Return Value:
-// - a reference to the console's link title.
-const std::wstring& CONSOLE_INFORMATION::GetLinkTitle() const noexcept
+// - the console's link title.
+const std::wstring_view CONSOLE_INFORMATION::GetLinkTitle() const noexcept
 {
     return _LinkTitle;
 }

src/host/getset.cpp

@@ -1660,33 +1660,21 @@ void DoSrvPrivateRefreshWindow(_In_ const SCREEN_INFORMATION& screenInfo)
         }
 
         // Get the appropriate title and length depending on the mode.
-        const wchar_t* pwszTitle;
-        size_t cchTitleLength;
-
-        if (isOriginal)
-        {
-            pwszTitle = gci.GetOriginalTitle().c_str();
-            cchTitleLength = gci.GetOriginalTitle().length();
-        }
-        else
-        {
-            pwszTitle = gci.GetTitle().c_str();
-            cchTitleLength = gci.GetTitle().length();
-        }
+        const std::wstring_view storedTitle = isOriginal ? gci.GetOriginalTitle() : gci.GetTitle();
 
         // Always report how much space we would need.
-        needed = cchTitleLength;
+        needed = storedTitle.size();
 
         // If we have a pointer to receive the data, then copy it out.
         if (title.has_value())
         {
-            HRESULT const hr = StringCchCopyNW(title->data(), title->size(), pwszTitle, cchTitleLength);
+            HRESULT const hr = StringCchCopyNW(title->data(), title->size(), storedTitle.data(), storedTitle.size());
 
             // Insufficient buffer is allowed. If we return a partial string, that's still OK by historical/compat standards.
             // Just say how much we managed to return.
             if (SUCCEEDED(hr) || STRSAFE_E_INSUFFICIENT_BUFFER == hr)
             {
-                written = std::min(title->size(), cchTitleLength);
+                written = std::min(title->size(), storedTitle.size());
             }
         }
         return S_OK;

src/host/renderData.cpp

@@ -318,7 +318,7 @@ const bool RenderData::IsGridLineDrawingAllowed() noexcept
 // - Retrieves the title information to be displayed in the frame/edge of the window
 // Return Value:
 // - String with title information
-const std::wstring RenderData::GetConsoleTitle() const noexcept
+const std::wstring_view RenderData::GetConsoleTitle() const noexcept
 {
     const CONSOLE_INFORMATION& gci = ServiceLocator::LocateGlobals().getConsoleInformation();
     return gci.GetTitleAndPrefix();

src/host/renderData.hpp

@@ -54,7 +54,7 @@ class RenderData final :
 
     const bool IsGridLineDrawingAllowed() noexcept override;
 
-    const std::wstring GetConsoleTitle() const noexcept override;
+    const std::wstring_view GetConsoleTitle() const noexcept override;
 
     const std::wstring GetHyperlinkUri(uint16_t id) const noexcept override;
     const std::wstring GetHyperlinkCustomId(uint16_t id) const noexcept override;

src/host/server.h

@@ -129,13 +129,13 @@ class CONSOLE_INFORMATION :
     std::pair<COLORREF, COLORREF> LookupAttributeColors(const TextAttribute& attr) const noexcept;
 
     void SetTitle(const std::wstring_view newTitle);
-    void SetTitlePrefix(const std::wstring& newTitlePrefix);
-    void SetOriginalTitle(const std::wstring& originalTitle);
-    void SetLinkTitle(const std::wstring& linkTitle);
-    const std::wstring& GetTitle() const noexcept;
-    const std::wstring& GetOriginalTitle() const noexcept;
-    const std::wstring& GetLinkTitle() const noexcept;
-    const std::wstring GetTitleAndPrefix() const;
+    void SetTitlePrefix(const std::wstring_view newTitlePrefix);
+    void SetOriginalTitle(const std::wstring_view originalTitle);
+    void SetLinkTitle(const std::wstring_view linkTitle);
+    const std::wstring_view GetTitle() const noexcept;
+    const std::wstring_view GetOriginalTitle() const noexcept;
+    const std::wstring_view GetLinkTitle() const noexcept;
+    const std::wstring_view GetTitleAndPrefix() const;
 
     [[nodiscard]] static NTSTATUS AllocateConsole(const std::wstring_view title);
     // MSFT:16886775 : get rid of friends
@@ -152,7 +152,8 @@ class CONSOLE_INFORMATION :
 private:
     CRITICAL_SECTION _csConsoleLock; // serialize input and output using this
     std::wstring _Title;
-    std::wstring _TitlePrefix; // Eg Select, Mark - things that we manually prepend to the title.
+    std::wstring _Prefix; // Eg Select, Mark - things that we manually prepend to the title.
+    std::wstring _TitleAndPrefix;
     std::wstring _OriginalTitle;
     std::wstring _LinkTitle; // Path to .lnk file
     SCREEN_INFORMATION* pCurrentScreenBuffer;

src/host/ut_host/ApiRoutinesTests.cpp

@@ -207,10 +207,12 @@ class ApiRoutinesTests
         CONSOLE_INFORMATION& gci = ServiceLocator::LocateGlobals().getConsoleInformation();
         gci.SetTitle(L"Test window title.");
 
+        const auto title = gci.GetTitle();
+
         int const iBytesNeeded = WideCharToMultiByte(gci.OutputCP,
                                                      0,
-                                                     gci.GetTitle().c_str(),
-                                                     -1,
+                                                     title.data(),
+                                                     gsl::narrow_cast<int>(title.size()),
                                                      nullptr,
                                                      0,
                                                      nullptr,
@@ -221,8 +223,8 @@ class ApiRoutinesTests
 
         VERIFY_WIN32_BOOL_SUCCEEDED(WideCharToMultiByte(gci.OutputCP,
                                                         0,
-                                                        gci.GetTitle().c_str(),
-                                                        -1,
+                                                        title.data(),
+                                                        gsl::narrow_cast<int>(title.size()),
                                                         pszExpected.get(),
                                                         iBytesNeeded,
                                                         nullptr,
@@ -251,21 +253,26 @@ class ApiRoutinesTests
         VERIFY_SUCCEEDED(_pApiRoutines->GetConsoleTitleWImpl(gsl::span<wchar_t>(pwszTitle, ARRAYSIZE(pwszTitle)), cchWritten, cchNeeded));
 
         VERIFY_ARE_NOT_EQUAL(0u, cchWritten);
+
+        const auto title = gci.GetTitle();
+
         // NOTE: W version of API returns string length. A version of API returns buffer length (string + null).
-        VERIFY_ARE_EQUAL(gci.GetTitle().length(), cchWritten);
-        VERIFY_ARE_EQUAL(gci.GetTitle().length(), cchNeeded);
-        VERIFY_ARE_EQUAL(WEX::Common::String(gci.GetTitle().c_str()), WEX::Common::String(pwszTitle));
+        VERIFY_ARE_EQUAL(title.length(), cchWritten);
+        VERIFY_ARE_EQUAL(title.length(), cchNeeded);
+        VERIFY_ARE_EQUAL(WEX::Common::String(title.data(), gsl::narrow_cast<int>(title.size())), WEX::Common::String(pwszTitle));
     }
 
     TEST_METHOD(ApiGetConsoleOriginalTitleA)
     {
         CONSOLE_INFORMATION& gci = ServiceLocator::LocateGlobals().getConsoleInformation();
         gci.SetOriginalTitle(L"Test original window title.");
 
+        const auto originalTitle = gci.GetOriginalTitle();
+
         int const iBytesNeeded = WideCharToMultiByte(gci.OutputCP,
                                                      0,
-                                                     gci.GetOriginalTitle().c_str(),
-                                                     -1,
+                                                     originalTitle.data(),
+                                                     gsl::narrow_cast<int>(originalTitle.size()),
                                                      nullptr,
                                                      0,
                                                      nullptr,
@@ -276,8 +283,8 @@ class ApiRoutinesTests
 
         VERIFY_WIN32_BOOL_SUCCEEDED(WideCharToMultiByte(gci.OutputCP,
                                                         0,
-                                                        gci.GetOriginalTitle().c_str(),
-                                                        -1,
+                                                        originalTitle.data(),
+                                                        gsl::narrow_cast<int>(originalTitle.size()),
                                                         pszExpected.get(),
                                                         iBytesNeeded,
                                                         nullptr,
@@ -306,10 +313,12 @@ class ApiRoutinesTests
         VERIFY_SUCCEEDED(_pApiRoutines->GetConsoleOriginalTitleWImpl(gsl::span<wchar_t>(pwszTitle, ARRAYSIZE(pwszTitle)), cchWritten, cchNeeded));
 
         VERIFY_ARE_NOT_EQUAL(0u, cchWritten);
+
+        const auto originalTitle = gci.GetOriginalTitle();
         // NOTE: W version of API returns string length. A version of API returns buffer length (string + null).
-        VERIFY_ARE_EQUAL(gci.GetOriginalTitle().length(), cchWritten);
-        VERIFY_ARE_EQUAL(gci.GetOriginalTitle().length(), cchNeeded);
-        VERIFY_ARE_EQUAL(WEX::Common::String(gci.GetOriginalTitle().c_str()), WEX::Common::String(pwszTitle));
+        VERIFY_ARE_EQUAL(originalTitle.length(), cchWritten);
+        VERIFY_ARE_EQUAL(originalTitle.length(), cchNeeded);
+        VERIFY_ARE_EQUAL(WEX::Common::String(originalTitle.data(), gsl::narrow_cast<int>(originalTitle.size())), WEX::Common::String(pwszTitle));
     }
 
     static void s_AdjustOutputWait(const bool fShouldBlock)

src/host/ut_host/VtIoTests.cpp

@@ -355,9 +355,9 @@ class MockRenderData : public IRenderData, IUiaData
         return false;
     }
 
-    const std::wstring GetConsoleTitle() const noexcept override
+    const std::wstring_view GetConsoleTitle() const noexcept override
     {
-        return std::wstring{};
+        return std::wstring_view{};
     }
 
     const bool IsSelectionActive() const override

src/inc/til/bitmap.h

@@ -263,15 +263,15 @@ namespace til // Terminal Implementation Library. Also: "Today I Learned"
                 return const_iterator(_bits, _sz, _sz.area());
             }
 
-            const std::vector<til::rectangle, run_allocator_type>& runs() const
+            const gsl::span<const til::rectangle> runs() const
             {
                 // If we don't have cached runs, rebuild.
                 if (!_runs.has_value())
                 {
                     _runs.emplace(begin(), end());
                 }
 
-                // Return a reference to the runs.
+                // Return the runs.
                 return _runs.value();
             }
 

src/interactivity/onecore/BgfxEngine.cpp

@@ -230,15 +230,20 @@ BgfxEngine::BgfxEngine(PVOID SharedViewBase, LONG DisplayHeight, LONG DisplayWid
     return S_OK;
 }
 
-std::vector<til::rectangle> BgfxEngine::GetDirtyArea()
+[[nodiscard]] HRESULT BgfxEngine::GetDirtyArea(gsl::span<const til::rectangle>& area) noexcept
 {
     SMALL_RECT r;
     r.Bottom = _displayHeight > 0 ? (SHORT)(_displayHeight - 1) : 0;
     r.Top = 0;
     r.Left = 0;
     r.Right = _displayWidth > 0 ? (SHORT)(_displayWidth - 1) : 0;
 
-    return { r };
+    _dirtyArea = r;
+
+    area = { &_dirtyArea,
+             1 };
+
+    return S_OK;
 }
 
 [[nodiscard]] HRESULT BgfxEngine::GetFontSize(_Out_ COORD* const pFontSize) noexcept
@@ -260,7 +265,7 @@ std::vector<til::rectangle> BgfxEngine::GetDirtyArea()
 // - newTitle: the new string to use for the title of the window
 // Return Value:
 // - S_OK
-[[nodiscard]] HRESULT BgfxEngine::_DoUpdateTitle(_In_ const std::wstring& /*newTitle*/) noexcept
+[[nodiscard]] HRESULT BgfxEngine::_DoUpdateTitle(_In_ const std::wstring_view /*newTitle*/) noexcept
 {
     return S_OK;
 }

src/interactivity/onecore/BgfxEngine.hpp

@@ -67,19 +67,20 @@ namespace Microsoft::Console::Render
 
         [[nodiscard]] HRESULT GetProposedFont(const FontInfoDesired& fiFontInfoDesired, FontInfo& fiFontInfo, int const iDpi) noexcept override;
 
-        std::vector<til::rectangle> GetDirtyArea() override;
+        [[nodiscard]] HRESULT GetDirtyArea(gsl::span<const til::rectangle>& area) noexcept override;
         [[nodiscard]] HRESULT GetFontSize(_Out_ COORD* const pFontSize) noexcept override;
         [[nodiscard]] HRESULT IsGlyphWideByFont(const std::wstring_view glyph, _Out_ bool* const pResult) noexcept override;
 
     protected:
-        [[nodiscard]] HRESULT _DoUpdateTitle(_In_ const std::wstring& newTitle) noexcept override;
+        [[nodiscard]] HRESULT _DoUpdateTitle(_In_ const std::wstring_view newTitle) noexcept override;
 
     private:
         ULONG_PTR _sharedViewBase;
         SIZE_T _runLength;
 
         LONG _displayHeight;
         LONG _displayWidth;
+        til::rectangle _dirtyArea;
 
         COORD _fontSize;